From 70cd907e38757283f3696465771f723a342cc3d1 Mon Sep 17 00:00:00 2001 From: Mark Wielaard Date: Wed, 2 Dec 2015 16:57:44 +0100 Subject: nm: If the file is ET_REL and we need Dwarf use libdwfl to get it relocated. If we need Dwarf and the file is ET_REL use the same trick as in readelf to get a relocated Dwarf. Otherwise lots of references in the debug_info will come out as zero. This also explains the "bogus" Dwarf seen that caused the memory leak in the local_root that was fixed previously. Signed-off-by: Mark Wielaard --- src/ChangeLog | 10 ++++++ src/nm.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++++++----- 2 files changed, 116 insertions(+), 8 deletions(-) (limited to 'src') diff --git a/src/ChangeLog b/src/ChangeLog index ffc1b294..b5b5e4a4 100644 --- a/src/ChangeLog +++ b/src/ChangeLog @@ -1,3 +1,13 @@ +2015-12-02 Mark Wielaard + + * nm.c (process_file): Accept fd and pass it on. + (handle_elf): Likewise. + (find_no_debuginfo): New. + (struct getdbg): Likewise. + (getdbg_dwflmod): Likewise. + (show_symbols): Take fd. If the file is ET_REL use libdwfl to get + the relocated Dwarf. + 2015-12-02 Mark Wielaard * nm.c (get_local_names): Check for duplicates in local_root tree. diff --git a/src/nm.c b/src/nm.c index 69623fe8..2911afa8 100644 --- a/src/nm.c +++ b/src/nm.c @@ -45,6 +45,7 @@ #include #include "../libebl/libeblP.h" +#include "../libdwfl/libdwflP.h" /* Name and version of program. */ @@ -131,7 +132,7 @@ static int handle_ar (int fd, Elf *elf, const char *prefix, const char *fname, const char *suffix); /* Handle ELF file. */ -static int handle_elf (Elf *elf, const char *prefix, const char *fname, +static int handle_elf (int fd, Elf *elf, const char *prefix, const char *fname, const char *suffix); @@ -384,7 +385,7 @@ process_file (const char *fname, bool more_than_one) { if (elf_kind (elf) == ELF_K_ELF) { - int result = handle_elf (elf, more_than_one ? "" : NULL, + int result = handle_elf (fd, elf, more_than_one ? "" : NULL, fname, NULL); if (elf_end (elf) != 0) @@ -493,7 +494,7 @@ handle_ar (int fd, Elf *elf, const char *prefix, const char *fname, && strcmp (arhdr->ar_name, "/SYM64/") != 0) { if (elf_kind (subelf) == ELF_K_ELF) - result |= handle_elf (subelf, new_prefix, arhdr->ar_name, + result |= handle_elf (fd, subelf, new_prefix, arhdr->ar_name, new_suffix); else if (elf_kind (subelf) == ELF_K_AR) result |= handle_ar (fd, subelf, new_prefix, arhdr->ar_name, @@ -1153,8 +1154,63 @@ sort_by_name (const void *p1, const void *p2) return reverse_sort ? -result : result; } +/* Stub libdwfl callback, only the ELF handle already open is ever + used. Only used for finding the alternate debug file if the Dwarf + comes from the main file. We are not interested in separate + debuginfo. */ +static int +find_no_debuginfo (Dwfl_Module *mod, + void **userdata, + const char *modname, + Dwarf_Addr base, + const char *file_name, + const char *debuglink_file, + GElf_Word debuglink_crc, + char **debuginfo_file_name) +{ + Dwarf_Addr dwbias; + dwfl_module_info (mod, NULL, NULL, NULL, &dwbias, NULL, NULL, NULL); + + /* We are only interested if the Dwarf has been setup on the main + elf file but is only missing the alternate debug link. If dwbias + hasn't