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linux/arch/x86/kernel/signal.c
Brian Gerst 3a24a60854 x86/32: Remove lazy GS macros 
GS is always a user segment now.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20220325153953.162643-4-brgerst@gmail.com
2022-04-14 14:09:43 +02:00

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// 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>
#ifdef CONFIG_X86_64
#include <linux/compat.h>
#include <asm/proto.h>
#include <asm/ia32_unistd.h>
#include <asm/fpu/xstate.h>
#endif /* CONFIG_X86_64 */
#include <asm/syscall.h>
#include <asm/sigframe.h>
#include <asm/signal.h>
#ifdef CONFIG_X86_64
/*
* If regs->ss will cause an IRET fault, change it. Otherwise leave it
* alone. Using this generally makes no sense unless
* user_64bit_mode(regs) would return true.
*/
static void force_valid_ss(struct pt_regs *regs)
{
u32 ar;
asm volatile ("lar %[old_ss], %[ar]\n\t"
"jz 1f\n\t" /* If invalid: */
"xorl %[ar], %[ar]\n\t" /* set ar = 0 */
"1:"
: [ar] "=r" (ar)
: [old_ss] "rm" ((u16)regs->ss));
/*
* For a valid 64-bit user context, we need DPL 3, type
* read-write data or read-write exp-down data, and S and P
* set. We can't use VERW because VERW doesn't check the
* P bit.
*/
ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
regs->ss = __USER_DS;
}
# define CONTEXT_COPY_SIZE offsetof(struct sigcontext, reserved1)
#else
# define CONTEXT_COPY_SIZE sizeof(struct sigcontext)
#endif
static bool restore_sigcontext(struct pt_regs *regs,
struct sigcontext __user *usc,
unsigned long uc_flags)
{
struct sigcontext sc;
/* Always make any pending restarted system calls return -EINTR */
current->restart_block.fn = do_no_restart_syscall;
if (copy_from_user(&sc, usc, CONTEXT_COPY_SIZE))
return false;
#ifdef CONFIG_X86_32
loadsegment(gs, sc.gs);
regs->fs = sc.fs;
regs->es = sc.es;
regs->ds = sc.ds;
#endif /* CONFIG_X86_32 */
regs->bx = sc.bx;
regs->cx = sc.cx;
regs->dx = sc.dx;
regs->si = sc.si;
regs->di = sc.di;
regs->bp = sc.bp;
regs->ax = sc.ax;
regs->sp = sc.sp;
regs->ip = sc.ip;
#ifdef CONFIG_X86_64
regs->r8 = sc.r8;
regs->r9 = sc.r9;
regs->r10 = sc.r10;
regs->r11 = sc.r11;
regs->r12 = sc.r12;
regs->r13 = sc.r13;
regs->r14 = sc.r14;
regs->r15 = sc.r15;
#endif /* CONFIG_X86_64 */
/* Get CS/SS and force CPL3 */
regs->cs = sc.cs | 0x03;
regs->ss = sc.ss | 0x03;
regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
/* disable syscall checks */
regs->orig_ax = -1;
#ifdef CONFIG_X86_64
/*
* Fix up SS if needed for the benefit of old DOSEMU and
* CRIU.
