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494 lines
17 KiB
494 lines
17 KiB
/* SPDX-License-Identifier: GPL-2.0-only */ |
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/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com |
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*/ |
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#ifndef _LINUX_BPF_VERIFIER_H |
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#define _LINUX_BPF_VERIFIER_H 1 |
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|
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#include <linux/bpf.h> /* for enum bpf_reg_type */ |
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#include <linux/btf.h> /* for struct btf and btf_id() */ |
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#include <linux/filter.h> /* for MAX_BPF_STACK */ |
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#include <linux/tnum.h> |
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/* Maximum variable offset umax_value permitted when resolving memory accesses. |
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* In practice this is far bigger than any realistic pointer offset; this limit |
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* ensures that umax_value + (int)off + (int)size cannot overflow a u64. |
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*/ |
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#define BPF_MAX_VAR_OFF (1 << 29) |
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/* Maximum variable size permitted for ARG_CONST_SIZE[_OR_ZERO]. This ensures |
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* that converting umax_value to int cannot overflow. |
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*/ |
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#define BPF_MAX_VAR_SIZ (1 << 29) |
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/* Liveness marks, used for registers and spilled-regs (in stack slots). |
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* Read marks propagate upwards until they find a write mark; they record that |
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* "one of this state's descendants read this reg" (and therefore the reg is |
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* relevant for states_equal() checks). |
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* Write marks collect downwards and do not propagate; they record that "the |
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* straight-line code that reached this state (from its parent) wrote this reg" |
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* (and therefore that reads propagated from this state or its descendants |
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* should not propagate to its parent). |
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* A state with a write mark can receive read marks; it just won't propagate |
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* them to its parent, since the write mark is a property, not of the state, |
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* but of the link between it and its parent. See mark_reg_read() and |
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* mark_stack_slot_read() in kernel/bpf/verifier.c. |
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*/ |
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enum bpf_reg_liveness { |
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REG_LIVE_NONE = 0, /* reg hasn't been read or written this branch */ |
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REG_LIVE_READ32 = 0x1, /* reg was read, so we're sensitive to initial value */ |
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REG_LIVE_READ64 = 0x2, /* likewise, but full 64-bit content matters */ |
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REG_LIVE_READ = REG_LIVE_READ32 | REG_LIVE_READ64, |
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REG_LIVE_WRITTEN = 0x4, /* reg was written first, screening off later reads */ |
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REG_LIVE_DONE = 0x8, /* liveness won't be updating this register anymore */ |
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}; |
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struct bpf_reg_state { |
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/* Ordering of fields matters. See states_equal() */ |
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enum bpf_reg_type type; |
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/* Fixed part of pointer offset, pointer types only */ |
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s32 off; |
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union { |
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/* valid when type == PTR_TO_PACKET */ |
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int range; |
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/* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE | |
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* PTR_TO_MAP_VALUE_OR_NULL |
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*/ |
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struct bpf_map *map_ptr; |
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/* for PTR_TO_BTF_ID */ |
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struct { |
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struct btf *btf; |
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u32 btf_id; |
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}; |
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u32 mem_size; /* for PTR_TO_MEM | PTR_TO_MEM_OR_NULL */ |
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/* Max size from any of the above. */ |
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struct { |
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unsigned long raw1; |
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unsigned long raw2; |
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} raw; |
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}; |
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/* For PTR_TO_PACKET, used to find other pointers with the same variable |
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* offset, so they can share range knowledge. |
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* For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we |
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* came from, when one is tested for != NULL. |
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* For PTR_TO_MEM_OR_NULL this is used to identify memory allocation |
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* for the purpose of tracking that it's freed. |
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* For PTR_TO_SOCKET this is used to share which pointers retain the |
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* same reference to the socket, to determine proper reference freeing. |
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*/ |
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u32 id; |
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/* PTR_TO_SOCKET and PTR_TO_TCP_SOCK could be a ptr returned |
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* from a pointer-cast helper, bpf_sk_fullsock() and |
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* bpf_tcp_sock(). |
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* |
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* Consider the following where "sk" is a reference counted |
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* pointer returned from "sk = bpf_sk_lookup_tcp();": |
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* |
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* 1: sk = bpf_sk_lookup_tcp(); |
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* 2: if (!sk) { return 0; } |
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* 3: fullsock = bpf_sk_fullsock(sk); |
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* 4: if (!fullsock) { bpf_sk_release(sk); return 0; } |
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* 5: tp = bpf_tcp_sock(fullsock); |
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* 6: if (!tp) { bpf_sk_release(sk); return 0; } |
