Hi all,
My x86_64 allmodconfig build fail like this:
OBJCOPY arch/x86/boot/vmlinux.bin
AS arch/x86/boot/header.o
LD arch/x86/boot/setup.elf
OBJCOPY arch/x86/boot/setup.bin
BUILD arch/x86/boot/bzImage
Setup is 14768 bytes (padded to 14848 bytes).
System is 4766 kB
/bin/sh: line 1: 20126 Segmentation fault arch/x86/boot/tools/build arch/x86/boot/setup.bin arch/x86/boot/vmlinux.bin > arch/x86/boot/bzImage
I have bisected it down to commit
291f36325f9f252bd76ef5f603995f37e453fc60 ("x86, efi: EFI boot stub
support"). This may well be a compiler bug that this commit just happens
to poke.
The toolchain is PowerPC hosted cross tools:
x86_64-linux-gcc (GCC) 4.4.3
GNU ld (GNU Binutils) 2.20
I tried an allmodconfig build with my native compiler (gcc (Debian
4.6.2-14) 4.6.2, GNU gold (GNU Binutils for Debian 2.22) 1.11) and it
worked fine.
That is a large commit, so I am not sure where to go from here.
--
Cheers,
Stephen Rothwell [email protected]
Hi all,
On Mon, 20 Feb 2012 13:39:36 +1100 Stephen Rothwell <[email protected]> wrote:
>
> Hi all,
>
> My x86_64 allmodconfig build fail like this:
>
> OBJCOPY arch/x86/boot/vmlinux.bin
> AS arch/x86/boot/header.o
> LD arch/x86/boot/setup.elf
> OBJCOPY arch/x86/boot/setup.bin
> BUILD arch/x86/boot/bzImage
> Setup is 14768 bytes (padded to 14848 bytes).
> System is 4766 kB
> /bin/sh: line 1: 20126 Segmentation fault arch/x86/boot/tools/build arch/x86/boot/setup.bin arch/x86/boot/vmlinux.bin > arch/x86/boot/bzImage
>
> I have bisected it down to commit
> 291f36325f9f252bd76ef5f603995f37e453fc60 ("x86, efi: EFI boot stub
> support"). This may well be a compiler bug that this commit just happens
> to poke.
>
> The toolchain is PowerPC hosted cross tools:
> x86_64-linux-gcc (GCC) 4.4.3
> GNU ld (GNU Binutils) 2.20
>
> I tried an allmodconfig build with my native compiler (gcc (Debian
> 4.6.2-14) 4.6.2, GNU gold (GNU Binutils for Debian 2.22) 1.11) and it
> worked fine.
>
> That is a large commit, so I am not sure where to go from here.
Actually, that commit does the following:
diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c
index fdc60a0..4e9bd6b 100644
--- a/arch/x86/boot/tools/build.c
+++ b/arch/x86/boot/tools/build.c
@@ -135,6 +135,9 @@ static void usage(void)
int main(int argc, char ** argv)
{
+#ifdef CONFIG_EFI_STUB
+ unsigned int file_sz, pe_header;
+#endif
unsigned int i, sz, setup_sectors;
int c;
u32 sys_size;
@@ -194,6 +197,42 @@ int main(int argc, char ** argv)
buf[0x1f6] = sys_size >> 16;
buf[0x1f7] = sys_size >> 24;
+#ifdef CONFIG_EFI_STUB
+ file_sz = sz + i + ((sys_size * 16) - sz);
+
+ pe_header = *(unsigned int *)&buf[0x3c];
+
+ /* Size of code */
+ *(unsigned int *)&buf[pe_header + 0x1c] = file_sz;
+
+ /* Size of image */
+ *(unsigned int *)&buf[pe_header + 0x50] = file_sz;
+
+#ifdef CONFIG_X86_32
+ /* Address of entry point */
+ *(unsigned int *)&buf[pe_header + 0x28] = i;
+
+ /* .text size */
+ *(unsigned int *)&buf[pe_header + 0xb0] = file_sz;
+
+ /* .text size of initialised data */
+ *(unsigned int *)&buf[pe_header + 0xb8] = file_sz;
+#else
+ /*
+ * Address of entry point. startup_32 is at the beginning and
+ * the 64-bit entry point (startup_64) is always 512 bytes
+ * after.
+ */
+ *(unsigned int *)&buf[pe_header + 0x28] = i + 512;
+
+ /* .text size */
+ *(unsigned int *)&buf[pe_header + 0xc0] = file_sz;
+
+ /* .text size of initialised data */
+ *(unsigned int *)&buf[pe_header + 0xc8] = file_sz;
+#endif /* CONFIG_X86_32 */
+#endif /* CONFIG_EFI_STUB */
+
crc = partial_crc32(buf, i, crc);
if (fwrite(buf, 1, i, stdout) != i)
die("Writing setup failed");
Which is all endian specific code that will run on the host when building
the kernel ...
--
Cheers,
Stephen Rothwell [email protected]
http://www.canb.auug.org.au/~sfr/
On Mon, 2012-02-20 at 14:22 +1100, Stephen Rothwell wrote:
> Which is all endian specific code that will run on the host when building
> the kernel ...
