auxv.c

#include <stdio.h>
#include <elf.h>
#include <fcntl.h>
#include <assert.h>
#include <unistd.h>

#if defined(__GLIBC__) && defined(__GLIBC_PREREQ)
#if __GLIBC_PREREQ(2, 16)
#include <sys/auxv.h>
#endif
#endif

int main() {
	int auxv_fd;
	Elf64_auxv_t auxv;

#if defined(__GLIBC__) && defined(__GLIBC_PREREQ)
#if __GLIBC_PREREQ(2, 16)
	puts("Reading using getauxval");
	printf("REG_HWCAP: %lx\n", getauxval(AT_HWCAP));
	printf("REG_HWCAP2: %lx\n", getauxval(AT_HWCAP2));
	printf("PLATFORM_STR: %s\n", (char *)getauxval(AT_PLATFORM));
	puts("---");
#endif
#endif
	puts("Reading from /proc/self/auxv");
	auxv_fd = open("/proc/self/auxv", O_RDONLY);
	assert(auxv_fd != -1);
	while (read(auxv_fd, &auxv, sizeof(auxv)) == sizeof(auxv)) {
		if (auxv.a_type == AT_HWCAP) {
			printf("REG_HWCAP: %lx\n", auxv.a_un.a_val);
		} else if (auxv.a_type == AT_HWCAP2) {
			printf("REG_HWCAP2: %lx\n", auxv.a_un.a_val);
		} else if (auxv.a_type == AT_PLATFORM) {
			printf("PLATFORM_STR: %s\n", (char *)auxv.a_un.a_val);
		}
	}
	close(auxv_fd);	
	puts("---");

	return 0;
}