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* 7: bpf_sk_release(sk); |
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* 8: snd_cwnd = tp->snd_cwnd; // verifier will complain |
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* |
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* After bpf_sk_release(sk) at line 7, both "fullsock" ptr and |
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* "tp" ptr should be invalidated also. In order to do that, |
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* the reg holding "fullsock" and "sk" need to remember |
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* the original refcounted ptr id (i.e. sk_reg->id) in ref_obj_id |
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* such that the verifier can reset all regs which have |
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* ref_obj_id matching the sk_reg->id. |
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* |
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* sk_reg->ref_obj_id is set to sk_reg->id at line 1. |
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* sk_reg->id will stay as NULL-marking purpose only. |
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* After NULL-marking is done, sk_reg->id can be reset to 0. |
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* |
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* After "fullsock = bpf_sk_fullsock(sk);" at line 3, |
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* fullsock_reg->ref_obj_id is set to sk_reg->ref_obj_id. |
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* |
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* After "tp = bpf_tcp_sock(fullsock);" at line 5, |
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* tp_reg->ref_obj_id is set to fullsock_reg->ref_obj_id |
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* which is the same as sk_reg->ref_obj_id. |
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* |
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* From the verifier perspective, if sk, fullsock and tp |
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* are not NULL, they are the same ptr with different |
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* reg->type. In particular, bpf_sk_release(tp) is also |
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* allowed and has the same effect as bpf_sk_release(sk). |
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*/ |
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u32 ref_obj_id; |
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/* For scalar types (SCALAR_VALUE), this represents our knowledge of |
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* the actual value. |
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* For pointer types, this represents the variable part of the offset |
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* from the pointed-to object, and is shared with all bpf_reg_states |
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* with the same id as us. |
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*/ |
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struct tnum var_off; |
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/* Used to determine if any memory access using this register will |
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* result in a bad access. |
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* These refer to the same value as var_off, not necessarily the actual |
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* contents of the register. |
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*/ |
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s64 smin_value; /* minimum possible (s64)value */ |
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s64 smax_value; /* maximum possible (s64)value */ |
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u64 umin_value; /* minimum possible (u64)value */ |
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u64 umax_value; /* maximum possible (u64)value */ |
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s32 s32_min_value; /* minimum possible (s32)value */ |
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s32 s32_max_value; /* maximum possible (s32)value */ |
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u32 u32_min_value; /* minimum possible (u32)value */ |
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u32 u32_max_value; /* maximum possible (u32)value */ |
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/* parentage chain for liveness checking */ |
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struct bpf_reg_state *parent; |
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/* Inside the callee two registers can be both PTR_TO_STACK like |
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* R1=fp-8 and R2=fp-8, but one of them points to this function stack |
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* while another to the caller's stack. To differentiate them 'frameno' |
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* is used which is an index in bpf_verifier_state->frame[] array |
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* pointing to bpf_func_state. |
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*/ |
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u32 frameno; |
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/* Tracks subreg definition. The stored value is the insn_idx of the |
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* writing insn. This is safe because subreg_def is used before any insn |
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* patching which only happens after main verification finished. |
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*/ |
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s32 subreg_def; |
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enum bpf_reg_liveness live; |
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/* if (!precise && SCALAR_VALUE) min/max/tnum don't affect safety */ |
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bool precise; |
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}; |
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enum bpf_stack_slot_type { |
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STACK_INVALID, /* nothing was stored in this stack slot */ |
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STACK_SPILL, /* register spilled into stack */ |
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STACK_MISC, /* BPF program wrote some data into this slot */ |
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STACK_ZERO, /* BPF program wrote constant zero */ |
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}; |
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#define BPF_REG_SIZE 8 /* size of eBPF register in bytes */ |
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struct bpf_stack_state { |
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struct bpf_reg_state spilled_ptr; |
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u8 slot_type[BPF_REG_SIZE]; |
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}; |
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struct bpf_reference_state { |
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/* Track each reference created with a unique id, even if the same |
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* instruction creates the reference multiple times (eg, via CALL). |
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*/ |
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int id; |
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/* Instruction where the allocation of this reference occurred. This |
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* is used purely to inform the user of a reference leak. |
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*/ |
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int insn_idx; |
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}; |
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/* state of the program: |
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* type of all registers and stack info |
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*/ |
