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534 lines
14 KiB
534 lines
14 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* FPU signal frame handling routines. |
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*/ |
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|
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#include <linux/compat.h> |
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#include <linux/cpu.h> |
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#include <linux/pagemap.h> |
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#include <asm/fpu/internal.h> |
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#include <asm/fpu/signal.h> |
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#include <asm/fpu/regset.h> |
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#include <asm/fpu/xstate.h> |
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#include <asm/sigframe.h> |
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#include <asm/trace/fpu.h> |
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static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32; |
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/* |
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* Check for the presence of extended state information in the |
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* user fpstate pointer in the sigcontext. |
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*/ |
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static inline int check_for_xstate(struct fxregs_state __user *buf, |
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void __user *fpstate, |
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struct _fpx_sw_bytes *fx_sw) |
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{ |
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int min_xstate_size = sizeof(struct fxregs_state) + |
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sizeof(struct xstate_header); |
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unsigned int magic2; |
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if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw))) |
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return -1; |
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/* Check for the first magic field and other error scenarios. */ |
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if (fx_sw->magic1 != FP_XSTATE_MAGIC1 || |
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fx_sw->xstate_size < min_xstate_size || |
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fx_sw->xstate_size > fpu_user_xstate_size || |
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fx_sw->xstate_size > fx_sw->extended_size) |
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return -1; |
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/* |
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* Check for the presence of second magic word at the end of memory |
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* layout. This detects the case where the user just copied the legacy |
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* fpstate layout with out copying the extended state information |
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* in the memory layout. |
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*/ |
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if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size)) |
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|| magic2 != FP_XSTATE_MAGIC2) |
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return -1; |
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return 0; |
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} |
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/* |
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* Signal frame handlers. |
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*/ |
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static inline int save_fsave_header(struct task_struct *tsk, void __user *buf) |
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{ |
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if (use_fxsr()) { |
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struct xregs_state *xsave = &tsk->thread.fpu.state.xsave; |
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struct user_i387_ia32_struct env; |
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struct _fpstate_32 __user *fp = buf; |
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fpregs_lock(); |
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if (!test_thread_flag(TIF_NEED_FPU_LOAD)) |
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copy_fxregs_to_kernel(&tsk->thread.fpu); |
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fpregs_unlock(); |
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convert_from_fxsr(&env, tsk); |
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if (__copy_to_user(buf, &env, sizeof(env)) || |
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__put_user(xsave->i387.swd, &fp->status) || |
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__put_user(X86_FXSR_MAGIC, &fp->magic)) |
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return -1; |
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} else { |
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struct fregs_state __user *fp = buf; |
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u32 swd; |
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if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status)) |
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return -1; |
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} |
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return 0; |
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} |
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static inline int save_xstate_epilog(void __user *buf, int ia32_frame) |
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{ |
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struct xregs_state __user *x = buf; |
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struct _fpx_sw_bytes *sw_bytes; |
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u32 xfeatures; |
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int err; |
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/* Setup the bytes not touched by the [f]xsave and reserved for SW. */ |
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sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved; |
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err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes)); |
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if (!use_xsave()) |
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return err; |
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err |= __put_user(FP_XSTATE_MAGIC2, |
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(__u32 __user *)(buf + fpu_user_xstate_size)); |
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/* |
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* Read the xfeatures which we copied (directly from the cpu or |
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* from the state in task struct) to the user buffers. |
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*/ |
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err |= __get_user(xfeatures, (__u32 __user *)&x->header.xfeatures); |
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/* |
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* For legacy compatible, we always set FP/SSE bits in the bit |
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* vector while saving the state to the user context. This will |
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* enable us capturing any changes(during sigreturn) to |
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* the FP/SSE bits by the legacy applications which don't touch |
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* xfeatures in the xsave header. |
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* |
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* xsave aware apps can change the xfeatures in the xsave |
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* header as well as change any contents in the memory layout. |
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* xrestore as part of sigreturn will capture all the changes. |
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*/ |
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xfeatures |= XFEATURE_MASK_FPSSE; |
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err |= __put_user(xfeatures, (__u32 __user *)&x->header.xfeatures); |
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return err; |
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} |
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static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf) |
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{ |
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int err; |
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if (use_xsave()) |
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err = copy_xregs_to_user(buf); |
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else if (use_fxsr()) |
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err = copy_fxregs_to_user((struct fxregs_state __user *) buf); |
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else |
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err = copy_fregs_to_user((struct fregs_state __user *) buf); |
