xref: /system/core/debuggerd/arm/machine.c

/* system/debuggerd/debuggerd.c
**
** Copyright 2006, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
**
**     http://www.apache.org/licenses/LICENSE-2.0
**
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/

#include <stdio.h>
#include <errno.h>
#include <signal.h>
#include <pthread.h>
#include <fcntl.h>
#include <sys/types.h>
#include <dirent.h>

#include <sys/ptrace.h>
#include <sys/wait.h>
#include <sys/exec_elf.h>
#include <sys/stat.h>

#include <cutils/sockets.h>
#include <cutils/properties.h>

#include <linux/input.h>
#include <linux/user.h>

#include "utility.h"

/* enable to dump memory pointed to by every register */
#define DUMP_MEM_FOR_ALL_REGS 0

#ifdef WITH_VFP
#ifdef WITH_VFP_D32
#define NUM_VFP_REGS 32
#else
#define NUM_VFP_REGS 16
#endif
#endif

/* Main entry point to get the backtrace from the crashing process */
extern int unwind_backtrace_with_ptrace(int tfd, pid_t pid, mapinfo *map,
                                        unsigned int sp_list[],
                                        int *frame0_pc_sane,
                                        bool at_fault);

/*
 * If this isn't clearly a null pointer dereference, dump the
 * /proc/maps entries near the fault address.
 */
static void show_nearby_maps(int tfd, int pid, mapinfo *map)
{
    siginfo_t si;

    memset(&si, 0, sizeof(si));
    if (ptrace(PTRACE_GETSIGINFO, pid, 0, &si)) {
        _LOG(tfd, false, "cannot get siginfo: %s\n", strerror(errno));
        return;
    }
    if (!signal_has_address(si.si_signo))
        return;

    uintptr_t addr = (uintptr_t) si.si_addr;
    addr &= ~0xfff;     /* round to 4K page boundary */
    if (addr == 0)      /* null-pointer deref */
        return;

    _LOG(tfd, false, "\nmemory map around addr %08x:\n", si.si_addr);

    /*
     * Search for a match, or for a hole where the match would be.  The list
     * is backward from the file content, so it starts at high addresses.
     */
    bool found = false;
    mapinfo *next = NULL;
    mapinfo *prev = NULL;
    while (map != NULL) {
        if (addr >= map->start && addr < map->end) {
            found = true;
            next = map->next;
            break;
        } else if (addr >= map->end) {
            /* map would be between "prev" and this entry */
            next = map;
            map = NULL;
            break;
        }

        prev = map;
        map = map->next;
    }

    /*
     * Show "next" then "match" then "prev" so that the addresses appear in
     * ascending order (like /proc/pid/maps).
     */
    if (next != NULL) {
        _LOG(tfd, false, "%08x-%08x %s\n", next->start, next->end, next->name);
    } else {
        _LOG(tfd, false, "(no map below)\n");
    }
    if (map != NULL) {
        _LOG(tfd, false, "%08x-%08x %s\n", map->start, map->end, map->name);
    } else {
        _LOG(tfd, false, "(no map for address)\n");
    }
    if (prev != NULL) {
        _LOG(tfd, false, "%08x-%08x %s\n", prev->start, prev->end, prev->name);
    } else {
        _LOG(tfd, false, "(no map above)\n");
    }
}

/*
 * Dumps a few bytes of memory, starting a bit before and ending a bit
 * after the specified address.
 */
static void dump_memory(int tfd, int pid, uintptr_t addr,
    bool only_in_tombstone)
{
    char code_buffer[64];       /* actual 8+1+((8+1)*4) + 1 == 45 */
    char ascii_buffer[32];      /* actual 16 + 1 == 17 */
    uintptr_t p, end;

    p = addr & ~3;
    p -= 32;
    if (p > addr) {
        /* catch underflow */
        p = 0;
    }
    end = p + 80;
    /* catch overflow; 'end - p' has to be multiples of 16 */
    while (end < p)
        end -= 16;

