1 files changed, 72 insertions, 24 deletions

diff --git a/tools/testing/selftests/x86/ldt_gdt.c b/tools/testing/selftests/x86/ldt_gdt.c
index 961e3ee26c27..1aef72df20a1 100644
--- a/tools/testing/selftests/x86/ldt_gdt.c
+++ b/tools/testing/selftests/x86/ldt_gdt.c
@@ -115,7 +115,14 @@ static void check_valid_segment(uint16_t index, int ldt,
 		return;
 	}
 
-	if (ar != expected_ar) {
+	/* The SDM says "bits 19:16 are undefined".  Thanks. */
+	ar &= ~0xF0000;
+
+	/*
+	 * NB: Different Linux versions do different things with the
+	 * accessed bit in set_thread_area().
+	 */
+	if (ar != expected_ar && ar != (expected_ar | AR_ACCESSED)) {
 		printf("[FAIL]\t%s entry %hu has AR 0x%08X but expected 0x%08X\n",
 		       (ldt ? "LDT" : "GDT"), index, ar, expected_ar);
 		nerrs++;
@@ -129,30 +136,51 @@ static void check_valid_segment(uint16_t index, int ldt,
 	}
 }
 
-static bool install_valid_mode(const struct user_desc *desc, uint32_t ar,
-			       bool oldmode)
+static bool install_valid_mode(const struct user_desc *d, uint32_t ar,
+			       bool oldmode, bool ldt)
 {
-	int ret = syscall(SYS_modify_ldt, oldmode ? 1 : 0x11,
-			  desc, sizeof(*desc));
-	if (ret < -1)
-		errno = -ret;
+	struct user_desc desc = *d;
+	int ret;
+
+	if (!ldt) {
+#ifndef __i386__
+		/* No point testing set_thread_area in a 64-bit build */
+		return false;
+#endif
+		if (!gdt_entry_num)
+			return false;
+		desc.entry_number = gdt_entry_num;
+
+		ret = syscall(SYS_set_thread_area, &desc);
+	} else {
+		ret = syscall(SYS_modify_ldt, oldmode ? 1 : 0x11,
+			      &desc, sizeof(desc));
+
+		if (ret < -1)
+			errno = -ret;
+
+		if (ret != 0 && errno == ENOSYS) {
+			printf("[OK]\tmodify_ldt returned -ENOSYS\n");
+			return false;
+		}
+	}
+
 	if (ret == 0) {
-		uint32_t limit = desc->limit;
-		if (desc->limit_in_pages)
+		uint32_t limit = desc.limit;
+		if (desc.limit_in_pages)
 			limit = (limit << 12) + 4095;
-		check_valid_segment(desc->entry_number, 1, ar, limit, true);
+		check_valid_segment(desc.entry_number, ldt, ar, limit, true);
 		return true;
-	} else if (errno == ENOSYS) {
-		printf("[OK]\tmodify_ldt returned -ENOSYS\n");
-		return false;
 	} else {
-		if (desc->seg_32bit) {
-			printf("[FAIL]\tUnexpected modify_ldt failure %d\n",
+		if (desc.seg_32bit) {
+			printf("[FAIL]\tUnexpected %s failure %d\n",
+			       ldt ? "modify_ldt" : "set_thread_area",
 			       errno);
 			nerrs++;
 			return false;
 		} else {
-			printf("[OK]\tmodify_ldt rejected 16 bit segment\n");
+			printf("[OK]\t%s rejected 16 bit segment\n",
+			       ldt ? "modify_ldt" : "set_thread_area");
 			return false;
 		}
 	}
@@ -160,7 +188,15 @@ static bool install_valid_mode(const struct user_desc *desc, uint32_t ar,
 
 static bool install_valid(const struct user_desc *desc, uint32_t ar)
 {
-	return install_valid_mode(desc, ar, false);
+	bool ret = install_valid_mode(desc, ar, false, true);
+
+	if (desc->contents <= 1 && desc->seg_32bit &&
+	    !desc->seg_not_present) {
+		/* Should work in the GDT, too. */
+		install_valid_mode(desc, ar, false, false);
+	}
+
+	return ret;
 }
 
 static void install_invalid(const struct user_desc *desc, bool oldmode)
@@ -367,9 +403,24 @@ static void do_simple_tests(void)
 	install_invalid(&desc, false);
 
 	desc.seg_not_present = 0;
-	desc.read_exec_only = 0;
 	desc.seg_32bit = 1;
+	desc.read_exec_only = 0;
+	desc.limit = 0xfffff;
+
 	install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S | AR_P | AR_DB);
+
+	desc.limit_in_pages = 1;
+
+	install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S | AR_P | AR_DB | AR_G);
+	desc.read_exec_only = 1;
+	install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA | AR_S | AR_P | AR_DB | AR_G);
+	desc.contents = 1;
+	desc.read_exec_only = 0;
+	install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA_EXPDOWN | AR_S | AR_P | AR_DB | AR_G);
+	desc.read_exec_only = 1;
+	install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA_EXPDOWN | AR_S | AR_P | AR_DB | AR_G);
+
+	desc.limit = 0;
 	install_invalid(&desc, true);
 }
 
@@ -575,13 +626,10 @@ static void do_multicpu_tests(void)
 static int finish_exec_test(void)
 {
 	/*
-	 * In a sensible world, this would be check_invalid_segment(0, 1);
-	 * For better or for worse, though, the LDT is inherited across exec.
-	 * We can probably change this safely, but for now we test it.
+	 * Older kernel versions did inherit the LDT on exec() which is
+	 * wrong because exec() starts from a clean state.
 	 */
-	check_valid_segment(0, 1,
-			    AR_DPL3 | AR_TYPE_XRCODE | AR_S | AR_P | AR_DB,
-			    42, true);
+	check_invalid_segment(0, 1);
 
 	return nerrs ? 1 : 0;
 }