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struct bpf_func_state { |
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struct bpf_reg_state regs[MAX_BPF_REG]; |
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/* index of call instruction that called into this func */ |
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int callsite; |
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/* stack frame number of this function state from pov of |
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* enclosing bpf_verifier_state. |
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* 0 = main function, 1 = first callee. |
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*/ |
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u32 frameno; |
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/* subprog number == index within subprog_info |
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* zero == main subprog |
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*/ |
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u32 subprogno; |
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/* The following fields should be last. See copy_func_state() */ |
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int acquired_refs; |
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struct bpf_reference_state *refs; |
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int allocated_stack; |
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struct bpf_stack_state *stack; |
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}; |
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struct bpf_idx_pair { |
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u32 prev_idx; |
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u32 idx; |
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}; |
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#define MAX_CALL_FRAMES 8 |
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struct bpf_verifier_state { |
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/* call stack tracking */ |
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struct bpf_func_state *frame[MAX_CALL_FRAMES]; |
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struct bpf_verifier_state *parent; |
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/* |
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* 'branches' field is the number of branches left to explore: |
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* 0 - all possible paths from this state reached bpf_exit or |
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* were safely pruned |
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* 1 - at least one path is being explored. |
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* This state hasn't reached bpf_exit |
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* 2 - at least two paths are being explored. |
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* This state is an immediate parent of two children. |
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* One is fallthrough branch with branches==1 and another |
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* state is pushed into stack (to be explored later) also with |
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* branches==1. The parent of this state has branches==1. |
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* The verifier state tree connected via 'parent' pointer looks like: |
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* 1 |
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* 1 |
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* 2 -> 1 (first 'if' pushed into stack) |
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* 1 |
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* 2 -> 1 (second 'if' pushed into stack) |
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* 1 |
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* 1 |
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* 1 bpf_exit. |
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* |
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* Once do_check() reaches bpf_exit, it calls update_branch_counts() |
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* and the verifier state tree will look: |
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* 1 |
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* 1 |
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* 2 -> 1 (first 'if' pushed into stack) |
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* 1 |
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* 1 -> 1 (second 'if' pushed into stack) |
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* 0 |
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* 0 |
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* 0 bpf_exit. |
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* After pop_stack() the do_check() will resume at second 'if'. |
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* |
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* If is_state_visited() sees a state with branches > 0 it means |
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* there is a loop. If such state is exactly equal to the current state |
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* it's an infinite loop. Note states_equal() checks for states |
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* equvalency, so two states being 'states_equal' does not mean |
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* infinite loop. The exact comparison is provided by |
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* states_maybe_looping() function. It's a stronger pre-check and |
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* much faster than states_equal(). |
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* |
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* This algorithm may not find all possible infinite loops or |
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* loop iteration count may be too high. |
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* In such cases BPF_COMPLEXITY_LIMIT_INSNS limit kicks in. |
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*/ |
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u32 branches; |
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u32 insn_idx; |
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u32 curframe; |
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u32 active_spin_lock; |
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bool speculative; |
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/* first and last insn idx of this verifier state */ |
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u32 first_insn_idx; |
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u32 last_insn_idx; |
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/* jmp history recorded from first to last. |
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* backtracking is using it to go from last to first. |
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* For most states jmp_history_cnt is [0-3]. |
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* For loops can go up to ~40. |
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*/ |
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struct bpf_idx_pair *jmp_history; |
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u32 jmp_history_cnt; |
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}; |
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#define bpf_get_spilled_reg(slot, frame) \ |
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(((slot < frame->allocated_stack / BPF_REG_SIZE) && \ |
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(frame->stack[slot].slot_type[0] == STACK_SPILL)) \ |
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? &frame->stack[slot].spilled_ptr : NULL) |
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/* Iterate over 'frame', setting 'reg' to either NULL or a spilled register. */ |
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#define bpf_for_each_spilled_reg(iter, frame, reg) \ |
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for (iter = 0, reg = bpf_get_spilled_reg(iter, frame); \ |
