From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 452DEFC08 for ; Mon, 15 May 2023 17:39:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9BF86C433EF; Mon, 15 May 2023 17:39:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1684172344; bh=RRIoDPuXekR6uHklDFVTidnQdvuPx4yhPCJHVC1+72k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1VJfv8XylJHVgpfIiluQiFYuhPNSYzi7fcus96WPNDnvmisgfuvR5L61bWc4UPSrU OVXfcv2fmy1ZT2xH4hm/mmzxkNxdI/SqM1ONKGuwpEqrhTjIs0LO8SRU0O+qvD7ekX jROdrsnHs/UFRTCionvEyKC9TY/8Uguyotmh5/V4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Wei Li , Sumit Garg , Douglas Anderson , Daniel Thompson , Will Deacon , Sasha Levin Subject: [PATCH 5.10 122/381] arm64: kgdb: Set PSTATE.SS to 1 to re-enable single-step Date: Mon, 15 May 2023 18:26:13 +0200 Message-Id: <20230515161742.338022338@linuxfoundation.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230515161736.775969473@linuxfoundation.org> References: <20230515161736.775969473@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Sumit Garg [ Upstream commit af6c0bd59f4f3ad5daad2f7b777954b1954551d5 ] Currently only the first attempt to single-step has any effect. After that all further stepping remains "stuck" at the same program counter value. Refer to the ARM Architecture Reference Manual (ARM DDI 0487E.a) D2.12, PSTATE.SS=1 should be set at each step before transferring the PE to the 'Active-not-pending' state. The problem here is PSTATE.SS=1 is not set since the second single-step. After the first single-step, the PE transferes to the 'Inactive' state, with PSTATE.SS=0 and MDSCR.SS=1, thus PSTATE.SS won't be set to 1 due to kernel_active_single_step()=true. Then the PE transferes to the 'Active-pending' state when ERET and returns to the debugger by step exception. Before this patch: ================== Entering kdb (current=0xffff3376039f0000, pid 1) on processor 0 due to Keyboard Entry [0]kdb> [0]kdb> [0]kdb> bp write_sysrq_trigger Instruction(i) BP #0 at 0xffffa45c13d09290 (write_sysrq_trigger) is enabled addr at ffffa45c13d09290, hardtype=0 installed=0 [0]kdb> go $ echo h > /proc/sysrq-trigger Entering kdb (current=0xffff4f7e453f8000, pid 175) on processor 1 due to Breakpoint @ 0xffffad651a309290 [1]kdb> ss Entering kdb (current=0xffff4f7e453f8000, pid 175) on processor 1 due to SS trap @ 0xffffad651a309294 [1]kdb> ss Entering kdb (current=0xffff4f7e453f8000, pid 175) on processor 1 due to SS trap @ 0xffffad651a309294 [1]kdb> After this patch: ================= Entering kdb (current=0xffff6851c39f0000, pid 1) on processor 0 due to Keyboard Entry [0]kdb> bp write_sysrq_trigger Instruction(i) BP #0 at 0xffffc02d2dd09290 (write_sysrq_trigger) is enabled addr at ffffc02d2dd09290, hardtype=0 installed=0 [0]kdb> go $ echo h > /proc/sysrq-trigger Entering kdb (current=0xffff6851c53c1840, pid 174) on processor 1 due to Breakpoint @ 0xffffc02d2dd09290 [1]kdb> ss Entering kdb (current=0xffff6851c53c1840, pid 174) on processor 1 due to SS trap @ 0xffffc02d2dd09294 [1]kdb> ss Entering kdb (current=0xffff6851c53c1840, pid 174) on processor 1 due to SS trap @ 0xffffc02d2dd09298 [1]kdb> ss Entering kdb (current=0xffff6851c53c1840, pid 174) on processor 1 due to SS trap @ 0xffffc02d2dd0929c [1]kdb> Fixes: 44679a4f142b ("arm64: KGDB: Add step debugging support") Co-developed-by: Wei Li Signed-off-by: Wei Li Signed-off-by: Sumit Garg Tested-by: Douglas Anderson Acked-by: Daniel Thompson Tested-by: Daniel Thompson Link: https://lore.kernel.org/r/20230202073148.657746-3-sumit.garg@linaro.org Signed-off-by: Will Deacon Signed-off-by: Sasha Levin --- arch/arm64/include/asm/debug-monitors.h | 1 + arch/arm64/kernel/debug-monitors.c | 5 +++++ arch/arm64/kernel/kgdb.c | 2 ++ 3 files changed, 8 insertions(+) diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h index 657c921fd784a..c16ed5b68768e 100644 --- a/arch/arm64/include/asm/debug-monitors.h +++ b/arch/arm64/include/asm/debug-monitors.h @@ -116,6 +116,7 @@ void user_regs_reset_single_step(struct user_pt_regs *regs, void kernel_enable_single_step(struct pt_regs *regs); void kernel_disable_single_step(void); int kernel_active_single_step(void); +void kernel_rewind_single_step(struct pt_regs *regs); #ifdef CONFIG_HAVE_HW_BREAKPOINT int reinstall_suspended_bps(struct pt_regs *regs); diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c index fa76151de6ff1..38a0213fdbeee 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -439,6 +439,11 @@ int kernel_active_single_step(void) } NOKPROBE_SYMBOL(kernel_active_single_step); +void kernel_rewind_single_step(struct pt_regs *regs) +{ + set_regs_spsr_ss(regs); +} + /* ptrace API */ void user_enable_single_step(struct task_struct *task) { diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c index 1a157ca33262d..e4e95821b1f6c 100644 --- a/arch/arm64/kernel/kgdb.c +++ b/arch/arm64/kernel/kgdb.c @@ -223,6 +223,8 @@ int kgdb_arch_handle_exception(int exception_vector, int signo, */ if (!kernel_active_single_step()) kernel_enable_single_step(linux_regs); + else + kernel_rewind_single_step(linux_regs); err = 0; break; default: -- 2.39.2