libproc: Improve .gnu_debuglink support.

As of r278658 libproc looks for debug files under /usr/lib/debug and will
use them if available. This change fleshes out that support a bit further:
- Check for a .gnu_debuglink section and use the file name specified
  there if one is present.
- Validate external debug files with the CRC in the .gnu_debuglink
  section so as to avoid using stale or corrupt debug files.
- Search for debug files in the directory containing the referencing
  object or in the .debug subdirectory, as GDB does.
This commit is contained in:
Mark Johnston 2016-12-06 04:18:09 +00:00
parent b1bb30e5c5
commit 76c6531c65
4 changed files with 277 additions and 54 deletions

View File

@ -5,7 +5,8 @@
PACKAGE=lib${LIB}
LIB= proc
SRCS= proc_bkpt.c \
SRCS= crc32.c \
proc_bkpt.c \
proc_create.c \
proc_regs.c \
proc_sym.c \

57
lib/libproc/crc32.c Normal file
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@ -0,0 +1,57 @@
/*-
* COPYRIGHT (C) 1986 Gary S. Brown. You may use this program, or
* code or tables extracted from it, as desired without restriction.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <stdint.h>
#include <crc32.h>
uint32_t crc32_tab[] = {
0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
};

28
lib/libproc/crc32.h Normal file
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@ -0,0 +1,28 @@
/*-
* COPYRIGHT (C) 1986 Gary S. Brown. You may use this program, or
* code or tables extracted from it, as desired without restriction.
*
* $FreeBSD$
*/
#ifndef _CRC32_H_
#define _CRC32_H_
#include <stdint.h> /* uint32_t */
#include <stdlib.h> /* size_t */
extern uint32_t crc32_tab[];
static __inline uint32_t
crc32(const void *buf, size_t size)
{
const uint8_t *p = buf;
uint32_t crc;
crc = ~0U;
while (size--)
crc = crc32_tab[(crc ^ *p++) & 0xFF] ^ (crc >> 8);
return (crc ^ ~0U);
}
#endif /* !_CRC32_H_ */

