[review] core: arm64: preserve PSTATE.PAN when making SPSR

Revert back to the old way of fabricating an SPSR, but preserve the PAN
bit in the saved SPSR.

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

core/arch/arm/include/kernel/thread_arch.h

@@ -394,8 +394,6 @@ static inline void thread_user_clear_vfp(struct user_mode_ctx *uctx __unused)
  * @returns stack pointer
  */
 vaddr_t thread_get_saved_thread_sp(void);
-
-uint64_t thread_get_spsr_from_pstate(void);
 #endif /*ARM64*/
 
 /*

core/arch/arm/kernel/abort.c

@@ -358,6 +358,8 @@ static void handle_user_mode_panic(struct abort_info *ai)
 static void handle_user_mode_panic(struct abort_info *ai)
 {
 	struct thread_ctx *tc __maybe_unused = NULL;
+	uint32_t daif = 0;
+	uint32_t pan_bit = 0;
 
 	/*
 	 * It was a user exception, stop user execution and return
@@ -368,7 +370,6 @@ static void handle_user_mode_panic(struct abort_info *ai)
 	ai->regs->x2 = 0xdeadbeef;
 	ai->regs->elr = (vaddr_t)thread_unwind_user_mode;
 	ai->regs->sp_el0 = thread_get_saved_thread_sp();
-	ai->regs->spsr = thread_get_spsr_from_pstate();
 
 #if defined(CFG_CORE_PAUTH)
 	/*
@@ -379,6 +380,13 @@ static void handle_user_mode_panic(struct abort_info *ai)
 	ai->regs->apiakey_hi = tc->keys.apia_hi;
 	ai->regs->apiakey_lo = tc->keys.apia_lo;
 #endif
+
+	/* Unless PAN is supported the PAN bit in SPSR is RES0 */
+	pan_bit = ai->regs->spsr & SPSR_64_PAN;
+	daif = (ai->regs->spsr >> SPSR_32_AIF_SHIFT) & SPSR_32_AIF_MASK;
+	/* XXX what about DAIF_D? */
+	ai->regs->spsr = SPSR_64(SPSR_64_MODE_EL1, SPSR_64_MODE_SP_EL0, daif) |
+			 pan_bit;
 }
 #endif /*ARM64*/
 

core/arch/arm/kernel/thread.c

@@ -412,7 +412,7 @@ void thread_resume_from_rpc(uint32_t thread_id, uint32_t a0, uint32_t a1,
 }
 
 #ifdef ARM64
-uint64_t thread_get_spsr_from_pstate(void)
+static uint64_t spsr_from_pstate(void)
 {
 	uint64_t spsr = SPSR_64(SPSR_64_MODE_EL1, SPSR_64_MODE_SP_EL0, 0);
 
@@ -426,7 +426,7 @@ uint64_t thread_get_spsr_from_pstate(void)
 
 void __thread_rpc(uint32_t rv[THREAD_RPC_NUM_ARGS])
 {
-	thread_rpc_spsr(rv, thread_get_spsr_from_pstate());
+	thread_rpc_spsr(rv, spsr_from_pstate());
 }
 
 vaddr_t thread_get_saved_thread_sp(void)
@@ -1089,7 +1089,7 @@ static void setup_unwind_user_mode(struct thread_scall_regs *regs)
 #endif
 #ifdef ARM64
 	regs->elr = (uintptr_t)thread_unwind_user_mode;
-	regs->spsr = thread_get_spsr_from_pstate();
+	regs->spsr = spsr_from_pstate();
 	/*
 	 * Regs is the value of stack pointer before calling the SVC
 	 * handler.  By the addition matches for the reserved space at the