*/
if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs)))
force_valid_ss(regs);
#endif
return fpu__restore_sig((void __user *)sc.fpstate,
IS_ENABLED(CONFIG_X86_32));
}
static __always_inline int
__unsafe_setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
struct pt_regs *regs, unsigned long mask)
{
#ifdef CONFIG_X86_32
unsigned int gs;
savesegment(gs, gs);
unsafe_put_user(gs, (unsigned int __user *)&sc->gs, Efault);
unsafe_put_user(regs->fs, (unsigned int __user *)&sc->fs, Efault);
unsafe_put_user(regs->es, (unsigned int __user *)&sc->es, Efault);
unsafe_put_user(regs->ds, (unsigned int __user *)&sc->ds, Efault);
#endif /* CONFIG_X86_32 */
unsafe_put_user(regs->di, &sc->di, Efault);
unsafe_put_user(regs->si, &sc->si, Efault);
unsafe_put_user(regs->bp, &sc->bp, Efault);
unsafe_put_user(regs->sp, &sc->sp, Efault);
unsafe_put_user(regs->bx, &sc->bx, Efault);
unsafe_put_user(regs->dx, &sc->dx, Efault);
unsafe_put_user(regs->cx, &sc->cx, Efault);
unsafe_put_user(regs->ax, &sc->ax, Efault);
#ifdef CONFIG_X86_64
unsafe_put_user(regs->r8, &sc->r8, Efault);
unsafe_put_user(regs->r9, &sc->r9, Efault);
unsafe_put_user(regs->r10, &sc->r10, Efault);
unsafe_put_user(regs->r11, &sc->r11, Efault);
unsafe_put_user(regs->r12, &sc->r12, Efault);
unsafe_put_user(regs->r13, &sc->r13, Efault);
unsafe_put_user(regs->r14, &sc->r14, Efault);
unsafe_put_user(regs->r15, &sc->r15, Efault);
#endif /* CONFIG_X86_64 */
unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
unsafe_put_user(current->thread.error_code, &sc->err, Efault);
unsafe_put_user(regs->ip, &sc->ip, Efault);
#ifdef CONFIG_X86_32
unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault);
unsafe_put_user(regs->flags, &sc->flags, Efault);
unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault);
unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault);
#else /* !CONFIG_X86_32 */
unsafe_put_user(regs->flags, &sc->flags, Efault);
unsafe_put_user(regs->cs, &sc->cs, Efault);
unsafe_put_user(0, &sc->gs, Efault);
unsafe_put_user(0, &sc->fs, Efault);
unsafe_put_user(regs->ss, &sc->ss, Efault);
#endif /* CONFIG_X86_32 */
unsafe_put_user(fpstate, (unsigned long __user *)&sc->fpstate, Efault);
/* non-iBCS2 extensions.. */
unsafe_put_user(mask, &sc->oldmask, Efault);
unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
return 0;
Efault:
return -EFAULT;
}
#define unsafe_put_sigcontext(sc, fp, regs, set, label) \
do { \
if (__unsafe_setup_sigcontext(sc, fp, regs, set->sig[0])) \
goto label; \
} while(0);
#define unsafe_put_sigmask(set, frame, label) \
unsafe_put_user(*(__u64 *)(set), \
(__u64 __user *)&(frame)->uc.uc_sigmask, \
label)
/*
* 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..
*/
static unsigned long align_sigframe(unsigned long sp)
{
#ifdef CONFIG_X86_32
/*
* 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 /* !CONFIG_X86_32 */
sp = round_down(sp, FRAME_ALIGNMENT) - 8;
#endif
return sp;
}
static void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
void __user **fpstate)
{
/* 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 (IS_ENABLED(CONFIG_X86_64))
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 (IS_ENABLED(CONFIG_X86_32) &&
!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, IS_ENABLED(CONFIG_X86_32),
&buf_fx, &math_size);
*fpstate = (void __user *)sp;
sp = align_sigframe(sp - frame_size);
/*
* 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;
}
#ifdef CONFIG_X86_32
static const struct {
u16 poplmovl;
u32 val;
u16 int80;
} __attribute__((packed)) retcode = {
0xb858, /* popl %eax; movl $..., %eax */
__NR_sigreturn,
0x80cd, /* int $0x80 */
};
static const struct {
u8 movl;
u32 val;
u16 int80;
u8 pad;
} __attribute__((packed)) rt_retcode = {
0xb8, /* movl $..., %eax */
__NR_rt_sigreturn,
0x80cd, /* int $0x80 */
0
};
static int
__setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
struct pt_regs *regs)
{
struct sigframe __user *frame;
void __user *restorer;
void __user *fp = NULL;
frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);
if (!user_access_begin(frame, sizeof(*frame)))
return -EFAULT;
unsafe_put_user(sig, &frame->sig, Efault);
unsafe_put_sigcontext(&frame->sc, fp, regs, set, Efault);
unsafe_put_user(set->sig[1], &frame->extramask[0], Efault);
if (current->mm->context.vdso)
restorer = current->mm->context.vdso +
vdso_image_32.sym___kernel_sigreturn;
else
restorer = &frame->retcode;
if (ksig->ka.sa.sa_flags & SA_RESTORER)
restorer = ksig->ka.sa.sa_restorer;
/* Set up to return from userspace. */
unsafe_put_user(restorer, &frame->pretcode, Efault);
/*
* This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
*
* WE DO NOT USE IT ANY MORE! It's only left here for historical
* reasons and because gdb uses it as a signature to notice
* signal handler stack frames.
