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linux/arch/arm/kernel/signal.c

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// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/arch/arm/kernel/signal.c
*
* Copyright (C) 1995-2009 Russell King
*/
#include <linux/errno.h>
#include <linux/random.h>
#include <linux/signal.h>
#include <linux/personality.h>
#include <linux/uaccess.h>
#include <linux/tracehook.h>
#include <linux/uprobes.h>
#include <linux/syscalls.h>
#include <asm/elf.h>
#include <asm/cacheflush.h>
#include <asm/traps.h>
#include <asm/unistd.h>
#include <asm/vfp.h>
#include "signal.h"
extern const unsigned long sigreturn_codes[17];
static unsigned long signal_return_offset;
#ifdef CONFIG_CRUNCH
static int preserve_crunch_context(struct crunch_sigframe __user *frame)
{
char kbuf[sizeof(*frame) + 8];
struct crunch_sigframe *kframe;
/* the crunch context must be 64 bit aligned */
kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
kframe->magic = CRUNCH_MAGIC;
kframe->size = CRUNCH_STORAGE_SIZE;
crunch_task_copy(current_thread_info(), &kframe->storage);
return __copy_to_user(frame, kframe, sizeof(*frame));
}
static int restore_crunch_context(char __user **auxp)
{
struct crunch_sigframe __user *frame =
(struct crunch_sigframe __user *)*auxp;
char kbuf[sizeof(*frame) + 8];
struct crunch_sigframe *kframe;
/* the crunch context must be 64 bit aligned */
kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
if (__copy_from_user(kframe, frame, sizeof(*frame)))
return -1;
if (kframe->magic != CRUNCH_MAGIC ||
kframe->size != CRUNCH_STORAGE_SIZE)
return -1;
*auxp += CRUNCH_STORAGE_SIZE;
crunch_task_restore(current_thread_info(), &kframe->storage);
return 0;
}
#endif
#ifdef CONFIG_IWMMXT
static int preserve_iwmmxt_context(struct iwmmxt_sigframe __user *frame)
{
char kbuf[sizeof(*frame) + 8];
struct iwmmxt_sigframe *kframe;
int err = 0;
/* the iWMMXt context must be 64 bit aligned */
kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
if (test_thread_flag(TIF_USING_IWMMXT)) {
kframe->magic = IWMMXT_MAGIC;
kframe->size = IWMMXT_STORAGE_SIZE;
iwmmxt_task_copy(current_thread_info(), &kframe->storage);
} else {
/*
* For bug-compatibility with older kernels, some space
* has to be reserved for iWMMXt even if it's not used.
* Set the magic and size appropriately so that properly
* written userspace can skip it reliably:
*/
*kframe = (struct iwmmxt_sigframe) {
.magic = DUMMY_MAGIC,
.size = IWMMXT_STORAGE_SIZE,
};
}
err = __copy_to_user(frame, kframe, sizeof(*kframe));
return err;
}
static int restore_iwmmxt_context(char __user **auxp)
{
struct iwmmxt_sigframe __user *frame =
(struct iwmmxt_sigframe __user *)*auxp;
char kbuf[sizeof(*frame) + 8];
struct iwmmxt_sigframe *kframe;
/* the iWMMXt context must be 64 bit aligned */
kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
if (__copy_from_user(kframe, frame, sizeof(*frame)))
return -1;
/*
* For non-iWMMXt threads: a single iwmmxt_sigframe-sized dummy
* block is discarded for compatibility with setup_sigframe() if
* present, but we don't mandate its presence. If some other
* magic is here, it's not for us:
*/
if (!test_thread_flag(TIF_USING_IWMMXT) &&
kframe->magic != DUMMY_MAGIC)
return 0;
if (kframe->size != IWMMXT_STORAGE_SIZE)
return -1;
if (test_thread_flag(TIF_USING_IWMMXT)) {
if (kframe->magic != IWMMXT_MAGIC)
return -1;
iwmmxt_task_restore(current_thread_info(), &kframe->storage);
}
*auxp += IWMMXT_STORAGE_SIZE;
return 0;
}
#endif
#ifdef CONFIG_VFP
static int preserve_vfp_context(struct vfp_sigframe __user *frame)
{
struct vfp_sigframe kframe;
int err = 0;
memset(&kframe, 0, sizeof(kframe));
kframe.magic = VFP_MAGIC;
kframe.size = VFP_STORAGE_SIZE;
err = vfp_preserve_user_clear_hwstate(&kframe.ufp, &kframe.ufp_exc);
if (err)
return err;
return __copy_to_user(frame, &kframe, sizeof(kframe));
}
static int restore_vfp_context(char __user **auxp)
{
struct vfp_sigframe frame;
int err;
err = __copy_from_user(&frame, *auxp, sizeof(frame));
if (err)
return err;
if (frame.magic != VFP_MAGIC || frame.size != VFP_STORAGE_SIZE)
return -EINVAL;
*auxp += sizeof(frame);
return vfp_restore_user_hwstate(&frame.ufp, &frame.ufp_exc);
}
#endif
/*
* Do a signal return; undo the signal stack. These are aligned to 64-bit.
