linux-kernel - [PATCH 6/8] arm64: patching: Add aarch64_insn_write_literal

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Date:   Mon,  9 Jan 2023 13:58:26 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     catalin.marinas@....com, lenb@...nel.org,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        mark.rutland@....com, mhiramat@...nel.org, ndesaulniers@...gle.com,
        ojeda@...nel.org, peterz@...radead.org, rafael.j.wysocki@...el.com,
        revest@...omium.org, robert.moore@...el.com, rostedt@...dmis.org,
        will@...nel.org
Subject: [PATCH 6/8] arm64: patching: Add aarch64_insn_write_literal_u64()

In subsequent patches we'll need to atomically write to a
naturally-aligned 64-bit literal embedded within the kernel text.

Add a helper for this. For consistency with other text patching code we
use copy_to_kernel_nofault(), which is atomic for naturally-aligned
accesses up to 64-bits.

Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Florent Revest <revest@...omium.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Will Deacon <will@...nel.org>
---
 arch/arm64/include/asm/patching.h |  2 ++
 arch/arm64/kernel/patching.c      | 17 +++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/arch/arm64/include/asm/patching.h b/arch/arm64/include/asm/patching.h
index 6bf5adc562950..68908b82b168f 100644
--- a/arch/arm64/include/asm/patching.h
+++ b/arch/arm64/include/asm/patching.h
@@ -7,6 +7,8 @@
 int aarch64_insn_read(void *addr, u32 *insnp);
 int aarch64_insn_write(void *addr, u32 insn);
 
+int aarch64_insn_write_literal_u64(void *addr, u64 val);
+
 int aarch64_insn_patch_text_nosync(void *addr, u32 insn);
 int aarch64_insn_patch_text(void *addrs[], u32 insns[], int cnt);
 
diff --git a/arch/arm64/kernel/patching.c b/arch/arm64/kernel/patching.c
index 33e0fabc0b79b..b4835f6d594bc 100644
--- a/arch/arm64/kernel/patching.c
+++ b/arch/arm64/kernel/patching.c
@@ -88,6 +88,23 @@ int __kprobes aarch64_insn_write(void *addr, u32 insn)
 	return __aarch64_insn_write(addr, cpu_to_le32(insn));
 }
 
+noinstr int aarch64_insn_write_literal_u64(void *addr, u64 val)
+{
+	u64 *waddr;
+	unsigned long flags;
+	int ret;
+
+	raw_spin_lock_irqsave(&patch_lock, flags);
+	waddr = patch_map(addr, FIX_TEXT_POKE0);
+
+	ret = copy_to_kernel_nofault(waddr, &val, sizeof(val));
+
+	patch_unmap(FIX_TEXT_POKE0);
+	raw_spin_unlock_irqrestore(&patch_lock, flags);
+
+	return ret;
+}
+
 int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn)
 {
 	u32 *tp = addr;
-- 
2.30.2