| /* |
| * vdso2c - A vdso image preparation tool |
| * Copyright (c) 2014 Andy Lutomirski and others |
| * Licensed under the GPL v2 |
| * |
| * vdso2c requires stripped and unstripped input. It would be trivial |
| * to fully strip the input in here, but, for reasons described below, |
| * we need to write a section table. Doing this is more or less |
| * equivalent to dropping all non-allocatable sections, but it's |
| * easier to let objcopy handle that instead of doing it ourselves. |
| * If we ever need to do something fancier than what objcopy provides, |
| * it would be straightforward to add here. |
| * |
| * We're keep a section table for a few reasons: |
| * |
| * The Go runtime had a couple of bugs: it would read the section |
| * table to try to figure out how many dynamic symbols there were (it |
| * shouldn't have looked at the section table at all) and, if there |
| * were no SHT_SYNDYM section table entry, it would use an |
| * uninitialized value for the number of symbols. An empty DYNSYM |
| * table would work, but I see no reason not to write a valid one (and |
| * keep full performance for old Go programs). This hack is only |
| * needed on x86_64. |
| * |
| * The bug was introduced on 2012-08-31 by: |
| * https://code.google.com/p/go/source/detail?r=56ea40aac72b |
| * and was fixed on 2014-06-13 by: |
| * https://code.google.com/p/go/source/detail?r=fc1cd5e12595 |
| * |
| * Binutils has issues debugging the vDSO: it reads the section table to |
| * find SHT_NOTE; it won't look at PT_NOTE for the in-memory vDSO, which |
| * would break build-id if we removed the section table. Binutils |
| * also requires that shstrndx != 0. See: |
| * https://sourceware.org/bugzilla/show_bug.cgi?id=17064 |
| * |
| * elfutils might not look for PT_NOTE if there is a section table at |
| * all. I don't know whether this matters for any practical purpose. |
| * |
| * For simplicity, rather than hacking up a partial section table, we |
| * just write a mostly complete one. We omit non-dynamic symbols, |
| * though, since they're rather large. |
| * |
| * Once binutils gets fixed, we might be able to drop this for all but |
| * the 64-bit vdso, since build-id only works in kernel RPMs, and |
| * systems that update to new enough kernel RPMs will likely update |
| * binutils in sync. build-id has never worked for home-built kernel |
| * RPMs without manual symlinking, and I suspect that no one ever does |
| * that. |
| */ |
| |
| #include <inttypes.h> |
| #include <stdint.h> |
| #include <unistd.h> |
| #include <stdarg.h> |
| #include <stdlib.h> |
| #include <stdio.h> |
| #include <string.h> |
| #include <fcntl.h> |
| #include <err.h> |
| |
| #include <sys/mman.h> |
| #include <sys/types.h> |
| |
| #include <tools/le_byteshift.h> |
| |
| #include <linux/elf.h> |
| #include <linux/types.h> |
| #include <linux/kernel.h> |
| |
| const char *outfilename; |
| |
| /* Symbols that we need in vdso2c. */ |
| enum { |
| sym_vvar_start, |
| sym_vvar_page, |
| sym_hpet_page, |
| sym_pvclock_page, |
| sym_hvclock_page, |
| }; |
| |
| const int special_pages[] = { |
| sym_vvar_page, |
| sym_hpet_page, |
| sym_pvclock_page, |
| sym_hvclock_page, |
| }; |
| |
| struct vdso_sym { |
| const char *name; |
| bool export; |
| }; |
| |
| struct vdso_sym required_syms[] = { |
| [sym_vvar_start] = {"vvar_start", true}, |
| [sym_vvar_page] = {"vvar_page", true}, |
| [sym_hpet_page] = {"hpet_page", true}, |
| [sym_pvclock_page] = {"pvclock_page", true}, |
| [sym_hvclock_page] = {"hvclock_page", true}, |
| {"VDSO32_NOTE_MASK", true}, |
| {"__kernel_vsyscall", true}, |
| {"__kernel_sigreturn", true}, |
| {"__kernel_rt_sigreturn", true}, |
| {"int80_landing_pad", true}, |
| }; |
| |
| __attribute__((format(printf, 1, 2))) __attribute__((noreturn)) |
