[PATCH v3 3/3] selftests/lam: Add test cases for different LAM tag widths
From: Maciej Wieczor-Retman
Date: Mon Mar 02 2026 - 10:40:09 EST
From: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx>
After the default tag width in LAM (Linear Address Masking) is set to 4
bits, the value isn't strictly related to the CPU features like LAM_U57
or LAM_U48. To emphasise this, remove mentions of _U57 from the selftest
and update the bit width.
Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx>
---
Changelog v3:
- Redo the patch after the removal of the debugfs part.
tools/testing/selftests/x86/lam.c | 86 +++++++++++++++----------------
1 file changed, 43 insertions(+), 43 deletions(-)
diff --git a/tools/testing/selftests/x86/lam.c b/tools/testing/selftests/x86/lam.c
index 1919fa6daec0..d8f75387b931 100644
--- a/tools/testing/selftests/x86/lam.c
+++ b/tools/testing/selftests/x86/lam.c
@@ -26,9 +26,9 @@
/* LAM modes, these definitions were copied from kernel code */
#define LAM_NONE 0
-#define LAM_U57_BITS 6
+#define LAM_BITS 4
-#define LAM_U57_MASK (0x3fULL << 57)
+#define LAM_MASK (0xfULL << 57)
/* arch prctl for LAM */
#define ARCH_GET_UNTAG_MASK 0x4001
#define ARCH_ENABLE_TAGGED_ADDR 0x4002
@@ -175,7 +175,7 @@ static int set_lam(unsigned long lam)
int ret = 0;
uint64_t ptr = 0;
- if (lam != LAM_U57_BITS && lam != LAM_NONE)
+ if (lam != LAM_BITS && lam != LAM_NONE)
return -1;
/* Skip check return */
@@ -185,8 +185,8 @@ static int set_lam(unsigned long lam)
syscall(SYS_arch_prctl, ARCH_GET_UNTAG_MASK, &ptr);
/* Check mask returned is expected */
- if (lam == LAM_U57_BITS)
- ret = (ptr != ~(LAM_U57_MASK));
+ if (lam == LAM_BITS)
+ ret = (ptr != ~(LAM_MASK));
else if (lam == LAM_NONE)
ret = (ptr != -1ULL);
@@ -204,8 +204,8 @@ static unsigned long get_default_tag_bits(void)
perror("Fork failed.");
} else if (pid == 0) {
/* Set LAM mode in child process */
- if (set_lam(LAM_U57_BITS) == 0)
- lam = LAM_U57_BITS;
+ if (set_lam(LAM_BITS) == 0)
+ lam = LAM_BITS;
else
lam = LAM_NONE;
exit(lam);
@@ -230,8 +230,8 @@ static int get_lam(void)
return -1;
/* Check mask returned is expected */
- if (ptr == ~(LAM_U57_MASK))
- ret = LAM_U57_BITS;
+ if (ptr == ~(LAM_MASK))
+ ret = LAM_BITS;
else if (ptr == -1ULL)
ret = LAM_NONE;
@@ -247,10 +247,10 @@ static uint64_t set_metadata(uint64_t src, unsigned long lam)
srand(time(NULL));
switch (lam) {
- case LAM_U57_BITS: /* Set metadata in bits 62:57 */
+ case LAM_BITS: /* Set metadata in bits 62:57 */
/* Get a random non-zero value as metadata */
- metadata = (rand() % ((1UL << LAM_U57_BITS) - 1) + 1) << 57;
- metadata |= (src & ~(LAM_U57_MASK));
+ metadata = (rand() % ((1UL << LAM_BITS) - 1) + 1) << 57;
+ metadata |= (src & ~(LAM_MASK));
break;
default:
metadata = src;
@@ -291,7 +291,7 @@ int handle_max_bits(struct testcases *test)
unsigned long bits = 0;
if (exp_bits != LAM_NONE)
- exp_bits = LAM_U57_BITS;
+ exp_bits = LAM_BITS;
/* Get LAM max tag bits */
if (syscall(SYS_arch_prctl, ARCH_GET_MAX_TAG_BITS, &bits) == -1)
@@ -719,8 +719,8 @@ int do_uring(unsigned long lam)
uint64_t addr = ((uint64_t)fi->iovecs[i].iov_base);
switch (lam) {
- case LAM_U57_BITS: /* Clear bits 62:57 */
- addr = (addr & ~(LAM_U57_MASK));
+ case LAM_BITS: /* Clear bits 62:57 */
+ addr = (addr & ~(LAM_MASK));
break;
}
free((void *)addr);
@@ -937,14 +937,14 @@ static void run_test(struct testcases *test, int count)
static struct testcases uring_cases[] = {
{
.later = 0,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = handle_uring,
- .msg = "URING: LAM_U57. Dereferencing pointer with metadata\n",
+ .msg = "URING: LAM. Dereferencing pointer with metadata\n",
},
{
.later = 1,
.expected = 1,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = handle_uring,
.msg = "URING:[Negative] Disable LAM. Dereferencing pointer with metadata.\n",
},
@@ -953,14 +953,14 @@ static struct testcases uring_cases[] = {
