Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Fix: make shmoverride.so initfirst #148

Merged
merged 1 commit into from
Oct 19, 2024
Merged

Fix: make shmoverride.so initfirst #148

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
22 changes: 20 additions & 2 deletions shmoverride/shmoverride.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,8 @@ static int (*real_munmap) (void *shmaddr, size_t len);
static int (*real_fstat64) (VER_ARG int fd, struct stat64 *buf);
static int (*real_fstat)(VER_ARG int fd, struct stat *buf);

static int try_init(void);

static struct stat global_buf;
static int gntdev_fd = -1;

Expand All @@ -84,7 +86,7 @@ static int xc_hnd;
static xengnttab_handle *xgt;
static char __shmid_filename[SHMID_FILENAME_LEN];
static char *shmid_filename = NULL;
static int idfd = -1, display = -1;
static int idfd = -1, display = -1, init_called = 0;

static uint8_t *mmap_mfns(struct shm_args_hdr *shm_args) {
uint8_t *map;
Expand Down Expand Up @@ -151,6 +153,8 @@ ASM_DEF(void *, mmap,
real_fstat = FSTAT;
}

try_init();

#if defined MAP_ANON && defined MAP_ANONYMOUS && (MAP_ANONYMOUS) != (MAP_ANON)
# error header bug (def mismatch)
#endif
Expand Down Expand Up @@ -217,6 +221,9 @@ ASM_DEF(int, munmap, void *addr, size_t len)
{
if (len > SIZE_MAX - XC_PAGE_SIZE)
abort();

try_init();

const uintptr_t addr_int = (uintptr_t)addr;
const uintptr_t rounded_addr = addr_int & ~(uintptr_t)(XC_PAGE_SIZE - 1);
return real_munmap((void *)rounded_addr, len + (addr_int - rounded_addr));
Expand Down Expand Up @@ -438,6 +445,7 @@ static int assign_off(off_t *off) {

#define STAT(id) \
ASM_DEF(int, f ## id, int filedes, struct id *buf) { \
try_init(); \
int res = real_f ## id(VER filedes, buf); \
if (res || \
!S_ISCHR(buf->st_mode) || \
Expand All @@ -454,6 +462,7 @@ STAT(stat64)
#ifdef _STAT_VER
#define STAT(id) \
ASM_DEF(int, __fx ## id, int ver, int filedes, struct id *buf) { \
try_init(); \
if (ver != _STAT_VER) { \
fprintf(stderr, \
"Wrong _STAT_VER: got %d, expected %d, libc has incompatibly changed\n", \
Expand All @@ -467,8 +476,13 @@ STAT(stat64)
#undef STAT
#endif

int __attribute__ ((constructor)) initfunc(void)
static int try_init(void)
{
// Ideally it is being called in constructor, if something is calling this before
// constructor - we're assuming it is not multi-threaded code.
if (__builtin_expect(init_called, 1)) return 0;
init_called = 1;

unsetenv("LD_PRELOAD");
fprintf(stderr, "shmoverride constructor running\n");
dlerror();
Expand Down Expand Up @@ -581,6 +595,10 @@ int __attribute__ ((constructor)) initfunc(void)
shm_args = NULL;
return 0;
}
int __attribute__ ((constructor)) initfunc(void)
{
return try_init();
}

int __attribute__ ((destructor)) descfunc(void)
{
Expand Down