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Merge pull request #84532 from al45tair/eng/PR-161391330-6.2.1

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[Linux][Backtracing] Don't try to use `process_vm_readv()`.
This commit is contained in:
Mishal Shah
2025-09-26 13:20:24 -07:00
committed by GitHub
parent 7e49c05e8c 9739a2f5d4
commit 64d688f85e
1 changed files with 17 additions and 30 deletions
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47
stdlib/public/runtime/CrashHandlerLinux.cpp
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@@ -655,7 +655,6 @@ wait_paused(uint32_t expected, const struct timespec *timeout)
char memserver_stack[4096] __attribute__((aligned(SWIFT_PAGE_SIZE)));
char memserver_buffer[4096];
int memserver_fd;
bool memserver_has_ptrace;
sigjmp_buf memserver_fault_buf;
pid_t memserver_pid;
@@ -712,21 +711,18 @@ memserver_fault(int sig) {
ssize_t __attribute__((noinline))
memserver_read(void *to, const void *from, size_t len) {
if (memserver_has_ptrace) {
// This won't run for older Android APIs anyway, but it can't be compiled
// either, as process_vm_readv() isn't available.
#if !(defined(__ANDROID_API__) && __ANDROID_API__ < 23)
struct iovec local = { to, len };
struct iovec remote = { const_cast<void *>(from), len };
return process_vm_readv(memserver_pid, &local, 1, &remote, 1, 0);
#endif
/* Earlier versions of this code tried to use process_vm_readv() if they
detected that CAP_SYS_PTRACE was enabled. This is theoretically
slightly safer than using signals and memcpy(), but in practice it
turns out that some kernels don't support process_vm_readv() even
when CAP_SYS_PTRACE is enabled.
It seems simpler just to use the signal handlers instead. */
if (!sigsetjmp(memserver_fault_buf, 1)) {
memcpy(to, from, len);
return len;
} else {
if (!sigsetjmp(memserver_fault_buf, 1)) {
memcpy(to, from, len);
return len;
} else {
return -1;
}
return -1;
}
}
@@ -739,21 +735,12 @@ memserver_entry(void *dummy __attribute__((unused))) {
prctl(PR_SET_NAME, "[backtrace]");
#endif
// process_vm_readv() is not available for older Android APIs.
#if defined(__ANDROID_API__) && __ANDROID_API__ < 23
memserver_has_ptrace = false;
#else
memserver_has_ptrace = !!prctl(PR_CAPBSET_READ, CAP_SYS_PTRACE);
#endif
if (!memserver_has_ptrace) {
struct sigaction sa;
sigfillset(&sa.sa_mask);
sa.sa_handler = memserver_fault;
sa.sa_flags = SA_NODEFER;
sigaction(SIGSEGV, &sa, NULL);
sigaction(SIGBUS, &sa, NULL);
}
struct sigaction sa;
sigfillset(&sa.sa_mask);
sa.sa_handler = memserver_fault;
sa.sa_flags = SA_NODEFER;
sigaction(SIGSEGV, &sa, NULL);
sigaction(SIGBUS, &sa, NULL);
for (;;) {
struct memserver_req req;