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selftests/x86/xstate: Refactor ptrace ABI test
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Following the refactoring of the context switching test, the ptrace test is
another component reusable for other xstate features. As part of this
restructuring, add a missing check to validate the
user_xstateregs->xstate_fx_sw field in the ABI.

Also, replace err() and fatal_error() with ksft_exit_fail_msg() for
consistency in error handling.

  Expected output:
  $ amx_64
  ...
  [RUN]   AMX Tile data: inject xstate via ptrace().
  [OK]    'xfeatures' in SW reserved area was correctly written
  [OK]    xstate was correctly updated.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250226010731.2456-6-chang.seok.bae@intel.com
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Chang S. Bae authored and Ingo Molnar committed Feb 26, 2025
1 parent 40f6852 commit 7cb2fbe
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Showing 3 changed files with 131 additions and 107 deletions.
108 changes: 1 addition & 107 deletions tools/testing/selftests/x86/amx.c
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Original file line number Diff line number Diff line change
Expand Up @@ -13,10 +13,8 @@
#include <sys/auxv.h>
#include <sys/mman.h>
#include <sys/shm.h>
#include <sys/ptrace.h>
#include <sys/syscall.h>
#include <sys/wait.h>
#include <sys/uio.h>

#include "helpers.h"
#include "xstate.h"
Expand All @@ -32,8 +30,6 @@
#define XFEATURE_MASK_XTILEDATA (1 << XFEATURE_XTILEDATA)
#define XFEATURE_MASK_XTILE (XFEATURE_MASK_XTILECFG | XFEATURE_MASK_XTILEDATA)

static uint32_t xbuf_size;

struct xstate_info xtiledata;

/* The helpers for managing XSAVE buffer and tile states: */
Expand Down Expand Up @@ -154,13 +150,6 @@ static inline bool load_rand_tiledata(struct xsave_buffer *xbuf)
return xrstor_safe(xbuf, XFEATURE_MASK_XTILEDATA);
}

/* Return XTILEDATA to its initial configuration. */
static inline void init_xtiledata(void)
{
clear_xstate_header(stashed_xsave);
xrstor_safe(stashed_xsave, XFEATURE_MASK_XTILEDATA);
}

enum expected_result { FAIL_EXPECTED, SUCCESS_EXPECTED };

/* arch_prctl() and sigaltstack() test */
Expand Down Expand Up @@ -489,99 +478,6 @@ static void test_fork(void)
_exit(0);
}

/* Ptrace test */

/*
* Make sure the ptracee has the expanded kernel buffer on the first
* use. Then, initialize the state before performing the state
* injection from the ptracer.
*/
static inline void ptracee_firstuse_tiledata(void)
{
load_rand_tiledata(stashed_xsave);
init_xtiledata();
}

/*
* Ptracer injects the randomized tile data state. It also reads
* before and after that, which will execute the kernel's state copy
* functions. So, the tester is advised to double-check any emitted
* kernel messages.
*/
static void ptracer_inject_tiledata(pid_t target)
{
struct xsave_buffer *xbuf;
struct iovec iov;

xbuf = alloc_xbuf();
if (!xbuf)
fatal_error("unable to allocate XSAVE buffer");

printf("\tRead the init'ed tiledata via ptrace().\n");

iov.iov_base = xbuf;
iov.iov_len = xbuf_size;

memset(stashed_xsave, 0, xbuf_size);

if (ptrace(PTRACE_GETREGSET, target, (uint32_t)NT_X86_XSTATE, &iov))
fatal_error("PTRACE_GETREGSET");

if (!__compare_tiledata_state(stashed_xsave, xbuf))
printf("[OK]\tThe init'ed tiledata was read from ptracee.\n");
else
printf("[FAIL]\tThe init'ed tiledata was not read from ptracee.\n");

printf("\tInject tiledata via ptrace().\n");

load_rand_tiledata(xbuf);

memcpy(&stashed_xsave->bytes[xtiledata.xbuf_offset],
&xbuf->bytes[xtiledata.xbuf_offset],
xtiledata.size);

if (ptrace(PTRACE_SETREGSET, target, (uint32_t)NT_X86_XSTATE, &iov))
fatal_error("PTRACE_SETREGSET");

if (ptrace(PTRACE_GETREGSET, target, (uint32_t)NT_X86_XSTATE, &iov))
fatal_error("PTRACE_GETREGSET");

if (!__compare_tiledata_state(stashed_xsave, xbuf))
printf("[OK]\tTiledata was correctly written to ptracee.\n");
else
printf("[FAIL]\tTiledata was not correctly written to ptracee.\n");
}

static void test_ptrace(void)
{
pid_t child;
int status;

child = fork();
if (child < 0) {
err(1, "fork");
} else if (!child) {
if (ptrace(PTRACE_TRACEME, 0, NULL, NULL))
err(1, "PTRACE_TRACEME");

ptracee_firstuse_tiledata();

raise(SIGTRAP);
_exit(0);
}

do {
wait(&status);
} while (WSTOPSIG(status) != SIGTRAP);

ptracer_inject_tiledata(child);

ptrace(PTRACE_DETACH, child, NULL, NULL);
wait(&status);
if (!WIFEXITED(status) || WEXITSTATUS(status))
err(1, "ptrace test");
}

int main(void)
{
const unsigned int ctxtsw_num_threads = 5, ctxtsw_iterations = 10;
Expand All @@ -594,8 +490,6 @@ int main(void)
return KSFT_SKIP;
}

xbuf_size = get_xbuf_size();

xtiledata = get_xstate_info(XFEATURE_XTILEDATA);
if (!xtiledata.size || !xtiledata.xbuf_offset) {
fatal_error("xstate cpuid: invalid tile data size/offset: %d/%d",
Expand All @@ -614,7 +508,7 @@ int main(void)

test_context_switch(XFEATURE_XTILEDATA, ctxtsw_num_threads, ctxtsw_iterations);

test_ptrace();
test_ptrace(XFEATURE_XTILEDATA);

clearhandler(SIGILL);
free_stashed_xsave();
Expand Down
129 changes: 129 additions & 0 deletions tools/testing/selftests/x86/xstate.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2,12 +2,25 @@

