arm64: compat: map SPSR_ELx<->PSR for signals

The SPSR_ELx format for exceptions taken from AArch32 differs from the
AArch32 PSR format. Thus, we must translate between the two when setting
up a compat sigframe, or restoring context from a compat sigframe.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Fixes: 7206dc9 ("arm64: Expose Arm v8.4 features")
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Suzuki Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/kernel/signal32.c

@@ -243,6 +243,7 @@ static int compat_restore_sigframe(struct pt_regs *regs,
 	int err;
 	sigset_t set;
 	struct compat_aux_sigframe __user *aux;
+	unsigned long psr;
 
 	err = get_sigset_t(&set, &sf->uc.uc_sigmask);
 	if (err == 0) {
@@ -266,7 +267,9 @@ static int compat_restore_sigframe(struct pt_regs *regs,
 	__get_user_error(regs->compat_sp, &sf->uc.uc_mcontext.arm_sp, err);
 	__get_user_error(regs->compat_lr, &sf->uc.uc_mcontext.arm_lr, err);
 	__get_user_error(regs->pc, &sf->uc.uc_mcontext.arm_pc, err);
-	__get_user_error(regs->pstate, &sf->uc.uc_mcontext.arm_cpsr, err);
+	__get_user_error(psr, &sf->uc.uc_mcontext.arm_cpsr, err);
+
+	regs->pstate = compat_psr_to_pstate(psr);
 
 	/*
 	 * Avoid compat_sys_sigreturn() restarting.
@@ -414,6 +417,7 @@ static int compat_setup_sigframe(struct compat_sigframe __user *sf,
 				 struct pt_regs *regs, sigset_t *set)
 {
 	struct compat_aux_sigframe __user *aux;
+	unsigned long psr = pstate_to_compat_psr(regs->pstate);
 	int err = 0;
 
 	__put_user_error(regs->regs[0], &sf->uc.uc_mcontext.arm_r0, err);
@@ -432,7 +436,7 @@ static int compat_setup_sigframe(struct compat_sigframe __user *sf,
 	__put_user_error(regs->compat_sp, &sf->uc.uc_mcontext.arm_sp, err);
 	__put_user_error(regs->compat_lr, &sf->uc.uc_mcontext.arm_lr, err);
 	__put_user_error(regs->pc, &sf->uc.uc_mcontext.arm_pc, err);
-	__put_user_error(regs->pstate, &sf->uc.uc_mcontext.arm_cpsr, err);
+	__put_user_error(psr, &sf->uc.uc_mcontext.arm_cpsr, err);
 
 	__put_user_error((compat_ulong_t)0, &sf->uc.uc_mcontext.trap_no, err);
 	/* set the compat FSR WnR */