Re: drivers/firmware/efi/libstub/efi-stub-helper.c:599:2: warning: implicit declaration of function 'memcpy'

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 17 Sep 2015 23:02:14 +0300 Andrey Ryabinin <ryabinin.a.a@gmail.com> wrote:

> 2015-09-17 22:37 GMT+03:00 Andrew Morton <akpm@linux-foundation.org>:
> > On Thu, 17 Sep 2015 09:17:56 +0800 kbuild test robot <fengguang.wu@intel.com> wrote:
> >
> >> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> >> head:   72714841b705a5b9bccf37ee85a62352bee3a3ef
> >> commit: 393f203f5fd54421fddb1e2a263f64d3876eeadb x86_64: kasan: add interceptors for memset/memmove/memcpy functions
> >> date:   7 months ago
> >> config: i386-randconfig-i0-201537 (attached as .config)
> >> reproduce:
> >>   git checkout 393f203f5fd54421fddb1e2a263f64d3876eeadb
> >>   # save the attached .config to linux build tree
> >>   make ARCH=i386
> >>
> >> All warnings (new ones prefixed by >>):
> >>
> >>    drivers/firmware/efi/libstub/efi-stub-helper.c: In function 'efi_relocate_kernel':
> >> >> drivers/firmware/efi/libstub/efi-stub-helper.c:599:2: warning: implicit declaration of function 'memcpy' [-Wimplicit-function-declaration]
> >>      memcpy((void *)new_addr, (void *)cur_image_addr, image_size);
> >
> > I can't reproduce this.
> >
> > But whatever.  I'll do this:
> >
> > --- a/drivers/firmware/efi/libstub/efi-stub-helper.c~drivers-firmware-efi-libstub-efi-stub-helperc-needs-stringh
> > +++ a/drivers/firmware/efi/libstub/efi-stub-helper.c
> > @@ -11,6 +11,7 @@
> >   */
> >
> >  #include <linux/efi.h>
> > +#include <linux/string.h>
> 
> This won't help.
> arch/x86/include/asm/string_32.h has several variants of #define memcpy()
> But it doesn't have declaration of memcpy function like:
>             void memcpy(const void *to, const void *from, size_t len);
> Thus '#undef memcpy' causes this warning, and including
> <linux/string.h> won't help (It probably already included)

Well, I can't tell either way because that warning doesn't come out for
me with the provided config.

> Patch from KASAN for arm64 series:
> http://marc.info/?l=linux-mm&m=144248270719929&w=2 ([PATCH v6 3/6]
> x86, efi, kasan: #undef memset/memcpy/memmove per arch.)
> should fix this warning, as it moves '#undef memcpy' under #ifdef
> X86_64 in arch/x86/include/asm/efi.h

hm, that patch was misfiled.  We want this for for 4.3-rc.  I'll queue
it up.  I hope it's independent of the rest of that patch series?


From: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Subject: x86, efi, kasan: #undef memset/memcpy/memmove per arch

In not-instrumented code KASAN replaces instrumented memset/memcpy/memmove
with not-instrumented analogues __memset/__memcpy/__memove.

However, on x86 the EFI stub is not linked with the kernel.  It uses
not-instrumented mem*() functions from arch/x86/boot/compressed/string.c

So we don't replace them with __mem*() variants in EFI stub.

On ARM64 the EFI stub is linked with the kernel, so we should replace
mem*() functions with __mem*(), because the EFI stub runs before KASAN
sets up early shadow.

So let's move these #undef mem* into arch's asm/efi.h which is also
included by the EFI stub.

Also, this will fix the warning in 32-bit build reported by kbuild test
robot:

	efi-stub-helper.c:599:2: warning: implicit declaration of function 'memcpy'

Signed-off-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Reported-by: Fengguang Wu <fengguang.wu@gmail.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Matt Fleming <matt.fleming@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/x86/include/asm/efi.h             |   12 ++++++++++++
 drivers/firmware/efi/libstub/efistub.h |    4 ----
 2 files changed, 12 insertions(+), 4 deletions(-)

diff -puN arch/x86/include/asm/efi.h~x86-efi-kasan-undef-memset-memcpy-memmove-per-arch arch/x86/include/asm/efi.h
--- a/arch/x86/include/asm/efi.h~x86-efi-kasan-undef-memset-memcpy-memmove-per-arch
+++ a/arch/x86/include/asm/efi.h
@@ -86,6 +86,18 @@ extern u64 asmlinkage efi_call(void *fp,
 extern void __iomem *__init efi_ioremap(unsigned long addr, unsigned long size,
 					u32 type, u64 attribute);
 
+/*
+ * CONFIG_KASAN may redefine memset to __memset.
+ * __memset function is present only in kernel binary.
+ * Since the EFI stub linked into a separate binary it
+ * doesn't have __memset(). So we should use standard
+ * memset from arch/x86/boot/compressed/string.c
+ * The same applies to memcpy and memmove.
+ */
+#undef memcpy
+#undef memset
+#undef memmove
+
 #endif /* CONFIG_X86_32 */
 
 extern struct efi_scratch efi_scratch;
diff -puN drivers/firmware/efi/libstub/efistub.h~x86-efi-kasan-undef-memset-memcpy-memmove-per-arch drivers/firmware/efi/libstub/efistub.h
--- a/drivers/firmware/efi/libstub/efistub.h~x86-efi-kasan-undef-memset-memcpy-memmove-per-arch
+++ a/drivers/firmware/efi/libstub/efistub.h
@@ -5,10 +5,6 @@
 /* error code which can't be mistaken for valid address */
 #define EFI_ERROR	(~0UL)
 
-#undef memcpy
-#undef memset
-#undef memmove
-
 void efi_char16_printk(efi_system_table_t *, efi_char16_t *);
 
 efi_status_t efi_open_volume(efi_system_table_t *sys_table_arg, void *__image,
_

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