powerpc/boot: add {get, put}_unaligned_be32 to xz_config.h [Linux 4.9.187]

This Linux kernel change "powerpc/boot: add {get, put}_unaligned_be32 to xz_config.h" is included in the Linux 4.9.187 release. This change is authored by Masahiro Yamada <yamada.masahiro [at] socionext.com> on Fri Jul 5 19:01:43 2019 +0900. The commit for this change in Linux stable tree is 34dd8fb (patch) which is from upstream commit 9e005b7. The same Linux upstream change may have been applied to various maintained Linux releases and you can find all Linux releases containing changes from upstream 9e005b7.

powerpc/boot: add {get, put}_unaligned_be32 to xz_config.h

[ Upstream commit 9e005b761e7ad153dcf40a6cba1d681fe0830ac6 ]

The next commit will make the way of passing CONFIG options more robust.
Unfortunately, it would uncover another hidden issue; without this
commit, skiroot_defconfig would be broken like this:

|   WRAP    arch/powerpc/boot/zImage.pseries
| arch/powerpc/boot/wrapper.a(decompress.o): In function `bcj_powerpc.isra.10':
| decompress.c:(.text+0x720): undefined reference to `get_unaligned_be32'
| decompress.c:(.text+0x7a8): undefined reference to `put_unaligned_be32'
| make[1]: *** [arch/powerpc/boot/Makefile;383: arch/powerpc/boot/zImage.pseries] Error 1
| make: *** [arch/powerpc/Makefile;295: zImage] Error 2

skiroot_defconfig is the only defconfig that enables CONFIG_KERNEL_XZ
for ppc, which has never been correctly built before.

I figured out the root cause in lib/decompress_unxz.c:

| #ifdef CONFIG_PPC
| #      define XZ_DEC_POWERPC
| #endif

CONFIG_PPC is undefined here in the ppc bootwrapper because autoconf.h
is not included except by arch/powerpc/boot/serial.c

XZ_DEC_POWERPC is not defined, therefore, bcj_powerpc() is not compiled
for the bootwrapper.

With the next commit passing CONFIG_PPC correctly, we would realize that
{get,put}_unaligned_be32 was missing.

Unlike the other decompressors, the ppc bootwrapper duplicates all the
necessary helpers in arch/powerpc/boot/.

The other architectures define __KERNEL__ and pull in helpers for
building the decompressors.

If ppc bootwrapper had defined __KERNEL__, lib/xz/xz_private.h would
have included <asm/unaligned.h>:

| #ifdef __KERNEL__
| #       include <linux/xz.h>
| #       include <linux/kernel.h>
| #       include <asm/unaligned.h>

However, doing so would cause tons of definition conflicts since the
bootwrapper has duplicated everything.

I just added copies of {get,put}_unaligned_be32, following the
bootwrapper coding convention.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190705100144.28785-1-yamada.masahiro@socionext.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

There are 20 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 arch/powerpc/boot/xz_config.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/powerpc/boot/xz_config.h b/arch/powerpc/boot/xz_config.h
index 5c6afdb..21b52c1 100644
--- a/arch/powerpc/boot/xz_config.h
+++ b/arch/powerpc/boot/xz_config.h
@@ -19,10 +19,30 @@ static inline uint32_t swab32p(void *p)

 #ifdef __LITTLE_ENDIAN__
 #define get_le32(p) (*((uint32_t *) (p)))
+#define cpu_to_be32(x) swab32(x)
+static inline u32 be32_to_cpup(const u32 *p)
+   return swab32p((u32 *)p);
 #define get_le32(p) swab32p(p)
+#define cpu_to_be32(x) (x)
+static inline u32 be32_to_cpup(const u32 *p)
+   return *p;

+static inline uint32_t get_unaligned_be32(const void *p)
+   return be32_to_cpup(p);
+static inline void put_unaligned_be32(u32 val, void *p)
+   *((u32 *)p) = cpu_to_be32(val);
 #define memeq(a, b, size) (memcmp(a, b, size) == 0)
 #define memzero(buf, size) memset(buf, 0, size)

Leave a Reply

Your email address will not be published. Required fields are marked *