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linux/arch/arm64/kernel/signal.c
Dave Martin 65896545b6 arm64: uaccess: Fix omissions from usercopy whitelist 
When the hardend usercopy support was added for arm64, it was
concluded that all cases of usercopy into and out of thread_struct
were statically sized and so didn't require explicit whitelisting
of the appropriate fields in thread_struct.

Testing with usercopy hardening enabled has revealed that this is
not the case for certain ptrace regset manipulation calls on arm64.
This occurs because the sizes of usercopies associated with the
regset API are dynamic by construction, and because arm64 does not
always stage such copies via the stack: indeed the regset API is
designed to avoid the need for that by adding some bounds checking.

This is currently believed to affect only the fpsimd and TLS
registers.

Because the whitelisted fields in thread_struct must be contiguous,
this patch groups them together in a nested struct.  It is also
necessary to be able to determine the location and size of that
struct, so rather than making the struct anonymous (which would
save on edits elsewhere) or adding an anonymous union containing
named and unnamed instances of the same struct (gross), this patch
gives the struct a name and makes the necessary edits to code that
references it (noisy but simple).

Care is needed to ensure that the new struct does not contain
padding (which the usercopy hardening would fail to protect).

For this reason, the presence of tp2_value is made unconditional,
since a padding field would be needed there in any case.  This pads
up to the 16-byte alignment required by struct user_fpsimd_state.

Acked-by: Kees Cook <keescook@chromium.org>
Reported-by: Mark Rutland <mark.rutland@arm.com>
Fixes: 9e8084d3f7 ("arm64: Implement thread_struct whitelist for hardened usercopy")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2018-03-28 15:25:44 +01:00

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/*
* Based on arch/arm/kernel/signal.c
*
* Copyright (C) 1995-2009 Russell King
* Copyright (C) 2012 ARM Ltd.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/compat.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/personality.h>
#include <linux/freezer.h>
#include <linux/stddef.h>
#include <linux/uaccess.h>
#include <linux/sizes.h>
#include <linux/string.h>
#include <linux/tracehook.h>
#include <linux/ratelimit.h>
#include <linux/syscalls.h>
#include <asm/daifflags.h>
#include <asm/debug-monitors.h>
#include <asm/elf.h>
#include <asm/cacheflush.h>
#include <asm/ucontext.h>
#include <asm/unistd.h>
#include <asm/fpsimd.h>
#include <asm/ptrace.h>
#include <asm/signal32.h>
#include <asm/traps.h>
#include <asm/vdso.h>
/*
* Do a signal return; undo the signal stack. These are aligned to 128-bit.
*/
struct rt_sigframe {
struct siginfo info;
struct ucontext uc;
};
struct frame_record {
u64 fp;
u64 lr;
};
struct rt_sigframe_user_layout {
struct rt_sigframe __user *sigframe;
struct frame_record __user *next_frame;
unsigned long size; /* size of allocated sigframe data */
unsigned long limit; /* largest allowed size */
unsigned long fpsimd_offset;
unsigned long esr_offset;
unsigned long sve_offset;
unsigned long extra_offset;
unsigned long end_offset;
};
#define BASE_SIGFRAME_SIZE round_up(sizeof(struct rt_sigframe), 16)
#define TERMINATOR_SIZE round_up(sizeof(struct _aarch64_ctx), 16)
#define EXTRA_CONTEXT_SIZE round_up(sizeof(struct extra_context), 16)
static void init_user_layout(struct rt_sigframe_user_layout *user)
{
const size_t reserved_size =
sizeof(user->sigframe->uc.uc_mcontext.__reserved);
memset(user, 0, sizeof(*user));
user->size = offsetof(struct rt_sigframe, uc.uc_mcontext.__reserved);
user->limit = user->size + reserved_size;
user->limit -= TERMINATOR_SIZE;
user->limit -= EXTRA_CONTEXT_SIZE;
/* Reserve space for extension and terminator ^ */
}
static size_t sigframe_size(struct rt_sigframe_user_layout const *user)
{
return round_up(max(user->size, sizeof(struct rt_sigframe)), 16);
}
/*
* Sanity limit on the approximate maximum size of signal frame we'll
* try to generate. Stack alignment padding and the frame record are
* not taken into account. This limit is not a guarantee and is
* NOT ABI.
