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librtld_db: Use the auxv to figure out where to look up loader symbols.

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Previously, librtld_db just hardcoded /libexec/ld-elf.so, which isn't
correct for processes that aren't using the native ABI. With this change,
librtld_db can be used to inspect non-native processes; in particular,
dtrace -c now works for 32-bit executables on amd64.

MFC after:	1 month
This commit is contained in:
Mark Johnston 2016-07-30 03:05:23 +00:00
parent e04d8562b6
commit a7e13d50fe
5 changed files with 176 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
Makefile.inc1
View File

@ -2095,7 +2095,9 @@ cddl/lib/libctf__L: lib/libz__L
# cddl/lib/libdtrace requires lib/libproc and lib/librtld_db; it's only built
# on select architectures though (see cddl/lib/Makefile)
.if ${MACHINE_CPUARCH} != "sparc64"
_prebuild_libs+= lib/libproc lib/librtld_db
_prebuild_libs+= lib/libprocstat lib/libproc lib/librtld_db
lib/libproc__L: lib/libprocstat__L
lib/librtld_db__L: lib/libprocstat__L
.endif
.if ${MK_CRYPT} != "no"

2
lib/librtld_db/Makefile
View File

@ -14,4 +14,6 @@ CFLAGS+= -I${.CURDIR}
# Avoid circular dependency, we only need the libproc.h header here.
CFLAGS+= -I${.CURDIR:H}/libproc
LIBADD+= elf procstat
.include <bsd.lib.mk>

