diff options
Diffstat (limited to 'arch/x86/kernel/signal.c')
| -rw-r--r-- | arch/x86/kernel/signal.c | 411 |
1 files changed, 411 insertions, 0 deletions
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c new file mode 100644 index 0000000000..65fe2094da --- /dev/null +++ b/arch/x86/kernel/signal.c @@ -0,0 +1,411 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 1991, 1992 Linus Torvalds + * Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs + * + * 1997-11-28 Modified for POSIX.1b signals by Richard Henderson + * 2000-06-20 Pentium III FXSR, SSE support by Gareth Hughes + * 2000-2002 x86-64 support by Andi Kleen + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/sched.h> +#include <linux/sched/task_stack.h> +#include <linux/mm.h> +#include <linux/smp.h> +#include <linux/kernel.h> +#include <linux/kstrtox.h> +#include <linux/errno.h> +#include <linux/wait.h> +#include <linux/unistd.h> +#include <linux/stddef.h> +#include <linux/personality.h> +#include <linux/uaccess.h> +#include <linux/user-return-notifier.h> +#include <linux/uprobes.h> +#include <linux/context_tracking.h> +#include <linux/entry-common.h> +#include <linux/syscalls.h> + +#include <asm/processor.h> +#include <asm/ucontext.h> +#include <asm/fpu/signal.h> +#include <asm/fpu/xstate.h> +#include <asm/vdso.h> +#include <asm/mce.h> +#include <asm/sighandling.h> +#include <asm/vm86.h> + +#include <asm/syscall.h> +#include <asm/sigframe.h> +#include <asm/signal.h> +#include <asm/shstk.h> + +static inline int is_ia32_compat_frame(struct ksignal *ksig) +{ + return IS_ENABLED(CONFIG_IA32_EMULATION) && + ksig->ka.sa.sa_flags & SA_IA32_ABI; +} + +static inline int is_ia32_frame(struct ksignal *ksig) +{ + return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig); +} + +static inline int is_x32_frame(struct ksignal *ksig) +{ + return IS_ENABLED(CONFIG_X86_X32_ABI) && + ksig->ka.sa.sa_flags & SA_X32_ABI; +} + +/* + * Set up a signal frame. + */ + +/* x86 ABI requires 16-byte alignment */ +#define FRAME_ALIGNMENT 16UL + +#define MAX_FRAME_PADDING (FRAME_ALIGNMENT - 1) + +/* + * Determine which stack to use.. + */ +void __user * +get_sigframe(struct ksignal *ksig, struct pt_regs *regs, size_t frame_size, + void __user **fpstate) +{ + struct k_sigaction *ka = &ksig->ka; + int ia32_frame = is_ia32_frame(ksig); + /* Default to using normal stack */ + bool nested_altstack = on_sig_stack(regs->sp); + bool entering_altstack = false; + unsigned long math_size = 0; + unsigned long sp = regs->sp; + unsigned long buf_fx = 0; + + /* redzone */ + if (!ia32_frame) + sp -= 128; + + /* This is the X/Open sanctioned signal stack switching. */ + if (ka->sa.sa_flags & SA_ONSTACK) { + /* + * This checks nested_altstack via sas_ss_flags(). Sensible + * programs use SS_AUTODISARM, which disables that check, and + * programs that don't use SS_AUTODISARM get compatible. + */ + if (sas_ss_flags(sp) == 0) { + sp = current->sas_ss_sp + current->sas_ss_size; + entering_altstack = true; + } + } else if (ia32_frame && + !nested_altstack && + regs->ss != __USER_DS && + !(ka->sa.sa_flags & SA_RESTORER) && + ka->sa.sa_restorer) { + /* This is the legacy signal stack switching. */ + sp = (unsigned long) ka->sa.sa_restorer; + entering_altstack = true; + } + + sp = fpu__alloc_mathframe(sp, ia32_frame, &buf_fx, &math_size); + *fpstate = (void __user *)sp; + + sp -= frame_size; + + if (ia32_frame) + /* + * Align the stack pointer according to the i386 ABI, + * i.e. so that on function entry ((sp + 4) & 15) == 0. + */ + sp = ((sp + 4) & -FRAME_ALIGNMENT) - 4; + else + sp = round_down(sp, FRAME_ALIGNMENT) - 8; + + /* + * If we are on the alternate signal stack and would overflow it, don't. + * Return an always-bogus address instead so we will die with SIGSEGV. + */ + if (unlikely((nested_altstack || entering_altstack) && + !