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[stable:PATCH,v4.19.235,04/22] arm64: entry.S: Add ventry overflow sanity checks

Message ID 20220318174842.2321061-5-james.morse@arm.com
State New
Headers show
Series arm64: Mitigate spectre style branch history side channels | expand

Commit Message

James Morse March 18, 2022, 5:48 p.m. UTC 
commit 4330e2c5c04c27bebf89d34e0bc14e6943413067 upstream.

Subsequent patches add even more code to the ventry slots.
Ensure kernels that overflow a ventry slot don't get built.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
 arch/arm64/kernel/entry.S | 3 +++
 1 file changed, 3 insertions(+)
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Patch

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 5f800384cb9a..297da3055793 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -70,6 +70,7 @@ 
 
 	.macro kernel_ventry, el, label, regsize = 64
 	.align 7
+.Lventry_start\@:
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
 alternative_if ARM64_UNMAP_KERNEL_AT_EL0
 	.if	\el == 0
@@ -127,6 +128,7 @@  alternative_else_nop_endif
 	mrs	x0, tpidrro_el0
 #endif
 	b	el\()\el\()_\label
+.org .Lventry_start\@ + 128	// Did we overflow the ventry slot?
 	.endm
 
 	.macro tramp_alias, dst, sym
@@ -984,6 +986,7 @@  alternative_insn isb, nop, ARM64_WORKAROUND_QCOM_FALKOR_E1003
 	add	x30, x30, #(1b - tramp_vectors)
 	isb
 	ret
+.org 1b + 128	// Did we overflow the ventry slot?
 	.endm
 
 	.macro tramp_exit, regsize = 64