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Improve crash handler on XNU

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This avoids an issue where a crash signal could cause the MacOS process
to freeze and consume all CPU rather than dying as it rightfully should
This commit is contained in:
Justine Tunney 2024-05-26 18:41:15 -07:00
parent 0a51241f7a
commit 086d7006da
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
5 changed files with 53 additions and 9 deletions
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18
libc/integral/c.inc
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@ -66,9 +66,10 @@
#endif
#if (!defined(__llvm__) && !__has_builtin(__builtin_assume))
#define __builtin_assume(x) \
do { \
if (!(x)) __builtin_unreachable(); \
#define __builtin_assume(x) \
do { \
if (!(x)) \
__builtin_unreachable(); \
} while (0)
#endif
@ -598,10 +599,21 @@ typedef struct {
#ifdef __x86_64__
#define DebugBreak() __asm__("int3")
#elif defined(__aarch64__)
#define DebugBreak() __asm__("brk\t#0x666")
#else
#define DebugBreak() __builtin_trap()
#endif
#ifdef __aarch64__
/* raise sigill (not sigtrap) like x86 does */
#define __builtin_trap() \
do { \
__asm__("udf\t#0x666"); \
__builtin_unreachable(); \
} while (0)
#endif
#endif /* _COSMO_SOURCE */
#define __veil(CONSTRAINT, EXPRESSION) \

17
libc/log/oncrash_amd64.c
View file

@ -192,8 +192,6 @@ void ShowCrashReportHook(int, int, int, struct siginfo *, ucontext_t *);
static relegated void ShowCrashReport(int err, int sig, struct siginfo *si,
ucontext_t *ctx) {
if (sig != SIGTRAP && sig != SIGQUIT)
sigaddset(&ctx->uc_sigmask, sig);
#pragma GCC push_options
#pragma GCC diagnostic ignored "-Walloca-larger-than="
long size = __get_safe_size(8192, 4096);
@ -276,6 +274,21 @@ relegated void __oncrash(int sig, struct siginfo *si, void *arg) {
int err = errno;
__restore_tty();
ShowCrashReport(err, sig, si, arg);
// ensure execution doesn't resume for anything but SIGTRAP / SIGQUIT
if (arg && sig != SIGTRAP && sig != SIGQUIT) {
if (!IsXnu()) {
sigaddset(&((ucontext_t *)arg)->uc_sigmask, sig);
} else {
sigdelset(&((ucontext_t *)arg)->uc_sigmask, sig);
struct sigaction sa;
sigemptyset(&sa.sa_mask);
sa.sa_handler = SIG_DFL;
sa.sa_flags = 0;
sigaction(sig, &sa, 0);
}
}
SpinUnlock(&lock);
ALLOW_CANCELATION;
}

23
libc/log/oncrash_arm64.c
View file

@ -191,8 +191,6 @@ static relegated char *GetSymbolName(struct SymbolTable *st, int symbol) {
static relegated void __oncrash_impl(int sig, struct siginfo *si,
ucontext_t *ctx) {
if (sig != SIGTRAP && sig != SIGQUIT)
sigaddset(&ctx->uc_sigmask, sig);
#pragma GCC push_options
#pragma GCC diagnostic ignored "-Walloca-larger-than="
long size = __get_safe_size(10000, 4096);
@ -396,6 +394,27 @@ relegated void __oncrash(int sig, struct siginfo *si, void *arg) {
BLOCK_CANCELATION;
SpinLock(&lock);
__oncrash_impl(sig, si, arg);
// unlike amd64, the instruction pointer on arm64 isn't advanced past
// the debugger breakpoint instruction automatically. we need this so
// execution can resume after __builtin_trap().
if (arg && sig == SIGTRAP)
((ucontext_t *)arg)->uc_mcontext.PC += 4;
// ensure execution doesn't resume for anything but SIGTRAP / SIGQUIT
if (arg && sig != SIGTRAP && sig != SIGQUIT) {
if (!IsXnu()) {
sigaddset(&((ucontext_t *)arg)->uc_sigmask, sig);
} else {
sigdelset(&((ucontext_t *)arg)->uc_sigmask, sig);
struct sigaction sa;
sigemptyset(&sa.sa_mask);
sa.sa_handler = SIG_DFL;
sa.sa_flags = 0;
sigaction(sig, &sa, 0);
}
}
SpinUnlock(&lock);
ALLOW_CANCELATION;
}

2
test/libc/calls/signal_test.c
View file

@ -53,7 +53,7 @@ void OnSigTrap(int sig, struct siginfo *si, void *ctx) {
void TrapBench(int n) {
for (int i = 0; i < n; ++i) {
__builtin_trap();
DebugBreak();
}
}

2
third_party/chibicc/test/BUILD.mk vendored
View file

@ -20,7 +20,7 @@ THIRD_PARTY_CHIBICC_TEST_FILES := $(wildcard third_party/chibicc/test/*)
THIRD_PARTY_CHIBICC_TEST_SRCS = $(filter %.c,$(THIRD_PARTY_CHIBICC_TEST_FILES))
THIRD_PARTY_CHIBICC_TEST_SRCS_TEST = $(filter %_test.c,$(THIRD_PARTY_CHIBICC_TEST_SRCS))
THIRD_PARTY_CHIBICC_TEST_HDRS = $(filter %.h,$(THIRD_PARTY_CHIBICC_TEST_FILES))
THIRD_PARTY_CHIBICC_TEST_TESTS = $(THIRD_PARTY_CHIBICC_TEST_COMS:%=%.ok)
# THIRD_PARTY_CHIBICC_TEST_TESTS = $(THIRD_PARTY_CHIBICC_TEST_COMS:%=%.ok)
THIRD_PARTY_CHIBICC_TEST_COMS = \
$(THIRD_PARTY_CHIBICC_TEST_SRCS_TEST:%_test.c=o/$(MODE)/%_test)