/* $NetBSD: backtrace.c,v 1.1.2.2 2024/02/24 13:07:19 martin Exp $ */ /* * Copyright (C) Internet Systems Consortium, Inc. ("ISC") * * SPDX-License-Identifier: MPL-2.0 * * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, you can obtain one at https://mozilla.org/MPL/2.0/. * * See the COPYRIGHT file distributed with this work for additional * information regarding copyright ownership. */ /*! \file */ #include #include #ifdef HAVE_LIBCTRACE #include #endif /* ifdef HAVE_LIBCTRACE */ #include #include #include #ifdef USE_BACKTRACE /* * Getting a back trace of a running process is tricky and highly platform * dependent. Our current approach is as follows: * 1. If the system library supports the "backtrace()" function, use it. * 2. Otherwise, if the compiler is gcc and the architecture is x86_64 or IA64, * then use gcc's (hidden) Unwind_Backtrace() function. Note that this * function doesn't work for C programs on many other architectures. * 3. Otherwise, if the architecture x86 or x86_64, try to unwind the stack * frame following frame pointers. This assumes the executable binary * compiled with frame pointers; this is not always true for x86_64 (rather, * compiler optimizations often disable frame pointers). The validation * checks in getnextframeptr() hopefully rejects bogus values stored in * the RBP register in such a case. If the backtrace function itself crashes * due to this problem, the whole package should be rebuilt with * --disable-backtrace. */ #ifdef HAVE_LIBCTRACE #define BACKTRACE_LIBC #elif defined(HAVE_UNWIND_BACKTRACE) #define BACKTRACE_GCC #elif defined(WIN32) #define BACKTRACE_WIN32 #elif defined(__x86_64__) || defined(__i386__) #define BACKTRACE_X86STACK #else /* ifdef HAVE_LIBCTRACE */ #define BACKTRACE_DISABLED #endif /* HAVE_LIBCTRACE */ #else /* USE_BACKTRACE */ #define BACKTRACE_DISABLED #endif /* USE_BACKTRACE */ #ifdef BACKTRACE_LIBC isc_result_t isc_backtrace_gettrace(void **addrs, int maxaddrs, int *nframes) { int n; /* * Validate the arguments: intentionally avoid using REQUIRE(). * See notes in backtrace.h. */ if (addrs == NULL || nframes == NULL) { return (ISC_R_FAILURE); } /* * backtrace(3) includes this function itself in the address array, * which should be eliminated from the returned sequence. */ n = backtrace(addrs, maxaddrs); if (n < 2) { return (ISC_R_NOTFOUND); } n--; memmove(addrs, &addrs[1], sizeof(void *) * n); *nframes = n; return (ISC_R_SUCCESS); } #elif defined(BACKTRACE_GCC) extern int _Unwind_Backtrace(void *fn, void *a); extern void * _Unwind_GetIP(void *ctx); typedef struct { void **result; int max_depth; int skip_count; int count; } trace_arg_t; static int btcallback(void *uc, void *opq) { trace_arg_t *arg = (trace_arg_t *)opq; if (arg->skip_count > 0) { arg->skip_count--; } else { arg->result[arg->count++] = (void *)_Unwind_GetIP(uc); } if (arg->count == arg->max_depth) { return (5); /* _URC_END_OF_STACK */ } return (0); /* _URC_NO_REASON */ } isc_result_t isc_backtrace_gettrace(void **addrs, int maxaddrs, int *nframes) { trace_arg_t arg; /* Argument validation: see above. */ if (addrs == NULL || nframes == NULL) { return (ISC_R_FAILURE); } arg.skip_count = 1; arg.result = addrs; arg.max_depth = maxaddrs; arg.count = 0; _Unwind_Backtrace(btcallback, &arg); *nframes = arg.count; return (ISC_R_SUCCESS); } #elif defined(BACKTRACE_WIN32) isc_result_t isc_backtrace_gettrace(void **addrs, int maxaddrs, int *nframes) { unsigned long ftc = (unsigned long)maxaddrs; *nframes = (int)CaptureStackBackTrace(1, ftc, addrs, NULL); return (ISC_R_SUCCESS); } #elif defined(BACKTRACE_X86STACK) #ifdef __x86_64__ static unsigned long getrbp(void) { unsigned long rbp; __asm("movq %%rbp, %0\n" : "=r"(rbp)); return rbp; } #endif /* ifdef __x86_64__ */ static void ** getnextframeptr(void **sp) { void **newsp = (void **)*sp; /* * Perform sanity check for the new frame pointer, derived from * google glog. This can actually be bogus depending on compiler. */ /* prohibit the stack frames from growing downwards */ if (newsp <= sp) { return (NULL); } /* A heuristics to reject "too large" frame: this actually happened. */ if ((char *)newsp - (char *)sp > 100000) { return (NULL); } /* * Not sure if other checks used in glog are needed at this moment. * For our purposes we don't have to consider non-contiguous frames, * for example. */ return (newsp); } isc_result_t isc_backtrace_gettrace(void **addrs, int maxaddrs, int *nframes) { int i = 0; void **sp; /* Argument validation: see above. */ if (addrs == NULL || nframes == NULL) { return (ISC_R_FAILURE); } #ifdef __x86_64__ sp = (void **)getrbp(); if (sp == NULL) { return (ISC_R_NOTFOUND); } /* * sp is the frame ptr of this function itself due to the call to * getrbp(), so need to unwind one frame for consistency. */ sp = getnextframeptr(sp); #else /* ifdef __x86_64__ */ /* * i386: the frame pointer is stored 2 words below the address for the * first argument. Note that the body of this function cannot be * inlined since it depends on the address of the function argument. */ sp = (void **)(void *)&addrs - 2; #endif /* ifdef __x86_64__ */ while (sp != NULL && i < maxaddrs) { addrs[i++] = *(sp + 1); sp = getnextframeptr(sp); } *nframes = i; return (ISC_R_SUCCESS); } #elif defined(BACKTRACE_DISABLED) isc_result_t isc_backtrace_gettrace(void **addrs, int maxaddrs, int *nframes) { /* Argument validation: see above. */ if (addrs == NULL || nframes == NULL) { return (ISC_R_FAILURE); } UNUSED(maxaddrs); return (ISC_R_NOTIMPLEMENTED); } #endif /* ifdef BACKTRACE_LIBC */ isc_result_t isc_backtrace_getsymbolfromindex(int idx, const void **addrp, const char **symbolp) { REQUIRE(addrp != NULL && *addrp == NULL); REQUIRE(symbolp != NULL && *symbolp == NULL); if (idx < 0 || idx >= isc__backtrace_nsymbols) { return (ISC_R_RANGE); } *addrp = isc__backtrace_symtable[idx].addr; *symbolp = isc__backtrace_symtable[idx].symbol; return (ISC_R_SUCCESS); } static int symtbl_compare(const void *addr, const void *entryarg) { const isc_backtrace_symmap_t *entry = entryarg; const isc_backtrace_symmap_t *end = &isc__backtrace_symtable[isc__backtrace_nsymbols - 1]; if (isc__backtrace_nsymbols == 1 || entry == end) { if (addr >= entry->addr) { /* * If addr is equal to or larger than that of the last * entry of the table, we cannot be sure if this is * within a valid range so we consider it valid. */ return (0); } return (-1); } /* entry + 1 is a valid entry from now on. */ if (addr < entry->addr) { return (-1); } else if (addr >= (entry + 1)->addr) { return (1); } return (0); } isc_result_t isc_backtrace_getsymbol(const void *addr, const char **symbolp, unsigned long *offsetp) { isc_result_t result = ISC_R_SUCCESS; isc_backtrace_symmap_t *found; /* * Validate the arguments: intentionally avoid using REQUIRE(). * See notes in backtrace.h. */ if (symbolp == NULL || *symbolp != NULL || offsetp == NULL) { return (ISC_R_FAILURE); } if (isc__backtrace_nsymbols < 1) { return (ISC_R_NOTFOUND); } /* * Search the table for the entry that meets: * entry.addr <= addr < next_entry.addr. */ found = bsearch(addr, isc__backtrace_symtable, isc__backtrace_nsymbols, sizeof(isc__backtrace_symtable[0]), symtbl_compare); if (found == NULL) { result = ISC_R_NOTFOUND; } else { *symbolp = found->symbol; *offsetp = (unsigned long)((const char *)addr - (char *)found->addr); } return (result); }