forked from Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
254 lines
6.9 KiB
254 lines
6.9 KiB
/* |
|
* 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_pvclock_page, |
|
sym_hvclock_page, |
|
sym_timens_page, |
|
}; |
|
|
|
const int special_pages[] = { |
|
sym_vvar_page, |
|
sym_pvclock_page, |
|
sym_hvclock_page, |
|
sym_timens_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_pvclock_page] = {"pvclock_page", true}, |
|
[sym_hvclock_page] = {"hvclock_page", true}, |
|
[sym_timens_page] = {"timens_page", true}, |
|
{"VDSO32_NOTE_MASK", true}, |
|
{"__kernel_vsyscall", true}, |
|
{"__kernel_sigreturn", true}, |
|
{"__kernel_rt_sigreturn", true}, |
|
{"int80_landing_pad", true}, |
|
{"vdso32_rt_sigreturn_landing_pad", true}, |
|
{"vdso32_sigreturn_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, "open(%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 instead. |
|
*/ |
|
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, "fopen(%s)", outfilename); |
|
|
|
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; |
|
}
|
|
|