/*      $NetBSD: backtrace.c,v 1.9 2025/01/23 12:08:12 christos Exp $   */

/*-
 * Copyright (c) 2012 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Christos Zoulas.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
#include <sys/cdefs.h>
__RCSID("$NetBSD: backtrace.c,v 1.9 2025/01/23 12:08:12 christos Exp $");

#include <sys/param.h>
#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <stdint.h>
#include <stddef.h>
#include <unistd.h>
#include <fcntl.h>
#include <dlfcn.h>
#include <elf.h>

#include "execinfo.h"
#include "symbol.h"
#include "symtab.h"

#ifdef __linux__
#define SELF    "/proc/self/exe"
#else
#include <sys/sysctl.h>
#define SELF    "/proc/curproc/file"
#endif

static int self_fd = -1;

static int
open_self(int flags)
{
        const char *pathname = SELF;
#ifdef KERN_PROC_PATHNAME
        static const int name[] = {
                CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME,
        };
        char path[MAXPATHLEN];
        size_t len;

        len = sizeof(path);
        if (sysctl(name, __arraycount(name), path, &len, NULL, 0) != -1)
                pathname = path;
#endif
        return open(pathname, flags);
}

int
backtrace_sandbox_init(void)
{

        if (self_fd == -1)
                self_fd = open_self(O_RDONLY);
        return self_fd >= 0 ? 0 : -1;
}

void
backtrace_sandbox_fini(void)
{
        assert(self_fd >= 0);

        close(self_fd);
        self_fd = -1;
}

static int __printflike(4, 5)
rasprintf(char **buf, size_t *bufsiz, size_t offs, const char *fmt, ...)
{
        for (;;) {
                size_t nbufsiz;
                char *nbuf;

                if (*buf && offs < *bufsiz) {
                        va_list ap;
                        int len;

                        va_start(ap, fmt);
                        len = vsnprintf(*buf + offs, *bufsiz - offs, fmt, ap);
                        va_end(ap);

                        if (len < 0 || (size_t)len + 1 < *bufsiz - offs)
                                return len;
                        nbufsiz = MAX(*bufsiz + 512, (size_t)len + 1);
                } else
                        nbufsiz = MAX(offs, *bufsiz) + 512;

                nbuf = realloc(*buf, nbufsiz);
                if (nbuf == NULL)
                        return -1;
                *buf = nbuf;
                *bufsiz = nbufsiz;
        }
}

/*
 * format specifiers:
 *      %a      = address
 *      %n      = symbol_name
 *      %d      = symbol_address - address
 *      %D      = if symbol_address == address "" else +%d
 *      %f      = filename
 */
static ssize_t
format_string(char **buf, size_t *bufsiz, size_t offs, const char *fmt,
    Dl_info *dli, const void *addr)
{
        const uintptr_t symaddr = SYMBOL_CANONICALIZE(dli->dli_saddr);
        ptrdiff_t diff = (const char *)addr - (const char *)symaddr;
        size_t o = offs;
        int len;

        for (; *fmt; fmt++) {
                if (*fmt != '%')
                        goto printone;
                switch (*++fmt) {
                case 'a':
                        len = rasprintf(buf, bufsiz, o, "%p", addr);
                        break;
                case 'n':
                        len = rasprintf(buf, bufsiz, o, "%s", dli->dli_sname);
                        break;
                case 'D':
                        if (diff)
                                len = rasprintf(buf, bufsiz, o, "+0x%tx", diff);
                        else
                                len = 0;
                        break;
                case 'd':
                        len = rasprintf(buf, bufsiz, o, "0x%tx", diff);
                        break;
                case 'f':
                        len = rasprintf(buf, bufsiz, o, "%s", dli->dli_fname);
                        break;
                default:
                printone:
                        len = rasprintf(buf, bufsiz, o, "%c", *fmt);
                        break;
                }
                if (len == -1)
                        return -1;
                o += len;
        }
        return o - offs;
}

static ssize_t
format_address(symtab_t *st, char **buf, size_t *bufsiz, size_t offs,
    const char *fmt, const void *addr)
{
        Dl_info dli;

        memset(&dli, 0, sizeof(dli));
        (void)dladdr(addr, &dli);
        if (st)
                symtab_find(st, addr, &dli);

        if (dli.dli_sname == NULL)
                dli.dli_sname = "???";
        if (dli.dli_fname == NULL)
                dli.dli_fname = "???";
        if (dli.dli_saddr == NULL)
                dli.dli_saddr = (void *)(intptr_t)addr;

        return format_string(buf, bufsiz, offs, fmt, &dli, addr);
}

char **
backtrace_symbols_fmt(void *const *trace, size_t len, const char *fmt)
{

        static const size_t slen = sizeof(char *) + 64; /* estimate */
        char *ptr;
        symtab_t *st;
        int fd = self_fd;

        if (fd != -1 || (fd = open_self(O_RDONLY)) != -1)
                st = symtab_create(fd, -1, STT_FUNC);
        else
                st = NULL;

        if ((ptr = calloc(len, slen)) == NULL)
                goto out;

        size_t psize = len * slen;
        size_t offs = len * sizeof(char *);

        /* We store only offsets in the first pass because of realloc */
        for (size_t i = 0; i < len; i++) {
                ssize_t x;
                ((char **)(void *)ptr)[i] = (void *)offs;
                x = format_address(st, &ptr, &psize, offs, fmt, trace[i]);
                if (x == -1) {
                        free(ptr);
                        ptr = NULL;
                        goto out;
                }
                offs += x;
                ptr[offs++] = '\0';
                assert(offs < psize);
        }

        /* Change offsets to pointers */
        for (size_t j = 0; j < len; j++)
                ((char **)(void *)ptr)[j] += (intptr_t)ptr;

out:
        symtab_destroy(st);
        if (fd != -1 && fd != self_fd)
                (void)close(fd);

        return (void *)ptr;
}

int
backtrace_symbols_fd_fmt(void *const *trace, size_t len, int fd,
    const char *fmt)
{
        char **s = backtrace_symbols_fmt(trace, len, fmt);
        if (s == NULL)
                return -1;
        for (size_t i = 0; i < len; i++)
                if (dprintf(fd, "%s\n", s[i]) < 0)
                        break;
        free(s);
        return 0;
}

static const char fmt[] = "%a <%n%D> at %f";

char **
backtrace_symbols(void *const *trace, size_t len)
{
        return backtrace_symbols_fmt(trace, len, fmt);
}

int
backtrace_symbols_fd(void *const *trace, size_t len, int fd)
{
        return backtrace_symbols_fd_fmt(trace, len, fd, fmt);
}