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Commit 0465045e authored by James Morse's avatar James Morse Committed by Gerrit - the friendly Code Review server
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arm64: entry: Free up another register on kpti's tramp_exit path 



commit 03aff3a77a58b5b52a77e00537a42090ad57b80b upstream.

Kpti stashes x30 in far_el1 while it uses x30 for all its work.

Making the vectors a per cpu data structure will require a second
register.

Allow tramp_exit two registers before it unmaps the kernel by
leaving x30 on the stack and stashing x29 in far_el1.

Change-Id: I324402ec90a8401780ac88d6ed91eaa50fb1911a
Reviewed-by: default avatarRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Git-commit: 51acb811
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: default avatarKishor Krishna Bhat <quic_kishkris@quicinc.com>
parent aa33c630

arch/arm64/kernel/entry.S

+12 −6
Original line number Diff line number Diff line
@@ -358,18 +358,20 @@ alternative_else_nop_endif 
	ldp	x24, x25, [sp, #16 * 12]

	ldp	x26, x27, [sp, #16 * 13]

	ldp	x28, x29, [sp, #16 * 14]

	ldr	lr, [sp, #S_LR]

	add	sp, sp, #S_FRAME_SIZE		// restore sp

	/*

	 * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on eret context synchronization

	 * when returning from IPI handler, and when returning to user-space.

	 */



	.if	\el == 0

alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0

alternative_if_not ARM64_UNMAP_KERNEL_AT_EL0

	ldr	lr, [sp, #S_LR]

	add	sp, sp, #S_FRAME_SIZE 		//restore sp

	eret

alternative_else_nop_endif

#ifdef CONFIG_UNMAP_KERNEL_AT_EL0

	bne	4f

	msr	far_el1, x30

	msr	far_el1, x29

	tramp_alias	x30, tramp_exit_native

	br	x30

4:
@@ -377,6 +379,8 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 
	br	x30

#endif

	.else

	ldr	lr, [sp, #S_LR]

	add	sp, sp, #S_FRAME_SIZE		// restore sp

	eret

	.endif

	.endm
@@ -1029,10 +1033,12 @@ alternative_insn isb, nop, ARM64_WORKAROUND_QCOM_FALKOR_E1003 
	.macro tramp_exit, regsize = 64

	adr	x30, tramp_vectors

	msr	vbar_el1, x30

	tramp_unmap_kernel	x30

	ldr	lr, [sp, #S_LR]

	tramp_unmap_kernel	x29

	.if	\regsize == 64

	mrs	x30, far_el1

	mrs	x29, far_el1

	.endif

	add	sp, sp, #S_FRAME_SIZE   //restore sp

	eret

	.endm