From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Stancek Date: Mon, 11 Feb 2019 17:11:37 -0500 (EST) Subject: [LTP] [PATCH] syscalls/mprotect04: align exec_func to 64 bytes In-Reply-To: References: <42aa7fc222cbfbf10136b2a9ae6f74b3b9a2235a.1549897252.git.jstancek@redhat.com> Message-ID: <856912859.250579.1549923097312.JavaMail.zimbra@redhat.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ltp@lists.linux.it ----- Original Message ----- > Consider consolidating page_sz (currently in get_func()) and copy_sz > (global) since they are now identical. Maybe make page_sz a global > variable. > > I had some concerns around "-falign-functions=64": For example, > https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html states > "Enabled at levels -O2, -O3.". The way I read this is that > -falign-functions is ignored for optimization levels other than O2 and > O3. An ad-hoc test with gcc 7.3.0, however, showed that functions are > indeed aligned on 64 byte boundaries even with O0. I also tried clang > (llvm), and it also behaves as desired (for x86-64 and aarch64). > > I guess one thing you could do is to calculate the difference between > the address of exec_func and the end of the page and programmatically > verify that there is enough cushion between the start of exec_func and > the end of the page. This would catch the case where some compiler > ignores "-falign-functions=64". That sounds like reasonable precaution, I'll send v2 shortly. > > On Mon, Feb 11, 2019 at 7:04 AM Jan Stancek wrote: > > > > exec_func() is dummy/empty function. If we make sure it's aligned, > > we can be pretty confident that it will located in single page and > > can drop code that deals with 2nd page. > > > > Signed-off-by: Jan Stancek > > --- > > testcases/kernel/syscalls/mprotect/Makefile | 2 ++ > > testcases/kernel/syscalls/mprotect/mprotect04.c | 12 ++---------- > > 2 files changed, 4 insertions(+), 10 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..3125f344795d 100644 > > --- a/testcases/kernel/syscalls/mprotect/mprotect04.c > > +++ b/testcases/kernel/syscalls/mprotect/mprotect04.c > > @@ -88,7 +88,7 @@ static void setup(void) > > { > > tst_tmpdir(); > > tst_sig(NOFORK, sighandler, cleanup); > > - copy_sz = getpagesize() * 2; > > + copy_sz = getpagesize(); > > > > TEST_PAUSE; > > } > > @@ -133,7 +133,7 @@ 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;; */ > > @@ -237,14 +237,6 @@ static void *get_func(void *mem) > > } > > 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); > > - > > clear_cache(mem_start, copy_sz); > > > > /* return pointer to area where copy of exec_func resides */ > > -- > > 1.8.3.1 > > >