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442 lines
12 KiB
442 lines
12 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* Signal Handling for ARC |
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* |
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) |
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* |
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* vineetg: Jan 2010 (Restarting of timer related syscalls) |
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* |
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* vineetg: Nov 2009 (Everything needed for TIF_RESTORE_SIGMASK) |
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* -do_signal() supports TIF_RESTORE_SIGMASK |
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* -do_signal() no loner needs oldset, required by OLD sys_sigsuspend |
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* -sys_rt_sigsuspend() now comes from generic code, so discard arch implemen |
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* -sys_sigsuspend() no longer needs to fudge ptregs, hence that arg removed |
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* -sys_sigsuspend() no longer loops for do_signal(), sets TIF_xxx and leaves |
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* the job to do_signal() |
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* |
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* vineetg: July 2009 |
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* -Modified Code to support the uClibc provided userland sigreturn stub |
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* to avoid kernel synthesing it on user stack at runtime, costing TLB |
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* probes and Cache line flushes. |
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* |
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* vineetg: July 2009 |
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* -In stash_usr_regs( ) and restore_usr_regs( ), save/restore of user regs |
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* in done in block copy rather than one word at a time. |
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* This saves around 2K of code and improves LMBench lat_sig <catch> |
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* |
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* rajeshwarr: Feb 2009 |
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* - Support for Realtime Signals |
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* |
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* vineetg: Aug 11th 2008: Bug #94183 |
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* -ViXS were still seeing crashes when using insmod to load drivers. |
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* It turned out that the code to change Execute permssions for TLB entries |
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* of user was not guarded for interrupts (mod_tlb_permission) |
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* This was causing TLB entries to be overwritten on unrelated indexes |
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* |
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* Vineetg: July 15th 2008: Bug #94183 |
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* -Exception happens in Delay slot of a JMP, and before user space resumes, |
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* Signal is delivered (Ctrl + C) = >SIGINT. |
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* setup_frame( ) sets up PC,SP,BLINK to enable user space signal handler |
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* to run, but doesn't clear the Delay slot bit from status32. As a result, |
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* on resuming user mode, signal handler branches off to BTA of orig JMP |
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* -FIX: clear the DE bit from status32 in setup_frame( ) |
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* |
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* Rahul Trivedi, Kanika Nema: Codito Technologies 2004 |
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*/ |
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#include <linux/signal.h> |
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#include <linux/ptrace.h> |
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#include <linux/personality.h> |
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#include <linux/uaccess.h> |
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#include <linux/syscalls.h> |
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#include <linux/resume_user_mode.h> |
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#include <linux/sched/task_stack.h> |
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#include <asm/ucontext.h> |
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struct rt_sigframe { |
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struct siginfo info; |
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struct ucontext uc; |
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#define MAGIC_SIGALTSTK 0x07302004 |
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unsigned int sigret_magic; |
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}; |
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static int save_arcv2_regs(struct sigcontext *mctx, struct pt_regs *regs) |
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{ |
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int err = 0; |
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#ifndef CONFIG_ISA_ARCOMPACT |
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struct user_regs_arcv2 v2abi; |
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v2abi.r30 = regs->r30; |
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#ifdef CONFIG_ARC_HAS_ACCL_REGS |
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v2abi.r58 = regs->r58; |
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v2abi.r59 = regs->r59; |
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#else |
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v2abi.r58 = v2abi.r59 = 0; |
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#endif |
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err = __copy_to_user(&mctx->v2abi, &v2abi, sizeof(v2abi)); |
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#endif |
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return err; |
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} |
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static int restore_arcv2_regs(struct sigcontext *mctx, struct pt_regs *regs) |
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{ |
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int err = 0; |
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#ifndef CONFIG_ISA_ARCOMPACT |
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struct user_regs_arcv2 v2abi; |
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err = __copy_from_user(&v2abi, &mctx->v2abi, sizeof(v2abi)); |
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regs->r30 = v2abi.r30; |
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#ifdef CONFIG_ARC_HAS_ACCL_REGS |
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regs->r58 = v2abi.r58; |
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regs->r59 = v2abi.r59; |
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#endif |
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#endif |
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return err; |
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} |
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static int |
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stash_usr_regs(struct rt_sigframe __user *sf, struct pt_regs *regs, |
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sigset_t *set) |
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{ |
