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wip: call previous handler on faults outside guard page

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This commit is contained in:
Matthew LeVan 2024-01-31 15:43:58 -05:00
parent c07a280ec4
commit 96b22426e2
1 changed files with 24 additions and 20 deletions
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44
rust/ares_guard/c-src/guard.c
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@ -14,8 +14,8 @@ static uint64_t *guard_p = 0;
static uint64_t **stack = 0; static uint64_t **stack = 0;
static uint64_t **alloc = 0; static uint64_t **alloc = 0;
static jmp_buf env_buffer; static jmp_buf env_buffer;
volatile sig_atomic_t err = guard_sound; volatile sig_atomic_t err = guard_sound;
static void (*prev_sigsegv_handler)(int, siginfo_t *, void *);
// Center the guard page. // Center the guard page.
@ -65,25 +65,28 @@ _focus_guard()
return guard_sound; return guard_sound;
} }
static guard_err
_slash_guard(void *addr)
{
if (addr >= (void *)guard_p && addr < (void *)guard_p + GD_PAGESIZE) {
fprintf(stderr, "guard: slash in guard\r\n");
return _focus_guard();
}
fprintf(stderr, "guard: slash outside guard\r\n");
return guard_weird;
}
static void static void
_signal_handler(int sig, siginfo_t *si, void *unused) _signal_handler(int sig, siginfo_t *si, void *unused)
{ {
switch (sig) { switch (sig) {
case SIGSEGV: case SIGSEGV:
fprintf(stderr, "guard: sigsegv at %p\r\n", si->si_addr); if (si->si_addr >= (void *)guard_p &&
err = _slash_guard(si->si_addr); si->si_addr < (void *)guard_p + GD_PAGESIZE)
{
fprintf(stderr, "guard: fault in guard\r\n");
err = _focus_guard();
break;
}
else {
fprintf(stderr, "guard: fault outside guard\r\n");
if (NULL != prev_sigsegv_handler) {
prev_sigsegv_handler(sig, si, unused);
break;
}
else {
err = guard_weird;
}
}
break; break;
case SIGINT: case SIGINT:
fprintf(stderr, "guard: sigint\r\n"); fprintf(stderr, "guard: sigint\r\n");
@ -95,7 +98,7 @@ _signal_handler(int sig, siginfo_t *si, void *unused)
if (err != guard_sound) { if (err != guard_sound) {
fprintf(stderr, "guard: error %d; long jumping\r\n", err); fprintf(stderr, "guard: error %d; long jumping\r\n", err);
longjmp(env_buffer, 1); siglongjmp(env_buffer, 1);
} }
} }
@ -103,16 +106,17 @@ static guard_err
_register_handler() _register_handler()
{ {
struct sigaction sa; struct sigaction sa;
struct sigaction prev_sa;
sa.sa_flags = SA_SIGINFO; sa.sa_flags = SA_SIGINFO;
sa.sa_sigaction = _signal_handler; sa.sa_sigaction = _signal_handler;
sigemptyset(&sa.sa_mask); sigemptyset(&sa.sa_mask);
sigaddset(&(sa.sa_mask), SIGSEGV);
// if (sigaction(SIGSEGV, &sa, 0) || sigaction(SIGINT, &sa, 0)) { if (sigaction(SIGSEGV, &sa, &prev_sa)) {
if (sigaction(SIGSEGV, &sa, 0)) {
fprintf(stderr, "guard: failed to register handler\r\n"); fprintf(stderr, "guard: failed to register handler\r\n");
return guard_weird; return guard_weird;
} }
prev_sigsegv_handler = prev_sa.sa_sigaction;
// fprintf(stderr, "guard: registered handler\r\n"); // fprintf(stderr, "guard: registered handler\r\n");
return guard_sound; return guard_sound;
@ -148,7 +152,7 @@ guard(
} }
void *result; void *result;
if (setjmp(env_buffer) == 0) { if (sigsetjmp(env_buffer, 1) == 0) {
result = f(user_data); result = f(user_data);
} }
else { else {