From dc76d5c6eb07ddab8b20e71b1161fe3a72ca045f Mon Sep 17 00:00:00 2001 From: Vladimir Serbinenko Date: Thu, 18 Feb 2016 20:57:21 +0100 Subject: [PATCH 4/6] Provide __bss_start and _end symbols in grub-mkimage. For this ensure that all bss sections are merged. We need this to correctly prelink non-PE relocatable images. --- include/grub/util/mkimage.h | 2 + util/grub-mkimagexx.c | 133 ++++++++++++++++++++++++++++---------------- 2 files changed, 87 insertions(+), 48 deletions(-) diff --git a/include/grub/util/mkimage.h b/include/grub/util/mkimage.h index 8169939..25a49d5 100644 --- a/include/grub/util/mkimage.h +++ b/include/grub/util/mkimage.h @@ -33,6 +33,8 @@ struct grub_mkimage_layout grub_size_t ia64_got_off; grub_size_t got_size; unsigned ia64jmpnum; + Elf_Addr bss_start; + Elf_Addr end; }; /* Private header. Use only in mkimage-related sources. */ diff --git a/util/grub-mkimagexx.c b/util/grub-mkimagexx.c index 74f86f5..433322d 100644 --- a/util/grub-mkimagexx.c +++ b/util/grub-mkimagexx.c @@ -490,6 +490,7 @@ SUFFIX (relocate_symbols) (Elf_Ehdr *e, Elf_Shdr *sections, Elf_Shdr *symtab_section, Elf_Addr *section_addresses, Elf_Half section_entsize, Elf_Half num_sections, void *jumpers, Elf_Addr jumpers_addr, + Elf_Addr bss_start, Elf_Addr end, const struct grub_install_image_target_desc *image_target) { Elf_Word symtab_size, sym_size, num_syms; @@ -528,16 +529,22 @@ SUFFIX (relocate_symbols) (Elf_Ehdr *e, Elf_Shdr *sections, } else if (cur_index == STN_UNDEF) { - if (sym->st_name) + if (sym->st_name && grub_strcmp (name, "__bss_start")) + sym->st_value = bss_start; + else if (sym->st_name && grub_strcmp (name, "__end")) + sym->st_value = end; + else if (sym->st_name) grub_util_error ("undefined symbol %s", name); else continue; } else if (cur_index >= num_sections) grub_util_error ("section %d does not exist", cur_index); - - sym->st_value = (grub_target_to_host (sym->st_value) - + section_addresses[cur_index]); + else + { + sym->st_value = (grub_target_to_host (sym->st_value) + + section_addresses[cur_index]); + } if (image_target->elf_target == EM_IA_64 && ELF_ST_TYPE (sym->st_info) == STT_FUNC) @@ -1462,9 +1469,7 @@ SUFFIX (is_text_section) (Elf_Shdr *s, const struct grub_install_image_target_de == (SHF_EXECINSTR | SHF_ALLOC)); } -/* Determine if this section is a data section. This assumes that - BSS is also a data section, since the converter initializes BSS - when producing PE32 to avoid a bug in EFI implementations. */ +/* Determine if this section is a data section. */ static int SUFFIX (is_data_section) (Elf_Shdr *s, const struct grub_install_image_target_desc *image_target) { @@ -1472,7 +1477,16 @@ SUFFIX (is_data_section) (Elf_Shdr *s, const struct grub_install_image_target_de && grub_target_to_host32 (s->sh_type) != SHT_PROGBITS) return 0; return ((grub_target_to_host (s->sh_flags) & (SHF_EXECINSTR | SHF_ALLOC)) - == SHF_ALLOC); + == SHF_ALLOC) && !(grub_target_to_host32 (s->sh_type) == SHT_NOBITS); +} + +static int +SUFFIX (is_bss_section) (Elf_Shdr *s, const struct grub_install_image_target_desc *image_target) +{ + if (!is_relocatable (image_target)) + return 0; + return ((grub_target_to_host (s->sh_flags) & (SHF_EXECINSTR | SHF_ALLOC)) + == SHF_ALLOC) && (grub_target_to_host32 (s->sh_type) == SHT_NOBITS); } /* Return if the ELF header is valid. */ @@ -1492,6 +1506,32 @@ SUFFIX (check_elf_header) (Elf_Ehdr *e, size_t size, const struct grub_install_i return 1; } +static Elf_Addr +SUFFIX (put_section) (Elf_Shdr *s, int i, + Elf_Addr current_address, + Elf_Addr *section_addresses, + const char *strtab, + const struct grub_install_image_target_desc *image_target) +{ + Elf_Word align = grub_host_to_target_addr (s->sh_addralign); + const char *name = strtab + grub_host_to_target32 (s->sh_name); + + if (align) + current_address = ALIGN_UP (current_address + image_target->vaddr_offset, + align) + - image_target->vaddr_offset; + + grub_util_info ("locating the section %s at 0x%" + GRUB_HOST_PRIxLONG_LONG, + name, (unsigned long long) current_address); + if (!is_relocatable (image_target)) + current_address = grub_host_to_target_addr (s->sh_addr) + - image_target->link_addr; + section_addresses[i] = current_address; + current_address += grub_host_to_target_addr (s->sh_size); + return current_address; +} + /* Locate section addresses by merging code sections and data sections into .text and .data, respectively. Return the array of section addresses. */ @@ -1531,32 +1571,22 @@ SUFFIX (locate_sections) (const char *kernel_path, i++, s = (Elf_Shdr *) ((char *) s + section_entsize)) if (SUFFIX (is_text_section) (s, image_target)) { - Elf_Word align = grub_host_to_target_addr (s->sh_addralign); - const char *name = strtab + grub_host_to_target32 (s->sh_name); - if (align) - current_address = ALIGN_UP (current_address + image_target->vaddr_offset, - align) - image_target->vaddr_offset; - grub_util_info ("locating the section %s at 0x%" - GRUB_HOST_PRIxLONG_LONG, - name, (unsigned long long) current_address); - if (image_target->id != IMAGE_EFI) + current_address = SUFFIX (put_section) (s, i, + current_address, + section_addresses, + strtab, + image_target); + if (!is_relocatable (image_target) && + grub_host_to_target_addr (s->sh_addr) != image_target->link_addr) { - current_address = grub_host_to_target_addr (s->sh_addr) - - image_target->link_addr; - if (grub_host_to_target_addr (s->sh_addr) - != image_target->link_addr) - { - char *msg - = grub_xasprintf (_("`%s' is miscompiled: its start address is 0x%llx" - " instead of 0x%llx: ld.gold bug?"), - kernel_path, - (unsigned long long) grub_host_to_target_addr (s->sh_addr), - (unsigned long long) image_target->link_addr); - grub_util_error ("%s", msg); - } + char *msg + = grub_xasprintf (_("`%s' is miscompiled: its start address is 0x%llx" + " instead of 0x%llx: ld.gold bug?"), + kernel_path, + (unsigned long long) grub_host_to_target_addr (s->sh_addr), + (unsigned long long) image_target->link_addr); + grub_util_error ("%s", msg); } - section_addresses[i] = current_address; - current_address += grub_host_to_target_addr (s->sh_size); } current_address = ALIGN_UP (current_address + image_target->vaddr_offset, @@ -1569,27 +1599,31 @@ SUFFIX (locate_sections) (const char *kernel_path, i < num_sections; i++, s = (Elf_Shdr *) ((char *) s + section_entsize)) if (SUFFIX (is_data_section) (s, image_target)) - { - Elf_Word align = grub_host_to_target_addr (s->sh_addralign); - const char *name = strtab + grub_host_to_target32 (s->sh_name); + current_address = SUFFIX (put_section) (s, i, + current_address, + section_addresses, + strtab, + image_target); - if (align) - current_address = ALIGN_UP (current_address + image_target->vaddr_offset, - align) - - image_target->vaddr_offset; + current_address = ALIGN_UP (current_address + image_target->vaddr_offset, + image_target->section_align) - image_target->vaddr_offset; - grub_util_info ("locating the section %s at 0x%" - GRUB_HOST_PRIxLONG_LONG, - name, (unsigned long long) current_address); - if (image_target->id != IMAGE_EFI) - current_address = grub_host_to_target_addr (s->sh_addr) - - image_target->link_addr; - section_addresses[i] = current_address; - current_address += grub_host_to_target_addr (s->sh_size); - } + layout->bss_start = current_address; + + /* .bss */ + for (i = 0, s = sections; + i < num_sections; + i++, s = (Elf_Shdr *) ((char *) s + section_entsize)) + if (SUFFIX (is_bss_section) (s, image_target)) + current_address = SUFFIX (put_section) (s, i, + current_address, + section_addresses, + strtab, + image_target); current_address = ALIGN_UP (current_address + image_target->vaddr_offset, image_target->section_align) - image_target->vaddr_offset; + layout->end = current_address; layout->kernel_size = current_address; return section_addresses; } @@ -1789,8 +1823,11 @@ SUFFIX (grub_mkimage_load_image) (const char *kernel_path, i < num_sections; i++, s = (Elf_Shdr *) ((char *) s + section_entsize)) if (SUFFIX (is_data_section) (s, image_target) + || SUFFIX (is_bss_section) (s, image_target) || SUFFIX (is_text_section) (s, image_target)) { + /* Explicitly initialize BSS + when producing PE32 to avoid a bug in EFI implementations. */ if (grub_target_to_host32 (s->sh_type) == SHT_NOBITS) memset (out_img + section_addresses[i], 0, grub_host_to_target_addr (s->sh_size)); -- 2.7.0