| /* Linux kernel image support for libdwfl. |
| Copyright (C) 2009-2011 Red Hat, Inc. |
| Copyright (C) 2022 Mark J. Wielaard <mark@klomp.org> |
| This file is part of elfutils. |
| |
| This file is free software; you can redistribute it and/or modify |
| it under the terms of either |
| |
| * the GNU Lesser General Public License as published by the Free |
| Software Foundation; either version 3 of the License, or (at |
| your option) any later version |
| |
| or |
| |
| * the GNU General Public License as published by the Free |
| Software Foundation; either version 2 of the License, or (at |
| your option) any later version |
| |
| or both in parallel, as here. |
| |
| 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 copies of the GNU General Public License and |
| the GNU Lesser General Public License along with this program. If |
| not, see <http://www.gnu.org/licenses/>. */ |
| |
| #ifdef HAVE_CONFIG_H |
| # include <config.h> |
| #endif |
| |
| #include "libdwflP.h" |
| #include "system.h" |
| |
| #include <unistd.h> |
| #include <endian.h> |
| |
| #if BYTE_ORDER == LITTLE_ENDIAN |
| # define LE16(x) (x) |
| #else |
| # define LE16(x) bswap_16 (x) |
| #endif |
| |
| /* See Documentation/x86/boot.txt in Linux kernel sources |
| for an explanation of these format details. */ |
| |
| #define MAGIC1 0xaa55 |
| #define MAGIC2 0x53726448 /* "HdrS" little-endian */ |
| #define MIN_VERSION 0x0208 |
| |
| #define H_START (H_SETUP_SECTS & -4) |
| #define H_SETUP_SECTS 0x1f1 |
| #define H_MAGIC1 0x1fe |
| #define H_MAGIC2 0x202 |
| #define H_VERSION 0x206 |
| #define H_PAYLOAD_OFFSET 0x248 |
| #define H_PAYLOAD_LENGTH 0x24c |
| #define H_END 0x250 |
| #define H_READ_SIZE (H_END - H_START) |
| |
| Dwfl_Error |
| internal_function |
| __libdw_image_header (int fd, off_t *start_offset, |
| void *mapped, size_t mapped_size) |
| { |
| if (likely (mapped_size > H_END)) |
| { |
| const void *header = mapped; |
| char header_buffer[H_READ_SIZE]; |
| if (header == NULL) |
| { |
| ssize_t n = pread_retry (fd, header_buffer, H_READ_SIZE, |
| *start_offset + H_START); |
| if (n < 0) |
| return DWFL_E_ERRNO; |
| if (n < H_READ_SIZE) |
| return DWFL_E_BADELF; |
| |
| header = header_buffer - H_START; |
| } |
| |
| uint16_t magic1; |
| uint32_t magic2; |
| uint16_t version; |
| memcpy (&magic1, header + H_MAGIC1, sizeof (uint16_t)); |
| memcpy (&magic2, header + H_MAGIC2, sizeof (uint32_t)); |
| memcpy (&version, header + H_VERSION, sizeof (uint16_t)); |
| if (magic1 == LE16 (MAGIC1) && magic2 == LE32 (MAGIC2) |
| && LE16 (version) >= MIN_VERSION) |
| { |
| /* The magic numbers match and the version field is sufficient. |
| Extract the payload bounds. */ |
| |
| uint32_t offset; |
| uint32_t length; |
| uint8_t sects; |
| memcpy (&offset, header + H_PAYLOAD_OFFSET, sizeof (uint32_t)); |
| memcpy (&length, header + H_PAYLOAD_LENGTH, sizeof (uint32_t)); |
| memcpy (§s, header + H_SETUP_SECTS, sizeof (uint8_t)); |
| offset = LE32 (offset); |
| length = LE32 (length); |
| |
| offset += ((sects ?: 4) + 1) * 512; |
| |
| if (offset > H_END && offset < mapped_size |
| && mapped_size - offset >= length) |
| { |
| /* It looks kosher. Use it! */ |
| *start_offset += offset; |
| return DWFL_E_NOERROR; |
| } |
| } |
| } |
| return DWFL_E_BADELF; |
| } |