From: Andy Lutomirski Date: Fri, 13 Jun 2014 00:53:09 +0000 (-0700) Subject: x86/vdso/doc: Rename vdso_test.c to vdso_standalone_test_x86.c X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=6e8f21584a30ba6ce73cfef34f316d5bf3fadaab;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git 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 --- diff --git a/Documentation/vDSO/vdso_standalone_test_x86.c b/Documentation/vDSO/vdso_standalone_test_x86.c new file mode 100644 index 000000000000..1523f5d681f3 --- /dev/null +++ b/Documentation/vDSO/vdso_standalone_test_x86.c @@ -0,0 +1,111 @@ +/* + * 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_standalone_test_x86.c parse_vdso.c + * 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" + ); 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" - );