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ebb5e78cc6
Add an initial implementation of a proper (i.e. an ELF shared library) VDSO. With this commit it does not export any symbols, it only replaces the current signal return trampoline page. A later commit will add user implementations of gettimeofday()/clock_gettime(). To support both new toolchains and old ones which don't generate ABI flags section, we define its content manually and then use a tool (genvdso) to patch up the section to have the correct name and type. genvdso also extracts symbol offsets ({,rt_}sigreturn) needed by the kernel, and generates a C file containing a "struct mips_vdso_image" containing both the VDSO data and these offsets. This C file is compiled into the kernel. On 64-bit kernels we require a different VDSO for each supported ABI, so we may build up to 3 different VDSOs. The VDSO to use is selected by the mips_abi structure. A kernel/user shared data page is created and mapped below the VDSO image. This is currently empty, but will be used by the user time function implementations which are added later. [markos.chandras@imgtec.com: - Add more comments - Move abi detection in genvdso.h since it's the get_symbol function that needs it. - Add an R6 specific way to calculate the base address of VDSO in order to avoid the branch instruction which affects performance. - Do not patch .gnu.attributes since it's not needed for dynamic linking. - Simplify Makefile a little bit. - checkpatch fixes - Restrict VDSO support for binutils < 2.25 for pre-R6 - Include atomic64.h for O32 variant on MIPS64] Signed-off-by: Alex Smith <alex.smith@imgtec.com> Signed-off-by: Markos Chandras <markos.chandras@imgtec.com> Cc: Matthew Fortune <matthew.fortune@imgtec.com> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/11337/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
188 lines
4.6 KiB
C
188 lines
4.6 KiB
C
/*
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* Copyright (C) 2015 Imagination Technologies
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* Author: Alex Smith <alex.smith@imgtec.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*/
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static inline bool FUNC(patch_vdso)(const char *path, void *vdso)
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{
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const ELF(Ehdr) *ehdr = vdso;
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void *shdrs;
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ELF(Shdr) *shdr;
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char *shstrtab, *name;
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uint16_t sh_count, sh_entsize, i;
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unsigned int local_gotno, symtabno, gotsym;
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ELF(Dyn) *dyn = NULL;
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shdrs = vdso + FUNC(swap_uint)(ehdr->e_shoff);
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sh_count = swap_uint16(ehdr->e_shnum);
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sh_entsize = swap_uint16(ehdr->e_shentsize);
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shdr = shdrs + (sh_entsize * swap_uint16(ehdr->e_shstrndx));
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shstrtab = vdso + FUNC(swap_uint)(shdr->sh_offset);
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for (i = 0; i < sh_count; i++) {
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shdr = shdrs + (i * sh_entsize);
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name = shstrtab + swap_uint32(shdr->sh_name);
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/*
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* Ensure there are no relocation sections - ld.so does not
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* relocate the VDSO so if there are relocations things will
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* break.
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*/
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switch (swap_uint32(shdr->sh_type)) {
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case SHT_REL:
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case SHT_RELA:
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fprintf(stderr,
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"%s: '%s' contains relocation sections\n",
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program_name, path);
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return false;
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case SHT_DYNAMIC:
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dyn = vdso + FUNC(swap_uint)(shdr->sh_offset);
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break;
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}
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/* Check for existing sections. */
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if (strcmp(name, ".MIPS.abiflags") == 0) {
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fprintf(stderr,
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"%s: '%s' already contains a '.MIPS.abiflags' section\n",
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program_name, path);
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return false;
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}
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if (strcmp(name, ".mips_abiflags") == 0) {
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strcpy(name, ".MIPS.abiflags");
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shdr->sh_type = swap_uint32(SHT_MIPS_ABIFLAGS);
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shdr->sh_entsize = shdr->sh_size;
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}
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}
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/*
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* Ensure the GOT has no entries other than the standard 2, for the same
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* reason we check that there's no relocation sections above.
