From fab5db97e44f76461f76b24adfa8ccb14d4df498 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Wed, 7 Jun 2006 16:14:40 +1000 Subject: [PATCH] powerpc: Implement support for setting little-endian mode via prctl This adds the PowerPC part of the code to allow processes to change their endian mode via prctl. This also extends the alignment exception handler to be able to fix up alignment exceptions that occur in little-endian mode, both for "PowerPC" little-endian and true little-endian. We always enter signal handlers in big-endian mode -- the support for little-endian mode does not amount to the creation of a little-endian user/kernel ABI. If the signal handler returns, the endian mode is restored to what it was when the signal was delivered. We have two new kernel CPU feature bits, one for PPC little-endian and one for true little-endian. Most of the classic 32-bit processors support PPC little-endian, and this is reflected in the CPU feature table. There are two corresponding feature bits reported to userland in the AT_HWCAP aux vector entry. This is based on an earlier patch by Anton Blanchard. Signed-off-by: Paul Mackerras --- arch/powerpc/kernel/process.c | 44 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) (limited to 'arch/powerpc/kernel/process.c') diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 2dd47d2dd99..2d35d83961b 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -708,6 +708,50 @@ int get_fpexc_mode(struct task_struct *tsk, unsigned long adr) return put_user(val, (unsigned int __user *) adr); } +int set_endian(struct task_struct *tsk, unsigned int val) +{ + struct pt_regs *regs = tsk->thread.regs; + + if ((val == PR_ENDIAN_LITTLE && !cpu_has_feature(CPU_FTR_REAL_LE)) || + (val == PR_ENDIAN_PPC_LITTLE && !cpu_has_feature(CPU_FTR_PPC_LE))) + return -EINVAL; + + if (regs == NULL) + return -EINVAL; + + if (val == PR_ENDIAN_BIG) + regs->msr &= ~MSR_LE; + else if (val == PR_ENDIAN_LITTLE || val == PR_ENDIAN_PPC_LITTLE) + regs->msr |= MSR_LE; + else + return -EINVAL; + + return 0; +} + +int get_endian(struct task_struct *tsk, unsigned long adr) +{ + struct pt_regs *regs = tsk->thread.regs; + unsigned int val; + + if (!cpu_has_feature(CPU_FTR_PPC_LE) && + !cpu_has_feature(CPU_FTR_REAL_LE)) + return -EINVAL; + + if (regs == NULL) + return -EINVAL; + + if (regs->msr & MSR_LE) { + if (cpu_has_feature(CPU_FTR_REAL_LE)) + val = PR_ENDIAN_LITTLE; + else + val = PR_ENDIAN_PPC_LITTLE; + } else + val = PR_ENDIAN_BIG; + + return put_user(val, (unsigned int __user *)adr); +} + #define TRUNC_PTR(x) ((typeof(x))(((unsigned long)(x)) & 0xffffffff)) int sys_clone(unsigned long clone_flags, unsigned long usp, -- cgit v1.2.3-70-g09d2