View File

@ -51,8 +51,11 @@ __FBSDID("$FreeBSD$");
#endif
#include <libutil.h>
#include "crc32.h"
#include "_libproc.h"
#define PATH_DEBUG_DIR "/usr/lib/debug"
#ifdef NO_CTF
typedef struct ctf_file ctf_file_t;
#endif
@ -63,6 +66,22 @@ extern char *__cxa_demangle(const char *, char *, size_t *, int *);
static void proc_rdl2prmap(rd_loadobj_t *, prmap_t *);
static int
crc32_file(int fd, uint32_t *crc)
{
uint8_t buf[PAGE_SIZE], *p;
size_t n;
*crc = ~0;
while ((n = read(fd, buf, sizeof(buf))) > 0) {
p = &buf[0];
while (n-- > 0)
*crc = crc32_tab[(*crc ^ *p++) & 0xff] ^ (*crc >> 8);
}
*crc = ~*crc;
return (n);
}
static void
demangle(const char *symbol, char *buf, size_t len)
{
@ -83,18 +102,150 @@ demangle(const char *symbol, char *buf, size_t len)
}
static int
find_dbg_obj(const char *path)
open_debug_file(char *path, const char *debugfile, uint32_t crc)
{
size_t n;
uint32_t compcrc;
int fd;
char dbg_path[PATH_MAX];
snprintf(dbg_path, sizeof(dbg_path),
"/usr/lib/debug/%s.debug", path);
fd = open(dbg_path, O_RDONLY);
if (fd >= 0)
fd = -1;
if ((n = strlcat(path, "/", PATH_MAX)) >= PATH_MAX)
return (fd);
else
return (open(path, O_RDONLY));
if (strlcat(path, debugfile, PATH_MAX) >= PATH_MAX)
goto out;
if ((fd = open(path, O_RDONLY | O_CLOEXEC)) < 0)
goto out;
if (crc32_file(fd, &compcrc) != 0 || crc != compcrc) {
DPRINTFX("ERROR: CRC32 mismatch for %s", path);
(void)close(fd);
fd = -1;
}
out:
path[n] = '\0';
return (fd);
}
/*
* Obtain an ELF descriptor for the specified mapped object. If a GNU debuglink
* section is present, a descriptor for the corresponding debug file is
* returned.
*/
static int
open_object(prmap_t *map, Elf **elfp, int *fdp)
{
char path[PATH_MAX];
GElf_Shdr shdr;
Elf *e, *e2;
Elf_Data *data;
Elf_Scn *scn;
const char *debugfile, *scnname;
size_t ndx;
uint32_t crc;
int fd, fd2;
if ((fd = open(map->pr_mapname, O_RDONLY | O_CLOEXEC)) < 0) {
DPRINTF("ERROR: open %s failed", map->pr_mapname);
return (-1);
}
if ((e = elf_begin(fd, ELF_C_READ, NULL)) == NULL) {
DPRINTFX("ERROR: elf_begin() failed: %s", elf_errmsg(-1));
goto err;
}
scn = NULL;
while ((scn = elf_nextscn(e, scn)) != NULL) {
if (gelf_getshdr(scn, &shdr) != &shdr) {
DPRINTFX("ERROR: gelf_getshdr failed: %s",
elf_errmsg(-1));
goto err;
}
if (shdr.sh_type != SHT_PROGBITS)
continue;
if (elf_getshdrstrndx(e, &ndx) != 0) {
DPRINTFX("ERROR: elf_getshdrstrndx failed: %s",
elf_errmsg(-1));
goto err;
}
if ((scnname = elf_strptr(e, ndx, shdr.sh_name)) == NULL)
continue;
if (strcmp(scnname, ".gnu_debuglink") == 0)
break;
}
if (scn == NULL)
goto internal;
if ((data = elf_getdata(scn, NULL)) == NULL) {
DPRINTFX("ERROR: elf_getdata failed: %s", elf_errmsg(-1));
goto err;
}
/*
* The data contains a null-terminated file name followed by a 4-byte
* CRC.
*/
if (data->d_size < sizeof(crc) + 1) {
DPRINTFX("ERROR: debuglink section is too small (%zd bytes)",
data->d_size);
goto internal;
}
if (strnlen(data->d_buf, data->d_size) >= data->d_size - sizeof(crc)) {
DPRINTFX("ERROR: no null-terminator in gnu_debuglink section");
goto internal;
}
debugfile = data->d_buf;
memcpy(&crc, (char *)data->d_buf + data->d_size - sizeof(crc),
sizeof(crc));
/*
* Search for the debug file using the algorithm described in the gdb
* documentation:
* - look in the directory containing the object,
* - look in the subdirectory ".debug" of the directory containing the
* object,
* - look in the global debug directories (currently /usr/lib/debug).
*/
(void)strlcpy(path, map->pr_mapname, sizeof(path));
(void)dirname(path);
if ((fd2 = open_debug_file(path, debugfile, crc)) >= 0)
goto external;
if (strlcat(path, "/.debug", sizeof(path)) < sizeof(path) &&
(fd2 = open_debug_file(path, debugfile, crc)) >= 0)
goto external;
(void)snprintf(path, sizeof(path), PATH_DEBUG_DIR);
if (strlcat(path, map->pr_mapname, sizeof(path)) < sizeof(path)) {
(void)dirname(path);
if ((fd2 = open_debug_file(path, debugfile, crc)) >= 0)
goto external;
}
internal:
/* We didn't find a debug file, just return the object's descriptor. */
*elfp = e;
*fdp = fd;
return (0);
external:
if ((e2 = elf_begin(fd2, ELF_C_READ, NULL)) == NULL) {
DPRINTFX("ERROR: elf_begin failed: %s", elf_errmsg(-1));
(void)close(fd2);
goto err;
}
(void)elf_end(e);
(void)close(fd);
