diff options
Diffstat (limited to 'tests/backtrace.c')
| -rw-r--r-- | tests/backtrace.c | 464 |
1 files changed, 464 insertions, 0 deletions
diff --git a/tests/backtrace.c b/tests/backtrace.c new file mode 100644 index 00000000..64f90c43 --- /dev/null +++ b/tests/backtrace.c @@ -0,0 +1,464 @@ +/* Test program for unwinding of frames. + Copyright (C) 2013 Red Hat, Inc. + This file is part of elfutils. + + This file is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + elfutils is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. */ + +#include <config.h> +#include <assert.h> +#include <inttypes.h> +#include <stdio.h> +#include <stdio_ext.h> +#include <locale.h> +#include <dirent.h> +#include <stdlib.h> +#include <errno.h> +#include <error.h> +#include <unistd.h> +#include <dwarf.h> +#include <sys/resource.h> +#include <sys/ptrace.h> +#include <signal.h> +#include <sys/types.h> +#include <sys/wait.h> +#include <sys/user.h> +#include <fcntl.h> +#include <string.h> +#include <argp.h> +#include ELFUTILS_HEADER(dwfl) + +static int +dump_modules (Dwfl_Module *mod, void **userdata __attribute__ ((unused)), + const char *name, Dwarf_Addr start, + void *arg __attribute__ ((unused))) +{ + Dwarf_Addr end; + dwfl_module_info (mod, NULL, NULL, &end, NULL, NULL, NULL, NULL); + printf ("%#" PRIx64 "\t%#" PRIx64 "\t%s\n", (uint64_t) start, (uint64_t) end, + name); + return DWARF_CB_OK; +} + +static bool is_x86_64_native; +static pid_t check_tid; + +static void +callback_verify (pid_t tid, unsigned frameno, Dwarf_Addr pc, + const char *symname, Dwfl *dwfl) +{ + static bool seen_main = false; + if (symname && *symname == '.') + symname++; + if (symname && strcmp (symname, "main") == 0) + seen_main = true; + if (pc == 0) + { + assert (seen_main); + return; + } + if (check_tid == 0) + check_tid = tid; + if (tid != check_tid) + { + // For the main thread we are only interested if we can unwind till + // we see the "main" symbol. + return; + } + Dwfl_Module *mod; + static bool reduce_frameno = false; + if (reduce_frameno) + frameno--; + if (! is_x86_64_native && frameno >= 2) + frameno += 2; + const char *symname2 = NULL; + switch (frameno) + { + case 0: + if (! reduce_frameno && symname + && strcmp (symname, "__kernel_vsyscall") == 0) + reduce_frameno = true; + else + assert (symname && strcmp (symname, "raise") == 0); + break; + case 1: + assert (symname != NULL && strcmp (symname, "sigusr2") == 0); + break; + case 2: // x86_64 only + /* __restore_rt - glibc maybe does not have to have this symbol. */ + break; + case 3: // x86_64 only + if (is_x86_64_native) + { + /* Verify we trapped on the very first instruction of jmp. */ + assert (symname != NULL && strcmp (symname, "jmp") == 0); + mod = dwfl_addrmodule (dwfl, pc - 1); + if (mod) + symname2 = dwfl_module_addrname (mod, pc - 1); + assert (symname2 == NULL || strcmp (symname2, "jmp") != 0); + break; + } + /* PASSTHRU */ + case 4: + assert (symname != NULL && strcmp (symname, "stdarg") == 0); + break; + case 5: + /* Verify we trapped on the very last instruction of child. */ + assert (symname != NULL && strcmp (symname, "backtracegen") == 0); + mod = dwfl_addrmodule (dwfl, pc); + if (mod) + symname2 = dwfl_module_addrname (mod, pc); + + // Note that the following assert might in theory even fail on x86_64, + // there is no guarantee that the compiler doesn't reorder the + // instructions or even inserts some padding instructions at the end + // (which apparently happens on ppc64). + if (is_x86_64_native) + assert (symname2 == NULL || strcmp (symname2, "backtracegen") != 0); + break; + } +} + +static int +frame_callback (Dwfl_Frame *state, void *frame_arg) +{ + int *framenop = frame_arg; + Dwarf_Addr pc; + bool isactivation; + if (! dwfl_frame_pc (state, &pc, &isactivation)) + { + error (0, 0, "%s", dwfl_errmsg (-1)); + return DWARF_CB_ABORT; + } + Dwarf_Addr pc_adjusted = pc - (isactivation ? 