[PATCH] tools: relocate-rela: Fix ELF decoding on big-endian hosts

Michal Simek michal.simek at amd.com
Fri Jul 15 09:35:15 CEST 2022


Hi,

On 7/15/22 08:40, Samuel Holland wrote:
> The new ELF decoding logic assumed that the target binary has the same
> endianness as the host, which broke building ARM64 firmware binaries on
> big-endian machines.
> 
> This commit fixes the ELF64 decoding to be host-endianness-neutral, and
> applies the same changes to the ELF32 decoding. It does not fix the
> microblaze-specific dynamic symbol decoding.
> 
> It also corrects the functions used for byte swapping in rela_elf64()
> and rela_elf32(). The result is the same, but semantically the code is
> converting bytes read from a foreign-endianness file to host byte order.
> 
> Fixes: 4c9e2d643460 ("tools: relocate-rela: Read rela start/end directly from ELF")
> Fixes: a1405d9cfedb ("tools: relocate-rela: Check that relocation works only for EM_AARCH64")
> Signed-off-by: Samuel Holland <samuel at sholland.org>
> ---
> 
>   tools/relocate-rela.c | 125 +++++++++++++++++++++++-------------------
>   1 file changed, 68 insertions(+), 57 deletions(-)
> 
> diff --git a/tools/relocate-rela.c b/tools/relocate-rela.c
> index 090fb1acb20c..fcf3fb201f07 100644
> --- a/tools/relocate-rela.c
> +++ b/tools/relocate-rela.c
> @@ -60,7 +60,9 @@ static int decode_elf64(FILE *felf, char **argv)
>   {
>   	size_t size;
>   	Elf64_Ehdr header;
> -	uint64_t section_header_base, section_header_size, sh_offset, sh_size;
> +	uint64_t section_header_base, section_header_size;
> +	uint64_t sh_addr, sh_offset, sh_size;
> +	Elf64_Half sh_index, sh_num;
>   	Elf64_Shdr *sh_table; /* Elf symbol table */
>   	int ret, i, machine;
>   	char *sh_str;
> @@ -76,7 +78,7 @@ static int decode_elf64(FILE *felf, char **argv)
>   		return 25;
>   	}
>   
> -	machine = header.e_machine;
> +	machine = le16_to_cpu(header.e_machine);
>   	debug("Machine\t%d\n", machine);
>   
>   	if (machine != EM_AARCH64) {
> @@ -84,9 +86,10 @@ static int decode_elf64(FILE *felf, char **argv)
>   		return 30;
>   	}
>   
> -	text_base = header.e_entry;
> -	section_header_base = header.e_shoff;
> -	section_header_size = header.e_shentsize * header.e_shnum;
> +	text_base = le64_to_cpu(header.e_entry);
> +	section_header_base = le64_to_cpu(header.e_shoff);
> +	section_header_size = le16_to_cpu(header.e_shentsize) *
> +			      le16_to_cpu(header.e_shnum);
>   
>   	sh_table = malloc(section_header_size);
>   	if (!sh_table) {
> @@ -114,9 +117,9 @@ static int decode_elf64(FILE *felf, char **argv)
>   		return 27;
>   	}
>   
> -	sh_size = sh_table[header.e_shstrndx].sh_size;
> -	debug("e_shstrndx\t0x%08x\n", header.e_shstrndx);
> -	debug("sh_size\t\t0x%08lx\n", sh_size);
> +	sh_index = le16_to_cpu(header.e_shstrndx);
> +	sh_size = le64_to_cpu(sh_table[sh_index].sh_size);
> +	debug("e_shstrndx %x, sh_size %lx\n", sh_index, sh_size);
>   
>   	sh_str = malloc(sh_size);
>   	if (!sh_str) {
> @@ -130,9 +133,8 @@ static int decode_elf64(FILE *felf, char **argv)
>   	 * Specifies the byte offset from the beginning of the file
>   	 * to the first byte in the section.
>   	 */
> -	sh_offset = sh_table[header.e_shstrndx].sh_offset;
> -
> -	debug("sh_offset\t0x%08x\n", header.e_shnum);
> +	sh_offset = le64_to_cpu(sh_table[sh_index].sh_offset);
> +	sh_num = le16_to_cpu(header.e_shnum);
>   
>   	ret = fseek(felf, sh_offset, SEEK_SET);
>   	if (ret) {
> @@ -153,18 +155,22 @@ static int decode_elf64(FILE *felf, char **argv)
>   		return 30;
>   	}
>   
> -	for (i = 0; i < header.e_shnum; i++) {
> -		/* fprintf(stderr, "%s\n", sh_str + sh_table[i].sh_name); Debug only */
> -		if (!strcmp(".rela.dyn", (sh_str + sh_table[i].sh_name))) {
> +	for (i = 0; i < sh_num; i++) {
> +		char *sh_name = sh_str + le32_to_cpu(sh_table[i].sh_name);
> +
> +		debug("%s\n", sh_name);
> +
> +		sh_addr = le64_to_cpu(sh_table[i].sh_addr);
> +		sh_offset = le64_to_cpu(sh_table[i].sh_offset);
> +		sh_size = le64_to_cpu(sh_table[i].sh_size);

