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Improve stack overflow recovery

Browse source 
It's now possible to use sigaltstack() to recover from stack overflows
on Windows. Several bugs in sigaltstack() have been fixed, for all our
supported platforms. There's a newer better example showing how to use
this, along with three independent unit tests just to further showcase
the various techniques.
This commit is contained in:
Justine Tunney 2023-10-04 07:07:43 -07:00
parent 1694edf85c
commit 4631d34d0d
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GPG key ID: BE714B4575D6E328
24 changed files with 590 additions and 274 deletions
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63
libc/calls/sigaltstack.c
View file

@ -57,51 +57,36 @@ static void sigaltstack2linux(struct sigaltstack *linux,
static textwindows int sigaltstack_cosmo(const struct sigaltstack *neu,
struct sigaltstack *old) {
struct CosmoTib *tib;
tib = __get_tls();
struct CosmoTib *tib = __get_tls();
char *bp = __builtin_frame_address(0);
if (old) {
old->ss_sp = tib->tib_sigstack_addr;
old->ss_size = tib->tib_sigstack_size;
old->ss_flags = tib->tib_sigstack_flags;
old->ss_flags = tib->tib_sigstack_flags & ~SS_ONSTACK;
}
if (neu) {
tib->tib_sigstack_addr = (char *)ROUNDUP((uintptr_t)neu->ss_sp, 16);
tib->tib_sigstack_size = ROUNDDOWN(neu->ss_size, 16);
tib->tib_sigstack_flags &= SS_ONSTACK;
tib->tib_sigstack_flags |= neu->ss_flags & SS_DISABLE;
tib->tib_sigstack_flags = neu->ss_flags & SS_DISABLE;
}
if (tib->tib_sigstack_addr <= bp &&
bp <= tib->tib_sigstack_addr + tib->tib_sigstack_size) {
if (old) old->ss_flags |= SS_ONSTACK;
tib->tib_sigstack_flags = SS_ONSTACK; // can't disable if on it
} else if (!tib->tib_sigstack_size) {
if (old) old->ss_flags = SS_DISABLE;
tib->tib_sigstack_flags = SS_DISABLE;
}
return 0;
}
static int sigaltstack_sysv(const struct sigaltstack *neu,
struct sigaltstack *old) {
void *b;
const void *a;
struct sigaltstack_bsd bsd;
if (IsLinux()) {
a = neu;
b = old;
} else {
if (neu) {
sigaltstack2bsd(&bsd, neu);
a = &bsd;
} else {
a = 0;
}
if (old) {
b = &bsd;
} else {
b = 0;
}
}
if (!sys_sigaltstack(a, b)) {
if (IsBsd() && old) {
sigaltstack2linux(old, &bsd);
}
return 0;
} else {
return -1;
}
static int sigaltstack_bsd(const struct sigaltstack *neu,
struct sigaltstack *old) {
struct sigaltstack_bsd oldbsd, neubsd, *neup = 0;
if (neu) sigaltstack2bsd(&neubsd, neu), neup = &neubsd;
if (sys_sigaltstack(neup, &oldbsd) == -1) return -1;
if (old) sigaltstack2linux(old, &oldbsd);
return 0;
}
/**
@ -131,13 +116,13 @@ int sigaltstack(const struct sigaltstack *neu, struct sigaltstack *old) {
rc = efault();
} else if (neu && ((neu->ss_size >> 32) || //
(neu->ss_flags & ~(SS_ONSTACK | SS_DISABLE)))) {
return einval();
rc = einval();
} else if (neu && neu->ss_size < __get_minsigstksz()) {
rc = enomem();
} else if (IsLinux() || IsBsd()) {
if (!(rc = sigaltstack_sysv(neu, old))) {
sigaltstack_cosmo(neu, old);
}
} else if (IsLinux()) {
rc = sys_sigaltstack(neu, old);
} else if (IsBsd()) {
rc = sigaltstack_bsd(neu, old);
} else {
rc = sigaltstack_cosmo(neu, old);
}