linux-kernel - [RFC PATCH 3/6] kvm: arm64: Fix up RELR relocation in hyp code/data

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Message-Id: <20201119162543.78001-4-dbrazdil@google.com>
Date:   Thu, 19 Nov 2020 16:25:40 +0000
From:   David Brazdil <dbrazdil@...gle.com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        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>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Scull <ascull@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>, kernel-team@...roid.com,
        David Brazdil <dbrazdil@...gle.com>
Subject: [RFC PATCH 3/6] kvm: arm64: Fix up RELR relocation in hyp code/data

The arm64 kernel also supports packing of relocation data using the RELR
format. Implement a parser of RELR data and fixup the relocations using
the same infra as RELA relocs.

Signed-off-by: David Brazdil <dbrazdil@...gle.com>
---
 arch/arm64/kvm/va_layout.c | 41 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c
index b80fab974896..7f45a98eacfd 100644
--- a/arch/arm64/kvm/va_layout.c
+++ b/arch/arm64/kvm/va_layout.c
@@ -145,6 +145,43 @@ static void __fixup_hyp_rela(void)
 		__fixup_hyp_rel(rel[i].r_offset);
 }
 
+#ifdef CONFIG_RELR
+static void __fixup_hyp_relr(void)
+{
+	u64 *rel, *end;
+
+	rel = (u64*)(kimage_vaddr + __load_elf_u64(__relr_offset));
+	end = rel + (__load_elf_u64(__relr_size) / sizeof(*rel));
+
+	while (rel < end) {
+		unsigned n;
+		u64 addr = *(rel++);
+
+		/* Address must not have the LSB set. */
+		BUG_ON(addr & BIT(0));
+
+		/* Fix up the first address of the chain. */
+		__fixup_hyp_rel(addr);
+
+		/*
+		 * Loop over bitmaps, i.e. as long as words' LSB is 1.
+		 * Each bit (ordered from LSB to MSB) represents one word from
+		 * the last full address (exclusive). If the corresponding bit
+		 * is 1, there is a relative relocation on that word.
+		 */
+		for (n = 0; rel < end && (*rel & BIT(0)); n++) {
+			unsigned i;
+			u64 bitmap = *(rel++);
+
+			for (i = 1; i < 64; ++i) {
+				if ((bitmap & BIT(i)))
+					__fixup_hyp_rel(addr + 8 * (63 * n + i));
+			}
+		}
+	}
+}
+#endif
+
 /*
  * The kernel relocated pointers to kernel VA. Iterate over relocations in
  * the hypervisor ELF sections and convert them to hyp VA. This avoids the
@@ -156,6 +193,10 @@ __init void kvm_fixup_hyp_relocations(void)
 		return;
 
 	__fixup_hyp_rela();
+
+#ifdef CONFIG_RELR
+	__fixup_hyp_relr();
+#endif
 }
 
 static u32 compute_instruction(int n, u32 rd, u32 rn)
-- 
2.29.2.299.gdc1121823c-goog