mirrors/cosmopolitan
1
0
Fork 0
mirror of https://github.com/jart/cosmopolitan.git synced 2025-05-22 21:32:31 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

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
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
24 changed files with 590 additions and 274 deletions
Download patch file Download diff file Expand all files Collapse all files

42
libc/runtime/isstackoverflow.c
View file

@ -19,45 +19,19 @@
#include "libc/calls/struct/siginfo.h"
#include "libc/calls/struct/ucontext.internal.h"
#include "libc/calls/ucontext.h"
#include "libc/intrin/kprintf.h"
#include "libc/macros.internal.h"
#include "libc/runtime/runtime.h"
#include "libc/sysv/consts/auxv.h"
#include "libc/sysv/consts/sig.h"
#include "libc/thread/posixthread.internal.h"
#include "libc/thread/thread.h"
#include "libc/thread/tls.h"
/**
* Returns true if signal is likely a stack overflow.
* Returns true if signal is most likely a stack overflow.
*/
char __is_stack_overflow(siginfo_t *si, void *ucontext) {
// check if signal has the information we need
ucontext_t *uc = ucontext;
if (!si) return false;
if (!uc) return false;
char __is_stack_overflow(siginfo_t *si, void *arg) {
ucontext_t *uc = arg;
if (!si || !uc) return false;
if (si->si_signo != SIGSEGV && si->si_signo != SIGBUS) return false;
// with threads we know exactly where the guard page is
int pagesz = getauxval(AT_PAGESZ);
uintptr_t addr = (uintptr_t)si->si_addr;
struct PosixThread *pt = _pthread_self();
if (pt->attr.__stacksize) {
uintptr_t stack = (uintptr_t)pt->attr.__stackaddr;
uintptr_t guard = pt->attr.__guardsize;
uintptr_t bot, top;
if (guard) {
bot = stack;
top = bot + guard;
} else {
bot = stack - pagesz;
top = stack;
}
return addr >= bot && addr < top;
}
// it's easy to guess with the main stack
// even though it's hard to know its exact boundaries
uintptr_t sp = uc->uc_mcontext.SP;
return addr <= sp && addr >= sp - pagesz;
intptr_t sp = uc->uc_mcontext.SP;
intptr_t fp = (intptr_t)si->si_addr;
return ABS(fp - sp) < getauxval(AT_PAGESZ);
}