kselftest/arm64/mte: Register mte signal handler with SA_EXPOSE_TAGBITS

To test address tag[63:60] and memory tag[59:56] is preserved
when memory tag fault happen, Let mte_register_signal() to register
signal handler with SA_EXPOSE_TAGBITS.

Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20250618084513.1761345-6-yeoreum.yun@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: LeviYeoReum

tools/testing/selftests/arm64/mte/check_buffer_fill.c

@@ -415,7 +415,7 @@ int main(int argc, char *argv[])
 		return err;
 
 	/* Register SIGSEGV handler */
-	mte_register_signal(SIGSEGV, mte_default_handler);
+	mte_register_signal(SIGSEGV, mte_default_handler, false);
 
 	/* Set test plan */
 	ksft_set_plan(20);

tools/testing/selftests/arm64/mte/check_child_memory.c

@@ -160,8 +160,8 @@ int main(int argc, char *argv[])
 		return err;
 
 	/* Register SIGSEGV handler */
-	mte_register_signal(SIGSEGV, mte_default_handler);
-	mte_register_signal(SIGBUS, mte_default_handler);
+	mte_register_signal(SIGSEGV, mte_default_handler, false);
+	mte_register_signal(SIGBUS, mte_default_handler, false);
 
 	/* Set test plan */
 	ksft_set_plan(12);

tools/testing/selftests/arm64/mte/check_hugetlb_options.c

@@ -235,8 +235,8 @@ int main(int argc, char *argv[])
 		return err;
 
 	/* Register signal handlers */
-	mte_register_signal(SIGBUS, mte_default_handler);
-	mte_register_signal(SIGSEGV, mte_default_handler);
+	mte_register_signal(SIGBUS, mte_default_handler, false);
+	mte_register_signal(SIGSEGV, mte_default_handler, false);
 
 	allocate_hugetlb();
 

tools/testing/selftests/arm64/mte/check_ksm_options.c

@@ -141,8 +141,8 @@ int main(int argc, char *argv[])
 		return KSFT_FAIL;
 	}
 	/* Register signal handlers */
-	mte_register_signal(SIGBUS, mte_default_handler);
-	mte_register_signal(SIGSEGV, mte_default_handler);
+	mte_register_signal(SIGBUS, mte_default_handler, false);
+	mte_register_signal(SIGSEGV, mte_default_handler, false);
 
 	/* Set test plan */
 	ksft_set_plan(4);

tools/testing/selftests/arm64/mte/check_mmap_options.c

@@ -201,8 +201,8 @@ int main(int argc, char *argv[])
 	sizes[item - 1] = page_size + 1;
 
 	/* Register signal handlers */
-	mte_register_signal(SIGBUS, mte_default_handler);
-	mte_register_signal(SIGSEGV, mte_default_handler);
+	mte_register_signal(SIGBUS, mte_default_handler, false);
+	mte_register_signal(SIGSEGV, mte_default_handler, false);
 
 	/* Set test plan */
 	ksft_set_plan(22);

tools/testing/selftests/arm64/mte/check_tags_inclusion.c

@@ -180,7 +180,7 @@ int main(int argc, char *argv[])
 		return err;
 
 	/* Register SIGSEGV handler */
-	mte_register_signal(SIGSEGV, mte_default_handler);
+	mte_register_signal(SIGSEGV, mte_default_handler, false);
 
 	/* Set test plan */
 	ksft_set_plan(4);

tools/testing/selftests/arm64/mte/check_user_mem.c

@@ -211,7 +211,7 @@ int main(int argc, char *argv[])
 		return err;
 
 	/* Register signal handlers */
-	mte_register_signal(SIGSEGV, mte_default_handler);
+	mte_register_signal(SIGSEGV, mte_default_handler, false);
 
 	/* Set test plan */
 	ksft_set_plan(64);

tools/testing/selftests/arm64/mte/mte_common_util.c

@@ -19,6 +19,10 @@
 #include "mte_common_util.h"
 #include "mte_def.h"
 
+#ifndef SA_EXPOSE_TAGBITS
+#define SA_EXPOSE_TAGBITS 0x00000800
+#endif
+
 #define INIT_BUFFER_SIZE       256
 
 struct mte_fault_cxt cur_mte_cxt;
@@ -79,12 +83,17 @@ void mte_default_handler(int signum, siginfo_t *si, void *uc)
 	}
 }
 
-void mte_register_signal(int signal, void (*handler)(int, siginfo_t *, void *))
+void mte_register_signal(int signal, void (*handler)(int, siginfo_t *, void *),
+			 bool export_tags)
 {
 	struct sigaction sa;
 
 	sa.sa_sigaction = handler;
 	sa.sa_flags = SA_SIGINFO;
+
+	if (export_tags && signal == SIGSEGV)
+		sa.sa_flags |= SA_EXPOSE_TAGBITS;
+
 	sigemptyset(&sa.sa_mask);
 	sigaction(signal, &sa, NULL);
 }

tools/testing/selftests/arm64/mte/mte_common_util.h

@@ -40,7 +40,8 @@ extern struct mte_fault_cxt cur_mte_cxt;
 
 /* MTE utility functions */
 void mte_default_handler(int signum, siginfo_t *si, void *uc);
-void mte_register_signal(int signal, void (*handler)(int, siginfo_t *, void *));
+void mte_register_signal(int signal, void (*handler)(int, siginfo_t *, void *),
+			 bool export_tags);
 void mte_wait_after_trig(void);
 void *mte_allocate_memory(size_t size, int mem_type, int mapping, bool tags);
 void *mte_allocate_memory_tag_range(size_t size, int mem_type, int mapping,