arm64: simplify ptrauth initialization

Currently __cpu_setup conditionally initializes the address
authentication keys and enables them in SCTLR_EL1, doing so differently
for the primary CPU and secondary CPUs, and skipping this work for CPUs
returning from an idle state. For the latter case, cpu_do_resume
restores the keys and SCTLR_EL1 value after the MMU has been enabled.

This flow is rather difficult to follow, so instead let's move the
primary and secondary CPU initialization into their respective boot
paths. By following the example of cpu_do_resume and doing so once the
MMU is enabled, we can always initialize the keys from the values in
thread_struct, and avoid the machinery necessary to pass the keys in
secondary_data or open-coding initialization for the boot CPU.

This means we perform an additional RMW of SCTLR_EL1, but we already do
this in the cpu_do_resume path, and for other features in cpufeature.c,
so this isn't a major concern in a bringup path. Note that even while
the enable bits are clear, the key registers are accessible.

As this now renders the argument to __cpu_setup redundant, let's also
remove that entirely. Future extensions can follow a similar approach to
initialize values that differ for primary/secondary CPUs.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Reviewed-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200423101606.37601-3-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

4 files changed, 10 insertions, 14 deletions

diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 9981a0a5a87f..890ddd67b8bf 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -92,9 +92,6 @@ int main(void)
   BLANK();
   DEFINE(CPU_BOOT_STACK,	offsetof(struct secondary_data, stack));
   DEFINE(CPU_BOOT_TASK,		offsetof(struct secondary_data, task));
-#ifdef CONFIG_ARM64_PTR_AUTH
-  DEFINE(CPU_BOOT_PTRAUTH_KEY,	offsetof(struct secondary_data, ptrauth_key));
-#endif
   BLANK();
 #ifdef CONFIG_KVM_ARM_HOST
   DEFINE(VCPU_CONTEXT,		offsetof(struct kvm_vcpu, arch.ctxt));
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 57a91032b4c2..dc2b441d4ed8 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -13,6 +13,7 @@
 #include <linux/init.h>
 #include <linux/irqchip/arm-gic-v3.h>
 
+#include <asm/asm_pointer_auth.h>
 #include <asm/assembler.h>
 #include <asm/boot.h>
 #include <asm/ptrace.h>
@@ -118,7 +119,6 @@ SYM_CODE_START(stext)
 	 * On return, the CPU will be ready for the MMU to be turned on and
 	 * the TCR will have been set.
 	 */
-	mov	x0, #ARM64_CPU_BOOT_PRIMARY
 	bl	__cpu_setup			// initialise processor
 	b	__primary_switch
 SYM_CODE_END(stext)
@@ -417,6 +417,10 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 	adr_l	x5, init_task
 	msr	sp_el0, x5			// Save thread_info
 
+#ifdef CONFIG_ARM64_PTR_AUTH
+	__ptrauth_keys_init_cpu	x5, x6, x7, x8
+#endif
+
 	adr_l	x8, vectors			// load VBAR_EL1 with virtual
 	msr	vbar_el1, x8			// vector table address
 	isb
@@ -717,7 +721,6 @@ SYM_FUNC_START_LOCAL(secondary_startup)
 	 * Common entry point for secondary CPUs.
 	 */
 	bl	__cpu_secondary_check52bitva
-	mov	x0, #ARM64_CPU_BOOT_SECONDARY
 	bl	__cpu_setup			// initialise processor
 	adrp	x1, swapper_pg_dir
 	bl	__enable_mmu
@@ -739,6 +742,11 @@ SYM_FUNC_START_LOCAL(__secondary_switched)
 	msr	sp_el0, x2
 	mov	x29, #0
 	mov	x30, #0
+
+#ifdef CONFIG_ARM64_PTR_AUTH
+	ptrauth_keys_init_cpu x2, x3, x4, x5
+#endif
+
 	b	secondary_start_kernel
 SYM_FUNC_END(__secondary_switched)
 
diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
index 7b2f2e650c44..56b1fe9bfaa0 100644
--- a/arch/arm64/kernel/sleep.S
+++ b/arch/arm64/kernel/sleep.S
@@ -100,7 +100,6 @@ ENDPROC(__cpu_suspend_enter)
 	.pushsection ".idmap.text", "awx"
 ENTRY(cpu_resume)
 	bl	el2_setup		// if in EL2 drop to EL1 cleanly
-	mov	x0, #ARM64_CPU_RUNTIME
 	bl	__cpu_setup
 	/* enable the MMU early - so we can access sleep_save_stash by va */
 	adrp	x1, swapper_pg_dir
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 061f60fe452f..d6d337d036f0 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -114,10 +114,6 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 	 */
 	secondary_data.task = idle;
 	secondary_data.stack = task_stack_page(idle) + THREAD_SIZE;
-#if defined(CONFIG_ARM64_PTR_AUTH)
-	secondary_data.ptrauth_key.apia.lo = idle->thread.keys_kernel.apia.lo;
-	secondary_data.ptrauth_key.apia.hi = idle->thread.keys_kernel.apia.hi;
-#endif
 	update_cpu_boot_status(CPU_MMU_OFF);
 	__flush_dcache_area(&secondary_data, sizeof(secondary_data));
 
@@ -140,10 +136,6 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 	pr_crit("CPU%u: failed to come online\n", cpu);
 	secondary_data.task = NULL;
 	secondary_data.stack = NULL;
-#if defined(CONFIG_ARM64_PTR_AUTH)
-	secondary_data.ptrauth_key.apia.lo = 0;
-	secondary_data.ptrauth_key.apia.hi = 0;
-#endif
 	__flush_dcache_area(&secondary_data, sizeof(secondary_data));
 	status = READ_ONCE(secondary_data.status);
 	if (status == CPU_MMU_OFF)