*/
unsafe_put_user(*((u64 *)&retcode), (u64 *)frame->retcode, Efault);
user_access_end();
/* Set up registers for signal handler */
regs->sp = (unsigned long)frame;
regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
regs->ax = (unsigned long)sig;
regs->dx = 0;
regs->cx = 0;
regs->ds = __USER_DS;
regs->es = __USER_DS;
regs->ss = __USER_DS;
regs->cs = __USER_CS;
return 0;
Efault:
user_access_end();
return -EFAULT;
}
static int __setup_rt_frame(int sig, struct ksignal *ksig,
sigset_t *set, struct pt_regs *regs)
{
struct rt_sigframe __user *frame;
void __user *restorer;
void __user *fp = NULL;
frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);
if (!user_access_begin(frame, sizeof(*frame)))
return -EFAULT;
unsafe_put_user(sig, &frame->sig, Efault);
unsafe_put_user(&frame->info, &frame->pinfo, Efault);
unsafe_put_user(&frame->uc, &frame->puc, Efault);
/* Create the ucontext. */
if (static_cpu_has(X86_FEATURE_XSAVE))
unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
else
unsafe_put_user(0, &frame->uc.uc_flags, Efault);
unsafe_put_user(0, &frame->uc.uc_link, Efault);
unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
/* Set up to return from userspace. */
restorer = current->mm->context.vdso +
vdso_image_32.sym___kernel_rt_sigreturn;
if (ksig->ka.sa.sa_flags & SA_RESTORER)
restorer = ksig->ka.sa.sa_restorer;
unsafe_put_user(restorer, &frame->pretcode, Efault);
/*
* This is movl $__NR_rt_sigreturn, %ax ; int $0x80
*
* WE DO NOT USE IT ANY MORE! It's only left here for historical
* reasons and because gdb uses it as a signature to notice
* signal handler stack frames.
