[PATCH v3 4/7] arm64: kernel: use x30 for __enable_mmu return address
From: Ard Biesheuvel <hidden>
Date: 2016-08-31 11:05:14
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
Using x27 for passing to __enable_mmu what is essentially the return address makes the code look more complicated than it needs to be. So switch to x30/lr, and update the secondary and cpu_resume call sites to simply call __enable_mmu as an ordinary function, with a bl instruction. This requires the callers to be covered by .idmap.text. Reviewed-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Ard Biesheuvel <redacted> --- arch/arm64/kernel/head.S | 21 +++++++------------- arch/arm64/kernel/sleep.S | 8 ++------ 2 files changed, 9 insertions(+), 20 deletions(-)
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 5543068da3ae..45b865e022cc 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S@@ -675,9 +675,9 @@ secondary_startup: * Common entry point for secondary CPUs. */ bl __cpu_setup // initialise processor - - adr_l x27, __secondary_switch // address to jump to after enabling the MMU - b __enable_mmu + bl __enable_mmu + ldr x8, =__secondary_switched + br x8 ENDPROC(secondary_startup) __secondary_switched:
@@ -716,9 +716,9 @@ ENDPROC(__secondary_switched) * Enable the MMU. * * x0 = SCTLR_EL1 value for turning on the MMU. - * x27 = *virtual* address to jump to upon completion * - * Other registers depend on the function called upon completion. + * Returns to the caller via x30/lr. This requires the caller to be covered + * by the .idmap.text section. * * Checks if the selected granule size is supported by the CPU. * If it isn't, park the CPU
@@ -744,7 +744,7 @@ ENTRY(__enable_mmu) ic iallu dsb nsh isb - br x27 + ret ENDPROC(__enable_mmu) __no_granule_support:
@@ -789,9 +789,7 @@ __primary_switch: mrs x20, sctlr_el1 // preserve old SCTLR_EL1 value #endif - adr x27, 0f - b __enable_mmu -0: + bl __enable_mmu #ifdef CONFIG_RELOCATABLE bl __relocate_kernel #ifdef CONFIG_RANDOMIZE_BASE
@@ -822,8 +820,3 @@ __primary_switch: ldr x8, =__primary_switched br x8 ENDPROC(__primary_switch) - -__secondary_switch: - ldr x8, =__secondary_switched - br x8 -ENDPROC(__secondary_switch)
diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
index 6adc76bf8f91..0f7e0b2ac64c 100644
--- a/arch/arm64/kernel/sleep.S
+++ b/arch/arm64/kernel/sleep.S@@ -100,14 +100,10 @@ ENTRY(cpu_resume) bl el2_setup // if in EL2 drop to EL1 cleanly bl __cpu_setup /* enable the MMU early - so we can access sleep_save_stash by va */ - adr_l x27, _resume_switched /* __enable_mmu will branch here */ - b __enable_mmu -ENDPROC(cpu_resume) - -_resume_switched: + bl __enable_mmu ldr x8, =_cpu_resume br x8 -ENDPROC(_resume_switched) +ENDPROC(cpu_resume) .ltorg .popsection
--
2.7.4