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Thu, 22 Sep 2016 18:35:07 -0700 Date: Thu, 22 Sep 2016 21:35:03 -0400 From: Konrad Rzeszutek Wilk To: Julien Grall Message-ID: <20160923013502.GC29985@localhost.localdomain> References: <1474479154-20991-1-git-send-email-konrad.wilk@oracle.com> <1474479154-20991-17-git-send-email-konrad.wilk@oracle.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.1 (2016-04-27) X-Source-IP: aserv0022.oracle.com [141.146.126.234] Cc: sstabellini@kernel.org, ross.lagerwall@citrix.com, Andrew Cooper , Jan Beulich , xen-devel@lists.xenproject.org Subject: Re: [Xen-devel] [PATCH v5 16/16] livepatch: arm[32, 64], x86: NOP test-case X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" X-Virus-Scanned: ClamAV using ClamSMTP .snip.. > > While on ARM32 there are 24 bytes: > > > > e52db004 push {fp} > > e28db000 add fp, sp, #0 <- NOP > > e3a00008 mov r0, #8 <- NOP > > e24bd000 sub sp, fp, #0 <- NOP > > e49db004 pop {fp} > > e12fff1e bx lr > > > > And we can NOP instruction 2,3, and 4. > > Why don't you NOP push {fp} and pop {fp}? At first glance, I am a bit > surprised that the compiler is generating them (maybe it is because you have > debug enabled?) and would have expect to have: > > mov r0, #8 > bx lr > > NOPing all the instructions but the last one would simplify at lot the test > case below. > > [...] ..snip.. > With my suggestion above, the two ARM code could become: > > #ifdef CONFIG_ARM > .old_addr = (void *)MINOR_VERSION_ADDR, > .new_size = MINOR_VERSION_SIZE - 4, > #endif > > The "- 4" is to avoid replacing the return. Done! From 8ade51e1866b86c7660277bb19100db337d432b4 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Sat, 10 Sep 2016 20:41:24 -0400 Subject: [PATCH v6] livepatch: arm[32,64],x86: NOP test-case The test-case is quite simple - we NOP the 'xen_minor_version'. The amount of NOPs depends on the architecture. On x86 the function is 11 bytes long: 55 push %rbp <- NOP 48 89 e5 mov %rsp,%rbp <- NOP b8 04 00 00 00 mov $0x4,%eax <- NOP 5d pop %rbp <- NOP c3 retq We can NOP everything but the last instruction (so 10 bytes). On ARM64 its 8 bytes: 52800100 mov w0, #0x8 <- NOP d65f03c0 ret We can NOP the first instruction. While on ARM32 there are 24 bytes: e52db004 push {fp} <- NOP e28db000 add fp, sp, #0 <- NOP e3a00008 mov r0, #8 <- NOP e24bd000 sub sp, fp, #0 <- NOP e49db004 pop {fp} <- NOP e12fff1e bx lr And we can NOP instructions 1 through 5. Granted this code may be different per compiler! Hence if anybody does run this test-case - they should verify that the assumptions made here are correct. Signed-off-by: Konrad Rzeszutek Wilk Acked-by: Julien Grall --- Cc: Julien Grall Cc: Stefano Stabellini Cc: Jan Beulich Cc: Andrew Cooper v3: New submission. v4: Redo the ARM code to NOP over push/pop as well. --- xen/test/livepatch/Makefile | 15 +++++++++++++- xen/test/livepatch/xen_nop.c | 48 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 62 insertions(+), 1 deletion(-) create mode 100644 xen/test/livepatch/xen_nop.c diff --git a/xen/test/livepatch/Makefile b/xen/test/livepatch/Makefile index 9439f62..76a779a 100644 --- a/xen/test/livepatch/Makefile +++ b/xen/test/livepatch/Makefile @@ -18,6 +18,7 @@ CODE_SZ=$(shell nm --defined -S $(1) | grep $(2) | awk '{ print "0x"$$2}') LIVEPATCH := xen_hello_world.livepatch LIVEPATCH_BYE := xen_bye_world.livepatch LIVEPATCH_REPLACE := xen_replace_world.livepatch +LIVEPATCH_NOP := xen_nop.livepatch default: livepatch @@ -25,10 +26,12 @@ install: livepatch $(INSTALL_DATA) $(LIVEPATCH) $(DESTDIR)$(DEBUG_DIR)/$(LIVEPATCH) $(INSTALL_DATA) $(LIVEPATCH_BYE) $(DESTDIR)$(DEBUG_DIR)/$(LIVEPATCH_BYE) $(INSTALL_DATA) $(LIVEPATCH_REPLACE) $(DESTDIR)$(DEBUG_DIR)/$(LIVEPATCH_REPLACE) + $(INSTALL_DATA) $(LIVEPATCH_NOP) $(DESTDIR)$(DEBUG_DIR)/$(LIVEPATCH_NOP) uninstall: rm -f $(DESTDIR)$(DEBUG_DIR)/$(LIVEPATCH) rm -f $(DESTDIR)$(DEBUG_DIR)/$(LIVEPATCH_BYE) rm -f $(DESTDIR)$(DEBUG_DIR)/$(LIVEPATCH_REPLACE) + rm -f $(DESTDIR)$(DEBUG_DIR)/$(LIVEPATCH_NOP) .PHONY: clean clean:: @@ -41,9 +44,13 @@ clean:: .PHONY: config.h config.h: OLD_CODE_SZ=$(call CODE_SZ,$(BASEDIR)/xen-syms,xen_extra_version) config.h: NEW_CODE_SZ=$(call CODE_SZ,$<,xen_hello_world) +config.h: MINOR_VERSION_SZ=$(call CODE_SZ,$(BASEDIR)/xen-syms,xen_minor_version) +config.h: MINOR_VERSION_ADDR=$(call CODE_ADDR,$(BASEDIR)/xen-syms,xen_minor_version) config.h: xen_hello_world_func.o (set -e; \ echo "#define NEW_CODE_SZ $(NEW_CODE_SZ)"; \ + echo "#define MINOR_VERSION_SZ $(MINOR_VERSION_SZ)"; \ + echo "#define MINOR_VERSION_ADDR $(MINOR_VERSION_ADDR)"; \ echo "#define OLD_CODE_SZ $(OLD_CODE_SZ)") > $@ xen_hello_world.o: config.h @@ -91,5 +98,11 @@ xen_replace_world.o: config.h $(LIVEPATCH_REPLACE): xen_replace_world_func.o xen_replace_world.o note.o $(LD) $(LDFLAGS) $(build_id_linker) -r -o $(LIVEPATCH_REPLACE) $^ +xen_nop.o: config.h + +.PHONY: $(LIVEPATCH_NOP) +$(LIVEPATCH_NOP): xen_nop.o note.o + $(LD) $(LDFLAGS) $(build_id_linker) -r -o $(LIVEPATCH_NOP) $^ + .PHONY: livepatch -livepatch: $(LIVEPATCH) $(LIVEPATCH_BYE) $(LIVEPATCH_REPLACE) +livepatch: $(LIVEPATCH) $(LIVEPATCH_BYE) $(LIVEPATCH_REPLACE) $(LIVEPATCH_NOP) diff --git a/xen/test/livepatch/xen_nop.c b/xen/test/livepatch/xen_nop.c new file mode 100644 index 0000000..69dcbca --- /dev/null +++ b/xen/test/livepatch/xen_nop.c @@ -0,0 +1,48 @@ +/* + * Copyright (c) 2016 Oracle and/or its affiliates. All rights reserved. + * + */ + +#include "config.h" +#include + +#include + +/* + * All of the .new_size and .old_addr are based on assumptions that the + * code for 'xen_minor_version' is compiled in specific way. Before + * running this test-case you MUST verify that the assumptions are + * correct (Hint: make debug and look in xen.s). + */ +struct livepatch_func __section(".livepatch.funcs") livepatch_nop = { + .version = LIVEPATCH_PAYLOAD_VERSION, + .old_size = MINOR_VERSION_SZ, + +#ifdef CONFIG_X86 + .old_addr = (void *)MINOR_VERSION_ADDR, + /* Everything but the last instruction: "req". */ + .new_size = MINOR_VERSION_SZ-1, +#endif + +#ifdef CONFIG_ARM_64 + .old_addr = (void *)MINOR_VERSION_ADDR, + /* Replace the first one: "mov w0, #0x8". */ + .new_size = 4, +#endif + +#ifdef CONFIG_ARM_32 + .old_addr = (void *)MINOR_VERSION_ADDR, + /* And replace all but the return instruction. */ + .new_size = MINOR_VERSION_SZ-4, +#endif +}; + +/* + * Local variables: + * mode: C + * c-file-style: "BSD" + * c-basic-offset: 4 + * tab-width: 4 + * indent-tabs-mode: nil + * End: + */