Entering a signal handler, the kernel saves xstate in signal frame. The dynamic user state is better to be saved only when used. fpu->state_mask can help to exclude unused states.

Returning from a signal handler, XRSTOR re-initializes the excluded state components.

Add a test case to verify in the signal handler that the signal frame excludes AMX data when the signaled thread has initialized AMX state.

Signed-off-by: Chang S. Bae chang.seok.bae@intel.com Reviewed-by: Len Brown len.brown@intel.com Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-kselftest@vger.kernel.org --- Changes from v3: * Removed 'no functional changes' in the changelog. (Borislav Petkov)

Changes from v1: * Made it revertable (moved close to the end of the series). * Included the test case. --- arch/x86/include/asm/fpu/internal.h | 2 +- tools/testing/selftests/x86/amx.c | 66 +++++++++++++++++++++++++++++ 2 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index c467312d38d8..090eb5bb277b 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -354,7 +354,7 @@ static inline void copy_kernel_to_xregs(struct xregs_state *xstate, u64 mask) */ static inline int copy_xregs_to_user(struct xregs_state __user *buf) { - u64 mask = xfeatures_mask_user(); + u64 mask = current->thread.fpu.state_mask; u32 lmask = mask; u32 hmask = mask >> 32; int err; diff --git a/tools/testing/selftests/x86/amx.c b/tools/testing/selftests/x86/amx.c index f4ecdfd27ae9..a7386b886532 100644 --- a/tools/testing/selftests/x86/amx.c +++ b/tools/testing/selftests/x86/amx.c @@ -650,6 +650,71 @@ static void test_ptrace(void) test_tile_state_write(ptracee_loads_tiles); }

+/* Signal handling test */ + +static int sigtrapped; +struct tile_data sig_tiles, sighdl_tiles; + +static void handle_sigtrap(int sig, siginfo_t *info, void *ctx_void) +{ + ucontext_t *uctxt = (ucontext_t *)ctx_void; + struct xsave_data xdata; + struct tile_config cfg; + struct tile_data tiles; + u64 header; + + header = __get_xsave_xstate_bv((void *)uctxt->uc_mcontext.fpregs); + + if (header & (1 << XFEATURE_XTILE_DATA)) + printf("[FAIL]\ttile data was written in sigframe\n"); + else + printf("[OK]\ttile data was skipped in sigframe\n"); + + set_tilecfg(&cfg); + load_tilecfg(&cfg); + init_xdata(&xdata); + + make_tiles(&tiles); + copy_tiles_to_xdata(&xdata, &tiles); + restore_xdata(&xdata); + + save_xdata(&xdata); + if (compare_xdata_tiles(&xdata, &tiles)) + err(1, "tile load file"); + + printf("\tsignal handler: load tile data\n"); + + sigtrapped = sig; +} + +static void test_signal_handling(void) +{ + struct xsave_data xdata = { 0 }; + struct tile_data tiles = { 0 }; + + sethandler(SIGTRAP, handle_sigtrap, 0); + sigtrapped = 0; + + printf("[RUN]\tCheck tile state management in handling signal\n"); + + printf("\tbefore signal: initial tile data state\n"); + + raise(SIGTRAP); + + if (sigtrapped == 0) + err(1, "sigtrap"); + + save_xdata(&xdata); + if (compare_xdata_tiles(&xdata, &tiles)) { + printf("[FAIL]\ttile data was not loaded at sigreturn\n"); + nerrs++; + } else { + printf("[OK]\ttile data was re-initialized at sigreturn\n"); + } + + clearhandler(SIGTRAP); +} + int main(void) { /* Check hardware availability at first */ @@ -672,6 +737,7 @@ int main(void) test_fork(); test_context_switch(); test_ptrace(); + test_signal_handling();

return nerrs ? 1 : 0; }