// 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 * * 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 #include #include #include #include #include #include #include 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 userpsace * 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)) tracehook_notify_resume(regs); }