    /* Dump the code around PC as:
     *  addr     contents                             ascii
     *  00008d34 ef000000 e8bd0090 e1b00000 512fff1e  ............../Q
     *  00008d44 ea00b1f9 e92d0090 e3a070fc ef000000  ......-..p......
     */
    while (p < end) {
        char* asc_out = ascii_buffer;

        sprintf(code_buffer, "%08x ", p);

        int i;
        for (i = 0; i < 4; i++) {
            /*
             * If we see (data == -1 && errno != 0), we know that the ptrace
             * call failed, probably because we're dumping memory in an
             * unmapped or inaccessible page.  I don't know if there's
             * value in making that explicit in the output -- it likely
             * just complicates parsing and clarifies nothing for the
             * enlightened reader.
             */
            long data = ptrace(PTRACE_PEEKTEXT, pid, (void*)p, NULL);
            sprintf(code_buffer + strlen(code_buffer), "%08lx ", data);

            int j;
            for (j = 0; j < 4; j++) {
                /*
                 * Our isprint() allows high-ASCII characters that display
                 * differently (often badly) in different viewers, so we
                 * just use a simpler test.
                 */
                char val = (data >> (j*8)) & 0xff;
                if (val >= 0x20 && val < 0x7f) {
                    *asc_out++ = val;
                } else {
                    *asc_out++ = '.';
                }
            }
            p += 4;
        }
        *asc_out = '\0';
        _LOG(tfd, only_in_tombstone, "%s %s\n", code_buffer, ascii_buffer);
    }

}

void dump_stack_and_code(int tfd, int pid, mapinfo *map,
                         int unwind_depth, unsigned int sp_list[],
                         bool at_fault)
{
    struct pt_regs r;
    int sp_depth;
    bool only_in_tombstone = !at_fault;

    if(ptrace(PTRACE_GETREGS, pid, 0, &r)) return;

    if (DUMP_MEM_FOR_ALL_REGS && at_fault) {
        /*
         * If configured to do so, dump memory around *all* registers
         * for the crashing thread.
         *
         * TODO: remove duplicates.
         */
        static const char REG_NAMES[] = "R0R1R2R3R4R5R6R7R8R9SLFPIPSPLRPC";

        int reg;
        for (reg = 0; reg < 16; reg++) {
            /* this may not be a valid way to access, but it'll do for now */
            uintptr_t addr = r.uregs[reg];

            /*
             * Don't bother if it looks like a small int or ~= null, or if
             * it's in the kernel area.
             */
            if (addr < 4096 || addr >= 0xc0000000) {
                continue;
            }

            _LOG(tfd, only_in_tombstone, "\nmem near %.2s:\n",
                &REG_NAMES[reg*2]);
            dump_memory(tfd, pid, addr, false);
        }
    } else {
        unsigned int pc, lr;
        pc = r.ARM_pc;
        lr = r.ARM_lr;

        _LOG(tfd, only_in_tombstone, "\ncode around pc:\n");
        dump_memory(tfd, pid, (uintptr_t) pc, only_in_tombstone);

        if (lr != pc) {
            _LOG(tfd, only_in_tombstone, "\ncode around lr:\n");
            dump_memory(tfd, pid, (uintptr_t) lr, only_in_tombstone);
        }
    }

    show_nearby_maps(tfd, pid, map);

    unsigned int p, end;
    unsigned int sp = r.ARM_sp;

    p = sp - 64;
    if (p > sp)
        p = 0;
    p &= ~3;
    if (unwind_depth != 0) {
        if (unwind_depth < STACK_CONTENT_DEPTH) {
            end = sp_list[unwind_depth-1];
        }
        else {
            end = sp_list[STACK_CONTENT_DEPTH-1];
        }
    }
    else {
        end = p + 256;
        /* 'end - p' has to be multiples of 4 */
        if (end < p)
            end = ~7;
    }

    _LOG(tfd, only_in_tombstone, "\nstack:\n");

