From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.213 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794554205; b=Km21IiUpXV1+EqaKplkC2vrAYPzf6sqU6opUw3eaRbU36LUW2UrUOU1Op9251FBqMjVU VlXlX/qqwvYFIKC6+NVWjiAU5947fOrd5SSvkiiTBHVvxPkK+yUUKe8JLef9P6EKzbWZ7 SnArCoIrlxIYaZkXpYLeM9vQMfa7lbPFqi6pYBzWt6wiY72DW8Aj+gMUpsf9y7l54MrGZ RZYnTrBeaBX9O5Aa6kX4Ib+hUi68WIymkDJcyTfSCAdEiSRPYuR4BnHMZDkYaqPEztNFw 8hYniwnaV7sqM+eo0SIyT2TPXoERidybjt/ZrY5qTpOcnM3WCex4RsJmTvLHoQdmi7Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794554205; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:From:To:Cc:Subject:Date:Message-ID: X-Mailer:In-Reply-To:References:MIME-Version:Content-Type: Content-Transfer-Encoding; bh=PY/h1faCj7YLTRJygAQBGN17l9LlZH+uqkX+EFa6XOI=; b=fpw5vkX1cwC2QphiucS+h9ocs0IthDzqXVhEatNVSX3GcsQPLbIcYainppPTO/c6qVBD IDC9hnjDwAGoB42nwjW6j9itwp+7VpPGzcpxZqlonmxyz7NBYoGtDfHi4uMkOE5YqiU1v tAJg9Tt0UbnSMi0XK6jQruY+432aFV1tbdzeyHkBgz45o9BtDMmhmD0JMxUmeLqD56Ye/ Rhgnxvy3gDTCqjTOLn8pipSUCAWfMXp2liMJPx3tRXXKX7J9sYH9XLEF68eY3IXxXLTVC sikWmuBTWEhWdWhX0/E96/YZCn1YqJ2bCjwQjxOwqmZJVPmik9ZYI3jHnjNsFsb23Cg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=nhEKbwwB; arc=none smtp.remote-ip=91.218.175.213 Received: from mta0.migadu.com (out-213.mta0.migadu.com [91.218.175.213]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C2B1A606A323 for ; Fri, 13 Nov 2026 07:16:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org C2B1A606A323 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=nhEKbwwB X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=8t8H4CQ8gn3R9f8nurhquSa//ipjY+XXPYQiq2AQR7Q=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1794554203; v=1; x=1795159003; b=nhEKbwwBNg/lBaKxIE59HIloDCsDEEPFLOKnNEKX3NcXwu1Kbar/SLH8txrDuHPnhcYtvF9p TUeWih+JPiPN17y/I/npOThvyRBT86Vg0hBXX4YaHdyaRWLF/hMF8Uf95iaM9BpW5w1xtNf8n1b +Ncok1IybhXuwqe9umoT+LIY= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 211d82633146b9fb; Fri, 13 Nov 2026 07:16:42 +0000 X-Mizu-Trace-ID: 211d82633146b9fb X-Migadu-Flow: FLOW_OUT From: =?UTF-8?q?Cl=C3=A9ment=20L=C3=A9ger?= To: Paul Walmsley , Palmer Dabbelt , Albert Ou Cc: =?UTF-8?q?Cl=C3=A9ment=20L=C3=A9ger?= , Alexandre Ghiti , WangYuli , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/3] riscv: kgdb: use patch_insn_write() to set breakpoints Date: Fri, 13 Nov 2026 08:16:12 +0100 Message-ID: <20261113071616.219623-2-clement.leger@linux.dev> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261113071616.219623-1-clement.leger@linux.dev> References: <20261113071616.219623-1-clement.leger@linux.dev> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When using CONFIG_STRICT_KERNEL_RWX, the text section is not writable and copy_to_kernel_nofault() returns -EFAULT. Fix this by using patch_insn_write() were applicable and implement kgdb_arch_set_breakpoint()/kgdb_arch_remove_breakpoint(). patch_insn_write() correctly remaps the text as writable using a fixmap alias. Signed-off-by: Clément Léger --- arch/riscv/kernel/kgdb.c | 34 +++++++++++++++++++++++++++++----- 1 file changed, 29 insertions(+), 5 deletions(-) diff --git a/arch/riscv/kernel/kgdb.c b/arch/riscv/kernel/kgdb.c index 0bf629204c76..4ad817698af8 100644 --- a/arch/riscv/kernel/kgdb.c +++ b/arch/riscv/kernel/kgdb.c @@ -12,6 +12,7 @@ #include #include #include +#include enum { NOT_KGDB_BREAK = 0, @@ -134,9 +135,9 @@ static int do_single_step(struct pt_regs *regs) stepped_address = addr; /* Replace the op code with the break instruction */ - error = copy_to_kernel_nofault((void *)stepped_address, - arch_kgdb_ops.gdb_bpt_instr, - BREAK_INSTR_SIZE); + error = patch_insn_write((void *)stepped_address, + arch_kgdb_ops.gdb_bpt_instr, + BREAK_INSTR_SIZE); /* Flush and return */ if (!error) { flush_icache_range(addr, addr + BREAK_INSTR_SIZE); @@ -154,8 +155,8 @@ static int do_single_step(struct pt_regs *regs) static void undo_single_step(struct pt_regs *regs) { if (stepped_opcode != 0) { - copy_to_kernel_nofault((void *)stepped_address, - (void *)&stepped_opcode, BREAK_INSTR_SIZE); + patch_insn_write((void *)stepped_address, + (void *)&stepped_opcode, BREAK_INSTR_SIZE); flush_icache_range(stepped_address, stepped_address + BREAK_INSTR_SIZE); } @@ -261,6 +262,29 @@ noinline void arch_kgdb_breakpoint(void) "kgdb_compiled_break: ebreak\n"); } +/* + * Kernel text may be read-only (CONFIG_STRICT_KERNEL_RWX), so software + * breakpoints must be planted through the writable patch alias instead of + * writing the text address directly. + */ +int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt) +{ + int err; + + err = copy_from_kernel_nofault(bpt->saved_instr, (char *)bpt->bpt_addr, + BREAK_INSTR_SIZE); + if (err) + return err; + return patch_insn_write((void *)bpt->bpt_addr, + arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE); +} + +int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt) +{ + return patch_insn_write((void *)bpt->bpt_addr, bpt->saved_instr, + BREAK_INSTR_SIZE); +} + void kgdb_arch_handle_qxfer_pkt(char *remcom_in_buffer, char *remcom_out_buffer) { -- 2.55.0