linux-kernel - [PATCH] KVM: arm64: Support PREL/PLT relocs in EL2 code

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Message-Id: <20210331133048.63311-1-dbrazdil@google.com>
Date:   Wed, 31 Mar 2021 13:30:48 +0000
From:   David Brazdil <dbrazdil@...gle.com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     Marc Zyngier <maz@...nel.org>, James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, David Brazdil <dbrazdil@...gle.com>
Subject: [PATCH] KVM: arm64: Support PREL/PLT relocs in EL2 code

gen-hyprel tool parses object files of the EL2 portion of KVM
and generates runtime relocation data. While only filtering for
R_AARCH64_ABS64 relocations in the input object files, it has an
allow-list of relocation types that are used for relative
addressing. Other, unexpected, relocation types are rejected and
cause the build to fail.

This allow-list did not include the position-relative relocation
types R_AARCH64_PREL64/32/16 and the recently introduced _PLT32.
While not seen used by toolchains in the wild, add them to the
allow-list for completeness.

Fixes: 8c49b5d43d4c ("KVM: arm64: Generate hyp relocation data")
Cc: <stable@...r.kernel.org>
Reported-by: Will Deacon <will@...nel.org>
Signed-off-by: David Brazdil <dbrazdil@...gle.com>
---
 arch/arm64/kvm/hyp/nvhe/gen-hyprel.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/arm64/kvm/hyp/nvhe/gen-hyprel.c b/arch/arm64/kvm/hyp/nvhe/gen-hyprel.c
index ead02c6a7628..6bc88a756cb7 100644
--- a/arch/arm64/kvm/hyp/nvhe/gen-hyprel.c
+++ b/arch/arm64/kvm/hyp/nvhe/gen-hyprel.c
@@ -50,6 +50,18 @@
 #ifndef R_AARCH64_ABS64
 #define R_AARCH64_ABS64			257
 #endif
+#ifndef R_AARCH64_PREL64
+#define R_AARCH64_PREL64		260
+#endif
+#ifndef R_AARCH64_PREL32
+#define R_AARCH64_PREL32		261
+#endif
+#ifndef R_AARCH64_PREL16
+#define R_AARCH64_PREL16		262
+#endif
+#ifndef R_AARCH64_PLT32
+#define R_AARCH64_PLT32			314
+#endif
 #ifndef R_AARCH64_LD_PREL_LO19
 #define R_AARCH64_LD_PREL_LO19		273
 #endif
@@ -371,6 +383,12 @@ static void emit_rela_section(Elf64_Shdr *sh_rela)
 		case R_AARCH64_ABS64:
 			emit_rela_abs64(rela, sh_orig_name);
 			break;
+		/* Allow position-relative data relocations. */
+		case R_AARCH64_PREL64:
+		case R_AARCH64_PREL32:
+		case R_AARCH64_PREL16:
+		case R_AARCH64_PLT32:
+			break;
 		/* Allow relocations to generate PC-relative addressing. */
 		case R_AARCH64_LD_PREL_LO19:
 		case R_AARCH64_ADR_PREL_LO21:
-- 
2.31.0.291.g576ba9dcdaf-goog