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if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size)) |
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err = -EFAULT; |
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return err; |
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} |
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/* |
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* Save the fpu, extended register state to the user signal frame. |
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* |
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* 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save |
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* state is copied. |
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* 'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'. |
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* |
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* buf == buf_fx for 64-bit frames and 32-bit fsave frame. |
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* buf != buf_fx for 32-bit frames with fxstate. |
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* |
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* Try to save it directly to the user frame with disabled page fault handler. |
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* If this fails then do the slow path where the FPU state is first saved to |
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* task's fpu->state and then copy it to the user frame pointed to by the |
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* aligned pointer 'buf_fx'. |
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* |
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* If this is a 32-bit frame with fxstate, put a fsave header before |
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* the aligned state at 'buf_fx'. |
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* |
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* For [f]xsave state, update the SW reserved fields in the [f]xsave frame |
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* indicating the absence/presence of the extended state to the user. |
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*/ |
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int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size) |
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{ |
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struct task_struct *tsk = current; |
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int ia32_fxstate = (buf != buf_fx); |
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int ret; |
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ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) || |
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IS_ENABLED(CONFIG_IA32_EMULATION)); |
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if (!static_cpu_has(X86_FEATURE_FPU)) { |
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struct user_i387_ia32_struct fp; |
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fpregs_soft_get(current, NULL, (struct membuf){.p = &fp, |
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.left = sizeof(fp)}); |
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return copy_to_user(buf, &fp, sizeof(fp)) ? -EFAULT : 0; |
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} |
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if (!access_ok(buf, size)) |
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return -EACCES; |
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retry: |
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/* |
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* Load the FPU registers if they are not valid for the current task. |
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* With a valid FPU state we can attempt to save the state directly to |
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* userland's stack frame which will likely succeed. If it does not, |
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* resolve the fault in the user memory and try again. |
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*/ |
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fpregs_lock(); |
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if (test_thread_flag(TIF_NEED_FPU_LOAD)) |
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__fpregs_load_activate(); |
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pagefault_disable(); |
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ret = copy_fpregs_to_sigframe(buf_fx); |
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pagefault_enable(); |
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fpregs_unlock(); |
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if (ret) { |
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if (!fault_in_pages_writeable(buf_fx, fpu_user_xstate_size)) |
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goto retry; |
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return -EFAULT; |
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} |
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/* Save the fsave header for the 32-bit frames. */ |
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if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf)) |
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return -1; |
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if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate)) |
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return -1; |
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return 0; |
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} |
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static inline void |
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sanitize_restored_user_xstate(union fpregs_state *state, |
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struct user_i387_ia32_struct *ia32_env, |
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u64 user_xfeatures, int fx_only) |
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{ |
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struct xregs_state *xsave = &state->xsave; |
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struct xstate_header *header = &xsave->header; |
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if (use_xsave()) { |
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/* |
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* Note: we don't need to zero the reserved bits in the |
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* xstate_header here because we either didn't copy them at all, |
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* or we checked earlier that they aren't set. |
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*/ |
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/* |
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* 'user_xfeatures' might have bits clear which are |
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* set in header->xfeatures. This represents features that |
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* were in init state prior to a signal delivery, and need |
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* to be reset back to the init state. Clear any user |
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* feature bits which are set in the kernel buffer to get |
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* them back to the init state. |
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* |
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* Supervisor state is unchanged by input from userspace. |
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* Ensure supervisor state bits stay set and supervisor |
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* state is not modified. |
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*/ |
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if (fx_only) |
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header->xfeatures = XFEATURE_MASK_FPSSE; |
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else |
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header->xfeatures &= user_xfeatures | |
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xfeatures_mask_supervisor(); |
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} |
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if (use_fxsr()) { |
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/* |
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* mscsr reserved bits must be masked to zero for security |
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* reasons. |
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*/ |
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xsave->i387.mxcsr &= mxcsr_feature_mask; |
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if (ia32_env) |
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convert_to_fxsr(&state->fxsave, ia32_env); |
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} |
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} |
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/* |
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* Restore the extended state if present. Otherwise, restore the FP/SSE state. |
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*/ |
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static int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only) |
