| Message ID | 20190722213250.238685-1-ndesaulniers@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,1/2] x86/purgatory: do not use __builtin_memcpy and __builtin_memset | expand |
Joe,
Is it possible to have scripts/get_maintainer.pl always cc
linux-kernel@vger.kernel.org? I just sent out a series, and it seems
the cover letter didn't get sent to LKML. I usually use this shell
function to send patches:
```
function kpatch () {
patch=$1
shift
git send-email \
--cc-cmd="./scripts/get_maintainer.pl --norolestats $patch" \
$@ $patch
}
```
Invoked via:
```
$ mkdir purgatory
$ git format-patch HEAD~2 --cover-letter -o purgatory -v2
$ kpatch purgatory/v2-000* --cc peterz@infradead.org --cc
clang-built-linux@googlegroups.com
```
Maybe I should just add `--cc linux-kernel@vger.kernel.org` to my
shell function?
On Mon, Jul 22, 2019 at 2:33 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> 1. Reuse the implementation of memcpy and memset instead of relying on
> __builtin_memcpy and __builtin_memset as it causes infinite recursion
> in Clang (at any opt level) or GCC at -O2.
> 2. Don't reset KBUILD_CFLAGS, rather filter CONFIG_FUNCTION_TRACER flags
> via `CFLAGS_REMOVE_<file>.o = -pg`.
>
> The order of the patches are reversed; in case we ever need to bisect,
> the memcpy/memset infinite recursion would occur with just patch 2/2
> applied.
>
> V2 of: https://lkml.org/lkml/2019/7/17/755
>
> Nick Desaulniers (2):
> x86/purgatory: do not use __builtin_memcpy and __builtin_memset
> x86/purgatory: use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS
>
> arch/x86/purgatory/Makefile | 15 ++++++++++-----
> arch/x86/purgatory/purgatory.c | 6 ++++++
> arch/x86/purgatory/string.c | 23 -----------------------
> 3 files changed, 16 insertions(+), 28 deletions(-)
> delete mode 100644 arch/x86/purgatory/string.c
>
> --
> 2.22.0.657.g960e92d24f-goog
>
--
Thanks,
~Nick Desaulniers
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile index 3cf302b26332..91ef244026d2 100644 --- a/arch/x86/purgatory/Makefile +++ b/arch/x86/purgatory/Makefile @@ -6,6 +6,9 @@ purgatory-y := purgatory.o stack.o setup-x86_$(BITS).o sha256.o entry64.o string targets += $(purgatory-y) PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y)) +$(obj)/string.o: $(srctree)/arch/x86/boot/compressed/string.c FORCE + $(call if_changed_rule,cc_o_c) + $(obj)/sha256.o: $(srctree)/lib/sha256.c FORCE $(call if_changed_rule,cc_o_c) diff --git a/arch/x86/purgatory/purgatory.c b/arch/x86/purgatory/purgatory.c index 6d8d5a34c377..b607bda786f6 100644 --- a/arch/x86/purgatory/purgatory.c +++ b/arch/x86/purgatory/purgatory.c @@ -68,3 +68,9 @@ void purgatory(void) } copy_backup_region(); } + +/* + * Defined in order to reuse memcpy() and memset() from + * arch/x86/boot/compressed/string.c + */ +void warn(const char *msg) {} diff --git a/arch/x86/purgatory/string.c b/arch/x86/purgatory/string.c deleted file mode 100644 index 01ad43873ad9..000000000000 --- a/arch/x86/purgatory/string.c +++ /dev/null @@ -1,23 +0,0 @@ -// SPDX-License-Identifier: GPL-2.0-only -/* - * Simple string functions. - * - * Copyright (C) 2014 Red Hat Inc. - * - * Author: - * Vivek Goyal <vgoyal@redhat.com> - */ - -#include <linux/types.h> - -#include "../boot/string.c" - -void *memcpy(void *dst, const void *src, size_t len) -{ - return __builtin_memcpy(dst, src, len); -} - -void *memset(void *dst, int c, size_t len) -{ - return __builtin_memset(dst, c, len); -}
Implementing memcpy and memset in terms of __builtin_memcpy and __builtin_memset is problematic. GCC at -O2 will replace calls to the builtins with calls to memcpy and memset (but will generate an inline implementation at -Os). Clang will replace the builtins with these calls regardless of optimization level. $ llvm-objdump -dr arch/x86/purgatory/string.o | tail 0000000000000339 memcpy: 339: 48 b8 00 00 00 00 00 00 00 00 movabsq $0, %rax 000000000000033b: R_X86_64_64 memcpy 343: ff e0 jmpq *%rax 0000000000000345 memset: 345: 48 b8 00 00 00 00 00 00 00 00 movabsq $0, %rax 0000000000000347: R_X86_64_64 memset 34f: ff e0 Such code results in infinite recursion at runtime. This is observed when doing kexec. Instead, reuse an implementation from arch/x86/boot/compressed/string.c if we define warn as a symbol. Fixes: 8fc5b4d4121c ("purgatory: core purgatory functionality") Link: https://bugs.chromium.org/p/chromium/issues/detail?id=984056 Reported-by: Vaibhav Rustagi <vaibhavrustagi@google.com> Tested-by: Vaibhav Rustagi <vaibhavrustagi@google.com> Debugged-by: Vaibhav Rustagi <vaibhavrustagi@google.com> Debugged-by: Manoj Gupta <manojgupta@google.com> Suggested-by: Alistair Delva <adelva@google.com> Signed-off-by: Vaibhav Rustagi <vaibhavrustagi@google.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> --- Changes v1 -> v2: * Add Fixes tag. * Move this patch to first in the series. arch/x86/purgatory/Makefile | 3 +++ arch/x86/purgatory/purgatory.c | 6 ++++++ arch/x86/purgatory/string.c | 23 ----------------------- 3 files changed, 9 insertions(+), 23 deletions(-) delete mode 100644 arch/x86/purgatory/string.c -- 2.22.0.657.g960e92d24f-goog