*/
static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
{
struct sigcontext context;
char __user *aux;
sigset_t set;
int err;
err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
if (err == 0)
set_current_blocked(&set);
err |= __copy_from_user(&context, &sf->uc.uc_mcontext, sizeof(context));
if (err == 0) {
regs->ARM_r0 = context.arm_r0;
regs->ARM_r1 = context.arm_r1;
regs->ARM_r2 = context.arm_r2;
regs->ARM_r3 = context.arm_r3;
regs->ARM_r4 = context.arm_r4;
regs->ARM_r5 = context.arm_r5;
regs->ARM_r6 = context.arm_r6;
regs->ARM_r7 = context.arm_r7;
regs->ARM_r8 = context.arm_r8;
regs->ARM_r9 = context.arm_r9;
regs->ARM_r10 = context.arm_r10;
regs->ARM_fp = context.arm_fp;
regs->ARM_ip = context.arm_ip;
regs->ARM_sp = context.arm_sp;
regs->ARM_lr = context.arm_lr;
regs->ARM_pc = context.arm_pc;
regs->ARM_cpsr = context.arm_cpsr;
}
err |= !valid_user_regs(regs);
aux = (char __user *) sf->uc.uc_regspace;
#ifdef CONFIG_CRUNCH
if (err == 0)
err |= restore_crunch_context(&aux);
#endif
#ifdef CONFIG_IWMMXT
if (err == 0)
err |= restore_iwmmxt_context(&aux);
#endif
#ifdef CONFIG_VFP
if (err == 0)
err |= restore_vfp_context(&aux);
#endif
return err;
}
asmlinkage int sys_sigreturn(struct pt_regs *regs)
{
struct 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 64-bit boundary,
* then 'sp' should be word aligned here. If it's
* not, then the user is trying to mess with us.
*/
if (regs->ARM_sp & 7)
goto badframe;
frame = (struct sigframe __user *)regs->ARM_sp;
if (!access_ok(frame, sizeof (*frame)))
goto badframe;
if (restore_sigframe(regs, frame))
goto badframe;
return regs->ARM_r0;
badframe:
force_sig(SIGSEGV);
return 0;
}
asmlinkage int 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 64-bit boundary,
* then 'sp' should be word aligned here. If it's
* not, then the user is trying to mess with us.
*/
if (regs->ARM_sp & 7)
goto badframe;
frame = (struct rt_sigframe __user *)regs->ARM_sp;
if (!access_ok(frame, sizeof (*frame)))
goto badframe;
if (restore_sigframe(regs, &frame->sig))
goto badframe;
if (restore_altstack(&frame->sig.uc.uc_stack))
goto badframe;
return regs->ARM_r0;
badframe:
force_sig(SIGSEGV);
return 0;
}
static int
setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
{
struct aux_sigframe __user *aux;
struct sigcontext context;
int err = 0;
context = (struct sigcontext) {
.arm_r0 = regs->ARM_r0,
.arm_r1 = regs->ARM_r1,
.arm_r2 = regs->ARM_r2,
.arm_r3 = regs->ARM_r3,
.arm_r4 = regs->ARM_r4,
.arm_r5 = regs->ARM_r5,
.arm_r6 = regs->ARM_r6,
.arm_r7 = regs->ARM_r7,
.arm_r8 = regs->ARM_r8,
.arm_r9 = regs->ARM_r9,
.arm_r10 = regs->ARM_r10,
.arm_fp = regs->ARM_fp,
.arm_ip = regs->ARM_ip,
.arm_sp = regs->ARM_sp,
.arm_lr = regs->ARM_lr,
.arm_pc = regs->ARM_pc,
.arm_cpsr = regs->ARM_cpsr,
.trap_no = current->thread.trap_no,
.error_code = current->thread.error_code,
.fault_address = current->thread.address,
.oldmask = set->sig[0],
};
err |= __copy_to_user(&sf->uc.uc_mcontext, &context, sizeof(context));
err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
#ifdef CONFIG_CRUNCH
if (err == 0)
err |= preserve_crunch_context(&aux->crunch);
#endif
#ifdef CONFIG_IWMMXT
if (err == 0)
err |= preserve_iwmmxt_context(&aux->iwmmxt);
#endif
#ifdef CONFIG_VFP
if (err == 0)
err |= preserve_vfp_context(&aux->vfp);
#endif
err |= __put_user(0, &aux->end_magic);
return err;
}
static inline void __user *
get_sigframe(struct ksignal *ksig, struct pt_regs *regs, int framesize)
{
unsigned long sp = sigsp(regs->ARM_sp, ksig);
void __user *frame;
/*
* 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_return(struct pt_regs *regs, struct ksignal *ksig,
unsigned long __user *rc, void __user *frame)
{
unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler;
unsigned long handler_fdpic_GOT = 0;
unsigned long retcode;
unsigned int idx, thumb = 0;
unsigned long cpsr = regs->ARM_cpsr & ~(PSR_f | PSR_E_BIT);
bool fdpic = IS_ENABLED(CONFIG_BINFMT_ELF_FDPIC) &&
(current->personality & FDPIC_FUNCPTRS);
if (fdpic) {
unsigned long __user *fdpic_func_desc =
(unsigned long __user *)handler;
if (__get_user(handler, &fdpic_func_desc[0]) ||
__get_user(handler_fdpic_GOT, &fdpic_func_desc[1]))
return 1;
}
cpsr |= PSR_ENDSTATE;
/*
* Maybe we need to deliver a 32-bit signal to a 26-bit task.
