On 9 August 2018 at 05:21, Richard Henderson
<richard.hender...@linaro.org> wrote:
> Unlike aa32, endianness cannot be adjusted by userland in aa64.
>
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> ---
> target/arm/cpu.h | 27 +++++++++++++++++----------
> 1 file changed, 17 insertions(+), 10 deletions(-)
>
> diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> index 9526ed27cb..2d6d7d03aa 100644
> --- a/target/arm/cpu.h
> +++ b/target/arm/cpu.h
> @@ -2709,8 +2709,6 @@ static inline bool arm_sctlr_b(CPUARMState *env)
> /* Return true if the processor is in big-endian mode. */
> static inline bool arm_cpu_data_is_big_endian(CPUARMState *env)
> {
> - int cur_el;
> -
> /* In 32bit endianness is determined by looking at CPSR's E bit */
> if (!is_a64(env)) {
> return
> @@ -2729,15 +2727,24 @@ static inline bool
> arm_cpu_data_is_big_endian(CPUARMState *env)
> arm_sctlr_b(env) ||
> #endif
> ((env->uncached_cpsr & CPSR_E) ? 1 : 0);
> + } else {
> +#ifdef CONFIG_USER_ONLY
> + /* AArch64 does not have a SETEND instruction; endianness
> + * for usermode is fixed at compile-time.
> + */
> +# ifdef TARGET_WORDS_BIGENDIAN
> + return true;
> +# else
> + return false;
> +# endif
> +#else
> + int cur_el = arm_current_el(env);
> + if (cur_el == 0) {
> + return (env->cp15.sctlr_el[1] & SCTLR_E0E) != 0;
> + }
> + return (env->cp15.sctlr_el[cur_el] & SCTLR_EE) != 0;
> +#endif
> }
> -
> - cur_el = arm_current_el(env);
> -
> - if (cur_el == 0) {
> - return (env->cp15.sctlr_el[1] & SCTLR_E0E) != 0;
> - }
> -
> - return (env->cp15.sctlr_el[cur_el] & SCTLR_EE) != 0;
> }
>
When does this make a difference? For user-mode, we've already
dealt with the "aa32" case, so the code here is aa64-only.
In linux-user/aarch64/cpu_loop.c we set sctlr_el[1]'s E0E bit
if TARGET_WORDS_BIGENDIAN is defined, and cur_el is definitely
zero, so we should already be returning true from this function
if TARGET_WORDS_BIGENDIAN and false otherwise.
thanks
-- PMM