*/
#define SIGFRAME_MAXSZ SZ_64K
static int __sigframe_alloc(struct rt_sigframe_user_layout *user,
unsigned long *offset, size_t size, bool extend)
{
size_t padded_size = round_up(size, 16);
if (padded_size > user->limit - user->size &&
!user->extra_offset &&
extend) {
int ret;
user->limit += EXTRA_CONTEXT_SIZE;
ret = __sigframe_alloc(user, &user->extra_offset,
sizeof(struct extra_context), false);
if (ret) {
user->limit -= EXTRA_CONTEXT_SIZE;
return ret;
}
/* Reserve space for the __reserved[] terminator */
user->size += TERMINATOR_SIZE;
/*
* Allow expansion up to SIGFRAME_MAXSZ, ensuring space for
* the terminator:
*/
user->limit = SIGFRAME_MAXSZ - TERMINATOR_SIZE;
}
/* Still not enough space? Bad luck! */
if (padded_size > user->limit - user->size)
return -ENOMEM;
*offset = user->size;
user->size += padded_size;
return 0;
}
/*
* Allocate space for an optional record of <size> bytes in the user
* signal frame. The offset from the signal frame base address to the
* allocated block is assigned to *offset.
*/
static int sigframe_alloc(struct rt_sigframe_user_layout *user,
unsigned long *offset, size_t size)
{
return __sigframe_alloc(user, offset, size, true);
}
/* Allocate the null terminator record and prevent further allocations */
static int sigframe_alloc_end(struct rt_sigframe_user_layout *user)
{
int ret;
/* Un-reserve the space reserved for the terminator: */
user->limit += TERMINATOR_SIZE;
ret = sigframe_alloc(user, &user->end_offset,
sizeof(struct _aarch64_ctx));
if (ret)
return ret;
/* Prevent further allocation: */
user->limit = user->size;
return 0;
}
static void __user *apply_user_offset(
struct rt_sigframe_user_layout const *user, unsigned long offset)
{
char __user *base = (char __user *)user->sigframe;
return base + offset;
}
static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
{
struct user_fpsimd_state const *fpsimd =
&current->thread.uw.fpsimd_state;
int err;
/* copy the FP and status/control registers */
err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
__put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
__put_user_error(fpsimd->fpcr, &ctx->fpcr, err);
/* copy the magic/size information */
__put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
__put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);
return err ? -EFAULT : 0;
}
static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
{
struct user_fpsimd_state fpsimd;
__u32 magic, size;
int err = 0;
/* check the magic/size information */
__get_user_error(magic, &ctx->head.magic, err);
__get_user_error(size, &ctx->head.size, err);
if (err)
return -EFAULT;
if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context))
return -EINVAL;
/* copy the FP and status/control registers */
err = __copy_from_user(fpsimd.vregs, ctx->vregs,
sizeof(fpsimd.vregs));
__get_user_error(fpsimd.fpsr, &ctx->fpsr, err);
__get_user_error(fpsimd.fpcr, &ctx->fpcr, err);
clear_thread_flag(TIF_SVE);
/* load the hardware registers from the fpsimd_state structure */
if (!err)
fpsimd_update_current_state(&fpsimd);
return err ? -EFAULT : 0;
}
struct user_ctxs {
struct fpsimd_context __user *fpsimd;
struct sve_context __user *sve;
};
#ifdef CONFIG_ARM64_SVE
static int preserve_sve_context(struct sve_context __user *ctx)
{
int err = 0;
u16 reserved[ARRAY_SIZE(ctx->__reserved)];
unsigned int vl = current->thread.sve_vl;
unsigned int vq = 0;
if (test_thread_flag(TIF_SVE))
vq = sve_vq_from_vl(vl);
memset(reserved, 0, sizeof(reserved));
__put_user_error(SVE_MAGIC, &ctx->head.magic, err);
__put_user_error(round_up(SVE_SIG_CONTEXT_SIZE(vq), 16),
&ctx->head.size, err);
__put_user_error(vl, &ctx->vl, err);
BUILD_BUG_ON(sizeof(ctx->__reserved) != sizeof(reserved));
err |= __copy_to_user(&ctx->__reserved, reserved, sizeof(reserved));
if (vq) {
/*
* This assumes that the SVE state has already been saved to
* the task struct by calling preserve_fpsimd_context().
