source: mainline/uspace/app/taskdump/elf_core.c@ 8d2dd7f2

/*
 * Copyright (c) 2011 Jiri Svoboda
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

/** @addtogroup taskdump
 * @{
 */
/** @file Write ELF core files.
 *
 * Creates ELF core files. Core files do not seem to be specified by some
 * standard (the System V ABI explicitely states that it does not specify
 * them).
 *
 * Looking at core files produced by Linux, these don't have section headers,
 * only program headers, although objdump shows them as having sections.
 * Basically at the beginning there should be a note segment followed
 * by one loadable segment per memory area.
 *
 * The note segment contains a series of records with register state,
 * process info etc. We only write one record NT_PRSTATUS which contains
 * process/register state (anything which is not register state we fill
 * with zeroes).
 */

#include <align.h>
#include <elf/elf.h>
#include <elf/elf_linux.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stddef.h>
#include <errno.h>
#include <mem.h>
#include <as.h>
#include <udebug.h>
#include <macros.h>
#include <libarch/istate.h>
#include <vfs/vfs.h>

#include "elf_core.h"

static off64_t align_foff_up(off64_t, uintptr_t, size_t);
static int write_mem_area(int, aoff64_t *, as_area_info_t *, async_sess_t *);

#define BUFFER_SIZE 0x1000
static uint8_t buffer[BUFFER_SIZE];

/** Save ELF core file.
 *
 * @param file_name Name of file to save to.
 * @param ainfo     Array of @a n memory area info structures.
 * @param n         Number of memory areas.
 * @param sess      Debugging session.
 *
 * @return EOK on sucess.
 * @return ENOENT if file cannot be created.
 * @return ENOMEM on out of memory.
 * @return EIO on write error.
 *
 */
int elf_core_save(const char *file_name, as_area_info_t *ainfo, unsigned int n,
    async_sess_t *sess, istate_t *istate)
{
        elf_header_t elf_hdr;
        off64_t foff;
        size_t n_ph;
        elf_word flags;
        elf_segment_header_t *p_hdr;
        elf_prstatus_t pr_status;
        elf_note_t note;
        size_t word_size;
        aoff64_t pos = 0;

        int fd;
        ssize_t rc;
        unsigned int i;

#ifdef __32_BITS__
        word_size = 4;
#endif
#ifdef __64_BITS__
        /*
         * This should be 8 per the 64-bit ELF spec, but the Linux kernel
         * screws up and uses 4 anyway (and screws up elf_note_t as well)
         * and we are trying to be compatible with Linux GDB target. Sigh.
         */
        word_size = 4;
#endif
        memset(&pr_status, 0, sizeof(pr_status));
        istate_to_elf_regs(istate, &pr_status.regs);

        n_ph = n + 1;

        p_hdr = malloc(sizeof(elf_segment_header_t) * n_ph);
        if (p_hdr == NULL) {
                printf("Failed allocating memory.\n");
                return ENOMEM;
        }

        fd = vfs_lookup_open(file_name, WALK_REGULAR | WALK_MAY_CREATE,
            MODE_WRITE);
        if (fd < 0) {
                printf("Failed opening file.\n");
                free(p_hdr);
                return ENOENT;
        }

        /*
         * File layout:
         *
         *      ELF header
         *      program headers
         *      note segment
         * repeat:
         *      (pad for alignment)
         *      core segment
         * end repeat
         */

        memset(&elf_hdr, 0, sizeof(elf_hdr));
        elf_hdr.e_ident[EI_MAG0] = ELFMAG0;
        elf_hdr.e_ident[EI_MAG1] = ELFMAG1;
        elf_hdr.e_ident[EI_MAG2] = ELFMAG2;
        elf_hdr.e_ident[EI_MAG3] = ELFMAG3;
        elf_hdr.e_ident[EI_CLASS] = ELF_CLASS;
        elf_hdr.e_ident[EI_DATA] = ELF_DATA_ENCODING;
        elf_hdr.e_ident[EI_VERSION] = EV_CURRENT;

        elf_hdr.e_type = ET_CORE;
        elf_hdr.e_machine = ELF_MACHINE;
        elf_hdr.e_version = EV_CURRENT;
        elf_hdr.e_entry = 0;
        elf_hdr.e_phoff = sizeof(elf_header_t);
        elf_hdr.e_shoff = 0;
        elf_hdr.e_flags = 0;
        elf_hdr.e_ehsize = sizeof(elf_hdr);
        elf_hdr.e_phentsize = sizeof(elf_segment_header_t);
        elf_hdr.e_phnum = n_ph;
        elf_hdr.e_shentsize = 0;
        elf_hdr.e_shnum = 0;
        elf_hdr.e_shstrndx = 0;

