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Date: Thu, 31 Mar 2022 19:33:44 +0100 From: James Morse <james.morse@....com> To: stable@...r.kernel.org, linux-kernel@...r.kernel.org Cc: james.morse@....com, catalin.marinas@....com Subject: [stable:PATCH v4.14.274 11/27] 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. Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk> Reviewed-by: Catalin Marinas <catalin.marinas@....com> Signed-off-by: James Morse <james.morse@....com> --- arch/arm64/kernel/entry.S | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 1211e0da5476..b3014ed0ea8a 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -356,14 +356,16 @@ 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 .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: @@ -371,6 +373,8 @@ 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 @@ -1048,10 +1052,12 @@ 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 -- 2.30.2
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