[LTP] [PATCH v2] syscalls/mprotect: align exec_func to 64 bytes

[Jan Stancek]

exec_func() is dummy/empty function. Try to align it so we don't
need to worry about copying 2 pages. But also check that compiler
aligned it and there's sufficient space between start of func_exec
and end of page.

This patch also removes copy_sz, which is now replaced with page_sz.

Signed-off-by: Jan Stancek <jstancek@redhat.com>
---
 testcases/kernel/syscalls/mprotect/Makefile     |  2 +
 testcases/kernel/syscalls/mprotect/mprotect04.c | 55 +++++++++++--------------
 2 files changed, 27 insertions(+), 30 deletions(-)

diff --git a/testcases/kernel/syscalls/mprotect/Makefile b/testcases/kernel/syscalls/mprotect/Makefile
index bd617d806675..bc5c8bc10395 100644
--- a/testcases/kernel/syscalls/mprotect/Makefile
+++ b/testcases/kernel/syscalls/mprotect/Makefile
@@ -20,4 +20,6 @@ top_srcdir		?= ../../../..
 
 include $(top_srcdir)/include/mk/testcases.mk
 
+mprotect04: CFLAGS += -falign-functions=64
+
 include $(top_srcdir)/include/mk/generic_leaf_target.mk
diff --git a/testcases/kernel/syscalls/mprotect/mprotect04.c b/testcases/kernel/syscalls/mprotect/mprotect04.c
index 60941a4220d5..0f7890dca03b 100644
--- a/testcases/kernel/syscalls/mprotect/mprotect04.c
+++ b/testcases/kernel/syscalls/mprotect/mprotect04.c
@@ -55,7 +55,7 @@ int TST_TOTAL = ARRAY_SIZE(testfunc);
 
 static volatile int sig_caught;
 static sigjmp_buf env;
-static unsigned int copy_sz;
+static unsigned int page_sz;
 typedef void (*func_ptr_t)(void);
 
 int main(int ac, char **av)
@@ -88,7 +88,7 @@ static void setup(void)
 {
 	tst_tmpdir();
 	tst_sig(NOFORK, sighandler, cleanup);
-	copy_sz = getpagesize() * 2;
+	page_sz = getpagesize();
 
 	TEST_PAUSE;
 }
@@ -96,12 +96,9 @@ static void setup(void)
 static void testfunc_protnone(void)
 {
 	char *addr;
-	int page_sz;
 
 	sig_caught = 0;
 
-	page_sz = getpagesize();
-
 	addr = SAFE_MMAP(cleanup, 0, page_sz, PROT_READ | PROT_WRITE,
 					 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 
@@ -133,7 +130,7 @@ static void testfunc_protnone(void)
 
 #ifdef __ia64__
 
-static char exec_func[] = {
+static char exec_func[] __attribute__ ((aligned (64))) = {
 	0x11, 0x00, 0x00, 0x00, 0x01, 0x00, /* nop.m 0x0             */
 	0x00, 0x00, 0x00, 0x02, 0x00, 0x80, /* nop.i 0x0             */
 	0x08, 0x00, 0x84, 0x00,             /* br.ret.sptk.many b0;; */
@@ -210,42 +207,33 @@ typedef struct {
  * Copy page where &exec_func resides. Also try to copy subsequent page
  * in case exec_func is close to page boundary.
  */
-static void *get_func(void *mem)
+static void *get_func(void *mem, uintptr_t *func_page_offset)
 {
 	uintptr_t page_sz = getpagesize();
 	uintptr_t page_mask = ~(page_sz - 1);
-	uintptr_t func_page_offset;
 	void *func_copy_start, *page_to_copy;
 	void *mem_start = mem;
 
 #ifdef USE_FUNCTION_DESCRIPTORS
 	func_descr_t *opd =  (func_descr_t *)&exec_func;
-	func_page_offset = (uintptr_t)opd->entry & (page_sz - 1);
-	func_copy_start = mem + func_page_offset;
+	*func_page_offset = (uintptr_t)opd->entry & (page_sz - 1);
+	func_copy_start = mem + *func_page_offset;
 	page_to_copy = (void *)((uintptr_t)opd->entry & page_mask);
 #else
-	func_page_offset = (uintptr_t)&exec_func & (page_sz - 1);
-	func_copy_start = mem + func_page_offset;
+	*func_page_offset = (uintptr_t)&exec_func & (page_sz - 1);
+	func_copy_start = mem + *func_page_offset;
 	page_to_copy = (void *)((uintptr_t)&exec_func & page_mask);
 #endif
+	tst_resm(TINFO, "exec_func: %p, page_to_copy: %p",
+		&exec_func, page_to_copy);
 
 	/* copy 1st page, if it's not present something is wrong */
-	if (!page_present(page_to_copy)) {
-		tst_resm(TINFO, "exec_func: %p, page_to_copy: %p\n",
-			&exec_func, page_to_copy);
+	if (!page_present(page_to_copy))
 		tst_brkm(TBROK, cleanup, "page_to_copy not present\n");
-	}
-	memcpy(mem, page_to_copy, page_sz);
 
-	/* copy 2nd page if possible */
-	mem += page_sz;
-	page_to_copy += page_sz;
-	if (page_present(page_to_copy))
-		memcpy(mem, page_to_copy, page_sz);
-	else
-		memset(mem, 0, page_sz);
+	memcpy(mem, page_to_copy, page_sz);
 
-	clear_cache(mem_start, copy_sz);
+	clear_cache(mem_start, page_sz);
 
 	/* return pointer to area where copy of exec_func resides */
 	return func_copy_start;
@@ -256,23 +244,30 @@ static void *get_func(void *mem)
 static void testfunc_protexec(void)
 {
 	func_ptr_t func;
+	uintptr_t func_page_offset;
 	void *p;
 
 	sig_caught = 0;
 
-	p = SAFE_MMAP(cleanup, 0, copy_sz, PROT_READ | PROT_WRITE,
+	p = SAFE_MMAP(cleanup, 0, page_sz, PROT_READ | PROT_WRITE,
 		 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 
 #ifdef USE_FUNCTION_DESCRIPTORS
 	func_descr_t opd;
-	opd.entry = (uintptr_t)get_func(p);
+	opd.entry = (uintptr_t)get_func(p, &func_page_offset);
 	func = (func_ptr_t)&opd;
 #else
-	func = get_func(p);
+	func = get_func(p, &func_page_offset);
 #endif
 
+	if (func_page_offset + 64 >= page_sz) {
+		SAFE_MUNMAP(cleanup, p, page_sz);
+		tst_brkm(TCONF, cleanup, "func too close to page boundary, "
+			"maybe your compiler ignores -falign-functions?");
+	}
+
 	/* Change the protection to PROT_EXEC. */
-	TEST(mprotect(p, copy_sz, PROT_EXEC));
+	TEST(mprotect(p, page_sz, PROT_EXEC));
 
 	if (TEST_RETURN == -1) {
 		tst_resm(TFAIL | TTERRNO, "mprotect failed");
@@ -294,7 +289,7 @@ static void testfunc_protexec(void)
 		}
 	}
 
-	SAFE_MUNMAP(cleanup, p, copy_sz);
+	SAFE_MUNMAP(cleanup, p, page_sz);
 }
 
 static void cleanup(void)
-- 
1.8.3.1