        /* foff is used for allocation of file space for segment data. */
        foff = elf_hdr.e_phoff + n_ph * sizeof(elf_segment_header_t);

        memset(&p_hdr[0], 0, sizeof(p_hdr[0]));
        p_hdr[0].p_type = PT_NOTE;
        p_hdr[0].p_offset = foff;
        p_hdr[0].p_vaddr = 0;
        p_hdr[0].p_paddr = 0;
        p_hdr[0].p_filesz = sizeof(elf_note_t)
            + ALIGN_UP((str_size("CORE") + 1), word_size)
            + ALIGN_UP(sizeof(elf_prstatus_t), word_size);
        p_hdr[0].p_memsz = 0;
        p_hdr[0].p_flags = 0;
        p_hdr[0].p_align = 1;

        foff += p_hdr[0].p_filesz;

        for (i = 0; i < n; ++i) {
                foff = align_foff_up(foff, ainfo[i].start_addr, PAGE_SIZE);

                flags = 0;
                if (ainfo[i].flags & AS_AREA_READ)
                        flags |= PF_R;
                if (ainfo[i].flags & AS_AREA_WRITE)
                        flags |= PF_W;
                if (ainfo[i].flags & AS_AREA_EXEC)
                        flags |= PF_X;

                memset(&p_hdr[i + 1], 0, sizeof(p_hdr[i + 1]));
                p_hdr[i + 1].p_type = PT_LOAD;
                p_hdr[i + 1].p_offset = foff;
                p_hdr[i + 1].p_vaddr = ainfo[i].start_addr;
                p_hdr[i + 1].p_paddr = 0;
                p_hdr[i + 1].p_filesz = ainfo[i].size;
                p_hdr[i + 1].p_memsz = ainfo[i].size;
                p_hdr[i + 1].p_flags = flags;
                p_hdr[i + 1].p_align = PAGE_SIZE;

                foff += ainfo[i].size;
        }

        rc = vfs_write(fd, &pos, &elf_hdr, sizeof(elf_hdr));
        if (rc != sizeof(elf_hdr)) {
                printf("Failed writing ELF header.\n");
                free(p_hdr);
                return EIO;
        }

        for (i = 0; i < n_ph; ++i) {
                rc = vfs_write(fd, &pos, &p_hdr[i], sizeof(p_hdr[i]));
                if (rc != sizeof(p_hdr[i])) {
                        printf("Failed writing program header.\n");
                        free(p_hdr);
                        return EIO;
                }
        }

        pos = p_hdr[0].p_offset;

        /*
         * Write note header
         */
        note.namesz = str_size("CORE") + 1;
        note.descsz = sizeof(elf_prstatus_t);
        note.type = NT_PRSTATUS;

        rc = vfs_write(fd, &pos, &note, sizeof(elf_note_t));
        if (rc != sizeof(elf_note_t)) {
                printf("Failed writing note header.\n");
                free(p_hdr);
                return EIO;
        }

        rc = vfs_write(fd, &pos, "CORE", note.namesz);
        if (rc != (ssize_t) note.namesz) {
                printf("Failed writing note header.\n");
                free(p_hdr);
                return EIO;
        }

        pos = ALIGN_UP(pos, word_size);

        rc = vfs_write(fd, &pos, &pr_status, sizeof(elf_prstatus_t));
        if (rc != sizeof(elf_prstatus_t)) {
                printf("Failed writing register data.\n");
                free(p_hdr);
                return EIO;
        }

        for (i = 1; i < n_ph; ++i) {
                pos = p_hdr[i].p_offset;
                if (write_mem_area(fd, &pos, &ainfo[i - 1], sess) != EOK) {
                        printf("Failed writing memory data.\n");
                        free(p_hdr);
                        return EIO;
                }
        }

        free(p_hdr);

        return EOK;
}

/** Align file offset up to be congruent with vaddr modulo page size. */
static off64_t align_foff_up(off64_t foff, uintptr_t vaddr, size_t page_size)
{
        off64_t rva = vaddr % page_size;
        off64_t rfo = foff % page_size;

        if (rva >= rfo)
                return (foff + (rva - rfo));

        return (foff + (page_size + (rva - rfo)));
}

/** Write memory area from application to core file.
 *
 * @param fd   File to write to.
 * @param pos  Pointer to the position to write to.
 * @param area Memory area info structure.
 * @param sess Debugging session.
 *
 * @return EOK on success, EIO on failure.
 *
 */
static int write_mem_area(int fd, aoff64_t *pos, as_area_info_t *area,
    async_sess_t *sess)
{
        size_t to_copy;
        size_t total;
        uintptr_t addr;
        ssize_t rc;

        addr = area->start_addr;
        total = 0;

        while (total < area->size) {
                to_copy = min(area->size - total, BUFFER_SIZE);
                rc = udebug_mem_read(sess, buffer, addr, to_copy);
                if (rc < 0) {
                        printf("Failed reading task memory.\n");
                        return EIO;
                }

                rc = vfs_write(fd, pos, buffer, to_copy);
                if (rc != (ssize_t) to_copy) {
                        printf("Failed writing memory contents.\n");
                        return EIO;
                }

                addr += to_copy;
                total += to_copy;
        }

        return EOK;
}

/** @}
 */