443 lines
12 KiB
C
443 lines
12 KiB
C
// 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/tracehook.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 userpsace
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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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tracehook_notify_resume(regs);
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}
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