Jan Kiszka <jan.kis...@siemens.com> writes:
> From: Jan Kiszka <jan.kis...@siemens.com>
>
> Modern gcc can claim r7 for own purposes, denying the syscall code to
> assign it directly. Work around this by saving/restoring it around the
> syscall.
>
> Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
> ---
> lib/cobalt/arch/arm/include/asm/xenomai/syscall.h | 13 ++++---------
> 1 file changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/lib/cobalt/arch/arm/include/asm/xenomai/syscall.h
> b/lib/cobalt/arch/arm/include/asm/xenomai/syscall.h
> index 8f48eb16f2..0941e6c845 100644
> --- a/lib/cobalt/arch/arm/include/asm/xenomai/syscall.h
> +++ b/lib/cobalt/arch/arm/include/asm/xenomai/syscall.h
> @@ -89,15 +89,11 @@
> #define __sys1(x) __sys2(x)
>
> #ifdef __ARM_EABI__
> -#define __SYS_REG , "r7"
> -#define __SYS_REG_DECL register unsigned long __r7 __asm__ ("r7")
> -#define __SYS_REG_SET __r7 = XENO_ARM_SYSCALL
> -#define __SYS_REG_INPUT ,"r" (__r7)
> -#define __SYS_CALLOP "swi\t0"
> +#define __SYS_REG_DECL unsigned long __r7 = XENO_ARM_SYSCALL
> +#define __SYS_REG_INPUT , [__r7] "r" (__r7)
> +#define __SYS_CALLOP "push {r7}; mov %%r7,%[__r7]; swi\t0; pop {r7}"
> #else
> -#define __SYS_REG
> #define __SYS_REG_DECL
> -#define __SYS_REG_SET
> #define __SYS_REG_INPUT
> #define __NR_OABI_SYSCALL_BASE 0x900000
> #define __SYS_CALLOP "swi\t" __sys1(__NR_OABI_SYSCALL_BASE +
> XENO_ARM_SYSCALL) ""
> @@ -109,9 +105,8 @@
> __SYS_REG_DECL; \
> LOADARGS_##nr(__xn_syscode(op), args); \
> __asm__ __volatile__ ("" : /* */ : /* */ : \
> - CLOBBER_REGS_##nr __SYS_REG); \
> + CLOBBER_REGS_##nr); \
> LOADREGS_##nr; \
> - __SYS_REG_SET; \
> __asm__ __volatile__ ( \
> __SYS_CALLOP \
> : "=r" (__r0) \
Mm, this does indeed look like a workaround more than a fix. Eventually,
we may be better off providing out-of-line syscall wrappers directly
written in asm, or as naked C routines with bells and suspenders
(no_instrument and the like) including the code produced by the
XENOMAI_SYSCALL macro exclusively.
--
Philippe.
