tools/testing/selftests/vDSO/vdso_test_getrandom.c

Source file repositories/reference/linux-study-clean/tools/testing/selftests/vDSO/vdso_test_getrandom.c

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/vDSO/vdso_test_getrandom.c
Extension
.c
Size
8946 bytes
Lines
323
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

if ((vsp)->tv_nsec < 0) {				\
			(vsp)->tv_sec--;				\
			(vsp)->tv_nsec += 1000000000L;			\
		}							\
	} while (0)
#endif

#define ksft_assert(condition) \
	do { if (!(condition)) ksft_exit_fail_msg("Assertion failed: %s\n", #condition); } while (0)

static struct {
	pthread_mutex_t lock;
	void **states;
	size_t len, cap;
	ssize_t(*fn)(void *, size_t, unsigned long, void *, size_t);
	struct vgetrandom_opaque_params params;
} vgrnd = {
	.lock = PTHREAD_MUTEX_INITIALIZER
};

static void *vgetrandom_get_state(void)
{
	void *state = NULL;

	pthread_mutex_lock(&vgrnd.lock);
	if (!vgrnd.len) {
		size_t page_size = getpagesize();
		size_t new_cap;
		size_t alloc_size, num = sysconf(_SC_NPROCESSORS_ONLN); /* Just a decent heuristic. */
		size_t state_size_aligned, cache_line_size = sysconf(_SC_LEVEL1_DCACHE_LINESIZE) ?: 1;
		void *new_block, *new_states;

		state_size_aligned = (vgrnd.params.size_of_opaque_state + cache_line_size - 1) & (~(cache_line_size - 1));
		alloc_size = (num * state_size_aligned + page_size - 1) & (~(page_size - 1));
		num = (page_size / state_size_aligned) * (alloc_size / page_size);
		new_block = mmap(0, alloc_size, vgrnd.params.mmap_prot, vgrnd.params.mmap_flags, -1, 0);
		if (new_block == MAP_FAILED)
			goto out;

		new_cap = vgrnd.cap + num;
		new_states = reallocarray(vgrnd.states, new_cap, sizeof(*vgrnd.states));
		if (!new_states)
			goto unmap;
		vgrnd.cap = new_cap;
		vgrnd.states = new_states;

		for (size_t i = 0; i < num; ++i) {
			if (((uintptr_t)new_block & (page_size - 1)) + vgrnd.params.size_of_opaque_state > page_size)
				new_block = (void *)(((uintptr_t)new_block + page_size - 1) & (~(page_size - 1)));
			vgrnd.states[i] = new_block;
			new_block += state_size_aligned;
		}
		vgrnd.len = num;
		goto success;

	unmap:
		munmap(new_block, alloc_size);
		goto out;
	}
success:
	state = vgrnd.states[--vgrnd.len];

out:
	pthread_mutex_unlock(&vgrnd.lock);
	return state;
}

__attribute__((unused)) /* Example for libc implementors */
static void vgetrandom_put_state(void *state)
{
	if (!state)
		return;
	pthread_mutex_lock(&vgrnd.lock);
	vgrnd.states[vgrnd.len++] = state;
	pthread_mutex_unlock(&vgrnd.lock);
}

static void vgetrandom_init(void)
{
	const char *version = versions[VDSO_VERSION];
	const char *name = names[VDSO_NAMES][6];
	unsigned long sysinfo_ehdr = getauxval(AT_SYSINFO_EHDR);
	ssize_t ret;

	if (!sysinfo_ehdr)
		ksft_exit_skip("AT_SYSINFO_EHDR is not present\n");
	vdso_init_from_sysinfo_ehdr(sysinfo_ehdr);
	vgrnd.fn = (__typeof__(vgrnd.fn))vdso_sym(version, name);
	if (!vgrnd.fn)
		ksft_exit_skip("%s@%s symbol is missing from vDSO\n", name, version);

Annotation

Implementation Notes