Messages in this thread | | | Subject | Re: [PATCH 3/5] LoongArch: Support relocation against _GLOBAL_OFFSET_TABLE_ | From | Jinyang He <> | Date | Thu, 28 Jul 2022 09:02:57 +0800 |
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On 07/28/2022 12:28 AM, Xi Ruoyao wrote: > With the stack-based relocations, the assembler emits three relocations > to push the PC-relative offset of a GOT entry: > > R_LARCH_SOP_PUSH_PCREL _GLOBAL_OFFSET_TABLE_ > R_LARCH_SOP_PUSH_GPREL foo > R_LARCH_SOP_ADD > > "_GLOBAL_OFFSET_TABLE_" does not really exist in the symtab and the BFD > linker handles it with special hack. Implement a similar hack for > kernel so we will be able to really use R_LARCH_SOP_PUSH_GPREL > relocation. > > Signed-off-by: Xi Ruoyao <xry111@xry111.site> > --- > arch/loongarch/kernel/module-sections.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/arch/loongarch/kernel/module-sections.c b/arch/loongarch/kernel/module-sections.c > index 509c0b86b1e9..73976addbf60 100644 > --- a/arch/loongarch/kernel/module-sections.c > +++ b/arch/loongarch/kernel/module-sections.c > @@ -89,6 +89,9 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, > char *secstrings, struct module *mod) > { > unsigned int i, num_plts = 0, num_gots = 0; > + Elf_Shdr *symtab = NULL; > + Elf_Sym *symbols; > + char *strings; > > /* > * Find the empty .plt sections. > @@ -100,6 +103,8 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, > mod->arch.plt_idx.shdr = sechdrs + i; > else if (!strcmp(secstrings + sechdrs[i].sh_name, ".got")) > mod->arch.got.shdr = sechdrs + i; > + else if (sechdrs[i].sh_type == SHT_SYMTAB) > + symtab = sechdrs + i; > } > > if (!mod->arch.plt.shdr) { > @@ -115,6 +120,22 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, > return -ENOEXEC; > } > > + if (!symtab) { > + pr_err("%s: module symbol table missing\n", mod->name); > + return -ENOEXEC; > + } > + > + symbols = (void *) ehdr + symtab->sh_offset; > + strings = (void *) ehdr + sechdrs[symtab->sh_link].sh_offset; > + > + for (i = 0; i < symtab->sh_size / sizeof(Elf_Sym); i++) > + if (symbols[i].st_shndx == SHN_UNDEF && > + strcmp(strings + symbols[i].st_name, > + "_GLOBAL_OFFSET_TABLE_") == 0) { > + symbols[i].st_shndx = mod->arch.got.shdr - sechdrs; > + symbols[i].st_value = 0; > + } > + > /* Calculate the maxinum number of entries */ > for (i = 0; i < ehdr->e_shnum; i++) { > int num_rela = sechdrs[i].sh_size / sizeof(Elf_Rela);
Hi, Ruoyao,
It is possible to create a symbol when linking, which means maybe we can add _GLOBAL_OFFSET_TABLE_ in 'module.lds.h'. What do you think about it?
Thanks,
Jinyang
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