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int err; |
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struct user_regs_struct uregs; |
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uregs.scratch.bta = regs->bta; |
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uregs.scratch.lp_start = regs->lp_start; |
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uregs.scratch.lp_end = regs->lp_end; |
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uregs.scratch.lp_count = regs->lp_count; |
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uregs.scratch.status32 = regs->status32; |
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uregs.scratch.ret = regs->ret; |
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uregs.scratch.blink = regs->blink; |
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uregs.scratch.fp = regs->fp; |
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uregs.scratch.gp = regs->r26; |
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uregs.scratch.r12 = regs->r12; |
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uregs.scratch.r11 = regs->r11; |
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uregs.scratch.r10 = regs->r10; |
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uregs.scratch.r9 = regs->r9; |
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uregs.scratch.r8 = regs->r8; |
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uregs.scratch.r7 = regs->r7; |
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uregs.scratch.r6 = regs->r6; |
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uregs.scratch.r5 = regs->r5; |
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uregs.scratch.r4 = regs->r4; |
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uregs.scratch.r3 = regs->r3; |
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uregs.scratch.r2 = regs->r2; |
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uregs.scratch.r1 = regs->r1; |
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uregs.scratch.r0 = regs->r0; |
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uregs.scratch.sp = regs->sp; |
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err = __copy_to_user(&(sf->uc.uc_mcontext.regs.scratch), &uregs.scratch, |
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sizeof(sf->uc.uc_mcontext.regs.scratch)); |
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if (is_isa_arcv2()) |
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err |= save_arcv2_regs(&(sf->uc.uc_mcontext), regs); |
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err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(sigset_t)); |
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return err ? -EFAULT : 0; |
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} |
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static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf) |
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{ |
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sigset_t set; |
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int err; |
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struct user_regs_struct uregs; |
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err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set)); |
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err |= __copy_from_user(&uregs.scratch, |
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&(sf->uc.uc_mcontext.regs.scratch), |
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sizeof(sf->uc.uc_mcontext.regs.scratch)); |
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if (is_isa_arcv2()) |
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err |= restore_arcv2_regs(&(sf->uc.uc_mcontext), regs); |
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if (err) |
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return -EFAULT; |
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set_current_blocked(&set); |
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regs->bta = uregs.scratch.bta; |
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regs->lp_start = uregs.scratch.lp_start; |
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regs->lp_end = uregs.scratch.lp_end; |
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regs->lp_count = uregs.scratch.lp_count; |
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regs->status32 = uregs.scratch.status32; |
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regs->ret = uregs.scratch.ret; |
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regs->blink = uregs.scratch.blink; |
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regs->fp = uregs.scratch.fp; |
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regs->r26 = uregs.scratch.gp; |
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regs->r12 = uregs.scratch.r12; |
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regs->r11 = uregs.scratch.r11; |
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regs->r10 = uregs.scratch.r10; |
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regs->r9 = uregs.scratch.r9; |
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regs->r8 = uregs.scratch.r8; |
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regs->r7 = uregs.scratch.r7; |
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regs->r6 = uregs.scratch.r6; |
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regs->r5 = uregs.scratch.r5; |
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regs->r4 = uregs.scratch.r4; |
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regs->r3 = uregs.scratch.r3; |
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regs->r2 = uregs.scratch.r2; |
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regs->r1 = uregs.scratch.r1; |
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regs->r0 = uregs.scratch.r0; |
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regs->sp = uregs.scratch.sp; |
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return 0; |
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} |
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static inline int is_do_ss_needed(unsigned int magic) |
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{ |
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if (MAGIC_SIGALTSTK == magic) |
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return 1; |
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else |
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return 0; |
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} |
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SYSCALL_DEFINE0(rt_sigreturn) |
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{ |
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struct rt_sigframe __user *sf; |
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unsigned int magic; |
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struct pt_regs *regs = current_pt_regs(); |
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/* Always make any pending restarted system calls return -EINTR */ |
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current->restart_block.fn = do_no_restart_syscall; |
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/* Since we stacked the signal on a word boundary, |
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* then 'sp' should be word aligned here. If it's |
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* not, then the user is trying to mess with us. |
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*/ |
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if (regs->sp & 3) |
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goto badframe; |
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sf = (struct rt_sigframe __force __user *)(regs->sp); |
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if (!access_ok(sf, sizeof(*sf))) |
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goto badframe; |
