selftests/powerpc: Add test of load_unaligned_zero_pad()

It is a rarely exercised case, so we want to have a test to ensure it
works as required.

Signed-off-by: Anton Blanchard <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>

arch/powerpc/include/asm/word-at-a-time.h

···
 
 #endif
 
+/*
+ * We use load_unaligned_zero() in a selftest, which builds a userspace
+ * program. Some linker scripts seem to discard the .fixup section, so allow
+ * the test code to use a different section name.
+ */
+#ifndef FIXUP_SECTION
+#define FIXUP_SECTION ".fixup"
+#endif
+
 static inline unsigned long load_unaligned_zeropad(const void *addr)
 {
 	unsigned long ret, offset, tmp;
···
 	asm(
 	"1:	" PPC_LL "%[ret], 0(%[addr])\n"
 	"2:\n"
-	".section .fixup,\"ax\"\n"
+	".section " FIXUP_SECTION ",\"ax\"\n"
 	"3:	"
 #ifdef __powerpc64__
 	"clrrdi		%[tmp], %[addr], 3\n\t"
···
 
 	return ret;
 }
+
+#undef FIXUP_SECTION
 
 #endif /* _ASM_WORD_AT_A_TIME_H */

tools/testing/selftests/powerpc/Makefile

···
 
 export CC CFLAGS
 
-TARGETS = pmu copyloops mm tm
+TARGETS = pmu copyloops mm tm primitives
 
 endif
 

tools/testing/selftests/powerpc/primitives/Makefile

···
+CFLAGS += -I$(CURDIR)
+
+PROGS := load_unaligned_zeropad
+
+all: $(PROGS)
+
+$(PROGS): ../harness.c
+
+run_tests: all
+	@-for PROG in $(PROGS); do \
+		./$$PROG; \
+	done;
+
+clean:
+	rm -f $(PROGS) *.o
+
+.PHONY: all run_tests clean

tools/testing/selftests/powerpc/primitives/load_unaligned_zeropad.c

···
+/*
+ * Userspace test harness for load_unaligned_zeropad. Creates two
+ * pages and uses mprotect to prevent access to the second page and
+ * a SEGV handler that walks the exception tables and runs the fixup
+ * routine.
+ *
+ * The results are compared against a normal load that is that is
+ * performed while access to the second page is enabled via mprotect.
+ *
+ * Copyright (C) 2014 Anton Blanchard <[e-mail]>, IBM
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <signal.h>
+#include <unistd.h>
+#include <sys/mman.h>
+
+#define FIXUP_SECTION ".ex_fixup"
+
+#include "word-at-a-time.h"
+
+#include "utils.h"
+
+
+static int page_size;
+static char *mem_region;
+
+static int protect_region(void)
+{
+	if (mprotect(mem_region + page_size, page_size, PROT_NONE)) {
+		perror("mprotect");
+		return 1;
+	}
+
+	return 0;
+}
+
+static int unprotect_region(void)
+{
+	if (mprotect(mem_region + page_size, page_size, PROT_READ|PROT_WRITE)) {
+		perror("mprotect");
+		return 1;
+	}
+
+	return 0;
+}
+
+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 int segv_error;
+
+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);
+	segv_error++;
+}
+
+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);
+}
+
+static int do_one_test(char *p, int page_offset)
+{
+	unsigned long should;
+	unsigned long got;
+
+	FAIL_IF(unprotect_region());
+	should = *(unsigned long *)p;
+	FAIL_IF(protect_region());
+
+	got = load_unaligned_zeropad(p);
+
+	if (should != got)
+		printf("offset %u load_unaligned_zeropad returned 0x%lx, should be 0x%lx\n", page_offset, got, should);
+
+	return 0;
+}
+
+static int test_body(void)
+{
+	unsigned long i;
+
+	page_size = getpagesize();
+	mem_region = mmap(NULL, page_size * 2, PROT_READ|PROT_WRITE,
+		MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+
+	FAIL_IF(mem_region == MAP_FAILED);
+
+	for (i = 0; i < page_size; i++)
+		mem_region[i] = i;
+
+	memset(mem_region+page_size, 0, page_size);
+
+	setup_segv_handler();
+
+	for (i = 0; i < page_size; i++)
+		FAIL_IF(do_one_test(mem_region+i, i));
+
+	FAIL_IF(segv_error);
+
+	return 0;
+}
+
+int main(void)
+{
+	return test_harness(test_body, "load_unaligned_zeropad");
+}