On 19 January 2016 at 17:26, Peter Maydell <peter.mayd...@linaro.org> wrote: > On 18 January 2016 at 07:12, Peter Crosthwaite > <crosthwaitepe...@gmail.com> wrote: >> Don't set CPSR.E for BE32 linux-user mode. As linux-user mode models >> BE32, using normal BE (and system mode will not), a special case is >> needed for user-mode where if sctlr.b is set, the CPU identifies as BE. >> >> Signed-off-by: Peter Crosthwaite <crosthwaite.pe...@gmail.com> >> --- >> >> linux-user/main.c | 2 -- >> target-arm/cpu.h | 12 +++++++++++- >> 2 files changed, 11 insertions(+), 3 deletions(-) >> >> diff --git a/linux-user/main.c b/linux-user/main.c >> index d481458..60375fb 100644 >> --- a/linux-user/main.c >> +++ b/linux-user/main.c >> @@ -4496,8 +4496,6 @@ int main(int argc, char **argv, char **envp) >> env->uncached_cpsr |= CPSR_E; >> } else { >> env->cp15.sctlr_el[1] |= SCTLR_B; >> - /* We model BE32 as regular BE, so set CPSR_E */ >> - env->uncached_cpsr |= CPSR_E; > > ...this is undoing what we just did in the previous patch and > which I reviewed as being the wrong thing there... > >> } >> #endif >> } >> diff --git a/target-arm/cpu.h b/target-arm/cpu.h >> index 3edd56b..96b1e99 100644 >> --- a/target-arm/cpu.h >> +++ b/target-arm/cpu.h >> @@ -1812,7 +1812,17 @@ static bool arm_cpu_is_big_endian(CPUARMState *env) >> >> /* In 32bit endianness is determined by looking at CPSR's E bit */ >> if (!is_a64(env)) { >> - return (env->uncached_cpsr & CPSR_E) ? 1 : 0; >> + return >> +#ifdef CONFIG_USER_ONLY >> + /* In user mode, BE32 data accesses are just modelled as >> + * regular BE access. In system mode, BE32 is modelled as >> + * little endian, with the appropriate address translations on >> + * non-word accesses. So sctlr.b only affects overall >> + * endianness in user mode >> + */ >> + arm_sctlr_b(env) || >> +#endif >> + ((env->uncached_cpsr & CPSR_E) ? 1 : 0); >> } > > This doesn't seem quite right -- for system emulation we currently > pick MO_BE or MO_LE based on the TB flag which is set according > to (arm_cpu_is_big_endian(env). So if we ignore SCTLR.B in > system mode then we'll still try to do LE accesses.
Ah, no, looking at the next patch this is correct, it's just the comment is a touch confusing. I suggest /* In system mode, BE32 is modelled in line with the architecture * (as word-invariant big-endianness), where loads and stores are done * little endian but from addresses which are adjusted by XORing * with the appropriate constant. So the endianness to use for the * raw data access is not affected by SCTLR.B. * In user mode, however, we model BE32 as byte-invariant big-endianness * (because user-only code cannot tell the difference), and so we * need to use a data access endianness that depends on SCTLR.B. */ thanks -- PMM