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{ |
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u64 init_bv; |
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int r; |
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if (use_xsave()) { |
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if (fx_only) { |
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init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE; |
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r = copy_user_to_fxregs(buf); |
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if (!r) |
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copy_kernel_to_xregs(&init_fpstate.xsave, init_bv); |
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return r; |
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} else { |
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init_bv = xfeatures_mask_user() & ~xbv; |
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r = copy_user_to_xregs(buf, xbv); |
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if (!r && unlikely(init_bv)) |
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copy_kernel_to_xregs(&init_fpstate.xsave, init_bv); |
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return r; |
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} |
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} else if (use_fxsr()) { |
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return copy_user_to_fxregs(buf); |
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} else |
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return copy_user_to_fregs(buf); |
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} |
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static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size) |
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{ |
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struct user_i387_ia32_struct *envp = NULL; |
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int state_size = fpu_kernel_xstate_size; |
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int ia32_fxstate = (buf != buf_fx); |
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struct task_struct *tsk = current; |
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struct fpu *fpu = &tsk->thread.fpu; |
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struct user_i387_ia32_struct env; |
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u64 user_xfeatures = 0; |
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int fx_only = 0; |
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int ret = 0; |
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ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) || |
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IS_ENABLED(CONFIG_IA32_EMULATION)); |
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if (!buf) { |
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fpu__clear_user_states(fpu); |
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return 0; |
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} |
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if (!access_ok(buf, size)) |
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return -EACCES; |
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if (!static_cpu_has(X86_FEATURE_FPU)) |
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return fpregs_soft_set(current, NULL, |
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0, sizeof(struct user_i387_ia32_struct), |
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NULL, buf) != 0; |
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if (use_xsave()) { |
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struct _fpx_sw_bytes fx_sw_user; |
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if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) { |
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/* |
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* Couldn't find the extended state information in the |
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* memory layout. Restore just the FP/SSE and init all |
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* the other extended state. |
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*/ |
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state_size = sizeof(struct fxregs_state); |
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fx_only = 1; |
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trace_x86_fpu_xstate_check_failed(fpu); |
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} else { |
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state_size = fx_sw_user.xstate_size; |
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user_xfeatures = fx_sw_user.xfeatures; |
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} |
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} |
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if ((unsigned long)buf_fx % 64) |
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fx_only = 1; |
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if (!ia32_fxstate) { |
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/* |
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* Attempt to restore the FPU registers directly from user |
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* memory. For that to succeed, the user access cannot cause |
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* page faults. If it does, fall back to the slow path below, |
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* going through the kernel buffer with the enabled pagefault |
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* handler. |
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*/ |
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fpregs_lock(); |
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pagefault_disable(); |
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ret = copy_user_to_fpregs_zeroing(buf_fx, user_xfeatures, fx_only); |
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pagefault_enable(); |
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if (!ret) { |
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/* |
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* Restore supervisor states: previous context switch |
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* etc has done XSAVES and saved the supervisor states |
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* in the kernel buffer from which they can be restored |
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* now. |
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* |
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* We cannot do a single XRSTORS here - which would |
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* be nice - because the rest of the FPU registers are |
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* being restored from a user buffer directly. The |
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* single XRSTORS happens below, when the user buffer |
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* has been copied to the kernel one. |
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*/ |
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if (test_thread_flag(TIF_NEED_FPU_LOAD) && |
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xfeatures_mask_supervisor()) |
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copy_kernel_to_xregs(&fpu->state.xsave, |
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xfeatures_mask_supervisor()); |
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fpregs_mark_activate(); |
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fpregs_unlock(); |
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return 0; |
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} |
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fpregs_unlock(); |
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} else { |
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/* |
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* For 32-bit frames with fxstate, copy the fxstate so it can |
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* be reconstructed later. |
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*/ |
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ret = __copy_from_user(&env, buf, sizeof(env)); |
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if (ret) |
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goto err_out; |
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envp = &env; |
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} |
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/* |
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* By setting TIF_NEED_FPU_LOAD it is ensured that our xstate is |
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* not modified on context switch and that the xstate is considered |
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* to be loaded again on return to userland (overriding last_cpu avoids |
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* the optimisation). |
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*/ |
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fpregs_lock(); |
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if (!test_thread_flag(TIF_NEED_FPU_LOAD)) { |
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/* |
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* Supervisor states are not modified by user space input. Save |
