selftests/powerpc/64: Test exception cases in copy_tofrom_user

This adds a set of test cases to test the behaviour of
copy_tofrom_user when exceptions are encountered accessing the
source or destination.  Currently, copy_tofrom_user does not always
copy as many bytes as possible when an exception occurs on a store
to the destination, and that is reflected in failures in these tests.

Based on a test program from Anton Blanchard.

[paulus@ozlabs.org - test all three paths, wrote commit description,
 made EX_TABLE create an exception table.]
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/copyloops/.gitignore

@@ -8,3 +8,6 @@ memcpy_64_t1
 memcpy_64_t2
 memcpy_power7_t0
 memcpy_power7_t1
+copyuser_64_exc_t0
+copyuser_64_exc_t1
+copyuser_64_exc_t2

tools/testing/selftests/powerpc/copyloops/Makefile

@@ -12,9 +12,10 @@ ASFLAGS = $(CFLAGS) -Wa,-mpower4
 TEST_GEN_PROGS := copyuser_64_t0 copyuser_64_t1 copyuser_64_t2 \
 		copyuser_p7_t0 copyuser_p7_t1 \
 		memcpy_64_t0 memcpy_64_t1 memcpy_64_t2 \
-		memcpy_p7_t0 memcpy_p7_t1
+		memcpy_p7_t0 memcpy_p7_t1 \
+		copyuser_64_exc_t0 copyuser_64_exc_t1 copyuser_64_exc_t2
 
-EXTRA_SOURCES := validate.c ../harness.c
+EXTRA_SOURCES := validate.c ../harness.c stubs.S
 
 include ../../lib.mk
 
@@ -42,3 +43,10 @@ $(OUTPUT)/memcpy_p7_t%:	memcpy_power7.S $(EXTRA_SOURCES)
 		-D COPY_LOOP=test_memcpy_power7 \
 		-D SELFTEST_CASE=$(subst memcpy_p7_t,,$(notdir $@)) \
 		-o $@ $^
+
+$(OUTPUT)/copyuser_64_exc_t%: copyuser_64.S exc_validate.c ../harness.c \
+		copy_tofrom_user_reference.S stubs.S
+	$(CC) $(CPPFLAGS) $(CFLAGS) \
+		-D COPY_LOOP=test___copy_tofrom_user_base \
+		-D SELFTEST_CASE=$(subst copyuser_64_exc_t,,$(notdir $@)) \
+		-o $@ $^

tools/testing/selftests/powerpc/copyloops/asm/ppc_asm.h

 /* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __SELFTESTS_POWERPC_PPC_ASM_H
+#define __SELFTESTS_POWERPC_PPC_ASM_H
 #include <ppc-asm.h>
 
 #define CONFIG_ALTIVEC
@@ -26,25 +28,10 @@
 
 #define PPC_MTOCRF(A, B)	mtocrf A, B
 
-#define EX_TABLE(x, y)
-
-FUNC_START(enter_vmx_usercopy)
-	li	r3,1
-	blr
-
-FUNC_START(exit_vmx_usercopy)
-	li	r3,0
-	blr
-
-FUNC_START(enter_vmx_ops)
-	li	r3,1
-	blr
-
-FUNC_START(exit_vmx_ops)
-	blr
-
-FUNC_START(__copy_tofrom_user_base)
-	blr
+#define EX_TABLE(x, y)			\
+	.section __ex_table,"a";	\
+	.8byte	x, y;			\
+	.previous
 
 #define BEGIN_FTR_SECTION		.if test_feature
 #define FTR_SECTION_ELSE		.else
@@ -56,3 +43,5 @@ FUNC_START(__copy_tofrom_user_base)
 
 /* Default to taking the first of any alternative feature sections */
 test_feature = 1
+
+#endif /* __SELFTESTS_POWERPC_PPC_ASM_H */

tools/testing/selftests/powerpc/copyloops/copy_tofrom_user_reference.S

+#include <asm/ppc_asm.h>
+
+_GLOBAL(copy_tofrom_user_reference)
+	cmpdi	r5,0
+	beq	4f
+
+	mtctr	r5
+
+1:	lbz	r6,0(r4)
+2:	stb	r6,0(r3)
+	addi	r3,r3,1
+	addi	r4,r4,1
+	bdnz	1b
+
+3:	mfctr	r3
+	blr
+
+4:	mr	r3,r5
+	blr
+
+.section __ex_table,"a"
+	.llong	1b,3b
+	.llong	2b,3b
+.text

