From 6e8f21584a30ba6ce73cfef34f316d5bf3fadaab Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Thu, 12 Jun 2014 17:53:09 -0700 Subject: x86/vdso/doc: Rename vdso_test.c to vdso_standalone_test_x86.c This thing is hopelessly x86_64-specific: it's an example of how to access the vDSO without any runtime support at all. Signed-off-by: Andy Lutomirski Link: http://lkml.kernel.org/r/3efc170e0e166e15f0150c9fdb37d52488b9c0a4.1402620737.git.luto@amacapital.net Signed-off-by: H. Peter Anvin --- Documentation/vDSO/vdso_test.c | 111 ----------------------------------------- 1 file changed, 111 deletions(-) delete mode 100644 Documentation/vDSO/vdso_test.c (limited to 'Documentation/vDSO/vdso_test.c') diff --git a/Documentation/vDSO/vdso_test.c b/Documentation/vDSO/vdso_test.c deleted file mode 100644 index fff633432dff..000000000000 --- a/Documentation/vDSO/vdso_test.c +++ /dev/null @@ -1,111 +0,0 @@ -/* - * vdso_test.c: Sample code to test parse_vdso.c on x86_64 - * Copyright (c) 2011 Andy Lutomirski - * Subject to the GNU General Public License, version 2 - * - * You can amuse yourself by compiling with: - * gcc -std=gnu99 -nostdlib - * -Os -fno-asynchronous-unwind-tables -flto - * vdso_test.c parse_vdso.c -o vdso_test - * to generate a small binary with no dependencies at all. - */ - -#include -#include -#include -#include - -extern void *vdso_sym(const char *version, const char *name); -extern void vdso_init_from_sysinfo_ehdr(uintptr_t base); -extern void vdso_init_from_auxv(void *auxv); - -/* We need a libc functions... */ -int strcmp(const char *a, const char *b) -{ - /* This implementation is buggy: it never returns -1. */ - while (*a || *b) { - if (*a != *b) - return 1; - if (*a == 0 || *b == 0) - return 1; - a++; - b++; - } - - return 0; -} - -/* ...and two syscalls. This is x86_64-specific. */ -static inline long linux_write(int fd, const void *data, size_t len) -{ - - long ret; - asm volatile ("syscall" : "=a" (ret) : "a" (__NR_write), - "D" (fd), "S" (data), "d" (len) : - "cc", "memory", "rcx", - "r8", "r9", "r10", "r11" ); - return ret; -} - -static inline void linux_exit(int code) -{ - asm volatile ("syscall" : : "a" (__NR_exit), "D" (code)); -} - -void to_base10(char *lastdig, uint64_t n) -{ - while (n) { - *lastdig = (n % 10) + '0'; - n /= 10; - lastdig--; - } -} - -__attribute__((externally_visible)) void c_main(void **stack) -{ - /* Parse the stack */ - long argc = (long)*stack; - stack += argc + 2; - - /* Now we're pointing at the environment. Skip it. */ - while(*stack) - stack++; - stack++; - - /* Now we're pointing at auxv. Initialize the vDSO parser. */ - vdso_init_from_auxv((void *)stack); - - /* Find gettimeofday. */ - typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz); - gtod_t gtod = (gtod_t)vdso_sym("LINUX_2.6", "__vdso_gettimeofday"); - - if (!gtod) - linux_exit(1); - - struct timeval tv; - long ret = gtod(&tv, 0); - - if (ret == 0) { - char buf[] = "The time is .000000\n"; - to_base10(buf + 31, tv.tv_sec); - to_base10(buf + 38, tv.tv_usec); - linux_write(1, buf, sizeof(buf) - 1); - } else { - linux_exit(ret); - } - - linux_exit(0); -} - -/* - * This is the real entry point. It passes the initial stack into - * the C entry point. - */ -asm ( - ".text\n" - ".global _start\n" - ".type _start,@function\n" - "_start:\n\t" - "mov %rsp,%rdi\n\t" - "jmp c_main" - ); -- cgit v1.2.3