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* current supervisor states first and invalidate the FPU regs. |
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*/ |
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if (xfeatures_mask_supervisor()) |
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copy_supervisor_to_kernel(&fpu->state.xsave); |
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set_thread_flag(TIF_NEED_FPU_LOAD); |
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} |
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__fpu_invalidate_fpregs_state(fpu); |
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fpregs_unlock(); |
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if (use_xsave() && !fx_only) { |
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u64 init_bv = xfeatures_mask_user() & ~user_xfeatures; |
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if (using_compacted_format()) { |
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ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx); |
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} else { |
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ret = __copy_from_user(&fpu->state.xsave, buf_fx, state_size); |
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if (!ret && state_size > offsetof(struct xregs_state, header)) |
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ret = validate_user_xstate_header(&fpu->state.xsave.header); |
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} |
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if (ret) |
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goto err_out; |
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sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures, |
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fx_only); |
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fpregs_lock(); |
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if (unlikely(init_bv)) |
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copy_kernel_to_xregs(&init_fpstate.xsave, init_bv); |
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/* |
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* Restore previously saved supervisor xstates along with |
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* copied-in user xstates. |
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*/ |
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ret = copy_kernel_to_xregs_err(&fpu->state.xsave, |
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user_xfeatures | xfeatures_mask_supervisor()); |
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} else if (use_fxsr()) { |
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ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size); |
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if (ret) { |
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ret = -EFAULT; |
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goto err_out; |
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} |
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sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures, |
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fx_only); |
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fpregs_lock(); |
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if (use_xsave()) { |
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u64 init_bv; |
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init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE; |
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copy_kernel_to_xregs(&init_fpstate.xsave, init_bv); |
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} |
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ret = copy_kernel_to_fxregs_err(&fpu->state.fxsave); |
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} else { |
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ret = __copy_from_user(&fpu->state.fsave, buf_fx, state_size); |
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if (ret) |
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goto err_out; |
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fpregs_lock(); |
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ret = copy_kernel_to_fregs_err(&fpu->state.fsave); |
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} |
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if (!ret) |
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fpregs_mark_activate(); |
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else |
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fpregs_deactivate(fpu); |
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fpregs_unlock(); |
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err_out: |
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if (ret) |
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fpu__clear_user_states(fpu); |
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return ret; |
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} |
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static inline int xstate_sigframe_size(void) |
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{ |
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return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE : |
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fpu_user_xstate_size; |
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} |
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/* |
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* Restore FPU state from a sigframe: |
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*/ |
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int fpu__restore_sig(void __user *buf, int ia32_frame) |
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{ |
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void __user *buf_fx = buf; |
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int size = xstate_sigframe_size(); |
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if (ia32_frame && use_fxsr()) { |
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buf_fx = buf + sizeof(struct fregs_state); |
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size += sizeof(struct fregs_state); |
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} |
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return __fpu__restore_sig(buf, buf_fx, size); |
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} |
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unsigned long |
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fpu__alloc_mathframe(unsigned long sp, int ia32_frame, |
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unsigned long *buf_fx, unsigned long *size) |
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{ |
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unsigned long frame_size = xstate_sigframe_size(); |
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*buf_fx = sp = round_down(sp - frame_size, 64); |
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if (ia32_frame && use_fxsr()) { |
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frame_size += sizeof(struct fregs_state); |
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sp -= sizeof(struct fregs_state); |
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} |
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*size = frame_size; |
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return sp; |
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} |
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/* |
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* Prepare the SW reserved portion of the fxsave memory layout, indicating |
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* the presence of the extended state information in the memory layout |
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* pointed by the fpstate pointer in the sigcontext. |
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* This will be saved when ever the FP and extended state context is |
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* saved on the user stack during the signal handler delivery to the user. |
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*/ |
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void fpu__init_prepare_fx_sw_frame(void) |
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{ |
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int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE; |
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fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1; |
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fx_sw_reserved.extended_size = size; |
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fx_sw_reserved.xfeatures = xfeatures_mask_user(); |
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fx_sw_reserved.xstate_size = fpu_user_xstate_size; |
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if (IS_ENABLED(CONFIG_IA32_EMULATION) || |
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IS_ENABLED(CONFIG_X86_32)) { |
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int fsave_header_size = sizeof(struct fregs_state); |
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fx_sw_reserved_ia32 = fx_sw_reserved; |
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fx_sw_reserved_ia32.extended_size = size + fsave_header_size; |
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} |
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} |
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