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if (__get_user(magic, &sf->sigret_magic)) |
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goto badframe; |
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if (unlikely(is_do_ss_needed(magic))) |
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if (restore_altstack(&sf->uc.uc_stack)) |
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goto badframe; |
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if (restore_usr_regs(regs, sf)) |
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goto badframe; |
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/* Don't restart from sigreturn */ |
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syscall_wont_restart(regs); |
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/* |
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* Ensure that sigreturn always returns to user mode (in case the |
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* regs saved on user stack got fudged between save and sigreturn) |
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* Otherwise it is easy to panic the kernel with a custom |
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* signal handler and/or restorer which clobberes the status32/ret |
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* to return to a bogus location in kernel mode. |
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*/ |
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regs->status32 |= STATUS_U_MASK; |
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return regs->r0; |
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badframe: |
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force_sig(SIGSEGV); |
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return 0; |
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} |
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/* |
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* Determine which stack to use.. |
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*/ |
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static inline void __user *get_sigframe(struct ksignal *ksig, |
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struct pt_regs *regs, |
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unsigned long framesize) |
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{ |
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unsigned long sp = sigsp(regs->sp, ksig); |
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void __user *frame; |
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/* No matter what happens, 'sp' must be word |
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* aligned otherwise nasty things could happen |
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*/ |
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/* ATPCS B01 mandates 8-byte alignment */ |
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frame = (void __user *)((sp - framesize) & ~7); |
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/* Check that we can actually write to the signal frame */ |
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if (!access_ok(frame, framesize)) |
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frame = NULL; |
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return frame; |
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} |
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static int |
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setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs) |
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{ |
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struct rt_sigframe __user *sf; |
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unsigned int magic = 0; |
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int err = 0; |
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sf = get_sigframe(ksig, regs, sizeof(struct rt_sigframe)); |
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if (!sf) |
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return 1; |
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/* |
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* w/o SA_SIGINFO, struct ucontext is partially populated (only |
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* uc_mcontext/uc_sigmask) for kernel's normal user state preservation |
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* during signal handler execution. This works for SA_SIGINFO as well |
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* although the semantics are now overloaded (the same reg state can be |
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* inspected by userland: but are they allowed to fiddle with it ? |
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*/ |
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err |= stash_usr_regs(sf, regs, set); |
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/* |
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* SA_SIGINFO requires 3 args to signal handler: |
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* #1: sig-no (common to any handler) |
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* #2: struct siginfo |
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* #3: struct ucontext (completely populated) |
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*/ |
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if (unlikely(ksig->ka.sa.sa_flags & SA_SIGINFO)) { |
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err |= copy_siginfo_to_user(&sf->info, &ksig->info); |
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err |= __put_user(0, &sf->uc.uc_flags); |
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err |= __put_user(NULL, &sf->uc.uc_link); |
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err |= __save_altstack(&sf->uc.uc_stack, regs->sp); |
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/* setup args 2 and 3 for user mode handler */ |
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regs->r1 = (unsigned long)&sf->info; |
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regs->r2 = (unsigned long)&sf->uc; |
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/* |
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* small optim to avoid unconditionally calling do_sigaltstack |
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* in sigreturn path, now that we only have rt_sigreturn |
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*/ |
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magic = MAGIC_SIGALTSTK; |
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} |
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err |= __put_user(magic, &sf->sigret_magic); |
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if (err) |
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return err; |
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/* #1 arg to the user Signal handler */ |
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regs->r0 = ksig->sig; |
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/* setup PC of user space signal handler */ |
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regs->ret = (unsigned long)ksig->ka.sa.sa_handler; |
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/* |
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* handler returns using sigreturn stub provided already by userspace |
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* If not, nuke the process right away |
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*/ |
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if(!(ksig->ka.sa.sa_flags & SA_RESTORER)) |
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return 1; |
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regs->blink = (unsigned long)ksig->ka.sa.sa_restorer; |
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/* User Stack for signal handler will be above the frame just carved */ |
