linux-kernel - [PATCH v4 2/2] riscv: KGDB: Remove ".option norvc/.option rvc" for kgdb_compiled

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Message-ID: <8B431C6A4626225C+20250411073222.56820-2-wangyuli@uniontech.com>
Date: Fri, 11 Apr 2025 15:32:22 +0800
From: WangYuli <wangyuli@...ontech.com>
To: wangyuli@...ontech.com
Cc: alex@...ti.fr,
	aou@...s.berkeley.edu,
	chenhuacai@...nel.org,
	guanwentao@...ontech.com,
	linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	niecheng1@...ontech.com,
	palmer@...belt.com,
	palmerdabbelt@...gle.com,
	paul.walmsley@...ive.com,
	samuel.holland@...ive.com,
	vincent.chen@...ive.com,
	zhanjun@...ontech.com
Subject: [PATCH v4 2/2] riscv: KGDB: Remove ".option norvc/.option rvc" for kgdb_compiled_break

[ Quoting Samuel Holland: ]

  This is a separate issue, but using ".option rvc" here is a bug.
  It will unconditionally enable the C extension for the rest of
  the file, even if the kernel is being built with CONFIG_RISCV_ISA_C=n.

[ Quoting Palmer Dabbelt: ]

  We're just looking at the address of kgdb_compiled_break, so it's
  fine if it ends up as a c.ebreak.

[ Quoting Alexandre Ghiti: ]

  .option norvc is used to prevent the assembler from using compressed
  instructions, but it's generally used when we need to ensure the
  size of the instructions that are used, which is not the case here
  as noted by Palmer since we only care about the address. So yes
  it will work fine with C enabled :)

So let's just remove them all.

Link: https://lore.kernel.org/all/4b4187c1-77e5-44b7-885f-d6826723dd9a@sifive.com/
Link: https://lore.kernel.org/all/mhng-69513841-5068-441d-be8f-2aeebdc56a08@palmer-ri-x1c9a/
Link: https://lore.kernel.org/all/23693e7f-4fff-40f3-a437-e06d827278a5@ghiti.fr/
Fixes: fe89bd2be866 ("riscv: Add KGDB support")
Cc: Samuel Holland <samuel.holland@...ive.com>
Cc: Palmer Dabbelt <palmer@...belt.com>
Cc: Alexandre Ghiti <alex@...ti.fr>
Signed-off-by: WangYuli <wangyuli@...ontech.com>
---
 arch/riscv/kernel/kgdb.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/riscv/kernel/kgdb.c b/arch/riscv/kernel/kgdb.c
index 5d1ce8dacaf5..9f3db3503dab 100644
--- a/arch/riscv/kernel/kgdb.c
+++ b/arch/riscv/kernel/kgdb.c
@@ -257,9 +257,7 @@ void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
 noinline void arch_kgdb_breakpoint(void)
 {
 	asm(".global kgdb_compiled_break\n"
-	    ".option norvc\n"
-	    "kgdb_compiled_break: ebreak\n"
-	    ".option rvc\n");
+	    "kgdb_compiled_break: ebreak\n");
 }
 
 void kgdb_arch_handle_qxfer_pkt(char *remcom_in_buffer,
-- 
2.49.0