*elfp = e2;
*fdp = fd2;
return (0);
err:
if (e != NULL)
(void)elf_end(e);
(void)close(fd);
return (-1);
}
static void
@ -308,19 +459,17 @@ proc_addr2sym(struct proc_handle *p, uintptr_t addr, char *name,
u_long symtabstridx = 0, dynsymstridx = 0;
int fd, error = -1;
if ((map = proc_addr2map(p, addr)) == NULL)
if ((map = proc_addr2map(p, addr)) == NULL) {
DPRINTFX("ERROR: proc_addr2map failed to resolve 0x%jx", addr);
return (-1);
if ((fd = find_dbg_obj(map->pr_mapname)) < 0) {
DPRINTF("ERROR: open %s failed", map->pr_mapname);
goto err0;
}
if ((e = elf_begin(fd, ELF_C_READ, NULL)) == NULL) {
DPRINTFX("ERROR: elf_begin() failed: %s", elf_errmsg(-1));
goto err1;
if (open_object(map, &e, &fd) != 0) {
DPRINTFX("ERROR: failed to open object %s", map->pr_mapname);
return (-1);
}
if (gelf_getehdr(e, &ehdr) == NULL) {
DPRINTFX("ERROR: gelf_getehdr() failed: %s", elf_errmsg(-1));
goto err2;
goto err;
}
/*
@ -354,15 +503,13 @@ proc_addr2sym(struct proc_handle *p, uintptr_t addr, char *name,
error = lookup_addr(e, symtabscn, symtabstridx, off, addr, &s, symcopy);
if (error != 0)
goto err2;
goto err;
out:
demangle(s, name, namesz);
err2:
elf_end(e);
err1:
close(fd);
err0:
err:
(void)elf_end(e);
(void)close(fd);
free(map);
return (error);
}
@ -455,21 +602,18 @@ proc_name2sym(struct proc_handle *p, const char *object, const char *symbol,
int fd, error = -1;
if ((map = proc_name2map(p, object)) == NULL) {
DPRINTFX("ERROR: couldn't find object %s", object);
goto err0;
DPRINTFX("ERROR: proc_name2map failed to resolve %s", object);
return (-1);
}
if ((fd = find_dbg_obj(map->pr_mapname)) < 0) {
DPRINTF("ERROR: open %s failed", map->pr_mapname);
goto err0;
}
if ((e = elf_begin(fd, ELF_C_READ, NULL)) == NULL) {
DPRINTFX("ERROR: elf_begin() failed: %s", elf_errmsg(-1));
goto err1;
if (open_object(map, &e, &fd) != 0) {
DPRINTFX("ERROR: failed to open object %s", map->pr_mapname);
return (-1);
}
if (gelf_getehdr(e, &ehdr) == NULL) {
DPRINTFX("ERROR: gelf_getehdr() failed: %s", elf_errmsg(-1));
goto err2;
goto err;
}
/*
* Find the index of the STRTAB and SYMTAB sections to locate
* symbol names.
@ -505,13 +649,10 @@ proc_name2sym(struct proc_handle *p, const char *object, const char *symbol,
off = ehdr.e_type == ET_EXEC ? 0 : map->pr_vaddr;
symcopy->st_value += off;
err2:
elf_end(e);
err1:
close(fd);
err0:
err:
(void)elf_end(e);
(void)close(fd);
free(map);
return (error);
}
@ -543,7 +684,7 @@ proc_iter_symbyaddr(struct proc_handle *p, const char *object, int which,
Elf *e;
int i, fd;
prmap_t *map;
Elf_Scn *scn, *foundscn = NULL;
Elf_Scn *scn, *foundscn;
Elf_Data *data;
GElf_Ehdr ehdr;
GElf_Shdr shdr;
@ -552,24 +693,22 @@ proc_iter_symbyaddr(struct proc_handle *p, const char *object, int which,
char *s;
int error = -1;
if ((map = proc_name2map(p, object)) == NULL)
if ((map = proc_name2map(p, object)) == NULL) {
DPRINTFX("ERROR: proc_name2map failed to resolve %s", object);
return (-1);
if ((fd = find_dbg_obj(map->pr_mapname)) < 0) {
DPRINTF("ERROR: open %s failed", map->pr_mapname);
goto err0;
}
if ((e = elf_begin(fd, ELF_C_READ, NULL)) == NULL) {
DPRINTFX("ERROR: elf_begin() failed: %s", elf_errmsg(-1));
goto err1;
if (open_object(map, &e, &fd) != 0) {
DPRINTFX("ERROR: failed to open object %s", map->pr_mapname);
return (-1);
}
if (gelf_getehdr(e, &ehdr) == NULL) {
DPRINTFX("ERROR: gelf_getehdr() failed: %s", elf_errmsg(-1));
goto err2;
goto err;
}
/*
* Find the section we are looking for.
*/
scn = NULL;
foundscn = scn = NULL;
while ((scn = elf_nextscn(e, scn)) != NULL) {
gelf_getshdr(scn, &shdr);
if (which == PR_SYMTAB &&
@ -587,7 +726,7 @@ proc_iter_symbyaddr(struct proc_handle *p, const char *object, int which,
stridx = shdr.sh_link;
if ((data = elf_getdata(foundscn, NULL)) == NULL) {
DPRINTFX("ERROR: elf_getdata() failed: %s", elf_errmsg(-1));
goto err2;
goto err;
}
for (i = 0; gelf_getsym(data, i, &sym) != NULL; i++) {
if (GELF_ST_BIND(sym.st_info) == STB_LOCAL &&
@ -618,14 +757,12 @@ proc_iter_symbyaddr(struct proc_handle *p, const char *object, int which,
if (ehdr.e_type != ET_EXEC)
sym.st_value += map->pr_vaddr;
if ((error = (*func)(cd, &sym, s)) != 0)
goto err2;
goto err;
}
error = 0;
err2:
err:
elf_end(e);
err1:
close(fd);
err0:
free(map);
return (error);
}