Cc: Will Newton <will.newton@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The current packed struct implementation of unaligned access adds the
packed attribute only to the field within the unaligned struct rather than
to the struct as a whole. This is not sufficient to enforce proper
behaviour on architectures with a default struct alignment of more than
one byte.
For example, the current implementation of __get_unaligned_cpu16 when
compiled for arm with gcc -O1 -mstructure-size-boundary=32 assumes the
struct is on a 4 byte boundary so performs the load of the 16bit packed
field as if it were on a 4 byte boundary:
__get_unaligned_cpu16:
ldrh r0, [r0, #0]
bx lr
Moving the packed attribute to the struct rather than the field causes the
proper unaligned access code to be generated:
__get_unaligned_cpu16:
ldrb r3, [r0, #0] @ zero_extendqisi2
ldrb r0, [r0, #1] @ zero_extendqisi2
orr r0, r3, r0, asl #8
bx lr
Signed-off-by: Will Newton <will.newton@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When unaligned accesses are required for uncompressing a kernel (such as
for LZO decompression on ARM in a patch that follows), including
<linux/kernel.h> causes issues as it brings in a lot of things that are
not available in the decompression environment.
linux/kernel.h brings at least:
extern int console_printk[];
extern const char hex_asc[];
which causes errors at link-time as they are not available when
compiling the pre-boot environement. There are also a few others:
arch/arm/boot/compressed/misc.o: In function `valid_user_regs':
arch/arm/include/asm/ptrace.h:158: undefined reference to `elf_hwcap'
arch/arm/boot/compressed/misc.o: In function `console_silent':
include/linux/kernel.h:292: undefined reference to `console_printk'
arch/arm/boot/compressed/misc.o: In function `console_verbose':
include/linux/kernel.h:297: undefined reference to `console_printk'
arch/arm/boot/compressed/misc.o: In function `pack_hex_byte':
include/linux/kernel.h:360: undefined reference to `hex_asc'
arch/arm/boot/compressed/misc.o: In function `hweight_long':
include/linux/bitops.h:45: undefined reference to `hweight32'
arch/arm/boot/compressed/misc.o: In function `__cmpxchg_local_generic':
include/asm-generic/cmpxchg-local.h:21: undefined reference to `wrong_size_cmpxchg'
include/asm-generic/cmpxchg-local.h:42: undefined reference to `wrong_size_cmpxchg'
arch/arm/boot/compressed/misc.o: In function `__xchg':
arch/arm/include/asm/system.h:309: undefined reference to `__bad_xchg'
However, those files apparently use nothing from <linux/kernel.h>, all
they need is the declaration of types such as u32 or u64, so
<linux/types.h> should be enough
Signed-off-by: Albin Tonnerre <albin.tonnerre@free-electrons.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Phillip Lougher <phillip@lougher.demon.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Create a linux/unaligned directory similar in spirit to the linux/byteorder
folder to hold generic implementations collected from various arches.
Currently there are five implementations:
1) packed_struct.h: C-struct based, from asm-generic/unaligned.h
2) le_byteshift.h: Open coded byte-swapping, heavily based on asm-arm
3) be_byteshift.h: Open coded byte-swapping, heavily based on asm-arm
4) memmove.h: taken from multiple implementations in tree
5) access_ok.h: taken from x86 and others, unaligned access is ok.
All of the new implementations checks for sizes not equal to 1,2,4,8
and will fail to link.
API additions:
get_unaligned_{le16|le32|le64|be16|be32|be64}(p) which is meant to replace
code of the form:
le16_to_cpu(get_unaligned((__le16 *)p));
put_unaligned_{le16|le32|le64|be16|be32|be64}(val, pointer) which is meant to
replace code of the form:
put_unaligned(cpu_to_le16(val), (__le16 *)p);
The headers that arches should include from their asm/unaligned.h:
access_ok.h : Wrappers of the byteswapping functions in asm/byteorder
Choose a particular implementation for little-endian access:
le_byteshift.h
le_memmove.h (arch must be LE)
le_struct.h (arch must be LE)
Choose a particular implementation for big-endian access:
be_byteshift.h
be_memmove.h (arch must be BE)
be_struct.h (arch must be BE)
After including as needed from the above, include unaligned/generic.h and
define your arch's get/put_unaligned as (for LE):
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andrew Morton
Will Newton
Albin Tonnerre
Harvey Harrison