0 : 1); + + /* Get PC->SYMNAME. */ + Dwfl_Thread *thread = dwfl_frame_thread (state); + Dwfl *dwfl = dwfl_thread_dwfl (thread); + Dwfl_Module *mod = dwfl_addrmodule (dwfl, pc_adjusted); + const char *symname = NULL; + if (mod) + symname = dwfl_module_addrname (mod, pc_adjusted); + + printf ("#%2d %#" PRIx64 "%4s\t%s\n", *framenop, (uint64_t) pc, + ! isactivation ? "- 1" : "", symname); + pid_t tid = dwfl_thread_tid (thread); + callback_verify (tid, *framenop, pc, symname, dwfl); + (*framenop)++; + + return DWARF_CB_OK; +} + +static int +thread_callback (Dwfl_Thread *thread, void *thread_arg __attribute__((unused))) +{ + printf ("TID %ld:\n", (long) dwfl_thread_tid (thread)); + int frameno = 0; + switch (dwfl_thread_getframes (thread, frame_callback, &frameno)) + { + case 0: + break; + case DWARF_CB_ABORT: + return DWARF_CB_ABORT; + case -1: + error (0, 0, "dwfl_thread_getframes: %s", dwfl_errmsg (-1)); + /* All platforms do not have yet proper unwind termination. */ + break; + default: + abort (); + } + return DWARF_CB_OK; +} + +static void +dump (Dwfl *dwfl) +{ + ptrdiff_t ptrdiff = dwfl_getmodules (dwfl, dump_modules, NULL, 0); + assert (ptrdiff == 0); + bool err = false; + switch (dwfl_getthreads (dwfl, thread_callback, NULL)) + { + case 0: + break; + case DWARF_CB_ABORT: + err = true; + break; + case -1: + error (0, 0, "dwfl_getthreads: %s", dwfl_errmsg (-1)); + err = true; + break; + default: + abort (); + } + callback_verify (0, 0, 0, NULL, dwfl); + if (err) + exit (EXIT_FAILURE); +} + +struct see_exec_module +{ + Dwfl_Module *mod; + char selfpath[PATH_MAX + 1]; +}; + +static int +see_exec_module (Dwfl_Module *mod, void **userdata __attribute__ ((unused)), + const char *name __attribute__ ((unused)), + Dwarf_Addr start __attribute__ ((unused)), void *arg) +{ + struct see_exec_module *data = arg; + if (strcmp (name, data->selfpath) != 0) + return DWARF_CB_OK; + assert (data->mod == NULL); + data->mod = mod; + return DWARF_CB_OK; +} + +/* On x86_64 only: + PC will get changed to function 'jmp' by backtrace.c function + prepare_thread. Then SIGUSR2 will be signalled to backtrace-child + which will invoke function sigusr2. + This is all done so that signal interrupts execution of the very first + instruction of a function. Properly handled unwind should not slip into + the previous unrelated function. */ + +static void +prepare_thread (pid_t pid2 __attribute__ ((unused)), + void (*jmp) (void) __attribute__ ((unused))) +{ +#ifndef __x86_64__ + abort (); +#else /* x86_64 */ + long l; + errno = 0; + l = ptrace (PTRACE_POKEUSER, pid2, + (void *) (intptr_t) offsetof (struct user_regs_struct, rip), jmp); + assert_perror (errno); + assert (l == 0); + l = ptrace (PTRACE_CONT, pid2, NULL, (void *) (intptr_t) SIGUSR2); + int status; + pid_t got = waitpid (pid2, &status, __WALL); + assert_perror (errno); + assert (got == pid2); + assert (WIFSTOPPED (status)); + assert (WSTOPSIG (status) == SIGUSR1); +#endif /* __x86_64__ */ +} + +#include <asm/unistd.h> +#include <unistd.h> +#define tgkill(pid, tid, sig) syscall (__NR_tgkill, (pid), (tid), (sig)) + +static void +ptrace_detach_stopped (pid_t pid) +{ + errno = 0; + long l = ptrace (PTRACE_DETACH, pid, NULL, (void *) (intptr_t) SIGSTOP); + assert_perror (errno); + assert (l == 0); +} + +static void +report_pid (Dwfl *dwfl, pid_t pid) +{ + int result = dwfl_linux_proc_report (dwfl, pid); + if (result < 0) + error (2, 0, "dwfl_linux_proc_report: %s", dwfl_errmsg (-1)); + else if (result > 0) + error (2, result, "dwfl_linux_proc_report"); + + if (dwfl_report_end (dwfl, NULL, NULL) != 0) + error (2, 0, "dwfl_report_end: %s", dwfl_errmsg (-1)); + + result = dwfl_linux_proc_attach (dwfl, pid, false); + if (result < 0) + error (2, 0, "dwfl_linux_proc_attach: %s", dwfl_errmsg (-1)); + else if (result > 0) + error (2, result, "dwfl_linux_proc_attach"); +} + +static Dwfl * +pid_to_dwfl (pid_t pid) +{ + static char *debuginfo_path; + static const Dwfl_Callbacks proc_callbacks = + { + .find_debuginfo = dwfl_standard_find_debuginfo, + .debuginfo_path = &debuginfo_path, + + .find_elf = dwfl_linux_proc_find_elf, + }; + Dwfl *dwfl = dwfl_begin (&proc_callbacks); + if (dwfl == NULL) + error (2, 0, "dwfl_begin: %s", dwfl_errmsg (-1)); + report_pid (dwfl, pid); + return dwfl; +} + +static void +exec_dump (const char *exec) +{ + pid_t pid = fork (); + switch (pid) + { + case -1: + abort (); + case 0: + execl (exec, exec, "--ptraceme", NULL); + abort (); + default: + break; + } + + /* Catch the main thread. Catch it first otherwise the /proc evaluation of + PID may have caught still ourselves before executing execl above. */ + errno = 0; + int status; + pid_t got = waitpid (pid, &status, 0); + assert_perror (errno); + assert (got == pid); + assert (WIFSTOPPED (status)); + // Main thread will signal SIGUSR2. Other thread will signal SIGUSR1. + assert (WSTOPSIG (status) == SIGUSR2); + + /* Catch the spawned thread. Do not use __WCLONE as we could get racy + __WCLONE, probably despite pthread_create already had to be called the new + task is not yet alive enough for waitpid. */ + pid_t pid2 = waitpid (-1, &status, __WALL); + assert_perror (errno); + assert (pid2 > 0); + assert (pid2 != pid); + assert (WIFSTOPPED (status)); + // Main thread will signal SIGUSR2. Other thread will signal SIGUSR1. + assert (WSTOPSIG (status) == SIGUSR1); + + Dwfl *dwfl = pid_to_dwfl (pid); + char *selfpathname; + int i = asprintf (&selfpathname, "/proc/%ld/exe", (long) pid); + assert (i > 0); + struct see_exec_module data; + ssize_t ssize = readlink (selfpathname, data.selfpath, + sizeof (data.selfpath)); + free (selfpathname); + assert (ssize > 0 && ssize < (ssize_t) sizeof (data.selfpath)); + data.selfpath[ssize] = '\0'; + data.mod = NULL; + ptrdiff_t ptrdiff = dwfl_getmodules (dwfl, see_exec_module, &data, 0); + assert (ptrdiff == 0); + assert (data.mod != NULL); + GElf_Addr loadbase; + Elf *elf = dwfl_module_getelf (data.mod, &loadbase); + GElf_Ehdr ehdr_mem, *ehdr = gelf_getehdr (elf, &ehdr_mem); + assert (ehdr != NULL); + /* It is false also on x86_64 with i386 inferior. */ +#ifndef __x86_64__ + is_x86_64_native = false; +#else /* __x86_64__ */ + is_x86_64_native = ehdr->e_ident[EI_CLASS] == ELFCLASS64; +#endif /* __x86_64__ */ + void (*jmp) (void); + if (is_x86_64_native) + { + // Find inferior symbol named "jmp". + int nsym = dwfl_module_getsymtab (data.mod); + int symi; + for (symi = 1; symi < nsym; ++symi) + { + GElf_Sym symbol; + const char *symbol_name = dwfl_module_getsym (data.mod, symi, &symbol, NULL); + if (symbol_name == NULL) + continue; + switch (GELF_ST_TYPE (symbol.st_info)) + { + case STT_SECTION: + case STT_FILE: + case STT_TLS: + continue; + default: + if (strcmp (symbol_name, "jmp") != 0) + continue; + break; + } + /* LOADBASE is already applied here. */ + jmp = (void (*) (void)) (uintptr_t) symbol.st_value; + break; + } + assert (symi < nsym); + prepare_thread (pid2, jmp); + } + dwfl_end (dwfl); + ptrace_detach_stopped (pid); + ptrace_detach_stopped (pid2); + check_tid = pid2; + dwfl = pid_to_dwfl (pid); + dump (dwfl); + dwfl_end (dwfl); +} + +#define OPT_BACKTRACE_EXEC 0x100 + +static const struct argp_option options[] = + { + { "backtrace-exec", OPT_BACKTRACE_EXEC, "EXEC", 0, N_("Run executable"), 0 }, + { NULL, 0, NULL, 0, NULL, 0 } + }; + + +static error_t +parse_opt (int key, char *arg, struct argp_state *state) +{ + switch (key) + { + case ARGP_KEY_INIT: + state->child_inputs[0] = state->input; + break; + + case OPT_BACKTRACE_EXEC: + exec_dump (arg); + exit (0); + + default: + return ARGP_ERR_UNKNOWN; + } + return 0; +} + +int +main (int argc __attribute__ ((unused)), char **argv) +{ + /* We use no threads here which can interfere with handling a stream. */ + __fsetlocking (stdin, FSETLOCKING_BYCALLER); + __fsetlocking (stdout, FSETLOCKING_BYCALLER); + __fsetlocking (stderr, FSETLOCKING_BYCALLER); + + /* Set locale. */ + (void) setlocale (LC_ALL, ""); + + elf_version (EV_CURRENT); + + Dwfl *dwfl = NULL; + const struct argp_child argp_children[] = + { + { .argp = dwfl_standard_argp () }, + { .argp = NULL } + }; + const struct argp argp = + { + options, parse_opt, NULL, NULL, argp_children, NULL, NULL + }; + (void) argp_parse (&argp, argc, argv, 0, NULL, &dwfl); + assert (dwfl != NULL); + dump (dwfl); + dwfl_end (dwfl); + return 0; +} |