Commit 99ed3ed0 authored by Mark Rutland's avatar Mark Rutland Committed by Will Deacon
Browse files

arm64: don't reload GPRs after apply_ssbd 



Now that all of the syscall logic works on the saved pt_regs, apply_ssbd
can safely corrupt x0-x3 in the entry paths, and we no longer need to
restore them. So let's remove the logic doing so.

With that logic gone, we can fold the branch target into the macro, so
that callers need not deal with this. GAS provides \@, which provides a
unique value per macro invocation, which we can use to create a unique
label.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent d9be0325

arch/arm64/kernel/entry.S

+7 −13
Original line number Diff line number Diff line
@@ -130,20 +130,21 @@ alternative_else_nop_endif 


	// This macro corrupts x0-x3. It is the caller's duty

	// to save/restore them if required.

	.macro	apply_ssbd, state, targ, tmp1, tmp2

	.macro	apply_ssbd, state, tmp1, tmp2

#ifdef CONFIG_ARM64_SSBD

alternative_cb	arm64_enable_wa2_handling

	b	\targ

	b	.L__asm_ssbd_skip\@

alternative_cb_end

	ldr_this_cpu	\tmp2, arm64_ssbd_callback_required, \tmp1

	cbz	\tmp2, \targ

	cbz	\tmp2,	.L__asm_ssbd_skip\@

	ldr	\tmp2, [tsk, #TSK_TI_FLAGS]

	tbnz	\tmp2, #TIF_SSBD, \targ

	tbnz	\tmp2, #TIF_SSBD, .L__asm_ssbd_skip\@

	mov	w0, #ARM_SMCCC_ARCH_WORKAROUND_2

	mov	w1, #\state

alternative_cb	arm64_update_smccc_conduit

	nop					// Patched to SMC/HVC #0

alternative_cb_end

.L__asm_ssbd_skip\@:

#endif

	.endm
@@ -173,13 +174,7 @@ alternative_cb_end 
	ldr	x19, [tsk, #TSK_TI_FLAGS]	// since we can unmask debug

	disable_step_tsk x19, x20		// exceptions when scheduling.



	apply_ssbd 1, 1f, x22, x23



#ifdef CONFIG_ARM64_SSBD

	ldp	x0, x1, [sp, #16 * 0]

	ldp	x2, x3, [sp, #16 * 1]

#endif

1:

	apply_ssbd 1, x22, x23



	mov	x29, xzr			// fp pointed to user-space

	.else
@@ -321,8 +316,7 @@ alternative_if ARM64_WORKAROUND_845719 
alternative_else_nop_endif

#endif

3:

	apply_ssbd 0, 5f, x0, x1

5:

	apply_ssbd 0, x0, x1

	.endif



	msr	elr_el1, x21			// set up the return data

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