191
lib/librtld_db/rtld_db.c
View File

@ -26,19 +26,29 @@
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <machine/_inttypes.h>
#include <sys/types.h>
#include <sys/param.h>
#include <sys/queue.h>
#include <sys/sysctl.h>
#include <sys/user.h>
#include <assert.h>
#include <err.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <unistd.h>
#include <machine/elf.h>
#include <libelf.h>
#include <libproc.h>
#include <libprocstat.h>
#include <libutil.h>
#include "rtld_db.h"
@ -55,6 +65,8 @@ void
rd_delete(rd_agent_t *rdap)
{
if (rdap->rda_procstat != NULL)
procstat_close(rdap->rda_procstat);
free(rdap);
}
@ -146,9 +158,10 @@ rd_init(int version)
rd_err_e
rd_loadobj_iter(rd_agent_t *rdap, rl_iter_f *cb, void *clnt_data)
{
int cnt, i, lastvn = 0;
rd_loadobj_t rdl;
struct kinfo_vmentry *kves, *kve;
rd_loadobj_t rdl;
rd_err_e ret;
int cnt, i, lastvn;
DPRINTF("%s\n", __func__);
@ -156,6 +169,9 @@ rd_loadobj_iter(rd_agent_t *rdap, rl_iter_f *cb, void *clnt_data)
warn("ERROR: kinfo_getvmmap() failed");
return (RD_ERR);
}
ret = RD_OK;
lastvn = 0;
for (i = 0; i < cnt; i++) {
kve = kves + i;
if (kve->kve_type == KVME_TYPE_VNODE)
@ -174,12 +190,14 @@ rd_loadobj_iter(rd_agent_t *rdap, rl_iter_f *cb, void *clnt_data)
if (kve->kve_protection & KVME_PROT_EXEC)
rdl.rdl_prot |= RD_RDL_X;
strlcpy(rdl.rdl_path, kves[lastvn].kve_path,
sizeof(rdl.rdl_path));
(*cb)(&rdl, clnt_data);
sizeof(rdl.rdl_path));
if ((*cb)(&rdl, clnt_data) != 0) {
ret = RD_ERR;
break;
}
}
free(kves);
return (RD_OK);
return (ret);
}
void
@ -195,13 +213,18 @@ rd_new(struct proc_handle *php)
{
rd_agent_t *rdap;
rdap = malloc(sizeof(rd_agent_t));
if (rdap) {
memset(rdap, 0, sizeof(rd_agent_t));
rdap->rda_php = php;
rd_reset(rdap);
}
rdap = malloc(sizeof(*rdap));
if (rdap == NULL)
return (NULL);
memset(rdap, 0, sizeof(rd_agent_t));
rdap->rda_php = php;
rdap->rda_procstat = procstat_open_sysctl();
if (rd_reset(rdap) != RD_OK) {
rd_delete(rdap);
rdap = NULL;
}
return (rdap);
}
@ -231,24 +254,136 @@ rd_plt_resolution(rd_agent_t *rdap, uintptr_t pc, struct proc *proc,
return (RD_ERR);
}
static int
rtld_syms(rd_agent_t *rdap, const char *rtldpath, u_long base)
{
GElf_Shdr shdr;
GElf_Sym sym;
Elf *e;
Elf_Data *data;
Elf_Scn *scn;
const char *symname;
Elf64_Word strscnidx;
int fd, i, ret;
ret = 1;
e = NULL;
fd = open(rtldpath, O_RDONLY);
if (fd < 0)
goto err;
if (elf_version(EV_CURRENT) == EV_NONE)
goto err;
e = elf_begin(fd, ELF_C_READ, NULL);
if (e == NULL) {
close(fd);
goto err;
}
scn = NULL;
while ((scn = elf_nextscn(e, scn)) != NULL) {
gelf_getshdr(scn, &shdr);
if (shdr.sh_type == SHT_DYNSYM)
break;
}
if (scn == NULL)
goto err;
strscnidx = shdr.sh_link;
data = elf_getdata(scn, NULL);
if (data == NULL)
goto err;
for (i = 0; gelf_getsym(data, i, &sym) != NULL; i++) {
if (GELF_ST_TYPE(sym.st_info) != STT_FUNC ||
GELF_ST_BIND(sym.st_info) != STB_GLOBAL)
continue;
symname = elf_strptr(e, strscnidx, sym.st_name);
if (symname == NULL)
continue;
if (strcmp(symname, "r_debug_state") == 0) {
rdap->rda_preinit_addr = sym.st_value + base;
rdap->rda_dlactivity_addr = sym.st_value + base;
} else if (strcmp(symname, "_r_debug_postinit") == 0) {
rdap->rda_postinit_addr = sym.st_value + base;
}
}
if (rdap->rda_preinit_addr != 0 &&
rdap->rda_postinit_addr != 0 &&
rdap->rda_dlactivity_addr != 0)
ret = 0;
err:
if (e != NULL)
(void)elf_end(e);
if (fd >= 0)
(void)close(fd);
return (ret);
}
rd_err_e
rd_reset(rd_agent_t *rdap)
{
GElf_Sym sym;
struct kinfo_proc *kp;
struct kinfo_vmentry *kve;
Elf_Auxinfo *auxv;
const char *rtldpath;
u_long base;
rd_err_e rderr;
int count, i;
if (proc_name2sym(rdap->rda_php, "ld-elf.so.1", "r_debug_state",
&sym, NULL) < 0)
kp = NULL;
auxv = NULL;
kve = NULL;
rderr = RD_ERR;
kp = procstat_getprocs(rdap->rda_procstat, KERN_PROC_PID,
proc_getpid(rdap->rda_php), &count);
if (kp == NULL)
return (RD_ERR);
DPRINTF("found r_debug_state at 0x%lx\n", (unsigned long)sym.st_value);
rdap->rda_preinit_addr = sym.st_value;
rdap->rda_dlactivity_addr = sym.st_value;
assert(count == 1);
if (proc_name2sym(rdap->rda_php, "ld-elf.so.1", "_r_debug_postinit",
&sym, NULL) < 0)
return (RD_ERR);
DPRINTF("found _r_debug_postinit at 0x%lx\n",
(unsigned long)sym.st_value);
rdap->rda_postinit_addr = sym.st_value;
auxv = procstat_getauxv(rdap->rda_procstat, kp, &count);
if (auxv == NULL)
goto err;
return (RD_OK);
base = 0;
for (i = 0; i < count; i++) {
if (auxv[i].a_type == AT_BASE) {
base = auxv[i].a_un.a_val;
break;
}
}
if (i == count)
goto err;
rtldpath = NULL;
kve = procstat_getvmmap(rdap->rda_procstat, kp, &count);
if (kve == NULL)
goto err;
for (i = 0; i < count; i++) {
if (kve[i].kve_start == base) {
rtldpath = kve[i].kve_path;
break;
}
}
if (i == count)
goto err;
if (rtld_syms(rdap, rtldpath, base) != 0)
goto err;
rderr = RD_OK;
err:
if (kve != NULL)
procstat_freevmmap(rdap->rda_procstat, kve);
if (auxv != NULL)
procstat_freeauxv(rdap->rda_procstat, auxv);
if (kp != NULL)
procstat_freeprocs(rdap->rda_procstat, kp);
return (rderr);
}

9
lib/librtld_db/rtld_db.h
View File

@ -33,9 +33,6 @@
#define _RTLD_DB_H_
#include <sys/param.h>
#include <sys/cdefs.h>
#include <sys/types.h>
#define RD_VERSION 1
@ -49,11 +46,17 @@ typedef enum {
RD_NOMAPS
} rd_err_e;
/* XXX struct rd_agent should be private. */
struct procstat;
typedef struct rd_agent {
struct proc_handle *rda_php;
uintptr_t rda_dlactivity_addr;
uintptr_t rda_preinit_addr;
uintptr_t rda_postinit_addr;
struct procstat *rda_procstat;
} rd_agent_t;
typedef struct rd_loadobj {

1
share/mk/src.libnames.mk
View File

@ -243,6 +243,7 @@ _DP_radius= md
.else
_DP_radius= crypto
.endif
_DP_rtld_db= elf procstat
_DP_procstat= kvm util elf
.if ${MK_CXX} == "yes"
.if ${MK_LIBCPLUSPLUS} != "no"