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Subject[PATCH v2 5/6] arm64: consolidate signal injection on emulation errors
Date
The code for injecting a signal into userland if a trapped instruction
fails emulation due to a _userland_ error (like an illegal address)
will be used more often with the next patch.
Factor out the core functionality into a separate function and use
that both for the existing trap handler and for the deprecated
instructions emulation.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
arch/arm64/include/asm/traps.h | 2 ++
arch/arm64/kernel/armv8_deprecated.c | 23 +------------
arch/arm64/kernel/traps.c | 63 ++++++++++++++++++++++++++++--------
3 files changed, 53 insertions(+), 35 deletions(-)

diff --git a/arch/arm64/include/asm/traps.h b/arch/arm64/include/asm/traps.h
index 0cc2f29..816b293 100644
--- a/arch/arm64/include/asm/traps.h
+++ b/arch/arm64/include/asm/traps.h
@@ -34,6 +34,8 @@ struct undef_hook {
void register_undef_hook(struct undef_hook *hook);
void unregister_undef_hook(struct undef_hook *hook);

+void set_segfault(struct pt_regs *regs, unsigned long addr);
+
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static inline int __in_irqentry_text(unsigned long ptr)
{
diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
index c37202c..b619274 100644
--- a/arch/arm64/kernel/armv8_deprecated.c
+++ b/arch/arm64/kernel/armv8_deprecated.c
@@ -316,28 +316,6 @@ static void __init register_insn_emulation_sysctl(struct ctl_table *table)
*/
#define TYPE_SWPB (1 << 22)

-/*
- * Set up process info to signal segmentation fault - called on access error.
- */
-static void set_segfault(struct pt_regs *regs, unsigned long addr)
-{
- siginfo_t info;
-
- down_read(&current->mm->mmap_sem);
- if (find_vma(current->mm, addr) == NULL)
- info.si_code = SEGV_MAPERR;
- else
- info.si_code = SEGV_ACCERR;
- up_read(&current->mm->mmap_sem);
-
- info.si_signo = SIGSEGV;
- info.si_errno = 0;
- info.si_addr = (void *) instruction_pointer(regs);
-
- pr_debug("SWP{B} emulation: access caused memory abort!\n");
- arm64_notify_die("Illegal memory access", regs, &info, 0);
-}
-
static int emulate_swpX(unsigned int address, unsigned int *data,
unsigned int type)
{
@@ -430,6 +408,7 @@ ret:
return 0;

fault:
+ pr_debug("SWP{B} emulation: access caused memory abort!\n");
set_segfault(regs, address);

return 0;
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 2a43012..613b391 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -373,30 +373,67 @@ exit:
return fn ? fn(regs, instr) : 1;
}

-asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
+static void force_signal_inject(int signal, int code, struct pt_regs *regs,
+ unsigned long address)
{
siginfo_t info;
void __user *pc = (void __user *)instruction_pointer(regs);
+ const char *desc;

- /* check for AArch32 breakpoint instructions */
- if (!aarch32_break_handler(regs))
- return;
-
- if (call_undef_hook(regs) == 0)
- return;
+ switch (signal) {
+ case SIGILL:
+ desc = "undefined instruction";
+ break;
+ case SIGSEGV:
+ desc = "illegal memory access";
+ break;
+ default:
+ desc = "bad mode";
+ break;
+ }

- if (unhandled_signal(current, SIGILL) && show_unhandled_signals_ratelimited()) {
- pr_info("%s[%d]: undefined instruction: pc=%p\n",
- current->comm, task_pid_nr(current), pc);
+ if (unhandled_signal(current, signal) &&
+ show_unhandled_signals_ratelimited()) {
+ pr_info("%s[%d]: %s: pc=%p\n",
+ current->comm, task_pid_nr(current), desc, pc);
dump_instr(KERN_INFO, regs);
}

- info.si_signo = SIGILL;
+ info.si_signo = signal;
info.si_errno = 0;
- info.si_code = ILL_ILLOPC;
+ info.si_code = code;
info.si_addr = pc;

- arm64_notify_die("Oops - undefined instruction", regs, &info, 0);
+ arm64_notify_die(desc, regs, &info, 0);
+}
+
+/*
+ * Set up process info to signal segmentation fault - called on access error.
+ */
+void set_segfault(struct pt_regs *regs, unsigned long addr)
+{
+ int code;
+
+ down_read(&current->mm->mmap_sem);
+ if (find_vma(current->mm, addr) == NULL)
+ code = SEGV_MAPERR;
+ else
+ code = SEGV_ACCERR;
+ up_read(&current->mm->mmap_sem);
+
+ force_signal_inject(SIGSEGV, code, regs, addr);
+}
+
+asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
+{
+ /* check for AArch32 breakpoint instructions */
+ if (!aarch32_break_handler(regs))
+ return;
+
+ if (call_undef_hook(regs) == 0)
+ return;
+
+ force_signal_inject(SIGILL, ILL_ILLOPC, regs, 0);
}

long compat_arm_syscall(struct pt_regs *regs);
--
2.9.0
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