*/
unsafe_put_user(*((u64 *)&rt_retcode), (u64 *)frame->retcode, Efault);
unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
unsafe_put_sigmask(set, frame, Efault);
user_access_end();
if (copy_siginfo_to_user(&frame->info, &ksig->info))
return -EFAULT;
/* Set up registers for signal handler */
regs->sp = (unsigned long)frame;
regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
regs->ax = (unsigned long)sig;
regs->dx = (unsigned long)&frame->info;
regs->cx = (unsigned long)&frame->uc;
regs->ds = __USER_DS;
regs->es = __USER_DS;
regs->ss = __USER_DS;
regs->cs = __USER_CS;
return 0;
Efault:
user_access_end();
return -EFAULT;
}
#else /* !CONFIG_X86_32 */
static unsigned long frame_uc_flags(struct pt_regs *regs)
{
unsigned long flags;
if (boot_cpu_has(X86_FEATURE_XSAVE))
flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
else
flags = UC_SIGCONTEXT_SS;
if (likely(user_64bit_mode(regs)))
flags |= UC_STRICT_RESTORE_SS;
return flags;
}
static int __setup_rt_frame(int sig, struct ksignal *ksig,
sigset_t *set, struct pt_regs *regs)
{
struct rt_sigframe __user *frame;
void __user *fp = NULL;
unsigned long uc_flags;
/* x86-64 should always use SA_RESTORER. */
if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
return -EFAULT;
frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
uc_flags = frame_uc_flags(regs);
if (!user_access_begin(frame, sizeof(*frame)))
return -EFAULT;
/* Create the ucontext. */
unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault);
unsafe_put_user(0, &frame->uc.uc_link, Efault);
unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
/* Set up to return from userspace. If provided, use a stub
already in userspace. */
unsafe_put_user(ksig->ka.sa.sa_restorer, &frame->pretcode, Efault);
unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
unsafe_put_sigmask(set, frame, Efault);
user_access_end();
if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
if (copy_siginfo_to_user(&frame->info, &ksig->info))
return -EFAULT;
}
/* Set up registers for signal handler */
regs->di = sig;
/* In case the signal handler was declared without prototypes */
regs->ax = 0;
/* This also works for non SA_SIGINFO handlers because they expect the
next argument after the signal number on the stack. */
regs->si = (unsigned long)&frame->info;
regs->dx = (unsigned long)&frame->uc;
regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
regs->sp = (unsigned long)frame;
/*
* Set up the CS and SS registers to run signal handlers in
* 64-bit mode, even if the handler happens to be interrupting
* 32-bit or 16-bit code.
*
* SS is subtle. In 64-bit mode, we don't need any particular
* SS descriptor, but we do need SS to be valid. It's possible
* that the old SS is entirely bogus -- this can happen if the
* signal we're trying to deliver is #GP or #SS caused by a bad
* SS value. We also have a compatibility issue here: DOSEMU
* relies on the contents of the SS register indicating the
* SS value at the time of the signal, even though that code in
* DOSEMU predates sigreturn's ability to restore SS. (DOSEMU
* avoids relying on sigreturn to restore SS; instead it uses
* a trampoline.) So we do our best: if the old SS was valid,
* we keep it. Otherwise we replace it.
*/
regs->cs = __USER_CS;
if (unlikely(regs->ss != __USER_DS))
force_valid_ss(regs);
return 0;
Efault:
user_access_end();
return -EFAULT;
}
#endif /* CONFIG_X86_32 */
#ifdef CONFIG_X86_X32_ABI
static int x32_copy_siginfo_to_user(struct compat_siginfo __user *to,
const struct kernel_siginfo *from)
{
struct compat_siginfo new;
copy_siginfo_to_external32(&new, from);
if (from->si_signo == SIGCHLD) {
new._sifields._sigchld_x32._utime = from->si_utime;
new._sifields._sigchld_x32._stime = from->si_stime;
}
if (copy_to_user(to, &new, sizeof(struct compat_siginfo)))
return -EFAULT;
return 0;
}
int copy_siginfo_to_user32(struct compat_siginfo __user *to,
const struct kernel_siginfo *from)
{
if (in_x32_syscall())
return x32_copy_siginfo_to_user(to, from);
return __copy_siginfo_to_user32(to, from);
}
#endif /* CONFIG_X86_X32_ABI */
static int x32_setup_rt_frame(struct ksignal *ksig,
compat_sigset_t *set,
struct pt_regs *regs)
{
#ifdef CONFIG_X86_X32_ABI
struct rt_sigframe_x32 __user *frame;
unsigned long uc_flags;
void __user *restorer;
void __user *fp = NULL;
if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
return -EFAULT;
frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);
uc_flags = frame_uc_flags(regs);
if (!user_access_begin(frame, sizeof(*frame)))
return -EFAULT;
/* Create the ucontext. */
unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault);
unsafe_put_user(0, &frame->uc.uc_link, Efault);
unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
unsafe_put_user(0, &frame->uc.uc__pad0, Efault);
restorer = ksig->ka.sa.sa_restorer;
unsafe_put_user(restorer, (unsigned long __user *)&frame->pretcode, Efault);
unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
unsafe_put_sigmask(set, frame, Efault);
user_access_end();
if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
if (x32_copy_siginfo_to_user(&frame->info, &ksig->info))
return -EFAULT;
}
/* Set up registers for signal handler */
regs->sp = (unsigned long) frame;
regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
/* We use the x32 calling convention here... */
regs->di = ksig->sig;
regs->si = (unsigned long) &frame->info;
regs->dx = (unsigned long) &frame->uc;
loadsegment(ds, __USER_DS);
loadsegment(es, __USER_DS);
regs->cs = __USER_CS;
regs->ss = __USER_DS;
#endif /* CONFIG_X86_X32_ABI */
return 0;
#ifdef CONFIG_X86_X32_ABI
Efault:
user_access_end();
return -EFAULT;
#endif
}
/*
* Do a signal return; undo the signal stack.
