d/freebsd-skq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Rework get_string() to make it more robust when fetching strings of unknown

Browse Source 
length.  In particular, instead of blinding fetching 1k blocks, do an initial
fetch up to the end of the current page followed by page-sized fetches up to
the maximum size.  Previously if the 1k buffer crossed a page boundary and
the second page was not valid, the entire operation would fail.
This commit is contained in:
John Baldwin 2015-08-05 18:14:01 +00:00
parent 7582c8ea08
commit abb3f965d1
1 changed files with 29 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
usr.bin/truss/syscalls.c
View File

@ -539,44 +539,56 @@ get_struct(pid_t pid, void *offset, void *buf, int len)
}
#define MAXSIZE 4096
#define BLOCKSIZE 1024
/*
* get_string
* Copy a string from the process. Note that it is
* expected to be a C string, but if max is set, it will
* only get that much.
*/
static char *
get_string(pid_t pid, void *offset, int max)
get_string(pid_t pid, void *addr, int max)
{
struct ptrace_io_desc iorequest;
char *buf;
int diff, i, size, totalsize;
char *buf, *nbuf;
size_t offset, size, totalsize;
diff = 0;
totalsize = size = max ? (max + 1) : BLOCKSIZE;
offset = 0;
if (max)
size = max + 1;
else {
/* Read up to the end of the current page. */
size = PAGE_SIZE - ((uintptr_t)addr % PAGE_SIZE);
if (size > MAXSIZE)
size = MAXSIZE;
}
totalsize = size;
buf = malloc(totalsize);
if (buf == NULL)
return (NULL);
for (;;) {
diff = totalsize - size;
iorequest.piod_op = PIOD_READ_D;
iorequest.piod_offs = (char *)offset + diff;
iorequest.piod_addr = buf + diff;
iorequest.piod_offs = (char *)addr + offset;
iorequest.piod_addr = buf + offset;
iorequest.piod_len = size;
if (ptrace(PT_IO, pid, (caddr_t)&iorequest, 0) < 0) {
free(buf);
return (NULL);
}
for (i = 0 ; i < size; i++) {
if (buf[diff + i] == '\0')
if (memchr(buf + offset, '\0', size) != NULL)
return (buf);
offset += size;
if (totalsize < MAXSIZE && max == 0) {
size = MAXSIZE - totalsize;
if (size > PAGE_SIZE)
size = PAGE_SIZE;
nbuf = realloc(buf, totalsize + size);
if (nbuf == NULL) {
buf[totalsize - 1] = '\0';
return (buf);
}
if (totalsize < MAXSIZE - BLOCKSIZE && max == 0) {
totalsize += BLOCKSIZE;
buf = realloc(buf, totalsize);
size = BLOCKSIZE;
}
buf = nbuf;
totalsize += size;
} else {
buf[totalsize - 1] = '\0';
return (buf);