nit: We could move this below sh_name checking but that's fine.

> +
> +		if (!strcmp(".rela.dyn", sh_name)) {
>   			debug("Found section\t\".rela_dyn\"\n");
> -			debug(" at addr\t0x%08x\n",
> -			      (unsigned int)sh_table[i].sh_addr);
> -			debug(" at offset\t0x%08x\n",
> -			      (unsigned int)sh_table[i].sh_offset);
> -			debug(" of size\t0x%08x\n",
> -			      (unsigned int)sh_table[i].sh_size);
> -			rela_start = sh_table[i].sh_addr;
> -			rela_end = rela_start + sh_table[i].sh_size;
> +			debug(" at addr\t0x%08x\n", sh_addr);
> +			debug(" at offset\t0x%08x\n", sh_offset);
> +			debug(" of size\t0x%08x\n", sh_size);
> +			rela_start = sh_addr;
> +			rela_end = rela_start + sh_size;
>   			break;
>   		}
>   	}
> @@ -188,7 +194,9 @@ static int decode_elf32(FILE *felf, char **argv)
>   {
>   	size_t size;
>   	Elf32_Ehdr header;
> -	uint64_t section_header_base, section_header_size, sh_offset, sh_size;
> +	uint64_t section_header_base, section_header_size;
> +	uint32_t sh_addr, sh_offset, sh_size;
> +	Elf32_Half sh_index, sh_num;
>   	Elf32_Shdr *sh_table; /* Elf symbol table */
>   	int ret, i, machine;
>   	char *sh_str;
> @@ -204,7 +212,7 @@ static int decode_elf32(FILE *felf, char **argv)
>   		return 25;
>   	}
>   
> -	machine = header.e_machine;
> +	machine = le16_to_cpu(header.e_machine);
>   	debug("Machine %d\n", machine);
>   
>   	if (machine != EM_MICROBLAZE) {
> @@ -212,14 +220,10 @@ static int decode_elf32(FILE *felf, char **argv)
>   		return 30;
>   	}
>   
> -	text_base = header.e_entry;
> -	section_header_base = header.e_shoff;
> -
> -	debug("Section header base %x\n", section_header_base);
> -
> -	section_header_size = header.e_shentsize * header.e_shnum;
> -
> -	debug("Section header size %d\n", section_header_size);
> +	text_base = le32_to_cpu(header.e_entry);
> +	section_header_base = le32_to_cpu(header.e_shoff);
> +	section_header_size = le16_to_cpu(header.e_shentsize) *
> +			      le16_to_cpu(header.e_shnum);
>   
>   	sh_table = malloc(section_header_size);
>   	if (!sh_table) {
> @@ -247,8 +251,9 @@ static int decode_elf32(FILE *felf, char **argv)
>   		return 27;
>   	}
>   
> -	sh_size = sh_table[header.e_shstrndx].sh_size;
> -	debug("e_shstrndx %x, sh_size %lx\n", header.e_shstrndx, sh_size);
> +	sh_index = le16_to_cpu(header.e_shstrndx);
> +	sh_size = le32_to_cpu(sh_table[sh_index].sh_size);
> +	debug("e_shstrndx %x, sh_size %lx\n", sh_index, sh_size);
>   
>   	sh_str = malloc(sh_size);
>   	if (!sh_str) {
> @@ -262,9 +267,8 @@ static int decode_elf32(FILE *felf, char **argv)
>   	 * Specifies the byte offset from the beginning of the file
>   	 * to the first byte in the section.
>   	 */
> -	sh_offset = sh_table[header.e_shstrndx].sh_offset;
> -
> -	debug("sh_offset %x\n", header.e_shnum);
> +	sh_offset = le32_to_cpu(sh_table[sh_index].sh_offset);
> +	sh_num = le16_to_cpu(header.e_shnum);
>   
>   	ret = fseek(felf, sh_offset, SEEK_SET);
>   	if (ret) {
> @@ -277,7 +281,7 @@ static int decode_elf32(FILE *felf, char **argv)
>   
>   	size = fread(sh_str, 1, sh_size, felf);
>   	if (size != sh_size) {