even been setup, this is searching for separate debuginfo + for the main elf. We don't care in that case. */ + if (dwbias == (Dwarf_Addr) -1) + return -1; + + return dwfl_standard_find_debuginfo (mod, userdata, modname, base, + file_name, debuglink_file, + debuglink_crc, debuginfo_file_name); +} + +/* Get the Dwarf for the module/file we want. */ +struct getdbg +{ + const char *name; + Dwarf **dbg; +}; + +static int +getdbg_dwflmod (Dwfl_Module *dwflmod, + void **userdata __attribute__ ((unused)), + const char *name, + Dwarf_Addr base __attribute__ ((unused)), + void *arg) +{ + struct getdbg *get = (struct getdbg *) arg; + if (get != NULL && get->name != NULL && strcmp (get->name, name) == 0) + { + Dwarf_Addr bias; + *get->dbg = dwfl_module_getdwarf (dwflmod, &bias); + return DWARF_CB_ABORT; + } + + return DWARF_CB_OK; +} + static void -show_symbols (Ebl *ebl, GElf_Ehdr *ehdr, Elf_Scn *scn, Elf_Scn *xndxscn, +show_symbols (int fd, Ebl *ebl, GElf_Ehdr *ehdr, + Elf_Scn *scn, Elf_Scn *xndxscn, GElf_Shdr *shdr, const char *prefix, const char *fname, const char *fullname) { @@ -1194,9 +1250,48 @@ show_symbols (Ebl *ebl, GElf_Ehdr *ehdr, Elf_Scn *scn, Elf_Scn *xndxscn, /* Get a DWARF debugging descriptor. It's no problem if this isn't possible. We just won't print any line number information. */ Dwarf *dbg = NULL; + Dwfl *dwfl = NULL; if (format == format_sysv) { - dbg = dwarf_begin_elf (ebl->elf, DWARF_C_READ, NULL); + if (ehdr->e_type != ET_REL) + dbg = dwarf_begin_elf (ebl->elf, DWARF_C_READ, NULL); + else + { + /* Abuse libdwfl to do the relocations for us. This is just + for the ET_REL file containing Dwarf, so no need for + fancy lookups. */ + + /* Duplicate an fd for dwfl_report_offline to swallow. */ + int dwfl_fd = dup (fd); + if (likely (dwfl_fd >= 0)) + { + static const Dwfl_Callbacks callbacks = + { + .section_address = dwfl_offline_section_address, + .find_debuginfo = find_no_debuginfo + }; + dwfl = dwfl_begin (&callbacks); + if (likely (dwfl != NULL)) + { + /* Let 0 be the logical address of the file (or + first in archive). */ + dwfl->offline_next_address = 0; + if (dwfl_report_offline (dwfl, fname, fname, dwfl_fd) + == NULL) + { + /* Consumed on success, not on failure. */ + close (dwfl_fd); + } + else + { + dwfl_report_end (dwfl, NULL, NULL); + + struct getdbg get = { .name = fname, .dbg = &dbg }; + dwfl_getmodules (dwfl, &getdbg_dwflmod, &get, 0); + } + } + } + } if (dbg != NULL) { (void) dwarf_getpubnames (dbg, get_global, NULL, 0); @@ -1401,13 +1496,16 @@ show_symbols (Ebl *ebl, GElf_Ehdr *ehdr, Elf_Scn *scn, Elf_Scn *xndxscn, tdestroy (local_root, free); local_root = NULL; - (void) dwarf_end (dbg); + if (dwfl == NULL) + (void) dwarf_end (dbg); } + if (dwfl != NULL) + dwfl_end (dwfl); } static int -handle_elf (Elf *elf, const char *prefix, const char *fname, +handle_elf (int fd, Elf *elf, const char *prefix, const char *fname, const char *suffix) { size_t prefix_len = prefix == NULL ? 0 : strlen (prefix); @@ -1486,7 +1584,7 @@ handle_elf (Elf *elf, const char *prefix, const char *fname, } } - show_symbols (ebl, ehdr, scn, xndxscn, shdr, prefix, fname, + show_symbols (fd, ebl, ehdr, scn, xndxscn, shdr, prefix, fname, fullname); } } -- cgit v1.2.1