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osutil: get argv[0] on Linux more reliably

Browse Source 
Summary:
`environ` might be changed by `setenv` and would be wrong to locate `argv[0]`.
Linux >= 3.5 provides the `argv[0]` pointer in `/proc/self/stat`. Let's use
that instead.

Reviewed By: ikostia

Differential Revision: D12834877

fbshipit-source-id: d76804e8f4113cdf3adb0cceed817f7e93d1b6de
This commit is contained in:
Jun Wu 2018-10-30 14:08:24 -07:00 committed by Facebook Github Bot
parent 8940a7c464
commit 467daedf2e
1 changed files with 37 additions and 35 deletions
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72
mercurial/cext/osutil.c
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@ -751,30 +751,46 @@ bail:
#ifdef SETPROCNAME_USE_ARGVREWRITE
/* Find the original argc and argv. Return 0 on success. */
static int getargcargv(int* argc, char*** argv) {
/* Find the start of argv buffer (argv[0]) and its size */
static void getarg0size(char** argstart, size_t* argsize) {
#ifdef __APPLE__
/* osx: crt_externs keeps a copy of argc, argv */
*argv = *_NSGetArgv();
*argc = *_NSGetArgc();
return 0;
int argc = *_NSGetArgc();
char** argv = *_NSGetArgv();
char *argvend, *argvstart;
size_t argvsize = 0;
int i;
argvend = argvstart = argv[0];
for (i = 0; i < argc; ++i) {
if (argv[i] > argvend || argv[i] < argvstart)
break; /* not continuous */
size_t len = strlen(argv[i]);
argvend = argv[i] + len + 1 /* '\0' */;
}
if (argvend > argvstart) /* sanity check */
argvsize = argvend - argvstart;
*argstart = argvstart;
*argsize = argvsize;
#else
/* linux: read backwards from environ and get argv */
extern char** environ;
char buf[1024];
FILE* fp = fopen("/proc/self/cmdline", "rb");
/* On Linux >= 3.5, the 48 and 49 column of "/proc/self/stat" is the argv
start and end pointers. See "man 5 proc". */
FILE* fp;
unsigned long start = 0, end = 0;
fp = fopen("/proc/self/stat", "r");
if (fp) {
int nullcount = 0;
int ch = 0;
while ((ch = fgetc(fp)) != EOF) {
nullcount += (ch == 0);
/* Note: if "comm" name has rare chars like spaces, the fscanf will fail */
if (fscanf(
fp,
"%*d %*s %*c %*d %*d %*d %*d %*d %*u %*lu %*lu %*lu %*lu %*lu %*lu %*ld"
" %*ld %*ld %*ld %*ld %*ld %*llu %*lu %*ld %*lu %*lu %*lu %*lu %*lu %*lu"
" %*lu %*lu %*lu %*lu %*lu %*lu %*lu %*d %*d %*u %*u %*llu %*lu %*ld %*lu"
" %*lu %*lu %lu %lu",
&start,
&end) == 2) {
*argstart = (char*)start;
*argsize = end - start;
}
*argc = nullcount;
*argv = environ - nullcount - 1;
fclose(fp);
return 0;
} else {
return -1;
}
#endif
}
@ -793,23 +809,9 @@ static PyObject* setprocname(PyObject* self, PyObject* args) {
{
static char* argvstart = NULL;
static size_t argvsize = 0;
if (argvstart == NULL) {
int argc = 0, i;
char** argv = NULL;
char* argvend;
if (getargcargv(&argc, &argv) == 0) {
/* Check the memory we can use. Typically, argv[i] and
* argv[i + 1] are continuous. */
argvend = argvstart = argv[0];
for (i = 0; i < argc; ++i) {
if (argv[i] > argvend || argv[i] < argvstart)
break; /* not continuous */
size_t len = strlen(argv[i]);
argvend = argv[i] + len + 1 /* '\0' */;
}
if (argvend > argvstart) /* sanity check */
argvsize = argvend - argvstart;
}
if (argvstart == NULL && argvsize == 0) {
argvsize = 1; /* do not try to obtain arg0 again */
getarg0size(&argvstart, &argvsize);
}
if (argvstart && argvsize > 1) {