EFI expects a relocatable PE, and the loader will patch in the relocations from the COFF.
Since we are wrapping an ELF into a PE here, the EFI loader will not handle ELF relocations, and we need to patch the ELF .dynamic section manually on early boot. Signed-off-by: Varad Gautam <[email protected]> --- x86/efi_main.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) diff --git a/x86/efi_main.c b/x86/efi_main.c index 237d4e7..be3f9ab 100644 --- a/x86/efi_main.c +++ b/x86/efi_main.c @@ -1,9 +1,13 @@ #include <alloc_phys.h> #include <linux/uefi.h> +#include <elf.h> unsigned long __efiapi efi_main(efi_handle_t handle, efi_system_table_t *sys_tab); efi_system_table_t *efi_system_table = NULL; +extern char ImageBase; +extern char _DYNAMIC; + static void efi_free_pool(void *ptr) { efi_bs_call(free_pool, ptr); @@ -93,11 +97,70 @@ static efi_status_t exit_efi(void *handle) return EFI_SUCCESS; } +static efi_status_t elf_reloc(unsigned long image_base, unsigned long dynamic) +{ + long relsz = 0, relent = 0; + Elf64_Rel *rel = 0; + Elf64_Dyn *dyn = (Elf64_Dyn *) dynamic; + unsigned long *addr; + int i; + + for (i = 0; dyn[i].d_tag != DT_NULL; i++) { + switch (dyn[i].d_tag) { + case DT_RELA: + rel = (Elf64_Rel *) + ((unsigned long) dyn[i].d_un.d_ptr + image_base); + break; + case DT_RELASZ: + relsz = dyn[i].d_un.d_val; + break; + case DT_RELAENT: + relent = dyn[i].d_un.d_val; + break; + default: + break; + } + } + + if (!rel && relent == 0) + return EFI_SUCCESS; + + if (!rel || relent == 0) + return EFI_LOAD_ERROR; + + while (relsz > 0) { + /* apply the relocs */ + switch (ELF64_R_TYPE (rel->r_info)) { + case R_X86_64_NONE: + break; + case R_X86_64_RELATIVE: + addr = (unsigned long *) (image_base + rel->r_offset); + *addr += image_base; + break; + default: + break; + } + rel = (Elf64_Rel *) ((char *) rel + relent); + relsz -= relent; + } + return EFI_SUCCESS; +} + unsigned long __efiapi efi_main(efi_handle_t handle, efi_system_table_t *sys_tab) { + unsigned long image_base, dyn; efi_system_table = sys_tab; exit_efi(handle); + image_base = (unsigned long) &ImageBase; + dyn = image_base + (unsigned long) &_DYNAMIC; + + /* The EFI loader does not handle ELF relocations, so fixup + * .dynamic addresses before proceeding any further. */ + elf_reloc(image_base, dyn); + + start64(); + return 0; } -- 2.30.2 _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