*/
err |= __copy_to_user((char __user *)ctx + SVE_SIG_REGS_OFFSET,
current->thread.sve_state,
SVE_SIG_REGS_SIZE(vq));
}
return err ? -EFAULT : 0;
}
static int restore_sve_fpsimd_context(struct user_ctxs *user)
{
int err;
unsigned int vq;
struct user_fpsimd_state fpsimd;
struct sve_context sve;
if (__copy_from_user(&sve, user->sve, sizeof(sve)))
return -EFAULT;
if (sve.vl != current->thread.sve_vl)
return -EINVAL;
if (sve.head.size <= sizeof(*user->sve)) {
clear_thread_flag(TIF_SVE);
goto fpsimd_only;
}
vq = sve_vq_from_vl(sve.vl);
if (sve.head.size < SVE_SIG_CONTEXT_SIZE(vq))
return -EINVAL;
/*
* Careful: we are about __copy_from_user() directly into
* thread.sve_state with preemption enabled, so protection is
* needed to prevent a racing context switch from writing stale
* registers back over the new data.
*/
fpsimd_flush_task_state(current);
barrier();
/* From now, fpsimd_thread_switch() won't clear TIF_FOREIGN_FPSTATE */
set_thread_flag(TIF_FOREIGN_FPSTATE);
barrier();
/* From now, fpsimd_thread_switch() won't touch thread.sve_state */
sve_alloc(current);
err = __copy_from_user(current->thread.sve_state,
(char __user const *)user->sve +
SVE_SIG_REGS_OFFSET,
SVE_SIG_REGS_SIZE(vq));
if (err)
return -EFAULT;
set_thread_flag(TIF_SVE);
fpsimd_only:
/* copy the FP and status/control registers */
/* restore_sigframe() already checked that user->fpsimd != NULL. */
err = __copy_from_user(fpsimd.vregs, user->fpsimd->vregs,
sizeof(fpsimd.vregs));
__get_user_error(fpsimd.fpsr, &user->fpsimd->fpsr, err);
__get_user_error(fpsimd.fpcr, &user->fpsimd->fpcr, err);
/* load the hardware registers from the fpsimd_state structure */
if (!err)
fpsimd_update_current_state(&fpsimd);
return err ? -EFAULT : 0;
}
#else /* ! CONFIG_ARM64_SVE */
/* Turn any non-optimised out attempts to use these into a link error: */
extern int preserve_sve_context(void __user *ctx);
extern int restore_sve_fpsimd_context(struct user_ctxs *user);
#endif /* ! CONFIG_ARM64_SVE */
static int parse_user_sigframe(struct user_ctxs *user,
struct rt_sigframe __user *sf)
{
struct sigcontext __user *const sc = &sf->uc.uc_mcontext;
struct _aarch64_ctx __user *head;
char __user *base = (char __user *)&sc->__reserved;
size_t offset = 0;
size_t limit = sizeof(sc->__reserved);
bool have_extra_context = false;
char const __user *const sfp = (char const __user *)sf;
user->fpsimd = NULL;
user->sve = NULL;
if (!IS_ALIGNED((unsigned long)base, 16))
goto invalid;
while (1) {
int err = 0;
u32 magic, size;
char const __user *userp;
struct extra_context const __user *extra;
u64 extra_datap;
u32 extra_size;
struct _aarch64_ctx const __user *end;
u32 end_magic, end_size;
if (limit - offset < sizeof(*head))
goto invalid;
if (!IS_ALIGNED(offset, 16))
goto invalid;
head = (struct _aarch64_ctx __user *)(base + offset);
__get_user_error(magic, &head->magic, err);
__get_user_error(size, &head->size, err);
if (err)
return err;
if (limit - offset < size)
goto invalid;
switch (magic) {
case 0:
if (size)
goto invalid;
goto done;
case FPSIMD_MAGIC:
if (user->fpsimd)
goto invalid;
if (size < sizeof(*user->fpsimd))
goto invalid;
user->fpsimd = (struct fpsimd_context __user *)head;
break;
case ESR_MAGIC:
/* ignore */
break;
case SVE_MAGIC:
if (!system_supports_sve())
goto invalid;
if (user->sve)
goto invalid;
if (size < sizeof(*user->sve))
goto invalid;
user->sve = (struct sve_context __user *)head;
break;
case EXTRA_MAGIC:
if (have_extra_context)
goto invalid;
if (size < sizeof(*extra))
goto invalid;
userp = (char const __user *)head;
extra = (struct extra_context const __user *)userp;
userp += size;
__get_user_error(extra_datap, &extra->datap, err);
__get_user_error(extra_size, &extra->size, err);
if (err)
return err;
/* Check for the dummy terminator in __reserved[]: */
if (limit - offset - size < TERMINATOR_SIZE)
goto invalid;
end = (struct _aarch64_ctx const __user *)userp;
userp += TERMINATOR_SIZE;
__get_user_error(end_magic, &end->magic, err);
__get_user_error(end_size, &end->size, err);
if (err)
return err;