#define _GNU_SOURCE

#include <elf.h>
#include <pthread.h>
#include <stdbool.h>

#include <sys/ptrace.h>
#include <sys/uio.h>
#include <sys/wait.h>

#include "helpers.h"
#include "xstate.h"

static inline uint64_t xgetbv(uint32_t index)
{
uint32_t eax, edx;

asm volatile("xgetbv" : "=a" (eax), "=d" (edx) : "c" (index));
return eax + ((uint64_t)edx << 32);
}

static struct xstate_info xstate;

struct futex_info {
Expand All @@ -27,6 +40,19 @@ static inline void load_rand_xstate(struct xstate_info *xstate, struct xsave_buf
xrstor(xbuf, xstate->mask);
}

static inline void load_init_xstate(struct xstate_info *xstate, struct xsave_buffer *xbuf)
{
clear_xstate_header(xbuf);
xrstor(xbuf, xstate->mask);
}

static inline void copy_xstate(struct xsave_buffer *xbuf_dst, struct xsave_buffer *xbuf_src)
{
memcpy(&xbuf_dst->bytes[xstate.xbuf_offset],
&xbuf_src->bytes[xstate.xbuf_offset],
xstate.size);
}

static inline bool validate_xstate_same(struct xsave_buffer *xbuf1, struct xsave_buffer *xbuf2)
{
int ret;
Expand Down Expand Up @@ -196,3 +222,106 @@ void test_context_switch(uint32_t feature_num, uint32_t num_threads, uint32_t it

free(finfo);
}

/*
* Ptrace test for the ABI format as described in arch/x86/include/asm/user.h
*/

/*
* Make sure the ptracee has the expanded kernel buffer on the first use.
* Then, initialize the state before performing the state injection from
* the ptracer. For non-dynamic states, this is benign.
*/
static inline void ptracee_touch_xstate(void)
{
struct xsave_buffer *xbuf;

xbuf = alloc_xbuf();

load_rand_xstate(&xstate, xbuf);
load_init_xstate(&xstate, xbuf);

free(xbuf);
}

/*
* Ptracer injects the randomized xstate data. It also reads before and
* after that, which will execute the kernel's state copy functions.
*/
static void ptracer_inject_xstate(pid_t target)
{
uint32_t xbuf_size = get_xbuf_size();
struct xsave_buffer *xbuf1, *xbuf2;
struct iovec iov;

/*
* Allocate buffers to keep data while ptracer can write the
* other buffer
*/
xbuf1 = alloc_xbuf();
xbuf2 = alloc_xbuf();
if (!xbuf1 || !xbuf2)
ksft_exit_fail_msg("unable to allocate XSAVE buffer\n");

iov.iov_base = xbuf1;
iov.iov_len = xbuf_size;

if (ptrace(PTRACE_GETREGSET, target, (uint32_t)NT_X86_XSTATE, &iov))
ksft_exit_fail_msg("PTRACE_GETREGSET failed\n");

printf("[RUN]\t%s: inject xstate via ptrace().\n", xstate.name);

load_rand_xstate(&xstate, xbuf1);
copy_xstate(xbuf2, xbuf1);

if (ptrace(PTRACE_SETREGSET, target, (uint32_t)NT_X86_XSTATE, &iov))
ksft_exit_fail_msg("PTRACE_SETREGSET failed\n");

if (ptrace(PTRACE_GETREGSET, target, (uint32_t)NT_X86_XSTATE, &iov))
ksft_exit_fail_msg("PTRACE_GETREGSET failed\n");

if (*(uint64_t *)get_fpx_sw_bytes(xbuf1) == xgetbv(0))
printf("[OK]\t'xfeatures' in SW reserved area was correctly written\n");
else
printf("[FAIL]\t'xfeatures' in SW reserved area was not correctly written\n");

if (validate_xstate_same(xbuf2, xbuf1))
printf("[OK]\txstate was correctly updated.\n");
else
printf("[FAIL]\txstate was not correctly updated.\n");

free(xbuf1);
free(xbuf2);
}

void test_ptrace(uint32_t feature_num)
{
pid_t child;
int status;

xstate = get_xstate_info(feature_num);

child = fork();
if (child < 0) {
ksft_exit_fail_msg("fork() failed\n");
} else if (!child) {
if (ptrace(PTRACE_TRACEME, 0, NULL, NULL))
ksft_exit_fail_msg("PTRACE_TRACEME failed\n");

ptracee_touch_xstate();

raise(SIGTRAP);
_exit(0);
}

do {
wait(&status);
} while (WSTOPSIG(status) != SIGTRAP);

ptracer_inject_xstate(child);

ptrace(PTRACE_DETACH, child, NULL, NULL);
wait(&status);
if (!WIFEXITED(status) || WEXITSTATUS(status))
ksft_exit_fail_msg("ptracee exit error\n");
}
1 change: 1 addition & 0 deletions tools/testing/selftests/x86/xstate.h
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Original file line number Diff line number Diff line change
Expand Up @@ -190,5 +190,6 @@ static inline void set_rand_data(struct xstate_info *xstate, struct xsave_buffer
}

void test_context_switch(uint32_t feature_num, uint32_t num_threads, uint32_t iterations);
void test_ptrace(uint32_t feature_num);

#endif /* __SELFTESTS_X86_XSTATE_H */

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