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From:   James Morse <james.morse@arm.com>
To:     stable@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     james.morse@arm.com, catalin.marinas@arm.com
Subject: [stable:PATCH v4.14.274 20/27] arm64: entry: Add macro for reading symbol addresses from the trampoline
Date:   Thu, 31 Mar 2022 19:33:53 +0100
Message-Id: <20220331183400.73183-21-james.morse@arm.com>
In-Reply-To: <20220331183400.73183-1-james.morse@arm.com>
References: <20220331183400.73183-1-james.morse@arm.com>
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commit b28a8eebe81c186fdb1a0078263b30576c8e1f42 upstream.

The trampoline code needs to use the address of symbols in the wider
kernel, e.g. vectors. PC-relative addressing wouldn't work as the
trampoline code doesn't run at the address the linker expected.

tramp_ventry uses a literal pool, unless CONFIG_RANDOMIZE_BASE is
set, in which case it uses the data page as a literal pool because
the data page can be unmapped when running in user-space, which is
required for CPUs vulnerable to meltdown.

Pull this logic out as a macro, instead of adding a third copy
of it.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
[ Removed SDEI for stable backport ]
Signed-off-by: James Morse <james.morse@arm.com>
---
 arch/arm64/kernel/entry.S | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index caf6f9cb8fd6..4fe25954fbb0 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -1022,6 +1022,15 @@ alternative_else_nop_endif
 	sub	\dst, \dst, PAGE_SIZE
 	.endm
 
+	.macro tramp_data_read_var	dst, var
+#ifdef CONFIG_RANDOMIZE_BASE
+	tramp_data_page		\dst
+	add	\dst, \dst, #:lo12:__entry_tramp_data_\var
+	ldr	\dst, [\dst]
+#else
+	ldr	\dst, =\var
+#endif
+	.endm
 
 #define BHB_MITIGATION_NONE	0
 #define BHB_MITIGATION_LOOP	1
@@ -1052,13 +1061,8 @@ alternative_else_nop_endif
 	b	.
 2:
 	tramp_map_kernel	x30
-#ifdef CONFIG_RANDOMIZE_BASE
-	tramp_data_page		x30
 alternative_insn isb, nop, ARM64_WORKAROUND_QCOM_FALKOR_E1003
-	ldr	x30, [x30]
-#else
-	ldr	x30, =vectors
-#endif
+	tramp_data_read_var	x30, vectors
 	prfm	plil1strm, [x30, #(1b - \vector_start)]
 	msr	vbar_el1, x30
 	isb
@@ -1138,7 +1142,12 @@ END(tramp_exit_compat)
 	.align PAGE_SHIFT
 	.globl	__entry_tramp_data_start
 __entry_tramp_data_start:
+__entry_tramp_data_vectors:
 	.quad	vectors
+#ifdef CONFIG_ARM_SDE_INTERFACE
+__entry_tramp_data___sdei_asm_trampoline_next_handler:
+	.quad	__sdei_asm_handler
+#endif /* CONFIG_ARM_SDE_INTERFACE */
 	.popsection				// .rodata
 #endif /* CONFIG_RANDOMIZE_BASE */
 #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
-- 
2.30.2