*/
if (ksig->ka.sa.sa_flags & SA_THIRTYTWO)
cpsr = (cpsr & ~MODE_MASK) | USR_MODE;
#ifdef CONFIG_ARM_THUMB
if (elf_hwcap & HWCAP_THUMB) {
/*
* The LSB of the handler determines if we're going to
* be using THUMB or ARM mode for this signal handler.
*/
thumb = handler & 1;
/*
* Clear the If-Then Thumb-2 execution state. ARM spec
* requires this to be all 000s in ARM mode. Snapdragon
* S4/Krait misbehaves on a Thumb=>ARM signal transition
* without this.
*
* We must do this whenever we are running on a Thumb-2
* capable CPU, which includes ARMv6T2. However, we elect
* to always do this to simplify the code; this field is
* marked UNK/SBZP for older architectures.
*/
cpsr &= ~PSR_IT_MASK;
if (thumb) {
cpsr |= PSR_T_BIT;
} else
cpsr &= ~PSR_T_BIT;
}
#endif
if (ksig->ka.sa.sa_flags & SA_RESTORER) {
retcode = (unsigned long)ksig->ka.sa.sa_restorer;
if (fdpic) {
/*
* We need code to load the function descriptor.
* That code follows the standard sigreturn code
* (6 words), and is made of 3 + 2 words for each
* variant. The 4th copied word is the actual FD
* address that the assembly code expects.
*/
idx = 6 + thumb * 3;
if (ksig->ka.sa.sa_flags & SA_SIGINFO)
idx += 5;
if (__put_user(sigreturn_codes[idx], rc ) ||
__put_user(sigreturn_codes[idx+1], rc+1) ||
__put_user(sigreturn_codes[idx+2], rc+2) ||
__put_user(retcode, rc+3))
return 1;
goto rc_finish;
}
} else {
idx = thumb << 1;
if (ksig->ka.sa.sa_flags & SA_SIGINFO)
idx += 3;
/*
* Put the sigreturn code on the stack no matter which return
* mechanism we use in order to remain ABI compliant
*/
if (__put_user(sigreturn_codes[idx], rc) ||
__put_user(sigreturn_codes[idx+1], rc+1))
return 1;
rc_finish:
#ifdef CONFIG_MMU
if (cpsr & MODE32_BIT) {
struct mm_struct *mm = current->mm;
/*
* 32-bit code can use the signal return page
* except when the MPU has protected the vectors
* page from PL0
*/
retcode = mm->context.sigpage + signal_return_offset +
(idx << 2) + thumb;
} else
#endif
{
/*
* Ensure that the instruction cache sees
* the return code written onto the stack.
*/
flush_icache_range((unsigned long)rc,
(unsigned long)(rc + 3));
retcode = ((unsigned long)rc) + thumb;
}
}
regs->ARM_r0 = ksig->sig;
regs->ARM_sp = (unsigned long)frame;
regs->ARM_lr = retcode;
regs->ARM_pc = handler;
if (fdpic)
regs->ARM_r9 = handler_fdpic_GOT;
regs->ARM_cpsr = cpsr;
return 0;
}
static int
setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
{
struct sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
int err = 0;
if (!frame)
return 1;
/*
* Set uc.uc_flags to a value which sc.trap_no would never have.
