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Save and restore errno when calling process_madvise

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Slobodan Predolac 2025-08-13 17:59:36 -07:00 • committed by guangli-dai
parent 868a3b3fd6
commit 7c1cecc0d2
1 changed files with 19 additions and 1 deletions
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20
src/pages.c
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@ -622,6 +622,7 @@ pages_dodump(void *addr, size_t size) {
# include <sys/mman.h>
# include <sys/syscall.h>
static atomic_i_t process_madvise_pidfd = ATOMIC_INIT(-1);
static atomic_b_t process_madvise_gate = ATOMIC_INIT(true);
static bool
init_process_madvise(void) {
@ -646,9 +647,12 @@ init_process_madvise(void) {
static bool
pages_purge_process_madvise_impl(
void *vec, size_t vec_len, size_t total_bytes) {
if (!atomic_load_b(&process_madvise_gate, ATOMIC_RELAXED)) {
return true;
}
int pid_fd = atomic_load_i(&process_madvise_pidfd, ATOMIC_RELAXED);
while (pid_fd == -1) {
int newfd = syscall(SYS_pidfd_open, getpid(), 0);
int newfd = (int) syscall(SYS_pidfd_open, getpid(), 0);
if (newfd == -1) {
return true;
}
@ -663,8 +667,22 @@ pages_purge_process_madvise_impl(
pid_fd = newfd;
}
}
/*
* TODO: remove this save/restore of errno after supporting errno
* preservation for free() call properly.
*/
int saved_errno = get_errno();
size_t purged_bytes = (size_t)syscall(JE_SYS_PROCESS_MADVISE_NR, pid_fd,
(struct iovec *)vec, vec_len, MADV_DONTNEED, 0);
if (purged_bytes == (size_t) -1) {
if (errno == EPERM || errno == EINVAL || errno == ENOSYS) {
/* Process madvise not supported the way we need it. */
atomic_store_b(&process_madvise_gate, false,
ATOMIC_RELAXED);
}
set_errno(saved_errno);
}
return purged_bytes != total_bytes;
}