linux-kernel - [PATCH] RISC-V: probes: Treat the instruction stream as host-endian

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Message-Id: <20210123033429.2072716-1-palmer@dabbelt.com>
Date:   Fri, 22 Jan 2021 19:34:29 -0800
From:   Palmer Dabbelt <palmer@...belt.com>
To:         linux-riscv@...ts.infradead.org
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>, aou@...s.berkeley.edu,
        penberg@...nel.org, guoren@...ux.alibaba.com, me@...ki.ch,
        mhiramat@...nel.org, mingo@...nel.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, Palmer Dabbelt <palmerdabbelt@...gle.com>,
        kernel test robot <lkp@...el.com>
Subject: [PATCH] RISC-V: probes: Treat the instruction stream as host-endian

From: Palmer Dabbelt <palmerdabbelt@...gle.com>

Neither of these are actually correct: the instruction stream is defined
(for versions of the ISA manual newer than 2.2) as a stream of 16-bit
little-endian parcels, which is different than just being little-endian.
In theory we should represent this as a type, but we don't have any
concrete plans for the big endian stuff so it doesn't seem worth the
time -- we've got variants of this all over the place.

Instead I'm just dropping the unnecessary type conversion, which is a
NOP on LE systems but causes an sparse error as the types are all mixed
up.

Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
---
 arch/riscv/kernel/probes/decode-insn.c | 2 +-
 arch/riscv/kernel/probes/kprobes.c     | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/probes/decode-insn.c b/arch/riscv/kernel/probes/decode-insn.c
index 0876c304ca77..0ed043acc882 100644
--- a/arch/riscv/kernel/probes/decode-insn.c
+++ b/arch/riscv/kernel/probes/decode-insn.c
@@ -16,7 +16,7 @@
 enum probe_insn __kprobes
 riscv_probe_decode_insn(probe_opcode_t *addr, struct arch_probe_insn *api)
 {
-	probe_opcode_t insn = le32_to_cpu(*addr);
+	probe_opcode_t insn = *addr;
 
 	/*
 	 * Reject instructions list:
diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c
index e60893bd87db..a2ec18662fee 100644
--- a/arch/riscv/kernel/probes/kprobes.c
+++ b/arch/riscv/kernel/probes/kprobes.c
@@ -57,7 +57,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 	}
 
 	/* copy instruction */
-	p->opcode = le32_to_cpu(*p->addr);
+	p->opcode = *p->addr;
 
 	/* decode instruction */
 	switch (riscv_probe_decode_insn(p->addr, &p->ainsn.api)) {
-- 
2.30.0.280.ga3ce27912f-goog