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Implement __zipos_dup (#972)

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* Implement __zipos_dup

Makes ZiposHandle reference-counted by an `rc` field in a union with its
freelist `next` pointer. The functions `__zipos_free` and `__zipos_keep`
function as incref/decref for it. Adds `__zipos_postdup` to fix metadata
on file descriptors after dup-like operations, and adds zipos support to
`sys_dup_nt` + `sys_close_nt`.

* Remove noop __zipos_postdup

rc is never a zipos file because it is always a previously unused file
descriptor. fd is never a zipos file because that case has been handled
above by __zipos_fcntl.
This commit is contained in:
Jōshin 2023-12-01 03:08:30 -05:00 • committed by GitHub
parent 6556dd2673
commit d1a745c17c
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11 changed files with 138 additions and 39 deletions
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36
libc/runtime/zipos-open.c
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@ -78,7 +78,20 @@ static void *__zipos_mmap_space(size_t mapsize) {
return start + offset;
}
struct ZiposHandle *__zipos_keep(struct ZiposHandle *h) {
atomic_fetch_add_explicit(&h->refs, 1, memory_order_relaxed);
return h;
}
static bool __zipos_drop(struct ZiposHandle *h) {
int refs = atomic_load_explicit(&h->refs, memory_order_acquire);
return -1 == refs || -1 == atomic_fetch_sub(&h->refs, 1);
}
void __zipos_free(struct ZiposHandle *h) {
if (!__zipos_drop(h)) {
return;
}
if (IsAsan()) {
__asan_poison((char *)h + sizeof(struct ZiposHandle),
h->mapsize - sizeof(struct ZiposHandle), kAsanHeapFree);
@ -100,7 +113,7 @@ StartOver:
while ((h = *ph)) {
if (h->mapsize >= mapsize) {
if (!_cmpxchg(ph, h, h->next)) goto StartOver;
h->next = 0;
atomic_init(&h->refs, 0);
break;
}
ph = &h->next;
@ -209,6 +222,27 @@ static int __zipos_load(struct Zipos *zipos, size_t cf, int flags,
return -1;
}
void __zipos_postdup(int oldfd, int newfd) {
if (oldfd == newfd) {
return;
}
if (__isfdkind(newfd, kFdZip)) {
__zipos_free((struct ZiposHandle *)(intptr_t)g_fds.p[newfd].handle);
if (!__isfdkind(oldfd, kFdZip)) {
__fds_lock();
bzero(g_fds.p + newfd, sizeof(*g_fds.p));
__fds_unlock();
}
}
if (__isfdkind(oldfd, kFdZip)) {
__zipos_keep((struct ZiposHandle *)(intptr_t)g_fds.p[oldfd].handle);
__fds_lock();
__ensurefds_unlocked(newfd);
g_fds.p[newfd] = g_fds.p[oldfd];
__fds_unlock();
}
}
/**
* Loads compressed file from αcτµαlly pδrταblε εxεcµταblε object store.
*