diff options
Diffstat (limited to 'arch/arc/kernel/signal.c')
| -rw-r--r-- | arch/arc/kernel/signal.c | 443 |
1 files changed, 443 insertions, 0 deletions
diff --git a/arch/arc/kernel/signal.c b/arch/arc/kernel/signal.c new file mode 100644 index 0000000000..8f6f4a5429 --- /dev/null +++ b/arch/arc/kernel/signal.c @@ -0,0 +1,443 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Signal Handling for ARC + * + * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) + * + * vineetg: Jan 2010 (Restarting of timer related syscalls) + * + * vineetg: Nov 2009 (Everything needed for TIF_RESTORE_SIGMASK) + * -do_signal() supports TIF_RESTORE_SIGMASK + * -do_signal() no loner needs oldset, required by OLD sys_sigsuspend + * -sys_rt_sigsuspend() now comes from generic code, so discard arch implemen + * -sys_sigsuspend() no longer needs to fudge ptregs, hence that arg removed + * -sys_sigsuspend() no longer loops for do_signal(), sets TIF_xxx and leaves + * the job to do_signal() + * + * vineetg: July 2009 + * -Modified Code to support the uClibc provided userland sigreturn stub + * to avoid kernel synthesing it on user stack at runtime, costing TLB + * probes and Cache line flushes. + * + * vineetg: July 2009 + * -In stash_usr_regs( ) and restore_usr_regs( ), save/restore of user regs + * in done in block copy rather than one word at a time. + * This saves around 2K of code and improves LMBench lat_sig <catch> + * + * rajeshwarr: Feb 2009 + * - Support for Realtime Signals + * + * vineetg: Aug 11th 2008: Bug #94183 + * -ViXS were still seeing crashes when using insmod to load drivers. + * It turned out that the code to change Execute permssions for TLB entries + * of user was not guarded for interrupts (mod_tlb_permission) + * This was causing TLB entries to be overwritten on unrelated indexes + * + * Vineetg: July 15th 2008: Bug #94183 + * -Exception happens in Delay slot of a JMP, and before user space resumes, + * Signal is delivered (Ctrl + C) = >SIGINT. + * setup_frame( ) sets up PC,SP,BLINK to enable user space signal handler + * to run, but doesn't clear the Delay slot bit from status32. As a result, + * on resuming user mode, signal handler branches off to BTA of orig JMP + * -FIX: clear the DE bit from status32 in setup_frame( ) + * + * Rahul Trivedi, Kanika Nema: Codito Technologies 2004 + */ + +#include <linux/signal.h> +#include <linux/ptrace.h> +#include <linux/personality.h> +#include <linux/uaccess.h> +#include <linux/syscalls.h> +#include <linux/resume_user_mode.h> +#include <linux/sched/task_stack.h> + +#include <asm/ucontext.h> +#include <asm/entry.h> + +struct rt_sigframe { + struct siginfo info; + struct ucontext uc; +#define MAGIC_SIGALTSTK 0x07302004 + unsigned int sigret_magic; +}; + +static int save_arcv2_regs(struct sigcontext __user *mctx, struct pt_regs *regs) +{ + int err = 0; +#ifndef CONFIG_ISA_ARCOMPACT + struct user_regs_arcv2 v2abi; + + v2abi.r30 = regs->r30; +#ifdef CONFIG_ARC_HAS_ACCL_REGS + v2abi.r58 = regs->r58; + v2abi.r59 = regs->r59; +#else + v2abi.r58 = v2abi.r59 = 0; +#endif + err = __copy_to_user(&mctx->v2abi, (void const *)&v2abi, sizeof(v2abi)); +#endif + return err; +} + +static int restore_arcv2_regs(struct sigcontext __user *mctx, struct pt_regs *regs) +{ + int err = 0; +#ifndef CONFIG_ISA_ARCOMPACT + struct user_regs_arcv2 v2abi; + + err = __copy_from_user(&v2abi, &mctx->v2abi, sizeof(v2abi)); + + regs->r30 = v2abi.r30; +#ifdef CONFIG_ARC_HAS_ACCL_REGS + regs->r58 = v2abi.r58; + regs->r59 = v2abi.r59; +#endif +#endif + return err; +} + +static int +stash_usr_regs(struct rt_sigframe __user *sf, struct pt_regs *regs, + sigset_t *set) +{ + int err; + struct user_regs_struct uregs; + + uregs.scratch.bta = regs->bta; + uregs.scratch.lp_start = regs->lp_start; + uregs.scratch.lp_end = regs->lp_end; + uregs.scratch.lp_count = regs->lp_count; + uregs.scratch.status32 = regs->status32; + uregs.scratch.ret = regs->ret; + uregs.scratch.blink = regs->blink; + uregs.scratch.fp = regs->fp; + uregs.scratch.gp = regs->r26; + uregs.scratch.r12 = regs->r12; + uregs.scratch.r11 = regs->r11; + uregs.scratch.r10 = regs->r10; + uregs.scratch.r9 = regs->r9; + uregs.scratch.r8 = regs->r8; + uregs.scratch.r7 = regs->r7; + uregs.scratch.r6 = regs->r6; + uregs.scratch.r5 = regs->r5; + uregs.scratch.r4 = regs->r4; + uregs.scratch.r3 = regs->r3; + uregs.scratch.r2 = regs->r2; + uregs.scratch.r1 = regs->r1; + uregs.scratch.r0 = regs->r0; + uregs.scratch.sp = regs->sp; + + err = __copy_to_user(&(sf->uc.uc_mcontext.regs.scratch), &uregs.scratch, + sizeof(sf->uc.uc_mcontext.regs.scratch)); + + if (is_isa_arcv2()) + err |= save_arcv2_regs(&(sf->uc.uc_mcontext), regs); + + err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(sigset_t)); + + return err ? -EFAULT : 0; +} + +static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf) +{ + sigset_t set; + int err; + struct user_regs_struct uregs; + + err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set)); + err |= __copy_from_user(&uregs.scratch, + &(sf->uc.uc_mcontext.regs.scratch), + sizeof(sf->uc.uc_mcontext.regs.scratch)); + + if (is_isa_arcv2()) + err |= restore_arcv2_regs(&(sf->uc.uc_mcontext), regs); + + if (err) + return -EFAULT; + + set_current_blocked(&set); + regs->bta = uregs.scratch.bta; + regs->lp_start = uregs.scratch.lp_start; + regs->lp_end = uregs.scratch.lp_end; + regs->lp_count = uregs.scratch.lp_count; + regs->status32 = uregs.scratch.status32; + regs->ret = uregs.scratch.ret; + regs->blink = uregs.scratch.blink; + regs->fp = uregs.scratch.fp; + regs->r26 = uregs.scratch.gp; + regs->r12 = uregs.scratch.r12; + regs->r11 = uregs.scratch.r11; + regs->r10 = uregs.scratch.r10; + regs->r9 = uregs.scratch.r9; + regs->r8 = uregs.scratch.r8; + regs->r7 = uregs.scratch.r7; + regs->r6 = uregs.scratch.r6; + regs->r5 = uregs.scratch.r5; + regs->r4 = uregs.scratch.r4; + regs->r3 = uregs.scratch.r3; + regs->r2 = uregs.scratch.r2; + regs->r1 = uregs.scratch.r1; + regs->r0 = uregs.scratch.r0; + regs->sp = uregs.scratch.sp; + + return 0; +} + +static inline int is_do_ss_needed(unsigned int magic) +{ + if (MAGIC_SIGALTSTK == magic) + return 1; + else + return 0; +} + +SYSCALL_DEFINE0(rt_sigreturn) +{ + struct rt_sigframe __user *sf; + unsigned int magic; + struct pt_regs *regs = current_pt_regs(); + + /* Always make any pending restarted system calls return -EINTR */ + current->restart_block.fn = do_no_restart_syscall; + + /* Since we stacked the signal on a word boundary, + * then 'sp' should be word aligned here. If it's + * not, then the user is trying to mess with us. + */ + if (regs->sp & 3) + goto badframe; + + sf = (struct rt_sigframe __force __user *)(regs->sp); + + if (!access_ok(sf, sizeof(*sf))) + goto badframe; + + if (__get_user(magic, &sf->sigret_magic)) + goto badframe; + + if (unlikely(is_do_ss_needed(magic))) + if (restore_altstack(&sf->uc.uc_stack)) + goto badframe; + + if (restore_usr_regs(regs, sf)) + goto badframe; + + /* Don't restart from sigreturn */ + syscall_wont_restart(regs); + + /* + * Ensure that sigreturn always returns to user mode (in case the + * regs saved on user stack got fudged between save and sigreturn) + * Otherwise it is easy to panic the kernel with a custom + * signal handler and/or restorer which clobberes the status32/ret + * to return to a bogus location in kernel mode. + */ + regs->status32 |= STATUS_U_MASK; + + return regs->r0; + +badframe: + force_sig(SIGSEGV); + return 0; +} + +/* + * Determine which stack to use.. + */ +static inline void __user *get_sigframe(struct ksignal *ksig, + struct pt_regs *regs, + unsigned long framesize) +{ + unsigned long sp = sigsp(regs->sp, ksig); + void __user *frame; + + /* No matter what happens, 'sp' must be word + * aligned otherwise nasty things could happen + */ + + /* ATPCS B01 mandates 8-byte alignment */ + frame = (void __user *)((sp - framesize) & ~7); + + /* Check that we can actually write to the signal frame */ + if (!access_ok(frame, framesize)) + frame = NULL; + + return frame; +} + +static int +setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs) +{ + struct rt_sigframe __user *sf; + unsigned int magic = 0; + int err = 0; + + sf = get_sigframe(ksig, regs, sizeof(struct rt_sigframe)); + if (!sf) + return 1; + + /* + * w/o SA_SIGINFO, struct ucontext is partially populated (only + * uc_mcontext/uc_sigmask) for kernel's normal user state preservation + * during signal handler execution. This works for SA_SIGINFO as well + * although the semantics are now overloaded (the same reg