sigreturn: Test even more things

1 files changed, 75 insertions, 23 deletions

diff --git a/sigreturn.c b/sigreturn.c
index bbf13ce..e2de0e5 100644
--- a/sigreturn.c
+++ b/sigreturn.c
@@ -23,6 +23,10 @@ struct selectors {
 	unsigned short cs, gs, fs, ss;
 };
 
+static bool has_code16, has_data16, has_npcode32, has_npdata16;
+
+static int gdt_data16_idx;
+
 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
 		       int flags)
 {
@@ -58,6 +62,16 @@ asm (".pushsection .text\n\t"
      ".popsection");
 extern char int3[4096];
 
+static void add_ldt(const struct user_desc *desc, bool *var, const char *name)
+{
+	if (syscall(SYS_modify_ldt, 1, desc, sizeof(*desc)) == 0) {
+		*var = true;
+	} else {
+		printf("[NOTE]\tFailed to create %s segment\n", name);
+		*var = false;
+	}
+}
+
 static void setup_ldt(void)
 {
 	if ((unsigned long)stack16 > (1ULL << 32) - sizeof(stack16))
@@ -77,6 +91,8 @@ static void setup_ldt(void)
 		.seg_not_present = 0,
 		.useable         = 0
 	};
+	add_ldt(&code16_desc, &has_code16, "code16");
+
 	const struct user_desc data16_desc = {
 		.entry_number    = 1,
 		.base_addr       = (unsigned long)stack16,
@@ -88,7 +104,9 @@ static void setup_ldt(void)
 		.seg_not_present = 0,
 		.useable         = 0
 	};
-	const struct user_desc npcode16_desc = {
+	add_ldt(&data16_desc, &has_data16, "data16");
+
+	const struct user_desc npcode32_desc = {
 		.entry_number    = 3,
 		.base_addr       = (unsigned long)int3,
 		.limit           = 4095,
@@ -99,6 +117,8 @@ static void setup_ldt(void)
 		.seg_not_present = 1,
 		.useable         = 0
 	};
+	add_ldt(&npcode32_desc, &has_npcode32, "npcode32");
+
 	const struct user_desc npdata16_desc = {
 		.entry_number    = 4,
 		.base_addr       = (unsigned long)stack16,
@@ -110,15 +130,27 @@ static void setup_ldt(void)
 		.seg_not_present = 1,
 		.useable         = 0
 	};
+	add_ldt(&npdata16_desc, &has_npdata16, "npdata16");
+
+	struct user_desc gdt_data16_desc = {
+		.entry_number    = -1,
+		.base_addr       = (unsigned long)stack16,
+		.limit           = 0xffff,
+		.seg_32bit       = 0,
+		.contents        = 0, /* Data, grow-up */
+		.read_exec_only  = 0,
+		.limit_in_pages  = 0,
+		.seg_not_present = 0,
+		.useable         = 0
+	};
 
-	if (syscall(SYS_modify_ldt, 1, &code16_desc, sizeof code16_desc) != 0)
-		err(1, "modify_ldt");
-	if (syscall(SYS_modify_ldt, 1, &data16_desc, sizeof data16_desc) != 0)
-		err(1, "modify_ldt");
-	if (syscall(SYS_modify_ldt, 1, &npcode16_desc, sizeof npcode16_desc) != 0)
-		err(1, "modify_ldt");
-	if (syscall(SYS_modify_ldt, 1, &npdata16_desc, sizeof npdata16_desc) != 0)
-		err(1, "modify_ldt");
+	if (syscall(SYS_set_thread_area, &gdt_data16_desc) == 0) {
+		printf("[FAIL]\tset_thread_area allocated data16 at index %d\n",
+		       gdt_data16_desc.entry_number);
+		gdt_data16_idx = gdt_data16_desc.entry_number;
+	} else {
+		printf("[OK]\tset_thread_area refused 16-bit data\n");
+	}
 }
 
 static gregset_t initial_regs, requested_regs, resulting_regs;
@@ -253,21 +285,35 @@ int find_cs(int bitness)
 	return -1;
 }
 
-static int do_test(int cs_bits, bool use_16bit_ss)
+static int do_test(int cs_bits, bool use_16bit_ss, int force_ss)
 {
 	int cs = find_cs(cs_bits);
-	if (cs == -1)
+	if (cs == -1) {
+		printf("[SKIP]\tCode segment unavailable for %d-bit CS, %d-bit SS\n",
+		       cs_bits, use_16bit_ss ? 16 : 32);
 		return 0;
+	}
 
-	if (use_16bit_ss)
-		sig_ss = (1 << 3) | 7;	/* LDT selector 1, RPL = 3 */
-	else
-		asm volatile ("mov %%ss,%0" : "=r" (sig_ss));
+	if (force_ss != -1) {
+		sig_ss = force_ss;
+	} else {
+		if (use_16bit_ss) {
+			if (!has_data16) {
+				printf("[SKIP]\tData segment unavailable for %d-bit CS, 16-bit SS\n",
+				       cs_bits);
+				return 0;
+			}
+			sig_ss = (1 << 3) | 7;	/* LDT selector 1, RPL = 3 */
+		} else {
+			asm volatile ("mov %%ss,%0" : "=r" (sig_ss));
+		}
+	}
 
 	sig_cs = cs;
 
-	printf("[RUN]\t%d-bit CS (%hx), %d-bit SS (%hx)\n",
-	       cs_bits, sig_cs, use_16bit_ss ? 16 : 32, sig_ss);
+	printf("[RUN]\t%d-bit CS (%hx), %d-bit SS (%hx%s)\n",
+	       cs_bits, sig_cs, use_16bit_ss ? 16 : 32, sig_ss,
+	       (sig_ss & 4) ? "" : ", GDT");
 
 	raise(SIGUSR1);
 
@@ -404,12 +450,18 @@ int main()
 	sethandler(SIGUSR1, sigusr1, 0);
 	sethandler(SIGTRAP, sigtrap, SA_ONSTACK);
 
-	total_nerrs += do_test(64, false);
-	total_nerrs += do_test(32, false);
-	total_nerrs += do_test(16, false);
-	total_nerrs += do_test(64, true);
-	total_nerrs += do_test(32, true);
-	total_nerrs += do_test(16, true);
+	total_nerrs += do_test(64, false, -1);
+	total_nerrs += do_test(32, false, -1);
+	total_nerrs += do_test(16, false, -1);
+	total_nerrs += do_test(64, true, -1);
+	total_nerrs += do_test(32, true, -1);
+	total_nerrs += do_test(16, true, -1);
+
+	if (gdt_data16_idx) {
+		total_nerrs += do_test(64, true, (gdt_data16_idx << 3) | 3);
+		total_nerrs += do_test(32, true, (gdt_data16_idx << 3) | 3);
+		total_nerrs += do_test(16, true, (gdt_data16_idx << 3) | 3);
+	}
 
 	clearhandler(SIGTRAP);
 	sethandler(SIGSEGV, sigtrap, SA_ONSTACK);