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iter < frame->allocated_stack / BPF_REG_SIZE; \ |
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iter++, reg = bpf_get_spilled_reg(iter, frame)) |
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/* linked list of verifier states used to prune search */ |
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struct bpf_verifier_state_list { |
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struct bpf_verifier_state state; |
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struct bpf_verifier_state_list *next; |
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int miss_cnt, hit_cnt; |
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}; |
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/* Possible states for alu_state member. */ |
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#define BPF_ALU_SANITIZE_SRC (1U << 0) |
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#define BPF_ALU_SANITIZE_DST (1U << 1) |
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#define BPF_ALU_NEG_VALUE (1U << 2) |
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#define BPF_ALU_NON_POINTER (1U << 3) |
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#define BPF_ALU_IMMEDIATE (1U << 4) |
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#define BPF_ALU_SANITIZE (BPF_ALU_SANITIZE_SRC | \ |
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BPF_ALU_SANITIZE_DST) |
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struct bpf_insn_aux_data { |
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union { |
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enum bpf_reg_type ptr_type; /* pointer type for load/store insns */ |
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unsigned long map_ptr_state; /* pointer/poison value for maps */ |
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s32 call_imm; /* saved imm field of call insn */ |
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u32 alu_limit; /* limit for add/sub register with pointer */ |
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struct { |
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u32 map_index; /* index into used_maps[] */ |
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u32 map_off; /* offset from value base address */ |
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}; |
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struct { |
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enum bpf_reg_type reg_type; /* type of pseudo_btf_id */ |
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union { |
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struct { |
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struct btf *btf; |
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u32 btf_id; /* btf_id for struct typed var */ |
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}; |
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u32 mem_size; /* mem_size for non-struct typed var */ |
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}; |
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} btf_var; |
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}; |
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u64 map_key_state; /* constant (32 bit) key tracking for maps */ |
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int ctx_field_size; /* the ctx field size for load insn, maybe 0 */ |
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int sanitize_stack_off; /* stack slot to be cleared */ |
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u32 seen; /* this insn was processed by the verifier at env->pass_cnt */ |
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bool zext_dst; /* this insn zero extends dst reg */ |
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u8 alu_state; /* used in combination with alu_limit */ |
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/* below fields are initialized once */ |
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unsigned int orig_idx; /* original instruction index */ |
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bool prune_point; |
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}; |
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#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */ |
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#define MAX_USED_BTFS 64 /* max number of BTFs accessed by one BPF program */ |
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#define BPF_VERIFIER_TMP_LOG_SIZE 1024 |
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struct bpf_verifier_log { |
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u32 level; |
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char kbuf[BPF_VERIFIER_TMP_LOG_SIZE]; |
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char __user *ubuf; |
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u32 len_used; |
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u32 len_total; |
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}; |
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static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log) |
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{ |
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return log->len_used >= log->len_total - 1; |
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} |
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#define BPF_LOG_LEVEL1 1 |
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#define BPF_LOG_LEVEL2 2 |
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#define BPF_LOG_STATS 4 |
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#define BPF_LOG_LEVEL (BPF_LOG_LEVEL1 | BPF_LOG_LEVEL2) |
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#define BPF_LOG_MASK (BPF_LOG_LEVEL | BPF_LOG_STATS) |
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#define BPF_LOG_KERNEL (BPF_LOG_MASK + 1) /* kernel internal flag */ |
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static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log) |
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{ |
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return log && |
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((log->level && log->ubuf && !bpf_verifier_log_full(log)) || |
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log->level == BPF_LOG_KERNEL); |
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} |
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#define BPF_MAX_SUBPROGS 256 |
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struct bpf_subprog_info { |
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/* 'start' has to be the first field otherwise find_subprog() won't work */ |
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u32 start; /* insn idx of function entry point */ |
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u32 linfo_idx; /* The idx to the main_prog->aux->linfo */ |
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u16 stack_depth; /* max. stack depth used by this function */ |
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bool has_tail_call; |
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bool tail_call_reachable; |
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bool has_ld_abs; |
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}; |
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/* single container for all structs |
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* one verifier_env per bpf_check() call |
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*/ |
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struct bpf_verifier_env { |
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u32 insn_idx; |
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u32 prev_insn_idx; |
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struct bpf_prog *prog; /* eBPF program being verified */ |
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const struct bpf_verifier_ops *ops; |
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struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */ |
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int stack_size; /* number of states to be processed */ |
