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228 lines
5.8 KiB
228 lines
5.8 KiB
/* |
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* vdso2c - A vdso image preparation tool |
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* Copyright (c) 2014 Andy Lutomirski and others |
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* Licensed under the GPL v2 |
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* |
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* vdso2c requires stripped and unstripped input. It would be trivial |
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* to fully strip the input in here, but, for reasons described below, |
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* we need to write a section table. Doing this is more or less |
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* equivalent to dropping all non-allocatable sections, but it's |
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* easier to let objcopy handle that instead of doing it ourselves. |
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* If we ever need to do something fancier than what objcopy provides, |
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* it would be straightforward to add here. |
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* |
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* We keep a section table for a few reasons: |
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* |
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* Binutils has issues debugging the vDSO: it reads the section table to |
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* find SHT_NOTE; it won't look at PT_NOTE for the in-memory vDSO, which |
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* would break build-id if we removed the section table. Binutils |
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* also requires that shstrndx != 0. See: |
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* https://sourceware.org/bugzilla/show_bug.cgi?id=17064 |
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* |
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* elfutils might not look for PT_NOTE if there is a section table at |
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* all. I don't know whether this matters for any practical purpose. |
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* |
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* For simplicity, rather than hacking up a partial section table, we |
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* just write a mostly complete one. We omit non-dynamic symbols, |
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* though, since they're rather large. |
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* |
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* Once binutils gets fixed, we might be able to drop this for all but |
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* the 64-bit vdso, since build-id only works in kernel RPMs, and |
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* systems that update to new enough kernel RPMs will likely update |
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* binutils in sync. build-id has never worked for home-built kernel |
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* RPMs without manual symlinking, and I suspect that no one ever does |
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* that. |
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*/ |
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/* |
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* Copyright (c) 2017 Oracle and/or its affiliates. All rights reserved. |
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*/ |
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#include <inttypes.h> |
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#include <stdint.h> |
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#include <unistd.h> |
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#include <stdarg.h> |
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#include <stdlib.h> |
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#include <stdio.h> |
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#include <string.h> |
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#include <fcntl.h> |
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#include <err.h> |
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#include <sys/mman.h> |
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#include <sys/types.h> |
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#include <tools/be_byteshift.h> |
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#include <linux/elf.h> |
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#include <linux/types.h> |
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#include <linux/kernel.h> |
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const char *outfilename; |
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/* Symbols that we need in vdso2c. */ |
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enum { |
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sym_vvar_start, |
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sym_VDSO_FAKE_SECTION_TABLE_START, |
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sym_VDSO_FAKE_SECTION_TABLE_END, |
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}; |
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struct vdso_sym { |
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const char *name; |
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int export; |
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}; |
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struct vdso_sym required_syms[] = { |
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[sym_vvar_start] = {"vvar_start", 1}, |
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[sym_VDSO_FAKE_SECTION_TABLE_START] = { |
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"VDSO_FAKE_SECTION_TABLE_START", 0 |
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}, |
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[sym_VDSO_FAKE_SECTION_TABLE_END] = { |
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"VDSO_FAKE_SECTION_TABLE_END", 0 |
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}, |
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}; |
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__attribute__((format(printf, 1, 2))) __attribute__((noreturn)) |
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static void fail(const char *format, ...) |
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{ |
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va_list ap; |
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va_start(ap, format); |
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fprintf(stderr, "Error: "); |
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vfprintf(stderr, format, ap); |
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if (outfilename) |
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unlink(outfilename); |
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exit(1); |
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va_end(ap); |
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} |
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/* |
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* Evil macros for big-endian reads and writes |
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*/ |
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#define GBE(x, bits, ifnot) \ |
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__builtin_choose_expr( \ |
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(sizeof(*(x)) == bits/8), \ |
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(__typeof__(*(x)))get_unaligned_be##bits(x), ifnot) |
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#define LAST_GBE(x) \ |