*/
#ifdef CONFIG_X86_32
SYSCALL_DEFINE0(sigreturn)
{
struct pt_regs *regs = current_pt_regs();
struct sigframe __user *frame;
sigset_t set;
frame = (struct sigframe __user *)(regs->sp - 8);
if (!access_ok(frame, sizeof(*frame)))
goto badframe;
if (__get_user(set.sig[0], &frame->sc.oldmask) ||
__get_user(set.sig[1], &frame->extramask[0]))
goto badframe;
set_current_blocked(&set);
/*
* x86_32 has no uc_flags bits relevant to restore_sigcontext.
* Save a few cycles by skipping the __get_user.
*/
if (!restore_sigcontext(regs, &frame->sc, 0))
goto badframe;
return regs->ax;
badframe:
signal_fault(regs, frame, "sigreturn");
return 0;
}
#endif /* CONFIG_X86_32 */
SYSCALL_DEFINE0(rt_sigreturn)
{
struct pt_regs *regs = current_pt_regs();
struct rt_sigframe __user *frame;
sigset_t set;
unsigned long uc_flags;
frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
if (!access_ok(frame, sizeof(*frame)))
goto badframe;
if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask))
goto badframe;
if (__get_user(uc_flags, &frame->uc.uc_flags))
goto badframe;
set_current_blocked(&set);
if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
goto badframe;
if (restore_altstack(&frame->uc.uc_stack))
goto badframe;
return regs->ax;
badframe:
signal_fault(regs, frame, "rt_sigreturn");
return 0;
}
/*
* 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;
void __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);
}
unsigned long get_sigframe_size(void)
{
return max_frame_size;
}
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;
}
static int
setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
{
int usig = ksig->sig;
sigset_t *set = sigmask_to_save();
compat_sigset_t *cset = (compat_sigset_t *) set;
/* 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(usig, ksig, cset, regs);
else
return ia32_setup_frame(usig, ksig, cset, regs);
} else if (is_x32_frame(ksig)) {
return x32_setup_rt_frame(ksig, cset, regs);
} else {
return __setup_rt_frame(ksig->sig, ksig, set, regs);
}
}
static void
handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
bool stepping, failed;
struct fpu *fpu = &current->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);
}
__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(&current->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 */
#ifdef CONFIG_X86_X32_ABI
COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn)
{
struct pt_regs *regs = current_pt_regs();
struct rt_sigframe_x32 __user *frame;
sigset_t set;
unsigned long uc_flags;
frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
if (!access_ok(frame, sizeof(*frame)))
goto badframe;
if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask))
goto badframe;
if (__get_user(uc_flags, &frame->uc.uc_flags))
goto badframe;
set_current_blocked(&set);
if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
goto badframe;
if (compat_restore_altstack(&frame->uc.uc_stack))
goto badframe;
return regs->ax;
badframe:
signal_fault(regs, frame, "x32 rt_sigreturn");
return 0;
}
#endif
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