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bool strict_alignment; /* perform strict pointer alignment checks */ |
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bool test_state_freq; /* test verifier with different pruning frequency */ |
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struct bpf_verifier_state *cur_state; /* current verifier state */ |
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struct bpf_verifier_state_list **explored_states; /* search pruning optimization */ |
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struct bpf_verifier_state_list *free_list; |
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struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */ |
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struct btf_mod_pair used_btfs[MAX_USED_BTFS]; /* array of BTF's used by BPF program */ |
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u32 used_map_cnt; /* number of used maps */ |
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u32 used_btf_cnt; /* number of used BTF objects */ |
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u32 id_gen; /* used to generate unique reg IDs */ |
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bool allow_ptr_leaks; |
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bool allow_uninit_stack; |
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bool allow_ptr_to_map_access; |
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bool bpf_capable; |
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bool bypass_spec_v1; |
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bool bypass_spec_v4; |
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bool seen_direct_write; |
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struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */ |
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const struct bpf_line_info *prev_linfo; |
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struct bpf_verifier_log log; |
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struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1]; |
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struct { |
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int *insn_state; |
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int *insn_stack; |
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int cur_stack; |
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} cfg; |
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u32 pass_cnt; /* number of times do_check() was called */ |
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u32 subprog_cnt; |
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/* number of instructions analyzed by the verifier */ |
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u32 prev_insn_processed, insn_processed; |
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/* number of jmps, calls, exits analyzed so far */ |
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u32 prev_jmps_processed, jmps_processed; |
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/* total verification time */ |
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u64 verification_time; |
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/* maximum number of verifier states kept in 'branching' instructions */ |
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u32 max_states_per_insn; |
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/* total number of allocated verifier states */ |
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u32 total_states; |
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/* some states are freed during program analysis. |
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* this is peak number of states. this number dominates kernel |
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* memory consumption during verification |
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*/ |
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u32 peak_states; |
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/* longest register parentage chain walked for liveness marking */ |
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u32 longest_mark_read_walk; |
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}; |
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__printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log, |
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const char *fmt, va_list args); |
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__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env, |
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const char *fmt, ...); |
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__printf(2, 3) void bpf_log(struct bpf_verifier_log *log, |
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const char *fmt, ...); |
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static inline struct bpf_func_state *cur_func(struct bpf_verifier_env *env) |
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{ |
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struct bpf_verifier_state *cur = env->cur_state; |
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return cur->frame[cur->curframe]; |
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} |
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static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env) |
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{ |
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return cur_func(env)->regs; |
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} |
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int bpf_prog_offload_verifier_prep(struct bpf_prog *prog); |
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int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env, |
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int insn_idx, int prev_insn_idx); |
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int bpf_prog_offload_finalize(struct bpf_verifier_env *env); |
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void |
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bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off, |
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struct bpf_insn *insn); |
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void |
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bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt); |
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int check_ctx_reg(struct bpf_verifier_env *env, |
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const struct bpf_reg_state *reg, int regno); |
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int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg, |
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u32 regno, u32 mem_size); |
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|
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/* this lives here instead of in bpf.h because it needs to dereference tgt_prog */ |
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static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog, |
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struct btf *btf, u32 btf_id) |
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{ |
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if (tgt_prog) |
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return ((u64)tgt_prog->aux->id << 32) | btf_id; |
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else |
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return ((u64)btf_obj_id(btf) << 32) | 0x80000000 | btf_id; |
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} |
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int bpf_check_attach_target(struct bpf_verifier_log *log, |
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const struct bpf_prog *prog, |
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const struct bpf_prog *tgt_prog, |
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u32 btf_id, |
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struct bpf_attach_target_info *tgt_info); |
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#endif /* _LINUX_BPF_VERIFIER_H */
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