tools/testing/selftests/powerpc/copyloops/exc_validate.c

+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <signal.h>
+#include <unistd.h>
+#include <sys/mman.h>
+
+#include "utils.h"
+
+extern char __start___ex_table[];
+extern char __stop___ex_table[];
+
+#if defined(__powerpc64__)
+#define UCONTEXT_NIA(UC)	(UC)->uc_mcontext.gp_regs[PT_NIP]
+#elif defined(__powerpc__)
+#define UCONTEXT_NIA(UC)	(UC)->uc_mcontext.uc_regs->gregs[PT_NIP]
+#else
+#error implement UCONTEXT_NIA
+#endif
+
+static void segv_handler(int signr, siginfo_t *info, void *ptr)
+{
+	ucontext_t *uc = (ucontext_t *)ptr;
+	unsigned long addr = (unsigned long)info->si_addr;
+	unsigned long *ip = &UCONTEXT_NIA(uc);
+	unsigned long *ex_p = (unsigned long *)__start___ex_table;
+
+	while (ex_p < (unsigned long *)__stop___ex_table) {
+		unsigned long insn, fixup;
+
+		insn = *ex_p++;
+		fixup = *ex_p++;
+
+		if (insn == *ip) {
+			*ip = fixup;
+			return;
+		}
+	}
+
+	printf("No exception table match for NIA %lx ADDR %lx\n", *ip, addr);
+	abort();
+}
+
+static void setup_segv_handler(void)
+{
+	struct sigaction action;
+
+	memset(&action, 0, sizeof(action));
+	action.sa_sigaction = segv_handler;
+	action.sa_flags = SA_SIGINFO;
+	sigaction(SIGSEGV, &action, NULL);
+}
+
+unsigned long COPY_LOOP(void *to, const void *from, unsigned long size);
+unsigned long test_copy_tofrom_user_reference(void *to, const void *from, unsigned long size);
+
+static int total_passed;
+static int total_failed;
+
+static void do_one_test(char *dstp, char *srcp, unsigned long len)
+{
+	unsigned long got, expected;
+
+	got = COPY_LOOP(dstp, srcp, len);
+	expected = test_copy_tofrom_user_reference(dstp, srcp, len);
+
+	if (got != expected) {
+		total_failed++;
+		printf("FAIL from=%p to=%p len=%ld returned %ld, expected %ld\n",
+		       srcp, dstp, len, got, expected);
+		//abort();
+	} else
+		total_passed++;
+}
+
+//#define MAX_LEN 512
+#define MAX_LEN 16
+
+int test_copy_exception(void)
+{
+	int page_size;
+	static char *p, *q;
+	unsigned long src, dst, len;
+
+	page_size = getpagesize();
+	p = mmap(NULL, page_size * 2, PROT_READ|PROT_WRITE,
+		MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+
+	if (p == MAP_FAILED) {
+		perror("mmap");
+		exit(1);
+	}
+
+	memset(p, 0, page_size);
+
+	setup_segv_handler();
+
+	if (mprotect(p + page_size, page_size, PROT_NONE)) {
+		perror("mprotect");
+		exit(1);
+	}
+
+	q = p + page_size - MAX_LEN;
+
+	for (src = 0; src < MAX_LEN; src++) {
+		for (dst = 0; dst < MAX_LEN; dst++) {
+			for (len = 0; len < MAX_LEN+1; len++) {
+				// printf("from=%p to=%p len=%ld\n", q+dst, q+src, len);
+				do_one_test(q+dst, q+src, len);
+			}
+		}
+	}
+
+	printf("Totals:\n");
+	printf("  Pass: %d\n", total_passed);
+	printf("  Fail: %d\n", total_failed);
+
+	return 0;
+}
+
+int main(void)
+{
+	return test_harness(test_copy_exception, str(COPY_LOOP));
+}

tools/testing/selftests/powerpc/copyloops/stubs.S

+#include <asm/ppc_asm.h>
+
+FUNC_START(enter_vmx_usercopy)
+	li	r3,1
+	blr
+
+FUNC_START(exit_vmx_usercopy)
+	li	r3,0
+	blr
+
+FUNC_START(enter_vmx_ops)
+	li	r3,1
+	blr
+
+FUNC_START(exit_vmx_ops)
+	blr
+
+FUNC_START(__copy_tofrom_user_base)
+	blr