[PATCH v3 1/1] ARM: signal: sigreturn_codes should be endian neutral to work in BE8

[Dave Martin]

On Tue, Aug 27, 2013 at 10:41:57PM -0700, Victor Kamensky wrote:
> In case of BE8 kernel data is in BE order whereas code stays in LE
> order. Move sigreturn_codes to separate .S file and use proper
> assembler mnemonics for these code snippets. In this case compiler
> will take care of proper instructions byteswaps for BE8 case.
> Change assumes that sufficiently Thumb-capable tools are used to
> build kernel.
> 
> Problem was discovered during ltp testing of BE system: all rt_sig*
> tests failed. Tested against the same tests in both BE and LE modes.

This looks OK to me.

Reviewed-by: Dave Martin <Dave.Martin at arm.com>

> 
> Signed-off-by: Victor Kamensky <victor.kamensky at linaro.org>
> ---
>  arch/arm/kernel/Makefile          |  3 +-
>  arch/arm/kernel/signal.c          | 24 +-------------
>  arch/arm/kernel/sigreturn_codes.S | 69 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 72 insertions(+), 24 deletions(-)
>  create mode 100644 arch/arm/kernel/sigreturn_codes.S
> 
> diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
> index 86d10dd..0722155 100644
> --- a/arch/arm/kernel/Makefile
> +++ b/arch/arm/kernel/Makefile
> @@ -17,7 +17,8 @@ CFLAGS_REMOVE_return_address.o = -pg
>  
>  obj-y		:= elf.o entry-common.o irq.o opcodes.o \
>  		   process.o ptrace.o return_address.o \
> -		   setup.o signal.o stacktrace.o sys_arm.o time.o traps.o
> +		   setup.o signal.o sigreturn_codes.o \
> +		   stacktrace.o sys_arm.o time.o traps.o
>  
>  obj-$(CONFIG_ATAGS)		+= atags_parse.o
>  obj-$(CONFIG_ATAGS_PROC)	+= atags_proc.o
> diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
> index ab33042..64845fc 100644
> --- a/arch/arm/kernel/signal.c
> +++ b/arch/arm/kernel/signal.c
> @@ -21,29 +21,7 @@
>  #include <asm/unistd.h>
>  #include <asm/vfp.h>
>  
> -/*
> - * For ARM syscalls, we encode the syscall number into the instruction.
> - */
> -#define SWI_SYS_SIGRETURN	(0xef000000|(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE))
> -#define SWI_SYS_RT_SIGRETURN	(0xef000000|(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE))
> -
> -/*
> - * With EABI, the syscall number has to be loaded into r7.
> - */
> -#define MOV_R7_NR_SIGRETURN	(0xe3a07000 | (__NR_sigreturn - __NR_SYSCALL_BASE))
> -#define MOV_R7_NR_RT_SIGRETURN	(0xe3a07000 | (__NR_rt_sigreturn - __NR_SYSCALL_BASE))
> -
> -/*
> - * For Thumb syscalls, we pass the syscall number via r7.  We therefore
> - * need two 16-bit instructions.
> - */
> -#define SWI_THUMB_SIGRETURN	(0xdf00 << 16 | 0x2700 | (__NR_sigreturn - __NR_SYSCALL_BASE))
> -#define SWI_THUMB_RT_SIGRETURN	(0xdf00 << 16 | 0x2700 | (__NR_rt_sigreturn - __NR_SYSCALL_BASE))
> -
> -static const unsigned long sigreturn_codes[7] = {
> -	MOV_R7_NR_SIGRETURN,    SWI_SYS_SIGRETURN,    SWI_THUMB_SIGRETURN,
> -	MOV_R7_NR_RT_SIGRETURN, SWI_SYS_RT_SIGRETURN, SWI_THUMB_RT_SIGRETURN,
> -};
> +extern const unsigned long sigreturn_codes[7];
>  
>  static unsigned long signal_return_offset;
>  
> diff --git a/arch/arm/kernel/sigreturn_codes.S b/arch/arm/kernel/sigreturn_codes.S
> new file mode 100644
> index 0000000..c888c43
> --- /dev/null
> +++ b/arch/arm/kernel/sigreturn_codes.S
> @@ -0,0 +1,69 @@
> +/*
> + * sigreturn_codes.S - code sinpets for sigreturn syscalls
> + *
> + * Created by:	Victor Kamensky, 2013-08-13
> + * Copyright:	(C) 2013  Linaro Limited
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <asm/unistd.h>
> +
> +/*
> + * For ARM syscalls, we encode the syscall number into the instruction.
> + * With EABI, the syscall number has to be loaded into r7. As result
> + * ARM syscall sequence snippet will have move and svc in .arm encoding
> + *
> + * For Thumb syscalls, we pass the syscall number via r7.  We therefore
> + * need two 16-bit instructions in .thumb encoding
> + *
> + * Please note sigreturn_codes code are not executed in place. Instead
> + * they just copied by kernel into appropriate places. Code inside of
> + * arch/arm/kernel/signal.c is very sensitive to layout of these code
> + * snippets.
> + */
> +
> +	.section .rodata
> +	.global sigreturn_codes
> +	.type	sigreturn_codes, #object
> +
> +	.arm
> +
> +sigreturn_codes:
> +
> +	/* ARM sigreturn syscall code snippet */
> +	mov	r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)
> +	swi	#(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE)
> +
> +	/* Thumb sigreturn syscall code snippet */
> +	.thumb
> +	movs	r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)
> +	swi	#0
> +
> +	/* ARM sigreturn_rt syscall code snippet */
> +	.arm
> +	mov	r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)
> +	swi	#(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE)
> +
> +	/* Thumb sigreturn_rt syscall code snippet */
> +	.thumb
> +	movs	r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)
> +	swi	#0
> +
> +	/*
> +	 * Note on addtional space: setup_return in signal.c
> +	 * algorithm uses two words copy regardless whether
> +	 * it is thumb case or not, so we need additional
> +	 * word after real last entry.
> +	 */
> +	.arm
> +	.space	4
> +
> +	.size	sigreturn_codes, . - sigreturn_codes
> -- 
> 1.8.1.4
> 
> 
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