On Tue, Mar 1, 2022 at 6:22 PM Janosch Frank <fran...@linux.ibm.com> wrote:
>
> Offset calculations are easy enough to get wrong. Let's add a few
> variables to make moving around elf headers and data sections easier.
>
> Signed-off-by: Janosch Frank <fran...@linux.ibm.com>
Reviewed-by: Marc-André Lureau <marcandre.lur...@redhat.com>
> ---
> dump/dump.c | 34 ++++++++++++++--------------------
> include/sysemu/dump.h | 4 ++++
> 2 files changed, 18 insertions(+), 20 deletions(-)
>
> diff --git a/dump/dump.c b/dump/dump.c
> index ce3a5e7003..242f83db95 100644
> --- a/dump/dump.c
> +++ b/dump/dump.c
> @@ -137,13 +137,11 @@ static void write_elf64_header(DumpState *s, Error
> **errp)
> elf_header.e_machine = cpu_to_dump16(s, s->dump_info.d_machine);
> elf_header.e_version = cpu_to_dump32(s, EV_CURRENT);
> elf_header.e_ehsize = cpu_to_dump16(s, sizeof(elf_header));
> - elf_header.e_phoff = cpu_to_dump64(s, sizeof(Elf64_Ehdr));
> + elf_header.e_phoff = cpu_to_dump64(s, s->phdr_offset);
> elf_header.e_phentsize = cpu_to_dump16(s, sizeof(Elf64_Phdr));
> elf_header.e_phnum = cpu_to_dump16(s, phnum);
> if (s->shdr_num) {
> - uint64_t shoff = sizeof(Elf64_Ehdr) + sizeof(Elf64_Phdr) *
> s->phdr_num;
> -
> - elf_header.e_shoff = cpu_to_dump64(s, shoff);
> + elf_header.e_shoff = cpu_to_dump64(s, s->shdr_offset);
> elf_header.e_shentsize = cpu_to_dump16(s, sizeof(Elf64_Shdr));
> elf_header.e_shnum = cpu_to_dump16(s, s->shdr_num);
> }
> @@ -169,13 +167,11 @@ static void write_elf32_header(DumpState *s, Error
> **errp)
> elf_header.e_machine = cpu_to_dump16(s, s->dump_info.d_machine);
> elf_header.e_version = cpu_to_dump32(s, EV_CURRENT);
> elf_header.e_ehsize = cpu_to_dump16(s, sizeof(elf_header));
> - elf_header.e_phoff = cpu_to_dump32(s, sizeof(Elf32_Ehdr));
> + elf_header.e_phoff = cpu_to_dump32(s, s->phdr_offset);
> elf_header.e_phentsize = cpu_to_dump16(s, sizeof(Elf32_Phdr));
> elf_header.e_phnum = cpu_to_dump16(s, phnum);
> if (s->shdr_num) {
> - uint32_t shoff = sizeof(Elf32_Ehdr) + sizeof(Elf32_Phdr) *
> s->phdr_num;
> -
> - elf_header.e_shoff = cpu_to_dump32(s, shoff);
> + elf_header.e_shoff = cpu_to_dump32(s, s->shdr_offset);
> elf_header.e_shentsize = cpu_to_dump16(s, sizeof(Elf32_Shdr));
> elf_header.e_shnum = cpu_to_dump16(s, s->shdr_num);
> }
> @@ -238,12 +234,11 @@ static void write_elf32_load(DumpState *s,
> MemoryMapping *memory_mapping,
> static void write_elf64_note(DumpState *s, Error **errp)
> {
> Elf64_Phdr phdr;
> - hwaddr begin = s->memory_offset - s->note_size;
> int ret;
>
> memset(&phdr, 0, sizeof(Elf64_Phdr));
> phdr.p_type = cpu_to_dump32(s, PT_NOTE);
> - phdr.p_offset = cpu_to_dump64(s, begin);
> + phdr.p_offset = cpu_to_dump64(s, s->note_offset);
> phdr.p_paddr = 0;
> phdr.p_filesz = cpu_to_dump64(s, s->note_size);
> phdr.p_memsz = cpu_to_dump64(s, s->note_size);
> @@ -303,13 +298,12 @@ static void write_elf64_notes(WriteCoreDumpFunction f,
> DumpState *s,
>
> static void write_elf32_note(DumpState *s, Error **errp)
> {
> - hwaddr begin = s->memory_offset - s->note_size;
> Elf32_Phdr phdr;
> int ret;
>
> memset(&phdr, 0, sizeof(Elf32_Phdr));
> phdr.p_type = cpu_to_dump32(s, PT_NOTE);
> - phdr.p_offset = cpu_to_dump32(s, begin);
> + phdr.p_offset = cpu_to_dump32(s, s->note_offset);
> phdr.p_paddr = 0;
> phdr.p_filesz = cpu_to_dump32(s, s->note_size);
> phdr.p_memsz = cpu_to_dump32(s, s->note_size);
> @@ -1828,15 +1822,15 @@ static void dump_init(DumpState *s, int fd, bool
> has_format,
> }
>
> if (s->dump_info.d_class == ELFCLASS64) {
> - s->memory_offset = sizeof(Elf64_Ehdr) +
> - sizeof(Elf64_Phdr) * s->phdr_num +
> - sizeof(Elf64_Shdr) * s->shdr_num +
> - s->note_size;
> + s->phdr_offset = sizeof(Elf64_Ehdr);
> + s->shdr_offset = s->phdr_offset + sizeof(Elf64_Phdr) * s->phdr_num;
> + s->note_offset = s->shdr_offset + sizeof(Elf64_Shdr) * s->shdr_num;
> + s->memory_offset = s->note_offset + s->note_size;
> } else {
> - s->memory_offset = sizeof(Elf32_Ehdr) +
> - sizeof(Elf32_Phdr) * s->phdr_num +
> - sizeof(Elf32_Shdr) * s->shdr_num +
> - s->note_size;
> + s->phdr_offset = sizeof(Elf32_Ehdr);
> + s->shdr_offset = s->phdr_offset + sizeof(Elf32_Phdr) * s->phdr_num;
> + s->note_offset = s->shdr_offset + sizeof(Elf32_Shdr) * s->shdr_num;
> + s->memory_offset = s->note_offset + s->note_size;
> }
>
> return;
> diff --git a/include/sysemu/dump.h b/include/sysemu/dump.h
> index 19458bffbd..ffc2ea1072 100644
> --- a/include/sysemu/dump.h
> +++ b/include/sysemu/dump.h
> @@ -159,6 +159,10 @@ typedef struct DumpState {
> bool resume;
> bool detached;
> ssize_t note_size;
> + hwaddr shdr_offset;
> + hwaddr phdr_offset;
> + hwaddr section_offset;
> + hwaddr note_offset;
> hwaddr memory_offset;
> int fd;
>
> --
> 2.32.0
>