if (end_magic || end_size)
goto invalid;
/* Prevent looping/repeated parsing of extra_context */
have_extra_context = true;
base = (__force void __user *)extra_datap;
if (!IS_ALIGNED((unsigned long)base, 16))
goto invalid;
if (!IS_ALIGNED(extra_size, 16))
goto invalid;
if (base != userp)
goto invalid;
/* Reject "unreasonably large" frames: */
if (extra_size > sfp + SIGFRAME_MAXSZ - userp)
goto invalid;
/*
* Ignore trailing terminator in __reserved[]
* and start parsing extra data:
*/
offset = 0;
limit = extra_size;
if (!access_ok(VERIFY_READ, base, limit))
goto invalid;
continue;
default:
goto invalid;
}
if (size < sizeof(*head))
goto invalid;
if (limit - offset < size)
goto invalid;
offset += size;
}
done:
return 0;
invalid:
return -EINVAL;
}
static int restore_sigframe(struct pt_regs *regs,
struct rt_sigframe __user *sf)
{
sigset_t set;
int i, err;
struct user_ctxs user;
err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
if (err == 0)
set_current_blocked(&set);
for (i = 0; i < 31; i++)
__get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
err);
__get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
__get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
__get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
/*
* Avoid sys_rt_sigreturn() restarting.
*/
forget_syscall(regs);
err |= !valid_user_regs(&regs->user_regs, current);
if (err == 0)
err = parse_user_sigframe(&user, sf);
if (err == 0) {
if (!user.fpsimd)
return -EINVAL;
if (user.sve) {
if (!system_supports_sve())
return -EINVAL;
err = restore_sve_fpsimd_context(&user);
} else {
err = restore_fpsimd_context(user.fpsimd);
}
}
return err;
}
asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
{
struct rt_sigframe __user *frame;
/* Always make any pending restarted system calls return -EINTR */
current->restart_block.fn = do_no_restart_syscall;
/*
* Since we stacked the signal on a 128-bit boundary, then 'sp' should
* be word aligned here.
*/
if (regs->sp & 15)
goto badframe;
frame = (struct rt_sigframe __user *)regs->sp;
if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
goto badframe;
if (restore_sigframe(regs, frame))
goto badframe;
if (restore_altstack(&frame->uc.uc_stack))
goto badframe;
return regs->regs[0];
badframe:
arm64_notify_segfault(regs->sp);
return 0;
}
/* Determine the layout of optional records in the signal frame */
static int setup_sigframe_layout(struct rt_sigframe_user_layout *user)
{
int err;
err = sigframe_alloc(user, &user->fpsimd_offset,
sizeof(struct fpsimd_context));
if (err)
return err;
/* fault information, if valid */
if (current->thread.fault_code) {
err = sigframe_alloc(user, &user->esr_offset,
sizeof(struct esr_context));
if (err)
return err;
}
if (system_supports_sve()) {
unsigned int vq = 0;
if (test_thread_flag(TIF_SVE))
vq = sve_vq_from_vl(current->thread.sve_vl);
err = sigframe_alloc(user, &user->sve_offset,
SVE_SIG_CONTEXT_SIZE(vq));
if (err)
return err;
}
return sigframe_alloc_end(user);
}
static int setup_sigframe(struct rt_sigframe_user_layout *user,
struct pt_regs *regs, sigset_t *set)
{
int i, err = 0;
struct rt_sigframe __user *sf = user->sigframe;
/* set up the stack frame for unwinding */
__put_user_error(regs->regs[29], &user->next_frame->fp, err);
__put_user_error(regs->regs[30], &user->next_frame->lr, err);
for (i = 0; i < 31; i++)
__put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
err);
__put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
__put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
__put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
__put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
if (err == 0) {
struct fpsimd_context __user *fpsimd_ctx =
apply_user_offset(user, user->fpsimd_offset);
err |= preserve_fpsimd_context(fpsimd_ctx);
}
/* fault information, if valid */
if (err == 0 && user->esr_offset) {
struct esr_context __user *esr_ctx =
apply_user_offset(user, user->esr_offset);
