Hi Clément,
On Mon, Mar 18, 2019 at 08:16:47PM +0100, Clément Leger wrote:
> This patch add elf64 loading support to the elf loader. Since
> elf32 and elf64 uses completely different types, to avoid copying all
> the code and simply replace elf32 with elf64, use a macro which will
> return the appropriate field for each type of header. This macro
> generates getter for elf structures according to the class of the loaded
> elf.
> All direct elf struct dereference are then replaced by call to generated
> functions. This allows to keep a common loader code even if types are
> different.
>
> Signed-off-by: Clément Léger <clement.leger@xxxxxxxxx>
> ---
> common/elf.c | 46 +++++++++++++++++++++++-----------------------
> include/elf.h | 27 +++++++++++++++++++++++++++
> 2 files changed, 50 insertions(+), 23 deletions(-)
>
> diff --git a/common/elf.c b/common/elf.c
> index 8edf38856..bfb878954 100644
> --- a/common/elf.c
> +++ b/common/elf.c
> @@ -43,31 +43,32 @@ static void elf_release_regions(struct elf_image *elf)
> }
> }
>
> -
> static int load_elf_phdr_segment(struct elf_image *elf, void *src,
> - Elf32_Phdr *phdr)
> + void *phdr)
> {
> - void *dst = (void *)phdr->p_paddr;
> + void *dst = (void *) elf_phdr_p_paddr(elf, phdr);
> int ret;
> + unsigned long p_filesz = elf_phdr_p_filesz(elf, phdr);
> + unsigned long p_memsz = elf_phdr_p_memsz(elf, phdr);
>
> /* we care only about PT_LOAD segments */
> - if (phdr->p_type != PT_LOAD)
> + if (elf_phdr_p_type(elf, phdr) != PT_LOAD)
> return 0;
>
> - if (!phdr->p_filesz)
> + if (!p_filesz)
> return 0;
>
> - pr_debug("Loading phdr to 0x%p (%i bytes)\n", dst, phdr->p_filesz);
> + pr_debug("Loading phdr to 0x%p (%ld bytes)\n", dst, p_filesz);
%lu for p_filesz?
> @@ -400,6 +400,7 @@ static inline void arch_write_notes(struct file *file) { }
>
> struct elf_image {
> struct list_head list;
> + unsigned long class;
> unsigned long entry;
> void *buf;
> };
> @@ -407,4 +408,30 @@ struct elf_image {
> struct elf_image *elf_load_image(void *buf);
> void elf_release_image(struct elf_image *elf);
>
> +#define ELF_GET_FIELD(__s, __field, __type) \
> +static inline __type elf_##__s##_##__field(struct elf_image *elf, void *arg) { \
> + if (elf->class == ELFCLASS32) \
> + return (__type) ((struct elf32_##__s *) arg)->__field; \
> + else \
> + return (__type) ((struct elf64_##__s *) arg)->__field; \
> +}
> +
> +ELF_GET_FIELD(hdr, e_entry, unsigned long)
> +ELF_GET_FIELD(hdr, e_phnum, unsigned long)
> +ELF_GET_FIELD(hdr, e_phoff, unsigned long)
> +ELF_GET_FIELD(hdr, e_type, unsigned long)
> +ELF_GET_FIELD(phdr, p_paddr, unsigned long)
> +ELF_GET_FIELD(phdr, p_filesz, unsigned long)
> +ELF_GET_FIELD(phdr, p_memsz, unsigned long)
> +ELF_GET_FIELD(phdr, p_type, unsigned long)
> +ELF_GET_FIELD(phdr, p_offset, unsigned long)
When it's always unsigned long why do we have to pass in the type as an
argument?
I am undecided if this is the right approach. "unsigned long" is wrong
when a ELF file for a foreign architecture is loaded. This can happen
for example when code for the Cortex M4 cores is loaded from the 64bit
Cortex A cores is loaded on an i.MX8 for example. Using the bigger types
then is not a problem, but maybe it could happen the other way round,
loading a 64bit ELF on a 32bit architecture?
I can't see a real problem here, I just wanted to note. Are there other
opinions?
Sascha
--
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