    /* If the crash is due to PC == 0, there will be two frames that
     * have identical SP value.
     */
    if (sp_list[0] == sp_list[1]) {
        sp_depth = 1;
    }
    else {
        sp_depth = 0;
    }

    while (p <= end) {
         char *prompt;
         char level[16];
         long data = ptrace(PTRACE_PEEKTEXT, pid, (void*)p, NULL);
         if (p == sp_list[sp_depth]) {
             sprintf(level, "#%02d", sp_depth++);
             prompt = level;
         }
         else {
             prompt = "   ";
         }

         /* Print the stack content in the log for the first 3 frames. For the
          * rest only print them in the tombstone file.
          */
         _LOG(tfd, (sp_depth > 2) || only_in_tombstone,
              "%s %08x  %08x  %s\n", prompt, p, data,
              map_to_name(map, data, ""));
         p += 4;
    }
    /* print another 64-byte of stack data after the last frame */

    end = p+64;
    /* 'end - p' has to be multiples of 4 */
    if (end < p)
        end = ~7;

    while (p <= end) {
         long data = ptrace(PTRACE_PEEKTEXT, pid, (void*)p, NULL);
         _LOG(tfd, (sp_depth > 2) || only_in_tombstone,
              "    %08x  %08x  %s\n", p, data,
              map_to_name(map, data, ""));
         p += 4;
    }
}

void dump_pc_and_lr(int tfd, int pid, mapinfo *map, int unwound_level,
                    bool at_fault)
{
    struct pt_regs r;

    if(ptrace(PTRACE_GETREGS, pid, 0, &r)) {
        _LOG(tfd, !at_fault, "tid %d not responding!\n", pid);
        return;
    }

    if (unwound_level == 0) {
        _LOG(tfd, !at_fault, "         #%02d  pc %08x  %s\n", 0, r.ARM_pc,
             map_to_name(map, r.ARM_pc, "<unknown>"));
    }
    _LOG(tfd, !at_fault, "         #%02d  lr %08x  %s\n", 1, r.ARM_lr,
            map_to_name(map, r.ARM_lr, "<unknown>"));
}

void dump_registers(int tfd, int pid, bool at_fault)
{
    struct pt_regs r;
    bool only_in_tombstone = !at_fault;

    if(ptrace(PTRACE_GETREGS, pid, 0, &r)) {
        _LOG(tfd, only_in_tombstone,
             "cannot get registers: %s\n", strerror(errno));
        return;
    }

    _LOG(tfd, only_in_tombstone, " r0 %08x  r1 %08x  r2 %08x  r3 %08x\n",
         r.ARM_r0, r.ARM_r1, r.ARM_r2, r.ARM_r3);
    _LOG(tfd, only_in_tombstone, " r4 %08x  r5 %08x  r6 %08x  r7 %08x\n",
         r.ARM_r4, r.ARM_r5, r.ARM_r6, r.ARM_r7);
    _LOG(tfd, only_in_tombstone, " r8 %08x  r9 %08x  10 %08x  fp %08x\n",
         r.ARM_r8, r.ARM_r9, r.ARM_r10, r.ARM_fp);
    _LOG(tfd, only_in_tombstone,
         " ip %08x  sp %08x  lr %08x  pc %08x  cpsr %08x\n",
         r.ARM_ip, r.ARM_sp, r.ARM_lr, r.ARM_pc, r.ARM_cpsr);

#ifdef WITH_VFP
    struct user_vfp vfp_regs;
    int i;

    if(ptrace(PTRACE_GETVFPREGS, pid, 0, &vfp_regs)) {
        _LOG(tfd, only_in_tombstone,
             "cannot get registers: %s\n", strerror(errno));
        return;
    }

    for (i = 0; i < NUM_VFP_REGS; i += 2) {
        _LOG(tfd, only_in_tombstone,
             " d%-2d %016llx  d%-2d %016llx\n",
              i, vfp_regs.fpregs[i], i+1, vfp_regs.fpregs[i+1]);
    }
    _LOG(tfd, only_in_tombstone, " scr %08lx\n\n", vfp_regs.fpscr);
#endif
}