__put_user_error(ESR_MAGIC, &esr_ctx->head.magic, err);
__put_user_error(sizeof(*esr_ctx), &esr_ctx->head.size, err);
__put_user_error(current->thread.fault_code, &esr_ctx->esr, err);
}
/* Scalable Vector Extension state, if present */
if (system_supports_sve() && err == 0 && user->sve_offset) {
struct sve_context __user *sve_ctx =
apply_user_offset(user, user->sve_offset);
err |= preserve_sve_context(sve_ctx);
}
if (err == 0 && user->extra_offset) {
char __user *sfp = (char __user *)user->sigframe;
char __user *userp =
apply_user_offset(user, user->extra_offset);
struct extra_context __user *extra;
struct _aarch64_ctx __user *end;
u64 extra_datap;
u32 extra_size;
extra = (struct extra_context __user *)userp;
userp += EXTRA_CONTEXT_SIZE;
end = (struct _aarch64_ctx __user *)userp;
userp += TERMINATOR_SIZE;
/*
* extra_datap is just written to the signal frame.
* The value gets cast back to a void __user *
* during sigreturn.
*/
extra_datap = (__force u64)userp;
extra_size = sfp + round_up(user->size, 16) - userp;
__put_user_error(EXTRA_MAGIC, &extra->head.magic, err);
__put_user_error(EXTRA_CONTEXT_SIZE, &extra->head.size, err);
__put_user_error(extra_datap, &extra->datap, err);
__put_user_error(extra_size, &extra->size, err);
/* Add the terminator */
__put_user_error(0, &end->magic, err);
__put_user_error(0, &end->size, err);
}
/* set the "end" magic */
if (err == 0) {
struct _aarch64_ctx __user *end =
apply_user_offset(user, user->end_offset);
__put_user_error(0, &end->magic, err);
__put_user_error(0, &end->size, err);
}
return err;
}
static int get_sigframe(struct rt_sigframe_user_layout *user,
struct ksignal *ksig, struct pt_regs *regs)
{
unsigned long sp, sp_top;
int err;
init_user_layout(user);
err = setup_sigframe_layout(user);
if (err)
return err;
sp = sp_top = sigsp(regs->sp, ksig);
sp = round_down(sp - sizeof(struct frame_record), 16);
user->next_frame = (struct frame_record __user *)sp;
sp = round_down(sp, 16) - sigframe_size(user);
user->sigframe = (struct rt_sigframe __user *)sp;
/*
* Check that we can actually write to the signal frame.
*/
if (!access_ok(VERIFY_WRITE, user->sigframe, sp_top - sp))
return -EFAULT;
return 0;
}
static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
struct rt_sigframe_user_layout *user, int usig)
{
__sigrestore_t sigtramp;
regs->regs[0] = usig;
regs->sp = (unsigned long)user->sigframe;
regs->regs[29] = (unsigned long)&user->next_frame->fp;
regs->pc = (unsigned long)ka->sa.sa_handler;
if (ka->sa.sa_flags & SA_RESTORER)
sigtramp = ka->sa.sa_restorer;
else
sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
regs->regs[30] = (unsigned long)sigtramp;
}
static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
struct pt_regs *regs)
{
struct rt_sigframe_user_layout user;
struct rt_sigframe __user *frame;
int err = 0;
fpsimd_signal_preserve_current_state();
if (get_sigframe(&user, ksig, regs))
return 1;
frame = user.sigframe;
__put_user_error(0, &frame->uc.uc_flags, err);
__put_user_error(NULL, &frame->uc.uc_link, err);
err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
err |= setup_sigframe(&user, regs, set);
if (err == 0) {
setup_return(regs, &ksig->ka, &user, usig);
if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
err |= copy_siginfo_to_user(&frame->info, &ksig->info);
regs->regs[1] = (unsigned long)&frame->info;
regs->regs[2] = (unsigned long)&frame->uc;
}
}
return err;
}
static void setup_restart_syscall(struct pt_regs *regs)
{
if (is_compat_task())
compat_setup_restart_syscall(regs);
else
regs->regs[8] = __NR_restart_syscall;
}
/*
* OK, we're invoking a handler
*/
static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
struct task_struct *tsk = current;
sigset_t *oldset = sigmask_to_save();
int usig = ksig->sig;
int ret;
/*
* Set up the stack frame
*/
if (is_compat_task()) {
if (ksig->ka.sa.sa_flags & SA_SIGINFO)
ret = compat_setup_rt_frame(usig, ksig, oldset, regs);
else
ret = compat_setup_frame(usig, ksig, oldset, regs);
} else {
ret = setup_rt_frame(usig, ksig, oldset, regs);
}
/*
* Check that the resulting registers are actually sane.