__on_sig_stack(sp))) { + + if (show_unhandled_signals && printk_ratelimit()) + pr_info("%s[%d] overflowed sigaltstack\n", + current->comm, task_pid_nr(current)); + + return (void __user *)-1L; + } + + /* save i387 and extended state */ + if (!copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size)) + return (void __user *)-1L; + + return (void __user *)sp; +} + +/* + * There are four different struct types for signal frame: sigframe_ia32, + * rt_sigframe_ia32, rt_sigframe_x32, and rt_sigframe. Use the worst case + * -- the largest size. It means the size for 64-bit apps is a bit more + * than needed, but this keeps the code simple. + */ +#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) +# define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct sigframe_ia32) +#else +# define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct rt_sigframe) +#endif + +/* + * The FP state frame contains an XSAVE buffer which must be 64-byte aligned. + * If a signal frame starts at an unaligned address, extra space is required. + * This is the max alignment padding, conservatively. + */ +#define MAX_XSAVE_PADDING 63UL + +/* + * The frame data is composed of the following areas and laid out as: + * + * ------------------------- + * | alignment padding | + * ------------------------- + * | (f)xsave frame | + * ------------------------- + * | fsave header | + * ------------------------- + * | alignment padding | + * ------------------------- + * | siginfo + ucontext | + * ------------------------- + */ + +/* max_frame_size tells userspace the worst case signal stack size. */ +static unsigned long __ro_after_init max_frame_size; +static unsigned int __ro_after_init fpu_default_state_size; + +static int __init init_sigframe_size(void) +{ + fpu_default_state_size = fpu__get_fpstate_size(); + + max_frame_size = MAX_FRAME_SIGINFO_UCTXT_SIZE + MAX_FRAME_PADDING; + + max_frame_size += fpu_default_state_size + MAX_XSAVE_PADDING; + + /* Userspace expects an aligned size. */ + max_frame_size = round_up(max_frame_size, FRAME_ALIGNMENT); + + pr_info("max sigframe size: %lu\n", max_frame_size); + return 0; +} +early_initcall(init_sigframe_size); + +unsigned long get_sigframe_size(void) +{ + return max_frame_size; +} + +static int +setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs) +{ + /* Perform fixup for the pre-signal frame. */ + rseq_signal_deliver(ksig, regs); + + /* Set up the stack frame */ + if (is_ia32_frame(ksig)) { + if (ksig->ka.sa.sa_flags & SA_SIGINFO) + return ia32_setup_rt_frame(ksig, regs); + else + return ia32_setup_frame(ksig, regs); + } else if (is_x32_frame(ksig)) { + return x32_setup_rt_frame(ksig, regs); + } else { + return x64_setup_rt_frame(ksig, regs); + } +} + +static void +handle_signal(struct ksignal *ksig, struct pt_regs *regs) +{ + bool stepping, failed; + struct fpu *fpu = ¤t->thread.fpu; + + if (v8086_mode(regs)) + save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL); + + /* Are we from a system call? */ + if (syscall_get_nr(current, regs) != -1) { + /* If so, check system call restarting.. */ + switch (syscall_get_error(current, regs)) { + case -ERESTART_RESTARTBLOCK: + case -ERESTARTNOHAND: + regs->ax = -EINTR; + break; + + case -ERESTARTSYS: + if (!(ksig->ka.sa.sa_flags & SA_RESTART)) { + regs->ax = -EINTR; + break; + } + fallthrough; + case -ERESTARTNOINTR: + regs->ax = regs->orig_ax; + regs->ip -= 2; + break; + } + } + + /* + * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now + * so that register information in the sigcontext is correct and + * then notify the tracer before entering the signal handler. + */ + stepping = test_thread_flag(TIF_SINGLESTEP); + if (stepping) + user_disable_single_step(current); + + failed = (setup_rt_frame(ksig, regs) < 0); + if (!failed) { + /* + * Clear the direction flag as per the ABI for function entry. + * + * Clear RF when entering the signal handler, because + * it might disable possible debug exception from the + * signal handler. + * + * Clear TF for the case when it wasn't set by debugger to + * avoid the recursive send_sigtrap() in