From 76c6531c6549d171f3e4de9eed29aec18ac08b4b Mon Sep 17 00:00:00 2001 From: Mark Johnston Date: Tue, 6 Dec 2016 04:18:09 +0000 Subject: [PATCH] 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. --- lib/libproc/Makefile | 3 +- lib/libproc/crc32.c | 57 ++++++++++ lib/libproc/crc32.h | 28 +++++ lib/libproc/proc_sym.c | 243 ++++++++++++++++++++++++++++++++--------- 4 files changed, 277 insertions(+), 54 deletions(-) create mode 100644 lib/libproc/crc32.c create mode 100644 lib/libproc/crc32.h diff --git a/lib/libproc/Makefile b/lib/libproc/Makefile index 9744557e680d..939d3084365a 100644 --- a/lib/libproc/Makefile +++ b/lib/libproc/Makefile @@ -5,7 +5,8 @@ PACKAGE=lib${LIB} LIB= proc -SRCS= proc_bkpt.c \ +SRCS= crc32.c \ + proc_bkpt.c \ proc_create.c \ proc_regs.c \ proc_sym.c \ diff --git a/lib/libproc/crc32.c b/lib/libproc/crc32.c new file mode 100644 index 000000000000..90f022bc3878 --- /dev/null +++ b/lib/libproc/crc32.c @@ -0,0 +1,57 @@ +/*- + * COPYRIGHT (C) 1986 Gary S. Brown. You may use this program, or + * code or tables extracted from it, as desired without restriction. + */ + +#include +__FBSDID("$FreeBSD$"); + +#include + +#include + +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 +}; diff --git a/lib/libproc/crc32.h b/lib/libproc/crc32.h new file mode 100644 index 000000000000..3812a83f971f --- /dev/null +++ b/lib/libproc/crc32.h @@ -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 /* uint32_t */ +#include /* 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_ */ diff --git a/lib/libproc/proc_sym.c b/lib/libproc/proc_sym.c index 6ddc585b315b..dccf397b2ede 100644 --- a/lib/libproc/proc_sym.c +++ b/lib/libproc/proc_sym.c @@ -51,8 +51,11 @@ __FBSDID("$FreeBSD$"); #endif #include +#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); }