*/
ret |= !valid_user_regs(&regs->user_regs, current);
/*
* Fast forward the stepping logic so we step into the signal
* handler.
*/
if (!ret)
user_fastforward_single_step(tsk);
signal_setup_done(ret, ksig, 0);
}
/*
* 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.
*
* Note that we go through the signals twice: once to check the signals that
* the kernel can handle, and then we build all the user-level signal handling
* stack-frames in one go after that.
*/
static void do_signal(struct pt_regs *regs)
{
unsigned long continue_addr = 0, restart_addr = 0;
int retval = 0;
struct ksignal ksig;
/*
* If we were from a system call, check for system call restarting...
*/
if (in_syscall(regs)) {
continue_addr = regs->pc;
restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
retval = regs->regs[0];
/*
* Avoid additional syscall restarting via ret_to_user.
*/
forget_syscall(regs);
/*
* Prepare for system call restart. We do this here so that a
* debugger will see the already changed PC.
*/
switch (retval) {
case -ERESTARTNOHAND:
case -ERESTARTSYS:
case -ERESTARTNOINTR:
case -ERESTART_RESTARTBLOCK:
regs->regs[0] = regs->orig_x0;
regs->pc = restart_addr;
break;
}
}
/*
* Get the signal to deliver. When running under ptrace, at this point
* the debugger may change all of our registers.
*/
if (get_signal(&ksig)) {
/*
* Depending on the signal settings, we may need to revert the
* decision to restart the system call, but skip this if a
* debugger has chosen to restart at a different PC.
*/
if (regs->pc == restart_addr &&
(retval == -ERESTARTNOHAND ||
retval == -ERESTART_RESTARTBLOCK ||
(retval == -ERESTARTSYS &&
!(ksig.ka.sa.sa_flags & SA_RESTART)))) {
regs->regs[0] = -EINTR;
regs->pc = continue_addr;
}
handle_signal(&ksig, regs);
return;
}
/*
* Handle restarting a different system call. As above, if a debugger
* has chosen to restart at a different PC, ignore the restart.
*/
if (in_syscall(regs) && regs->pc == restart_addr) {
if (retval == -ERESTART_RESTARTBLOCK)
setup_restart_syscall(regs);
user_rewind_single_step(current);
}
restore_saved_sigmask();
}
asmlinkage void do_notify_resume(struct pt_regs *regs,
unsigned int thread_flags)
{
/*
* The assembly code enters us with IRQs off, but it hasn't
* informed the tracing code of that for efficiency reasons.
* Update the trace code with the current status.
*/
trace_hardirqs_off();
do {
/* Check valid user FS if needed */
addr_limit_user_check();
if (thread_flags & _TIF_NEED_RESCHED) {
/* Unmask Debug and SError for the next task */
local_daif_restore(DAIF_PROCCTX_NOIRQ);
schedule();
} else {
local_daif_restore(DAIF_PROCCTX);
if (thread_flags & _TIF_UPROBE)
uprobe_notify_resume(regs);
if (thread_flags & _TIF_SIGPENDING)
do_signal(regs);
if (thread_flags & _TIF_NOTIFY_RESUME) {
clear_thread_flag(TIF_NOTIFY_RESUME);
tracehook_notify_resume(regs);
}
if (thread_flags & _TIF_FOREIGN_FPSTATE)
fpsimd_restore_current_state();
}
local_daif_mask();
thread_flags = READ_ONCE(current_thread_info()->flags);
} while (thread_flags & _TIF_WORK_MASK);
}
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