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author | Andy Lutomirski <luto@amacapital.net> | 2014-06-13 04:53:10 +0400 |
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committer | H. Peter Anvin <hpa@zytor.com> | 2014-06-13 06:01:24 +0400 |
commit | 4ebbefd6b93c34d6da0d950b1d2e0dcca2f1e6ef (patch) | |
tree | 5d94b4e1dd26d5c1a4ce2866486936333ca2e96f /Documentation/vDSO/vdso_test.c | |
parent | 6e8f21584a30ba6ce73cfef34f316d5bf3fadaab (diff) | |
download | linux-4ebbefd6b93c34d6da0d950b1d2e0dcca2f1e6ef.tar.xz |
x86/vdso/doc: Make vDSO examples more portable
This adds a new vdso_test.c that's written entirely in C. It also
makes all of the vDSO examples work on 32-bit x86.
Cc: Stefani Seibold <stefani@seibold.net>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/62b701fc44b79f118ac2b2d64d19965fc5c291fb.1402620737.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'Documentation/vDSO/vdso_test.c')
-rw-r--r-- | Documentation/vDSO/vdso_test.c | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/Documentation/vDSO/vdso_test.c b/Documentation/vDSO/vdso_test.c new file mode 100644 index 000000000000..8daeb7d7032c --- /dev/null +++ b/Documentation/vDSO/vdso_test.c @@ -0,0 +1,52 @@ +/* + * vdso_test.c: Sample code to test parse_vdso.c + * Copyright (c) 2014 Andy Lutomirski + * Subject to the GNU General Public License, version 2 + * + * Compile with: + * gcc -std=gnu99 vdso_test.c parse_vdso.c + * + * Tested on x86, 32-bit and 64-bit. It may work on other architectures, too. + */ + +#include <stdint.h> +#include <elf.h> +#include <stdio.h> +#include <sys/auxv.h> +#include <sys/time.h> + +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); + +int main(int argc, char **argv) +{ + unsigned long sysinfo_ehdr = getauxval(AT_SYSINFO_EHDR); + if (!sysinfo_ehdr) { + printf("AT_SYSINFO_EHDR is not present!\n"); + return 0; + } + + vdso_init_from_sysinfo_ehdr(getauxval(AT_SYSINFO_EHDR)); + + /* 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) { + printf("Could not find __vdso_gettimeofday\n"); + return 1; + } + + struct timeval tv; + long ret = gtod(&tv, 0); + + if (ret == 0) { + printf("The time is %lld.%06lld\n", + (long long)tv.tv_sec, (long long)tv.tv_usec); + } else { + printf("__vdso_gettimeofday failed\n"); + } + + return 0; +} |