static struct testcases malloc_cases[] = {
{
.later = 0,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = handle_malloc,
- .msg = "MALLOC: LAM_U57. Dereferencing pointer with metadata\n",
+ .msg = "MALLOC: LAM. Dereferencing pointer with metadata\n",
},
{
.later = 1,
.expected = 2,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = handle_malloc,
.msg = "MALLOC:[Negative] Disable LAM. Dereferencing pointer with metadata.\n",
},
@@ -976,41 +976,41 @@ static struct testcases bits_cases[] = {
static struct testcases syscall_cases[] = {
{
.later = 0,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = handle_syscall,
- .msg = "SYSCALL: LAM_U57. syscall with metadata\n",
+ .msg = "SYSCALL: LAM. syscall with metadata\n",
},
{
.later = 1,
.expected = 1,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = handle_syscall,
.msg = "SYSCALL:[Negative] Disable LAM. Dereferencing pointer with metadata.\n",
},
{
.later = GET_USER_USER,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = get_user_syscall,
.msg = "GET_USER: get_user() and pass a properly tagged user pointer.\n",
},
{
.later = GET_USER_KERNEL_TOP,
.expected = 1,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = get_user_syscall,
.msg = "GET_USER:[Negative] get_user() with a kernel pointer and the top bit cleared.\n",
},
{
.later = GET_USER_KERNEL_BOT,
.expected = 1,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = get_user_syscall,
.msg = "GET_USER:[Negative] get_user() with a kernel pointer and the bottom sign-extension bit cleared.\n",
},
{
.later = GET_USER_KERNEL,
.expected = 1,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = get_user_syscall,
.msg = "GET_USER:[Negative] get_user() and pass a kernel pointer.\n",
},
@@ -1020,60 +1020,60 @@ static struct testcases mmap_cases[] = {
{
.later = 1,
.expected = 0,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.addr = HIGH_ADDR,
.test_func = handle_mmap,
- .msg = "MMAP: First mmap high address, then set LAM_U57.\n",
+ .msg = "MMAP: First mmap high address, then set LAM.\n",
},
{
.later = 0,
.expected = 0,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.addr = HIGH_ADDR,
.test_func = handle_mmap,
- .msg = "MMAP: First LAM_U57, then High address.\n",
+ .msg = "MMAP: First LAM, then High address.\n",
},
{
.later = 0,
.expected = 0,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.addr = LOW_ADDR,
.test_func = handle_mmap,
- .msg = "MMAP: First LAM_U57, then Low address.\n",
+ .msg = "MMAP: First LAM, then Low address.\n",
},
};
static struct testcases inheritance_cases[] = {
{
.expected = 0,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = handle_inheritance,
- .msg = "FORK: LAM_U57, child process should get LAM mode same as parent\n",
+ .msg = "FORK: LAM, child process should get LAM mode same as parent\n",
},
{
.expected = 0,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = handle_thread,
- .msg = "THREAD: LAM_U57, child thread should get LAM mode same as parent\n",
+ .msg = "THREAD: LAM, child thread should get LAM mode same as parent\n",
},
{
.expected = 1,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = handle_thread_enable,
.msg = "THREAD: [NEGATIVE] Enable LAM in child.\n",
},
{
.expected = 1,
.later = 1,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = handle_thread,
.msg = "THREAD: [NEGATIVE] Enable LAM in parent after thread created.\n",
},
{
.expected = 0,
- .lam = LAM_U57_BITS,
+ .lam = LAM_BITS,
.test_func = handle_execve,
- .msg = "EXECVE: LAM_U57, child process should get disabled LAM mode\n",
+ .msg = "EXECVE: LAM, child process should get disabled LAM mode\n",
},
};
@@ -1224,7 +1224,7 @@ int handle_pasid(struct testcases *test)
if (tmp & 0x1) {
/* run set lam mode*/
if ((runed & 0x1) == 0) {
- err = set_lam(LAM_U57_BITS);
+ err = set_lam(LAM_BITS);
runed = runed | 0x1;
} else
err = 1;
--
2.53.0