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

Use a deterministic hash for USDT symbol names.

Browse Source 
Previously libdtrace used ftok(3), which hashes the inode number of the
input object file.  To increase reproducibility of builds that embed
USDT probes, include a hash of the object file path in the symbol name
instead.

Reported and tested by:	bdrewery
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
This commit is contained in:
Mark Johnston 2020-01-07 21:56:20 +00:00
parent accd6aa25e
commit 938acb0869
1 changed files with 22 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
cddl/contrib/opensolaris/lib/libdtrace/common/dt_link.c
View File

@ -57,7 +57,6 @@
#include <sys/mman.h>
#endif
#include <assert.h>
#include <sys/ipc.h>
#include <dt_impl.h>
#include <dt_provider.h>
@ -1249,13 +1248,32 @@ dt_link_error(dtrace_hdl_t *dtp, Elf *elf, int fd, dt_link_pair_t *bufs,
return (dt_set_errno(dtp, EDT_COMPILER));
}
/*
* Provide a unique identifier used when adding global symbols to an object.
* This is the FNV-1a hash of an absolute path for the file.
*/
static unsigned int
hash_obj(const char *obj, int fd)
{
char path[PATH_MAX];
unsigned int h;
if (realpath(obj, path) == NULL)
return (-1);
for (h = 2166136261u, obj = &path[0]; *obj != '\0'; obj++)
h = (h ^ *obj) * 16777619;
h &= 0x7fffffff;
return (h);
}
static int
process_obj(dtrace_hdl_t *dtp, const char *obj, int *eprobesp)
{
static const char dt_prefix[] = "__dtrace";
static const char dt_enabled[] = "enabled";
static const char dt_symprefix[] = "$dtrace";
static const char dt_symfmt[] = "%s%ld.%s";
static const char dt_symfmt[] = "%s%u.%s";
static const char dt_weaksymfmt[] = "%s.%s";
char probename[DTRACE_NAMELEN];
int fd, i, ndx, eprobe, mod = 0;
@ -1272,7 +1290,7 @@ process_obj(dtrace_hdl_t *dtp, const char *obj, int *eprobesp)
dt_probe_t *prp;
uint32_t off, eclass, emachine1, emachine2;
size_t symsize, osym, nsym, isym, istr, len;
key_t objkey;
unsigned int objkey;
dt_link_pair_t *pair, *bufs = NULL;
dt_strtab_t *strtab;
void *tmp;
@ -1350,10 +1368,9 @@ process_obj(dtrace_hdl_t *dtp, const char *obj, int *eprobesp)
* system in order to disambiguate potential conflicts between files of
* the same name which contain identially named local symbols.
*/
if ((objkey = ftok(obj, 0)) == (key_t)-1) {
if ((objkey = hash_obj(obj, fd)) == (unsigned int)-1)
return (dt_link_error(dtp, elf, fd, bufs,
"failed to generate unique key for object file: %s", obj));
}
scn_rel = NULL;
while ((scn_rel = elf_nextscn(elf, scn_rel)) != NULL) {