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__builtin_choose_expr(sizeof(*(x)) == 1, *(x), (void)(0)) |
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#define GET_BE(x) \ |
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GBE(x, 64, GBE(x, 32, GBE(x, 16, LAST_GBE(x)))) |
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#define PBE(x, val, bits, ifnot) \ |
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__builtin_choose_expr( \ |
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(sizeof(*(x)) == bits/8), \ |
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put_unaligned_be##bits((val), (x)), ifnot) |
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#define LAST_PBE(x, val) \ |
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__builtin_choose_expr(sizeof(*(x)) == 1, *(x) = (val), (void)(0)) |
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#define PUT_BE(x, val) \ |
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PBE(x, val, 64, PBE(x, val, 32, PBE(x, val, 16, LAST_PBE(x, val)))) |
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#define NSYMS ARRAY_SIZE(required_syms) |
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#define BITSFUNC3(name, bits, suffix) name##bits##suffix |
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#define BITSFUNC2(name, bits, suffix) BITSFUNC3(name, bits, suffix) |
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#define BITSFUNC(name) BITSFUNC2(name, ELF_BITS, ) |
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#define INT_BITS BITSFUNC2(int, ELF_BITS, _t) |
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#define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x |
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#define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x) |
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#define ELF(x) ELF_BITS_XFORM(ELF_BITS, x) |
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#define ELF_BITS 64 |
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#include "vdso2c.h" |
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#undef ELF_BITS |
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#define ELF_BITS 32 |
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#include "vdso2c.h" |
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#undef ELF_BITS |
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static void go(void *raw_addr, size_t raw_len, |
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void *stripped_addr, size_t stripped_len, |
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FILE *outfile, const char *name) |
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{ |
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Elf64_Ehdr *hdr = (Elf64_Ehdr *)raw_addr; |
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if (hdr->e_ident[EI_CLASS] == ELFCLASS64) { |
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go64(raw_addr, raw_len, stripped_addr, stripped_len, |
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outfile, name); |
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} else if (hdr->e_ident[EI_CLASS] == ELFCLASS32) { |
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go32(raw_addr, raw_len, stripped_addr, stripped_len, |
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outfile, name); |
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} else { |
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fail("unknown ELF class\n"); |
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} |
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} |
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static void map_input(const char *name, void **addr, size_t *len, int prot) |
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{ |
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off_t tmp_len; |
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int fd = open(name, O_RDONLY); |
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if (fd == -1) |
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err(1, "%s", name); |
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tmp_len = lseek(fd, 0, SEEK_END); |
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if (tmp_len == (off_t)-1) |
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err(1, "lseek"); |
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*len = (size_t)tmp_len; |
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*addr = mmap(NULL, tmp_len, prot, MAP_PRIVATE, fd, 0); |
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if (*addr == MAP_FAILED) |
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err(1, "mmap"); |
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close(fd); |
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} |
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int main(int argc, char **argv) |
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{ |
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size_t raw_len, stripped_len; |
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void *raw_addr, *stripped_addr; |
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FILE *outfile; |
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char *name, *tmp; |
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int namelen; |
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if (argc != 4) { |
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printf("Usage: vdso2c RAW_INPUT STRIPPED_INPUT OUTPUT\n"); |
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return 1; |
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} |
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/* |
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* Figure out the struct name. If we're writing to a .so file, |
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* generate raw output insted. |
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*/ |
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name = strdup(argv[3]); |
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namelen = strlen(name); |
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if (namelen >= 3 && !strcmp(name + namelen - 3, ".so")) { |
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name = NULL; |
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} else { |
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tmp = strrchr(name, '/'); |
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if (tmp) |
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name = tmp + 1; |
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tmp = strchr(name, '.'); |
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if (tmp) |
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*tmp = '\0'; |
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for (tmp = name; *tmp; tmp++) |
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if (*tmp == '-') |
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*tmp = '_'; |
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} |
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map_input(argv[1], &raw_addr, &raw_len, PROT_READ); |
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map_input(argv[2], &stripped_addr, &stripped_len, PROT_READ); |
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outfilename = argv[3]; |
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outfile = fopen(outfilename, "w"); |
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if (!outfile) |
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err(1, "%s", argv[2]); |
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go(raw_addr, raw_len, stripped_addr, stripped_len, outfile, name); |
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munmap(raw_addr, raw_len); |
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munmap(stripped_addr, stripped_len); |
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fclose(outfile); |
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return 0; |
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}
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