> -		fprintf(stderr, "%s: Can't read section: %lx/%lx\n",
> +		fprintf(stderr, "%s: Can't read section: %lx/%x\n",
>   			argv[0], size, sh_size);
>   		free(sh_str);
>   		free(sh_table);
> @@ -285,22 +289,29 @@ static int decode_elf32(FILE *felf, char **argv)
>   		return 30;
>   	}
>   
> -	for (i = 0; i < header.e_shnum; i++) {
> -		debug("%s\n", sh_str + sh_table[i].sh_name);
> -		if (!strcmp(".rela.dyn", (sh_str + sh_table[i].sh_name))) {
> +	for (i = 0; i < sh_num; i++) {
> +		char *sh_name = sh_str + le32_to_cpu(sh_table[i].sh_name);
> +
> +		debug("%s\n", sh_name);
> +
> +		sh_addr = le64_to_cpu(sh_table[i].sh_addr);
> +		sh_offset = le64_to_cpu(sh_table[i].sh_offset);
> +		sh_size = le64_to_cpu(sh_table[i].sh_size);
> +
> +		if (!strcmp(".rela.dyn", sh_name)) {
>   			debug("Found section\t\".rela_dyn\"\n");
> -			debug(" at addr\t0x%08x\n", (unsigned int)sh_table[i].sh_addr);
> -			debug(" at offset\t0x%08x\n", (unsigned int)sh_table[i].sh_offset);
> -			debug(" of size\t0x%08x\n", (unsigned int)sh_table[i].sh_size);
> -			rela_start = sh_table[i].sh_addr;
> -			rela_end = rela_start + sh_table[i].sh_size;
> +			debug(" at addr\t0x%08x\n", sh_addr);
> +			debug(" at offset\t0x%08x\n", sh_offset);
> +			debug(" of size\t0x%08x\n", sh_size);
> +			rela_start = sh_addr;
> +			rela_end = rela_start + sh_size;
>   		}
> -		if (!strcmp(".dynsym", (sh_str + sh_table[i].sh_name))) {
> +		if (!strcmp(".dynsym", sh_name)) {
>   			debug("Found section\t\".dynsym\"\n");
> -			debug(" at addr\t0x%08x\n", (unsigned int)sh_table[i].sh_addr);
> -			debug(" at offset\t0x%08x\n", (unsigned int)sh_table[i].sh_offset);
> -			debug(" of size\t0x%08x\n", (unsigned int)sh_table[i].sh_size);
> -			dyn_start = sh_table[i].sh_addr;
> +			debug(" at addr\t0x%08x\n", sh_addr);
> +			debug(" at offset\t0x%08x\n", sh_offset);
> +			debug(" of size\t0x%08x\n", sh_size);
> +			dyn_start = sh_addr;
>   		}
>   	}
>   
> @@ -386,9 +397,9 @@ static int rela_elf64(char **argv, FILE *f)
>   			return 4;
>   		}
>   
> -		swrela.r_offset = cpu_to_le64(rela.r_offset);
> -		swrela.r_info = cpu_to_le64(rela.r_info);
> -		swrela.r_addend = cpu_to_le64(rela.r_addend);
> +		swrela.r_offset = le64_to_cpu(rela.r_offset);
> +		swrela.r_info = le64_to_cpu(rela.r_info);
> +		swrela.r_addend = le64_to_cpu(rela.r_addend);
>   
>   		if (!supported_rela(&swrela))
>   			continue;
> @@ -487,9 +498,9 @@ static int rela_elf32(char **argv, FILE *f)
>   		      PRIu32 " r_addend:\t%" PRIx32 "\n",
>   		      rela.r_offset, rela.r_info, rela.r_addend);
>   
> -		swrela.r_offset = cpu_to_le32(rela.r_offset);
> -		swrela.r_info = cpu_to_le32(rela.r_info);
> -		swrela.r_addend = cpu_to_le32(rela.r_addend);
> +		swrela.r_offset = le32_to_cpu(rela.r_offset);
> +		swrela.r_info = le32_to_cpu(rela.r_info);
> +		swrela.r_addend = le32_to_cpu(rela.r_addend);
>   
>   		debug("SWRela:\toffset:\t%" PRIx32 " r_info:\t%"
>   		      PRIu32 " r_addend:\t%" PRIx32 "\n",

I have tested it on arm64 and also microblaze and it works fine.

Applied.
M


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