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Rework the argv and env string fetching for execve to be more robust.

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Before truss would fetch 100 string pointers and happily walk off the end
of the array if it never found a NULL.  This also means for a short argv
list it could fail entirely if the 100 string pointers spanned into an
unmapped page.

Instead, fetch page-aligned blocks of string pointers in a loop fetching
each string until a NULL is found.

While here, make use of the open memstream file descriptor instead of
allocating a temporary array.  This allows us to fetch each string once
instead of twice.
This commit is contained in:
John Baldwin 2015-08-20 14:33:30 +00:00
parent 4a0589d1ba
commit 890843c15b
1 changed files with 43 additions and 25 deletions
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68
usr.bin/truss/syscalls.c
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@ -913,36 +913,54 @@ print_arg(struct syscall_args *sc, unsigned long *args, long retval,
break;
}
case StringArray: {
int num, size, i;
char *tmp2;
uintptr_t addr;
union {
char *strarray[0];
char buf[PAGE_SIZE];
} u;
char *string;
char *strarray[100]; /* XXX This is ugly. */
size_t len;
int first, i;
if (get_struct(pid, (void *)args[sc->offset],
(void *)&strarray, sizeof(strarray)) == -1)
err(1, "get_struct %p", (void *)args[sc->offset]);
num = 0;
size = 0;
/* Find out how large of a buffer we'll need. */
while (strarray[num] != NULL) {
string = get_string(pid, (void*)strarray[num], 0);
size += strlen(string);
free(string);
num++;
/*
* Read a page of pointers at a time. Punt if the top-level
* pointer is not aligned. Note that the first read is of
* a partial page.
*/
addr = args[sc->offset];
if (addr % sizeof(char *) != 0) {
fprintf(fp, "0x%lx", args[sc->offset]);
break;
}
size += 4 + (num * 4);
tmp = (char *)malloc(size);
tmp2 = tmp;
tmp2 += sprintf(tmp2, " [");
for (i = 0; i < num; i++) {
string = get_string(pid, (void*)strarray[i], 0);
tmp2 += sprintf(tmp2, " \"%s\"%c", string,
(i + 1 == num) ? ' ' : ',');
free(string);
len = PAGE_SIZE - (addr & PAGE_MASK);
if (get_struct(pid, (void *)addr, u.buf, len) == -1) {
fprintf(fp, "0x%lx", args[sc->offset]);
break;
}
tmp2 += sprintf(tmp2, "]");
fputc('[', fp);
first = 1;
i = 0;
while (u.strarray[i] != NULL) {
string = get_string(pid, u.strarray[i], 0);
fprintf(fp, "%s \"%s\"", first ? "" : ",", string);
free(string);
first = 0;
i++;
if (i == len / sizeof(char *)) {
addr += len;
len = PAGE_SIZE;
if (get_struct(pid, (void *)addr, u.buf, len) ==
-1) {
fprintf(fp, ", <inval>");
break;
}
i = 0;
}
}
fputs(" ]", fp);
break;
}
#ifdef __LP64__