Gah, right. I didn't think about cross-building this code.
Thanks Stephen, I'll fix this up.
On Mon, 2012-02-20 at 09:43 +0000, Matt Fleming wrote:
> On Mon, 2012-02-20 at 14:22 +1100, Stephen Rothwell wrote:
> > Which is all endian specific code that will run on the host when building
> > the kernel ...
>
> Gah, right. I didn't think about cross-building this code.
>
> Thanks Stephen, I'll fix this up.
Looks like the segfault is caused by an unaligned access? How does this
patch look?
>From 54b2707a6a911330d8db2f4ec2fb1baa5e38acf9 Mon Sep 17 00:00:00 2001
From: Matt Fleming <[email protected]>
Date: Mon, 20 Feb 2012 17:32:42 +0000
Subject: [PATCH] x86, efi: Fix segfault caused by unaligned access
We need to use memcpy() instead of directly dereferencing a pointer
because memcpy() correctly handles the case where the
source/destination are unaligned, which can lead to a segfault when
cross-building an x86 kernel on risc architectures.
Stephen Rothwell noticed this bug when he hit a segfault while
cross-building an x86_64 allmodconfig kernel on PowerPC.
Cc: H. Peter Anvin <[email protected]>
Reported-by: Stephen Rothwell <[email protected]>
Signed-off-by: Matt Fleming <[email protected]>
---
arch/x86/boot/tools/build.c | 26 ++++++++++++++------------
1 files changed, 14 insertions(+), 12 deletions(-)
diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c
index 4e9bd6b..b4d85b5 100644
--- a/arch/x86/boot/tools/build.c
+++ b/arch/x86/boot/tools/build.c
@@ -200,36 +200,38 @@ int main(int argc, char ** argv)
#ifdef CONFIG_EFI_STUB
file_sz = sz + i + ((sys_size * 16) - sz);
- pe_header = *(unsigned int *)&buf[0x3c];
+ memcpy(&pe_header, &buf[0x3c], sizeof(pe_header));
/* Size of code */
- *(unsigned int *)&buf[pe_header + 0x1c] = file_sz;
+ memcpy(&buf[pe_header + 0x1c], &file_sz, sizeof(file_sz));
/* Size of image */
- *(unsigned int *)&buf[pe_header + 0x50] = file_sz;
+ memcpy(&buf[pe_header + 0x50], &file_sz, sizeof(file_sz));
#ifdef CONFIG_X86_32
/* Address of entry point */
- *(unsigned int *)&buf[pe_header + 0x28] = i;
+ memcpy(&buf[pe_header + 0x28], &i, sizeof(i));
/* .text size */
- *(unsigned int *)&buf[pe_header + 0xb0] = file_sz;
+ memcpy(&buf[pe_header + 0xb0], &file_sz, sizeof(file_sz));
/* .text size of initialised data */
- *(unsigned int *)&buf[pe_header + 0xb8] = file_sz;
+ memcpy(&buf[pe_header + 0xb8], &file_sz, sizeof(file_sz));
#else
+ /* .text size */
+ memcpy(&buf[pe_header + 0xc0], &file_sz, sizeof(file_sz));
+
+ /* .text size of initialised data */
+ memcpy(&buf[pe_header + 0xc8], &file_sz, sizeof(file_sz));
+
/*
* Address of entry point. startup_32 is at the beginning and
* the 64-bit entry point (startup_64) is always 512 bytes
* after.
*/
- *(unsigned int *)&buf[pe_header + 0x28] = i + 512;
+ file_sz = i + 512;
+ memcpy(&buf[pe_header + 0x28], &file_sz, sizeof(file_sz));
- /* .text size */
- *(unsigned int *)&buf[pe_header + 0xc0] = file_sz;
-
- /* .text size of initialised data */
- *(unsigned int *)&buf[pe_header + 0xc8] = file_sz;
#endif /* CONFIG_X86_32 */
#endif /* CONFIG_EFI_STUB */
--
1.7.4.4
Hi Matt,
On Tue, 21 Feb 2012 10:01:57 +0000 Matt Fleming <[email protected]> wrote:
>
> Looks like the segfault is caused by an unaligned access? How does this
> patch look?
I didn't try it, but it won't work. PowerPC is big endian, the data you
are copying is little endian ....
--
Cheers,
Stephen Rothwell [email protected]
http://www.canb.auug.org.au/~sfr/
On Tue, 2012-02-21 at 21:38 +1100, Stephen Rothwell wrote:
> Hi Matt,
>
> On Tue, 21 Feb 2012 10:01:57 +0000 Matt Fleming <[email protected]> wrote:
> >
> > Looks like the segfault is caused by an unaligned access? How does this
> > patch look?
>
> I didn't try it, but it won't work. PowerPC is big endian, the data you
> are copying is little endian ....
Urgh, you must feel like you're talking to a brick wall. I forgot you
mentioned the endian issue in your original post, sorry. Let's try this
one more time...