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regs->sp = (unsigned long)sf; |
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/* |
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* Bug 94183, Clear the DE bit, so that when signal handler |
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* starts to run, it doesn't use BTA |
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*/ |
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regs->status32 &= ~STATUS_DE_MASK; |
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regs->status32 |= STATUS_L_MASK; |
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return err; |
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} |
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static void arc_restart_syscall(struct k_sigaction *ka, struct pt_regs *regs) |
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{ |
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switch (regs->r0) { |
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case -ERESTART_RESTARTBLOCK: |
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case -ERESTARTNOHAND: |
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/* |
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* ERESTARTNOHAND means that the syscall should |
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* only be restarted if there was no handler for |
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* the signal, and since we only get here if there |
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* is a handler, we don't restart |
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*/ |
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regs->r0 = -EINTR; /* ERESTART_xxx is internal */ |
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break; |
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case -ERESTARTSYS: |
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/* |
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* ERESTARTSYS means to restart the syscall if |
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* there is no handler or the handler was |
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* registered with SA_RESTART |
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*/ |
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if (!(ka->sa.sa_flags & SA_RESTART)) { |
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regs->r0 = -EINTR; |
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break; |
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} |
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fallthrough; |
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case -ERESTARTNOINTR: |
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/* |
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* ERESTARTNOINTR means that the syscall should |
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* be called again after the signal handler returns. |
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* Setup reg state just as it was before doing the trap |
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* r0 has been clobbered with sys call ret code thus it |
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* needs to be reloaded with orig first arg to syscall |
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* in orig_r0. Rest of relevant reg-file: |
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* r8 (syscall num) and (r1 - r7) will be reset to |
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* their orig user space value when we ret from kernel |
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*/ |
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regs->r0 = regs->orig_r0; |
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regs->ret -= is_isa_arcv2() ? 2 : 4; |
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break; |
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} |
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} |
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/* |
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* OK, we're invoking a handler |
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*/ |
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static void |
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handle_signal(struct ksignal *ksig, struct pt_regs *regs) |
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{ |
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sigset_t *oldset = sigmask_to_save(); |
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int failed; |
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/* Set up the stack frame */ |
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failed = setup_rt_frame(ksig, oldset, regs); |
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signal_setup_done(failed, ksig, 0); |
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} |
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void do_signal(struct pt_regs *regs) |
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{ |
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struct ksignal ksig; |
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int restart_scall; |
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restart_scall = in_syscall(regs) && syscall_restartable(regs); |
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if (test_thread_flag(TIF_SIGPENDING) && get_signal(&ksig)) { |
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if (restart_scall) { |
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arc_restart_syscall(&ksig.ka, regs); |
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syscall_wont_restart(regs); /* No more restarts */ |
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} |
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handle_signal(&ksig, regs); |
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return; |
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} |
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if (restart_scall) { |
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/* No handler for syscall: restart it */ |
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if (regs->r0 == -ERESTARTNOHAND || |
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regs->r0 == -ERESTARTSYS || regs->r0 == -ERESTARTNOINTR) { |
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regs->r0 = regs->orig_r0; |
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regs->ret -= is_isa_arcv2() ? 2 : 4; |
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} else if (regs->r0 == -ERESTART_RESTARTBLOCK) { |
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regs->r8 = __NR_restart_syscall; |
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regs->ret -= is_isa_arcv2() ? 2 : 4; |
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} |
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syscall_wont_restart(regs); /* No more restarts */ |
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} |
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/* If there's no signal to deliver, restore the saved sigmask back */ |
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restore_saved_sigmask(); |
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} |
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void do_notify_resume(struct pt_regs *regs) |
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{ |
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/* |
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* ASM glue guarantees that this is only called when returning to |
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* user mode |
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*/ |
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if (test_thread_flag(TIF_NOTIFY_RESUME)) |
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resume_user_mode_work(regs); |
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}
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