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* The standard two entries are:
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* - Lazy resolver
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* - Module pointer
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*/
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if (dyn) {
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local_gotno = symtabno = gotsym = 0;
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while (FUNC(swap_uint)(dyn->d_tag) != DT_NULL) {
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switch (FUNC(swap_uint)(dyn->d_tag)) {
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/*
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* This member holds the number of local GOT entries.
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*/
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case DT_MIPS_LOCAL_GOTNO:
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local_gotno = FUNC(swap_uint)(dyn->d_un.d_val);
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break;
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/*
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* This member holds the number of entries in the
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* .dynsym section.
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*/
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case DT_MIPS_SYMTABNO:
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symtabno = FUNC(swap_uint)(dyn->d_un.d_val);
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break;
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/*
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* This member holds the index of the first dynamic
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* symbol table entry that corresponds to an entry in
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* the GOT.
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*/
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case DT_MIPS_GOTSYM:
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gotsym = FUNC(swap_uint)(dyn->d_un.d_val);
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break;
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}
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dyn++;
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}
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if (local_gotno > 2 || symtabno - gotsym) {
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fprintf(stderr,
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"%s: '%s' contains unexpected GOT entries\n",
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program_name, path);
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return false;
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}
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}
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return true;
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}
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static inline bool FUNC(get_symbols)(const char *path, void *vdso)
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{
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const ELF(Ehdr) *ehdr = vdso;
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void *shdrs, *symtab;
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ELF(Shdr) *shdr;
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const ELF(Sym) *sym;
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char *strtab, *name;
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uint16_t sh_count, sh_entsize, st_count, st_entsize, i, j;
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uint64_t offset;
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uint32_t flags;
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shdrs = vdso + FUNC(swap_uint)(ehdr->e_shoff);
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sh_count = swap_uint16(ehdr->e_shnum);
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sh_entsize = swap_uint16(ehdr->e_shentsize);
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for (i = 0; i < sh_count; i++) {
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shdr = shdrs + (i * sh_entsize);
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if (swap_uint32(shdr->sh_type) == SHT_SYMTAB)
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break;
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}
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if (i == sh_count) {
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fprintf(stderr, "%s: '%s' has no symbol table\n", program_name,
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path);
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return false;
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}
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/* Get flags */
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flags = swap_uint32(ehdr->e_flags);
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if (elf_class == ELFCLASS64)
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elf_abi = ABI_N64;
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else if (flags & EF_MIPS_ABI2)
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elf_abi = ABI_N32;
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else
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elf_abi = ABI_O32;
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/* Get symbol table. */
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symtab = vdso + FUNC(swap_uint)(shdr->sh_offset);
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st_entsize = FUNC(swap_uint)(shdr->sh_entsize);
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st_count = FUNC(swap_uint)(shdr->sh_size) / st_entsize;
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/* Get string table. */
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shdr = shdrs + (swap_uint32(shdr->sh_link) * sh_entsize);
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strtab = vdso + FUNC(swap_uint)(shdr->sh_offset);
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/* Write offsets for symbols needed by the kernel. */
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for (i = 0; vdso_symbols[i].name; i++) {
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if (!(vdso_symbols[i].abis & elf_abi))
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continue;
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for (j = 0; j < st_count; j++) {
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sym = symtab + (j * st_entsize);
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name = strtab + swap_uint32(sym->st_name);
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if (!strcmp(name, vdso_symbols[i].name)) {
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offset = FUNC(swap_uint)(sym->st_value);
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fprintf(out_file,
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"\t.%s = 0x%" PRIx64 ",\n",
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vdso_symbols[i].offset_name, offset);
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break;
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}
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}
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if (j == st_count) {
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fprintf(stderr,
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"%s: '%s' is missing required symbol '%s'\n",
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program_name, path, vdso_symbols[i].name);
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return false;
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}
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}
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return true;
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}
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