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util: add get_fd_header helper in os_memory_fd

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Prepare for placed mapping.

Reviewed-by: Christian Gmeiner <cgmeiner@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38074>
This commit is contained in:
Yiwei Zhang 2025-10-27 20:18:02 -07:00 • committed by Marge Bot
parent e8f66ef197
commit 743b9a52d9
1 changed files with 18 additions and 13 deletions
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31
src/util/os_memory_fd.c
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@ -66,6 +66,23 @@ get_driver_id_sha1_hash(uint8_t sha1[SHA1_DIGEST_LENGTH], const char *driver_id)
_mesa_sha1_final(&sha1_ctx, sha1);
}
static bool
get_fd_header(int fd, struct memory_header *header, char const *driver_id)
{
lseek(fd, 0, SEEK_SET);
const int bytes_read = read(fd, header, sizeof(*header));
if (bytes_read != sizeof(*header))
return false;
// Check the uuid we put after the sizes in order to verify that the fd
// is a memfd that we created and not some random fd.
uint8_t sha1[SHA1_DIGEST_LENGTH];
get_driver_id_sha1_hash(sha1, driver_id);
assert(SHA1_DIGEST_LENGTH >= UUID_SIZE);
return memcmp(header->uuid, sha1, UUID_SIZE) == 0;
}
/**
* Imports memory from a file descriptor
*/
@ -75,21 +92,9 @@ os_import_memory_fd(int fd, void **ptr, uint64_t *size, char const *driver_id)
void *mapped_ptr;
struct memory_header header;
lseek(fd, 0, SEEK_SET);
int bytes_read = read(fd, &header, sizeof(header));
if(bytes_read != sizeof(header))
if (!get_fd_header(fd, &header, driver_id))
return false;
// Check the uuid we put after the sizes in order to verify that the fd
// is a memfd that we created and not some random fd.
uint8_t sha1[SHA1_DIGEST_LENGTH];
get_driver_id_sha1_hash(sha1, driver_id);
assert(SHA1_DIGEST_LENGTH >= UUID_SIZE);
if (memcmp(header.uuid, sha1, UUID_SIZE)) {
return false;
}
mapped_ptr = mmap(NULL, header.size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (mapped_ptr == MAP_FAILED) {
return false;