*/
err = __put_user(0x5ac3c35a, &frame->uc.uc_flags);
err |= setup_sigframe(frame, regs, set);
if (err == 0)
err = setup_return(regs, ksig, frame->retcode, frame);
return err;
}
static int
setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
{
struct rt_sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
int err = 0;
if (!frame)
return 1;
err |= copy_siginfo_to_user(&frame->info, &ksig->info);
err |= __put_user(0, &frame->sig.uc.uc_flags);
err |= __put_user(NULL, &frame->sig.uc.uc_link);
err |= __save_altstack(&frame->sig.uc.uc_stack, regs->ARM_sp);
err |= setup_sigframe(&frame->sig, regs, set);
if (err == 0)
err = setup_return(regs, ksig, frame->sig.retcode, frame);
if (err == 0) {
/*
* For realtime signals we must also set the second and third
* arguments for the signal handler.
* -- Peter Maydell <pmaydell@chiark.greenend.org.uk> 2000-12-06
*/
regs->ARM_r1 = (unsigned long)&frame->info;
regs->ARM_r2 = (unsigned long)&frame->sig.uc;
}
return err;
}
/*
* OK, we're invoking a handler
*/
static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
sigset_t *oldset = sigmask_to_save();
int ret;
/*
* Perform fixup for the pre-signal frame.
*/
rseq_signal_deliver(ksig, regs);
/*
* Set up the stack frame
*/
if (ksig->ka.sa.sa_flags & SA_SIGINFO)
ret = setup_rt_frame(ksig, oldset, regs);
else
ret = setup_frame(ksig, oldset, regs);
/*
* Check that the resulting registers are actually sane.
*/
ret |= !valid_user_regs(regs);
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 int do_signal(struct pt_regs *regs, int syscall)
{
unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
struct ksignal ksig;
int restart = 0;
/*
* If we were from a system call, check for system call restarting...
*/
if (syscall) {
continue_addr = regs->ARM_pc;
restart_addr = continue_addr - (thumb_mode(regs) ? 2 : 4);
retval = regs->ARM_r0;
/*
* Prepare for system call restart. We do this here so that a
* debugger will see the already changed PSW.
*/
switch (retval) {
case -ERESTART_RESTARTBLOCK:
restart -= 2;
fallthrough;
case -ERESTARTNOHAND:
case -ERESTARTSYS:
case -ERESTARTNOINTR:
restart++;
regs->ARM_r0 = regs->ARM_ORIG_r0;
regs->ARM_pc = restart_addr;
break;
}
}
/*
* Get the signal to deliver. When running under ptrace, at this
* point the debugger may change all our registers ...
*/
/*
* 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 (get_signal(&ksig)) {
/* handler */
if (unlikely(restart) && regs->ARM_pc == restart_addr) {
if (retval == -ERESTARTNOHAND ||
retval == -ERESTART_RESTARTBLOCK
|| (retval == -ERESTARTSYS
&& !(ksig.ka.sa.sa_flags & SA_RESTART))) {
regs->ARM_r0 = -EINTR;
regs->ARM_pc = continue_addr;
}
}
handle_signal(&ksig, regs);
} else {
/* no handler */
restore_saved_sigmask();
if (unlikely(restart) && regs->ARM_pc == restart_addr) {
regs->ARM_pc = continue_addr;
return restart;
}
}
return 0;
}
asmlinkage int
do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
{
/*
* 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 {
if (likely(thread_flags & _TIF_NEED_RESCHED)) {
schedule();
} else {
if (unlikely(!user_mode(regs)))
return 0;
local_irq_enable();
if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
int restart = do_signal(regs, syscall);
if (unlikely(restart)) {
/*
* Restart without handlers.
* Deal with it without leaving
* the kernel space.
*/
return restart;
}
syscall = 0;
} else if (thread_flags & _TIF_UPROBE) {
uprobe_notify_resume(regs);
} else {
tracehook_notify_resume(regs);
rseq_handle_notify_resume(NULL, regs);
}
}
local_irq_disable();
thread_flags = current_thread_info()->flags;
} while (thread_flags & _TIF_WORK_MASK);
return 0;
}
struct page *get_signal_page(void)
{
unsigned long ptr;
unsigned offset;
struct page *page;
void *addr;
page = alloc_pages(GFP_KERNEL, 0);
if (!page)
return NULL;
addr = page_address(page);
/* Poison the entire page */
memset32(addr, __opcode_to_mem_arm(0xe7fddef1),
PAGE_SIZE / sizeof(u32));
/* Give the signal return code some randomness */
offset = 0x200 + (get_random_int() & 0x7fc);
signal_return_offset = offset;
/* Copy signal return handlers into the page */
memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
/* Flush out all instructions in this page */
ptr = (unsigned long)addr;
flush_icache_range(ptr, ptr + PAGE_SIZE);
return page;
}
/* Defer to generic check */
asmlinkage void addr_limit_check_failed(void)
{
#ifdef CONFIG_MMU
addr_limit_user_check();
#endif
}
#ifdef CONFIG_DEBUG_RSEQ
asmlinkage void do_rseq_syscall(struct pt_regs *regs)
{
rseq_syscall(regs);
}
#endif
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