SIGTRAP handler. + */ + regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF); + /* + * Ensure the signal handler starts with the new fpu state. + */ + fpu__clear_user_states(fpu); + } + signal_setup_done(failed, ksig, stepping); +} + +static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs) +{ +#ifdef CONFIG_IA32_EMULATION + if (current->restart_block.arch_data & TS_COMPAT) + return __NR_ia32_restart_syscall; +#endif +#ifdef CONFIG_X86_X32_ABI + return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT); +#else + return __NR_restart_syscall; +#endif +} + +/* + * Note that 'init' is a special process: it doesn't get signals it doesn't + * want to handle. Thus you cannot kill init even with a SIGKILL even by + * mistake. + */ +void arch_do_signal_or_restart(struct pt_regs *regs) +{ + struct ksignal ksig; + + if (get_signal(&ksig)) { + /* Whee! Actually deliver the signal. */ + handle_signal(&ksig, regs); + return; + } + + /* Did we come from a system call? */ + if (syscall_get_nr(current, regs) != -1) { + /* Restart the system call - no handlers present */ + switch (syscall_get_error(current, regs)) { + case -ERESTARTNOHAND: + case -ERESTARTSYS: + case -ERESTARTNOINTR: + regs->ax = regs->orig_ax; + regs->ip -= 2; + break; + + case -ERESTART_RESTARTBLOCK: + regs->ax = get_nr_restart_syscall(regs); + regs->ip -= 2; + break; + } + } + + /* + * If there's no signal to deliver, we just put the saved sigmask + * back. + */ + restore_saved_sigmask(); +} + +void signal_fault(struct pt_regs *regs, void __user *frame, char *where) +{ + struct task_struct *me = current; + + if (show_unhandled_signals && printk_ratelimit()) { + printk("%s" + "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx", + task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG, + me->comm, me->pid, where, frame, + regs->ip, regs->sp, regs->orig_ax); + print_vma_addr(KERN_CONT " in ", regs->ip); + pr_cont("\n"); + } + + force_sig(SIGSEGV); +} + +#ifdef CONFIG_DYNAMIC_SIGFRAME +#ifdef CONFIG_STRICT_SIGALTSTACK_SIZE +static bool strict_sigaltstack_size __ro_after_init = true; +#else +static bool strict_sigaltstack_size __ro_after_init = false; +#endif + +static int __init strict_sas_size(char *arg) +{ + return kstrtobool(arg, &strict_sigaltstack_size) == 0; +} +__setup("strict_sas_size", strict_sas_size); + +/* + * MINSIGSTKSZ is 2048 and can't be changed despite the fact that AVX512 + * exceeds that size already. As such programs might never use the + * sigaltstack they just continued to work. While always checking against + * the real size would be correct, this might be considered a regression. + * + * Therefore avoid the sanity check, unless enforced by kernel + * configuration or command line option. + * + * When dynamic FPU features are supported, the check is also enforced when + * the task has permissions to use dynamic features. Tasks which have no + * permission are checked against the size of the non-dynamic feature set + * if strict checking is enabled. This avoids forcing all tasks on the + * system to allocate large sigaltstacks even if they are never going + * to use a dynamic feature. As this is serialized via sighand::siglock + * any permission request for a dynamic feature either happened already + * or will see the newly install sigaltstack size in the permission checks. + */ +bool sigaltstack_size_valid(size_t ss_size) +{ + unsigned long fsize = max_frame_size - fpu_default_state_size; + u64 mask; + + lockdep_assert_held(¤t->sighand->siglock); + + if (!fpu_state_size_dynamic() && !strict_sigaltstack_size) + return true; + + fsize += current->group_leader->thread.fpu.perm.__user_state_size; + if (likely(ss_size > fsize)) + return true; + + if (strict_sigaltstack_size) + return ss_size > fsize; + + mask = current->group_leader->thread.fpu.perm.__state_perm; + if (mask & XFEATURE_MASK_USER_DYNAMIC) + return ss_size > fsize; + + return true; +} +#endif /* CONFIG_DYNAMIC_SIGFRAME */ |