| static void fail(const char *format, ...) |
| { |
| va_list ap; |
| va_start(ap, format); |
| fprintf(stderr, "Error: "); |
| vfprintf(stderr, format, ap); |
| if (outfilename) |
| unlink(outfilename); |
| exit(1); |
| va_end(ap); |
| } |
| |
| /* |
| * Evil macros for little-endian reads and writes |
| */ |
| #define GLE(x, bits, ifnot) \ |
| __builtin_choose_expr( \ |
| (sizeof(*(x)) == bits/8), \ |
| (__typeof__(*(x)))get_unaligned_le##bits(x), ifnot) |
| |
| extern void bad_get_le(void); |
| #define LAST_GLE(x) \ |
| __builtin_choose_expr(sizeof(*(x)) == 1, *(x), bad_get_le()) |
| |
| #define GET_LE(x) \ |
| GLE(x, 64, GLE(x, 32, GLE(x, 16, LAST_GLE(x)))) |
| |
| #define PLE(x, val, bits, ifnot) \ |
| __builtin_choose_expr( \ |
| (sizeof(*(x)) == bits/8), \ |
| put_unaligned_le##bits((val), (x)), ifnot) |
| |
| extern void bad_put_le(void); |
| #define LAST_PLE(x, val) \ |
| __builtin_choose_expr(sizeof(*(x)) == 1, *(x) = (val), bad_put_le()) |
| |
| #define PUT_LE(x, val) \ |
| PLE(x, val, 64, PLE(x, val, 32, PLE(x, val, 16, LAST_PLE(x, val)))) |
| |
| |
| #define NSYMS ARRAY_SIZE(required_syms) |
| |
| #define BITSFUNC3(name, bits, suffix) name##bits##suffix |
| #define BITSFUNC2(name, bits, suffix) BITSFUNC3(name, bits, suffix) |
| #define BITSFUNC(name) BITSFUNC2(name, ELF_BITS, ) |
| |
| #define INT_BITS BITSFUNC2(int, ELF_BITS, _t) |
| |
| #define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x |
| #define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x) |
| #define ELF(x) ELF_BITS_XFORM(ELF_BITS, x) |
| |
| #define ELF_BITS 64 |
| #include "vdso2c.h" |
| #undef ELF_BITS |
| |
| #define ELF_BITS 32 |
| #include "vdso2c.h" |
| #undef ELF_BITS |
| |
| static void go(void *raw_addr, size_t raw_len, |
| void *stripped_addr, size_t stripped_len, |
| FILE *outfile, const char *name) |
| { |
| Elf64_Ehdr *hdr = (Elf64_Ehdr *)raw_addr; |
| |
| if (hdr->e_ident[EI_CLASS] == ELFCLASS64) { |
| go64(raw_addr, raw_len, stripped_addr, stripped_len, |
| outfile, name); |
| } else if (hdr->e_ident[EI_CLASS] == ELFCLASS32) { |
| go32(raw_addr, raw_len, stripped_addr, stripped_len, |
| outfile, name); |
| } else { |
| fail("unknown ELF class\n"); |
| } |
| } |
| |
| static void map_input(const char *name, void **addr, size_t *len, int prot) |
| { |
| off_t tmp_len; |
| |
| int fd = open(name, O_RDONLY); |
| if (fd == -1) |
| err(1, "%s", name); |
| |
| tmp_len = lseek(fd, 0, SEEK_END); |
| if (tmp_len == (off_t)-1) |
| err(1, "lseek"); |
| *len = (size_t)tmp_len; |
| |
| *addr = mmap(NULL, tmp_len, prot, MAP_PRIVATE, fd, 0); |
| if (*addr == MAP_FAILED) |
| err(1, "mmap"); |
| |
| close(fd); |
| } |
| |
| int main(int argc, char **argv) |
| { |
| size_t raw_len, stripped_len; |
| void *raw_addr, *stripped_addr; |
| FILE *outfile; |
| char *name, *tmp; |
| int namelen; |
| |
| if (argc != 4) { |
| printf("Usage: vdso2c RAW_INPUT STRIPPED_INPUT OUTPUT\n"); |
| return 1; |
| } |
| |
| /* |
| * Figure out the struct name. If we're writing to a .so file, |
| * generate raw output insted. |
| */ |
| name = strdup(argv[3]); |
| namelen = strlen(name); |
| if (namelen >= 3 && !strcmp(name + namelen - 3, ".so")) { |
| name = NULL; |
| } else { |
| tmp = strrchr(name, '/'); |
| if (tmp) |
| name = tmp + 1; |
| tmp = strchr(name, '.'); |
| if (tmp) |
| *tmp = '\0'; |
| for (tmp = name; *tmp; tmp++) |
| if (*tmp == '-') |
| *tmp = '_'; |
| } |
| |
| map_input(argv[1], &raw_addr, &raw_len, PROT_READ); |
| map_input(argv[2], &stripped_addr, &stripped_len, PROT_READ); |
| |
| outfilename = argv[3]; |
| outfile = fopen(outfilename, "w"); |
| if (!outfile) |
| err(1, "%s", argv[2]); |
| |
| go(raw_addr, raw_len, stripped_addr, stripped_len, outfile, name); |
| |
| munmap(raw_addr, raw_len); |
| munmap(stripped_addr, stripped_len); |
| fclose(outfile); |
| |
| return 0; |
| } |