linux-kernel - [PATCH 5.15 819/917] arm64: arm64_ftr_reg->name may not be a human-readable string

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Date:   Mon, 15 Nov 2021 18:05:14 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Reiji Watanabe <reijiw@...gle.com>,
        Oliver Upton <oupton@...gle.com>,
        Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 819/917] arm64: arm64_ftr_reg->name may not be a human-readable string

From: Reiji Watanabe <reijiw@...gle.com>

[ Upstream commit 9dc232a8ab18bb20f1dcb03c8e049e3607f3ed15 ]

The id argument of ARM64_FTR_REG_OVERRIDE() is used for two purposes:
one as the system register encoding (used for the sys_id field of
__ftr_reg_entry), and the other as the register name (stringified
and used for the name field of arm64_ftr_reg), which is debug
information. The id argument is supposed to be a macro that
indicates an encoding of the register (eg. SYS_ID_AA64PFR0_EL1, etc).

ARM64_FTR_REG(), which also has the same id argument,
uses ARM64_FTR_REG_OVERRIDE() and passes the id to the macro.
Since the id argument is completely macro-expanded before it is
substituted into a macro body of ARM64_FTR_REG_OVERRIDE(),
the stringified id in the body of ARM64_FTR_REG_OVERRIDE is not
a human-readable register name, but a string of numeric bitwise
operations.

Fix this so that human-readable register names are available as
debug information.

Fixes: 8f266a5d878a ("arm64: cpufeature: Add global feature override facility")
Signed-off-by: Reiji Watanabe <reijiw@...gle.com>
Reviewed-by: Oliver Upton <oupton@...gle.com>
Acked-by: Marc Zyngier <maz@...nel.org>
Link: https://lore.kernel.org/r/20211101045421.2215822-1-reijiw@google.com
Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm64/kernel/cpufeature.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 6ec7036ef7e18..7553c98f379fc 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -573,15 +573,19 @@ static const struct arm64_ftr_bits ftr_raz[] = {
 	ARM64_FTR_END,
 };
 
-#define ARM64_FTR_REG_OVERRIDE(id, table, ovr) {		\
+#define __ARM64_FTR_REG_OVERRIDE(id_str, id, table, ovr) {	\
 		.sys_id = id,					\
 		.reg = 	&(struct arm64_ftr_reg){		\
-			.name = #id,				\
+			.name = id_str,				\
 			.override = (ovr),			\
 			.ftr_bits = &((table)[0]),		\
 	}}
 
-#define ARM64_FTR_REG(id, table) ARM64_FTR_REG_OVERRIDE(id, table, &no_override)
+#define ARM64_FTR_REG_OVERRIDE(id, table, ovr)	\
+	__ARM64_FTR_REG_OVERRIDE(#id, id, table, ovr)
+
+#define ARM64_FTR_REG(id, table)		\
+	__ARM64_FTR_REG_OVERRIDE(#id, id, table, &no_override)
 
 struct arm64_ftr_override __ro_after_init id_aa64mmfr1_override;
 struct arm64_ftr_override __ro_after_init id_aa64pfr1_override;
-- 
2.33.0