>From b3885c72be4cb06b2647a5067432da6017ea7902 Mon Sep 17 00:00:00 2001
From: Matt Fleming <[email protected]>
Date: Mon, 20 Feb 2012 17:32:42 +0000
Subject: [PATCH] x86, efi: Fix unaligned access and endian issues
We need to read from and write to 'buf' a byte at a time otherwise
it's possible we'll perform an unaligned access, which can lead to a
segfault when cross-building an x86 kernel on risc architectures.
Also, we may need to convert the endianness of the data we read
from/write to buf, so let's add some helper functions to do that.
Stephen Rothwell noticed this bug when he hit a segfault while
cross-building an x86_64 allmodconfig kernel on PowerPC.
Cc: H. Peter Anvin <[email protected]>
Reported-by: Stephen Rothwell <[email protected]>
Signed-off-by: Matt Fleming <[email protected]>
---
arch/x86/boot/tools/build.c | 44 ++++++++++++++++++++++++++++++------------
1 files changed, 31 insertions(+), 13 deletions(-)
diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c
index 4e9bd6b..56efa6f 100644
--- a/arch/x86/boot/tools/build.c
+++ b/arch/x86/boot/tools/build.c
@@ -133,6 +133,26 @@ static void usage(void)
die("Usage: build setup system [> image]");
}
+static inline u32 read32_le(u8 *src)
+{
+ u32 data;
+
+ data = *src++;
+ data |= *src++ >> 8;
+ data |= *src++ >> 16;
+ data |= *src++ >> 24;
+
+ return data;
+}
+
+static inline void write32_le(u8 *dst, u32 data)
+{
+ *dst++ = data;
+ *dst++ = data >> 8;
+ *dst++ = data >> 16;
+ *dst++ = data >> 24;
+}
+
int main(int argc, char ** argv)
{
#ifdef CONFIG_EFI_STUB
@@ -192,44 +212,42 @@ int main(int argc, char ** argv)
/* Patch the setup code with the appropriate size parameters */
buf[0x1f1] = setup_sectors-1;
- buf[0x1f4] = sys_size;
- buf[0x1f5] = sys_size >> 8;
- buf[0x1f6] = sys_size >> 16;
- buf[0x1f7] = sys_size >> 24;
+ write32_le(&buf[0x1f4], sys_size);
#ifdef CONFIG_EFI_STUB
file_sz = sz + i + ((sys_size * 16) - sz);
- pe_header = *(unsigned int *)&buf[0x3c];
+ pe_header = read32_le(&buf[0x3c]);
/* Size of code */
- *(unsigned int *)&buf[pe_header + 0x1c] = file_sz;
+ write32_le(&buf[pe_header + 0x1c], file_sz);
/* Size of image */
- *(unsigned int *)&buf[pe_header + 0x50] = file_sz;
+ write32_le(&buf[pe_header + 0x50], file_sz);
#ifdef CONFIG_X86_32
/* Address of entry point */
- *(unsigned int *)&buf[pe_header + 0x28] = i;
+ write32_le(&buf[pe_header + 0x28], i);
/* .text size */
- *(unsigned int *)&buf[pe_header + 0xb0] = file_sz;
+ write32_le(&buf[pe_header + 0xb0], file_sz);
/* .text size of initialised data */
- *(unsigned int *)&buf[pe_header + 0xb8] = file_sz;
+ write32_le(&buf[pe_header + 0xb8], file_sz);
#else
/*
* Address of entry point. startup_32 is at the beginning and
* the 64-bit entry point (startup_64) is always 512 bytes
* after.
*/
- *(unsigned int *)&buf[pe_header + 0x28] = i + 512;
+ write32_le(&buf[pe_header + 0x28], i + 512);
/* .text size */
- *(unsigned int *)&buf[pe_header + 0xc0] = file_sz;
+ write32_le(&buf[pe_header + 0xc0], file_sz);
/* .text size of initialised data */
- *(unsigned int *)&buf[pe_header + 0xc8] = file_sz;
+ write32_le(&buf[pe_header + 0xc8], file_sz);
+
#endif /* CONFIG_X86_32 */
#endif /* CONFIG_EFI_STUB */
--
1.7.4.4
Hi Matt,
On Tue, 21 Feb 2012 11:32:13 +0000 Matt Fleming <[email protected]> wrote:
>
> +static inline u32 read32_le(u8 *src)
> +{
> + u32 data;
> +
> + data = *src++;
> + data |= *src++ >> 8;
> + data |= *src++ >> 16;
> + data |= *src++ >> 24;
Shouldn't these be "<<" ?
--
Cheers,
Stephen Rothwell [email protected]
http://www.canb.auug.org.au/~sfr/
On Tue, 2012-02-21 at 22:51 +1100, Stephen Rothwell wrote:
> Hi Matt,
>
> On Tue, 21 Feb 2012 11:32:13 +0000 Matt Fleming <[email protected]> wrote:
> >
> > +static inline u32 read32_le(u8 *src)
> > +{
> > + u32 data;
> > +
> > + data = *src++;
> > + data |= *src++ >> 8;
> > + data |= *src++ >> 16;
> > + data |= *src++ >> 24;
>
> Shouldn't these be "<<" ?
Oops. Yes.