vdso2c.c

#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 <linux/elf.h>
#include <linux/types.h>

const char *outfilename;

/* Symbols that we need in vdso2c. */
enum {
	sym_vvar_page,
	sym_hpet_page,
	sym_end_mapping,
};

const int special_pages[] = {
	sym_vvar_page,
	sym_hpet_page,
};

char const * const required_syms[] = {
	[sym_vvar_page] = "vvar_page",
	[sym_hpet_page] = "hpet_page",
	[sym_end_mapping] = "end_mapping",
	"VDSO32_NOTE_MASK",
	"VDSO32_SYSENTER_RETURN",
	"__kernel_vsyscall",
	"__kernel_sigreturn",
	"__kernel_rt_sigreturn",
};

__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);
	unlink(outfilename);
	exit(1);
	va_end(ap);
}

/*
 * Evil macros to do a little-endian read.
 */
#define __GET_TYPE(x, type, bits, ifnot)				\
	__builtin_choose_expr(						\
		__builtin_types_compatible_p(typeof(x), type),		\
		le##bits##toh((x)), ifnot)

extern void bad_get(uint64_t);

#define GET(x)								\
	__GET_TYPE((x), __u32, 32, __GET_TYPE((x), __u64, 64,		\
	__GET_TYPE((x), __s32, 32, __GET_TYPE((x), __s64, 64,		\
	__GET_TYPE((x), __u16, 16, bad_get(x))))))

#define NSYMS (sizeof(required_syms) / sizeof(required_syms[0]))

#define BITS 64
#define GOFUNC go64
#define Elf_Ehdr Elf64_Ehdr
#define Elf_Shdr Elf64_Shdr
#define Elf_Phdr Elf64_Phdr
#define Elf_Sym Elf64_Sym
#define Elf_Dyn Elf64_Dyn
#include "vdso2c.h"
#undef BITS
#undef GOFUNC
#undef Elf_Ehdr
#undef Elf_Shdr
#undef Elf_Phdr
#undef Elf_Sym
#undef Elf_Dyn

#define BITS 32
#define GOFUNC go32
#define Elf_Ehdr Elf32_Ehdr
#define Elf_Shdr Elf32_Shdr
#define Elf_Phdr Elf32_Phdr
#define Elf_Sym Elf32_Sym
#define Elf_Dyn Elf32_Dyn
#include "vdso2c.h"
#undef BITS
#undef GOFUNC
#undef Elf_Ehdr
#undef Elf_Shdr
#undef Elf_Phdr
#undef Elf_Sym
#undef Elf_Dyn

static void go(void *addr, size_t len, FILE *outfile, const char *name)
{
	Elf64_Ehdr *hdr = (Elf64_Ehdr *)addr;

	if (hdr->e_ident[EI_CLASS] == ELFCLASS64) {
		go64(addr, len, outfile, name);
	} else if (hdr->e_ident[EI_CLASS] == ELFCLASS32) {
		go32(addr, len, outfile, name);
	} else {
		fail("unknown ELF class\n");
	}
}

int main(int argc, char **argv)
{
	int fd;
	off_t len;
	void *addr;
	FILE *outfile;
	char *name, *tmp;
	int namelen;

	if (argc != 3) {
		printf("Usage: vdso2c 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[2]);
	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 = '_';
	}

	fd = open(argv[1], O_RDONLY);
	if (fd == -1)
		err(1, "%s", argv[1]);

	len = lseek(fd, 0, SEEK_END);
	if (len == (off_t)-1)
		err(1, "lseek");

	addr = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
	if (addr == MAP_FAILED)
		err(1, "mmap");

	outfilename = argv[2];
	outfile = fopen(outfilename, "w");
	if (!outfile)
		err(1, "%s", argv[2]);

	go(addr, (size_t)len, outfile, name);

	munmap(addr, len);
	fclose(outfile);

	return 0;
}