linux-kernel - [PATCH -next V13 3/7] riscv: entry: Add noinstr to prevent instrumentation inserted

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Message-Id: <20230107113838.3969149-4-guoren@kernel.org>
Date:   Sat,  7 Jan 2023 06:38:34 -0500
From:   guoren@...nel.org
To:     arnd@...db.de, guoren@...nel.org, palmer@...osinc.com,
        tglx@...utronix.de, peterz@...radead.org, luto@...nel.org,
        conor.dooley@...rochip.com, heiko@...ech.de, jszhang@...nel.org,
        lazyparser@...il.com, falcon@...ylab.org, chenhuacai@...nel.org,
        apatel@...tanamicro.com, atishp@...shpatra.org,
        mark.rutland@....com, ben@...adent.org.uk, bjorn@...nel.org
Cc:     linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        Guo Ren <guoren@...ux.alibaba.com>,
        Björn Töpel <bjorn@...osinc.com>
Subject: [PATCH -next V13 3/7] riscv: entry: Add noinstr to prevent instrumentation inserted

From: Guo Ren <guoren@...ux.alibaba.com>

Without noinstr the compiler is free to insert instrumentation (think
all the k*SAN, KCov, GCov, ftrace etc..) which can call code we're not
yet ready to run this early in the entry path, for instance it could
rely on RCU which isn't on yet, or expect lockdep state. (by peterz)

Link: https://lore.kernel.org/linux-riscv/YxcQ6NoPf3AH0EXe@hirez.programming.kicks-ass.net/
Reviewed-by: Björn Töpel <bjorn@...osinc.com>
Suggested-by: Peter Zijlstra <peterz@...radead.org>
Tested-by: Jisheng Zhang <jszhang@...nel.org>
Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
Signed-off-by: Guo Ren <guoren@...nel.org>
---
 arch/riscv/kernel/traps.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 549bde5c970a..96ec76c54ff2 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -95,9 +95,9 @@ static void do_trap_error(struct pt_regs *regs, int signo, int code,
 }
 
 #if defined(CONFIG_XIP_KERNEL) && defined(CONFIG_RISCV_ALTERNATIVE)
-#define __trap_section		__section(".xip.traps")
+#define __trap_section __noinstr_section(".xip.traps")
 #else
-#define __trap_section
+#define __trap_section noinstr
 #endif
 #define DO_ERROR_INFO(name, signo, code, str)				\
 asmlinkage __visible __trap_section void name(struct pt_regs *regs)	\
-- 
2.36.1