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Merge branch 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/lin…
…ux/kernel/git/tip/tip Pull x86 vdso fixes from Peter Anvin: "Fixes for x86/vdso. One is a simple build fix for bigendian hosts, one is to make "make vdso_install" work again, and the rest is about working around a bug in Google's Go language -- two are documentation patches that improves the sample code that the Go coders took, modified, and broke; the other two implements a workaround that keeps existing Go binaries from segfaulting at least" * 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/vdso: Fix vdso_install x86/vdso: Hack to keep 64-bit Go programs working x86/vdso: Add PUT_LE to store little-endian values x86/vdso/doc: Make vDSO examples more portable x86/vdso/doc: Rename vdso_test.c to vdso_standalone_test_x86.c x86, vdso: Remove one final use of htole16()
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,128 @@ | ||
| /* | ||
| * vdso_test.c: Sample code to test parse_vdso.c on x86 | ||
| * Copyright (c) 2011-2014 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 -lgcc_s | ||
| * vdso_standalone_test_x86.c parse_vdso.c | ||
| * to generate a small binary. On x86_64, you can omit -lgcc_s | ||
| * if you want the binary to be completely standalone. | ||
| */ | ||
|
|
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| #include <sys/syscall.h> | ||
| #include <sys/time.h> | ||
| #include <unistd.h> | ||
| #include <stdint.h> | ||
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| 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); | ||
|
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| /* 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++; | ||
| } | ||
|
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||
| return 0; | ||
| } | ||
|
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| /* ...and two syscalls. This is x86-specific. */ | ||
| static inline long x86_syscall3(long nr, long a0, long a1, long a2) | ||
| { | ||
| long ret; | ||
| #ifdef __x86_64__ | ||
| asm volatile ("syscall" : "=a" (ret) : "a" (nr), | ||
| "D" (a0), "S" (a1), "d" (a2) : | ||
| "cc", "memory", "rcx", | ||
| "r8", "r9", "r10", "r11" ); | ||
| #else | ||
| asm volatile ("int $0x80" : "=a" (ret) : "a" (nr), | ||
| "b" (a0), "c" (a1), "d" (a2) : | ||
| "cc", "memory" ); | ||
| #endif | ||
| return ret; | ||
| } | ||
|
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| static inline long linux_write(int fd, const void *data, size_t len) | ||
| { | ||
| return x86_syscall3(__NR_write, fd, (long)data, (long)len); | ||
| } | ||
|
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| static inline void linux_exit(int code) | ||
| { | ||
| x86_syscall3(__NR_exit, code, 0, 0); | ||
| } | ||
|
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| void to_base10(char *lastdig, uint64_t n) | ||
| { | ||
| while (n) { | ||
| *lastdig = (n % 10) + '0'; | ||
| n /= 10; | ||
| lastdig--; | ||
| } | ||
| } | ||
|
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||
| __attribute__((externally_visible)) void c_main(void **stack) | ||
| { | ||
| /* Parse the stack */ | ||
| long argc = (long)*stack; | ||
| stack += argc + 2; | ||
|
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| /* Now we're pointing at the environment. Skip it. */ | ||
| while(*stack) | ||
| stack++; | ||
| stack++; | ||
|
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| /* Now we're pointing at auxv. Initialize the vDSO parser. */ | ||
| vdso_init_from_auxv((void *)stack); | ||
|
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| /* Find gettimeofday. */ | ||
| typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz); | ||
| gtod_t gtod = (gtod_t)vdso_sym("LINUX_2.6", "__vdso_gettimeofday"); | ||
|
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| if (!gtod) | ||
| linux_exit(1); | ||
|
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| struct timeval tv; | ||
| long ret = gtod(&tv, 0); | ||
|
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||
| 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); | ||
| } | ||
|
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| linux_exit(0); | ||
| } | ||
|
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| /* | ||
| * 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" | ||
| #ifdef __x86_64__ | ||
| "mov %rsp,%rdi\n\t" | ||
| "jmp c_main" | ||
| #else | ||
| "push %esp\n\t" | ||
| "call c_main\n\t" | ||
| "int $3" | ||
| #endif | ||
| ); |
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