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authorWill Deacon <will@kernel.org>2020-06-22 13:09:49 +0100
committerWill Deacon <will@kernel.org>2020-06-23 14:56:24 +0100
commit8e411be6aad1387f40d60cb2c11d3260222c590b (patch)
treee647890d66331188c0b6fa42d6dfcf5737fc667c
parenta39060b009ca0b5b5fe0c0dab85ed437531aab52 (diff)
arm64: compat: Always use sigpage for sigreturn trampoline
The 32-bit sigreturn trampoline in the compat sigpage matches the binary representation of the arch/arm/ sigpage exactly. This is important for debuggers (e.g. GDB) and unwinders (e.g. libunwind) since they rely on matching the instruction sequence in order to identify that they are unwinding through a signal. The same cannot be said for the sigreturn trampoline in the compat vDSO, which defeats the unwinder heuristics and instead attempts to use unwind directives for the unwinding. This is in contrast to arch/arm/, which never uses the vDSO for sigreturn. Ensure compatibility with arch/arm/ and existing unwinders by always using the sigpage for the sigreturn trampoline, regardless of the presence of the compat vDSO. Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Will Deacon <will@kernel.org>
-rw-r--r--arch/arm64/kernel/signal32.c25
1 files changed, 0 insertions, 25 deletions
diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c
index 0aa0b33744de..2f507f565c48 100644
--- a/arch/arm64/kernel/signal32.c
+++ b/arch/arm64/kernel/signal32.c
@@ -342,30 +342,6 @@ static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
retcode = ptr_to_compat(ka->sa.sa_restorer);
} else {
/* Set up sigreturn pointer */
-#ifdef CONFIG_COMPAT_VDSO
- void *vdso_base = current->mm->context.vdso;
- void *vdso_trampoline;
-
- if (ka->sa.sa_flags & SA_SIGINFO) {
- if (thumb) {
- vdso_trampoline = VDSO_SYMBOL(vdso_base,
- compat_rt_sigreturn_thumb);
- } else {
- vdso_trampoline = VDSO_SYMBOL(vdso_base,
- compat_rt_sigreturn_arm);
- }
- } else {
- if (thumb) {
- vdso_trampoline = VDSO_SYMBOL(vdso_base,
- compat_sigreturn_thumb);
- } else {
- vdso_trampoline = VDSO_SYMBOL(vdso_base,
- compat_sigreturn_arm);
- }
- }
-
- retcode = ptr_to_compat(vdso_trampoline) + thumb;
-#else
unsigned int idx = thumb << 1;
if (ka->sa.sa_flags & SA_SIGINFO)
@@ -373,7 +349,6 @@ static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
retcode = (unsigned long)current->mm->context.sigpage +
(idx << 2) + thumb;
-#endif
}
regs->regs[0] = usig;