state can be + * inspected by userland: but are they allowed to fiddle with it ? + */ + err |= stash_usr_regs(sf, regs, set); + + /* + * SA_SIGINFO requires 3 args to signal handler: + * #1: sig-no (common to any handler) + * #2: struct siginfo + * #3: struct ucontext (completely populated) + */ + if (unlikely(ksig->ka.sa.sa_flags & SA_SIGINFO)) { + err |= copy_siginfo_to_user(&sf->info, &ksig->info); + err |= __put_user(0, &sf->uc.uc_flags); + err |= __put_user(NULL, &sf->uc.uc_link); + err |= __save_altstack(&sf->uc.uc_stack, regs->sp); + + /* setup args 2 and 3 for user mode handler */ + regs->r1 = (unsigned long)&sf->info; + regs->r2 = (unsigned long)&sf->uc; + + /* + * small optim to avoid unconditionally calling do_sigaltstack + * in sigreturn path, now that we only have rt_sigreturn + */ + magic = MAGIC_SIGALTSTK; + } + + err |= __put_user(magic, &sf->sigret_magic); + if (err) + return err; + + /* #1 arg to the user Signal handler */ + regs->r0 = ksig->sig; + + /* setup PC of user space signal handler */ + regs->ret = (unsigned long)ksig->ka.sa.sa_handler; + + /* + * handler returns using sigreturn stub provided already by userspace + * If not, nuke the process right away + */ + if(!(ksig->ka.sa.sa_flags & SA_RESTORER)) + return 1; + + regs->blink = (unsigned long)ksig->ka.sa.sa_restorer; + + /* User Stack for signal handler will be above the frame just carved */ + regs->sp = (unsigned long)sf; + + /* + * Bug 94183, Clear the DE bit, so that when signal handler + * starts to run, it doesn't use BTA + */ + regs->status32 &= ~STATUS_DE_MASK; + regs->status32 |= STATUS_L_MASK; + + return err; +} + +static void arc_restart_syscall(struct k_sigaction *ka, struct pt_regs *regs) +{ + switch (regs->r0) { + case -ERESTART_RESTARTBLOCK: + case -ERESTARTNOHAND: + /* + * ERESTARTNOHAND means that the syscall should + * only be restarted if there was no handler for + * the signal, and since we only get here if there + * is a handler, we don't restart + */ + regs->r0 = -EINTR; /* ERESTART_xxx is internal */ + break; + + case -ERESTARTSYS: + /* + * ERESTARTSYS means to restart the syscall if + * there is no handler or the handler was + * registered with SA_RESTART + */ + if (!(ka->sa.sa_flags & SA_RESTART)) { + regs->r0 = -EINTR; + break; + } + fallthrough; + + case -ERESTARTNOINTR: + /* + * ERESTARTNOINTR means that the syscall should + * be called again after the signal handler returns. + * Setup reg state just as it was before doing the trap + * r0 has been clobbered with sys call ret code thus it + * needs to be reloaded with orig first arg to syscall + * in orig_r0. Rest of relevant reg-file: + * r8 (syscall num) and (r1 - r7) will be reset to + * their orig user space value when we ret from kernel + */ + regs->r0 = regs->orig_r0; + regs->ret -= is_isa_arcv2() ? 2 : 4; + break; + } +} + +/* + * OK, we're invoking a handler + */ +static void +handle_signal(struct ksignal *ksig, struct pt_regs *regs) +{ + sigset_t *oldset = sigmask_to_save(); + int failed; + + /* Set up the stack frame */ + failed = setup_rt_frame(ksig, oldset, regs); + + signal_setup_done(failed, ksig, 0); +} + +void do_signal(struct pt_regs *regs) +{ + struct ksignal ksig; + int restart_scall; + + restart_scall = in_syscall(regs) && syscall_restartable(regs); + + if (test_thread_flag(TIF_SIGPENDING) && get_signal(&ksig)) { + if (restart_scall) { + arc_restart_syscall(&ksig.ka, regs); + syscall_wont_restart(regs); /* No more restarts */ + } + handle_signal(&ksig, regs); + return; + } + + if (restart_scall) { + /* No handler for syscall: restart it */ + if (regs->r0 == -ERESTARTNOHAND || + regs->r0 == -ERESTARTSYS || regs->r0 == -ERESTARTNOINTR) { + regs->r0 = regs->orig_r0; + regs->ret -= is_isa_arcv2() ? 2 : 4; + } else if (regs->r0 == -ERESTART_RESTARTBLOCK) { + regs->r8 = __NR_restart_syscall; + regs->ret -= is_isa_arcv2() ? 2 : 4; + } + syscall_wont_restart(regs); /* No more restarts */ + } + + /* If there's no signal to deliver, restore the saved sigmask back */ + restore_saved_sigmask(); +} + +void do_notify_resume(struct pt_regs *regs) +{ + /* + * ASM glue guarantees that this is only called when returning to + * user mode + */ + if (test_thread_flag(TIF_NOTIFY_RESUME)) + resume_user_mode_work(regs); +} |