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([223.178.213.5]) by smtp.gmail.com with ESMTPSA id 89-20020a17090a0fe200b0020087d7e778sm8832731pjz.37.2022.12.19.02.25.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Dec 2022 02:25:11 -0800 (PST) From: Sumit Garg To: will@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, daniel.thompson@linaro.org, dianders@chromium.org Cc: liwei391@huawei.com, mhiramat@kernel.org, maz@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Sumit Garg Subject: [PATCH v5 2/2] arm64: kgdb: Set PSTATE.SS to 1 to re-enable single-step Date: Mon, 19 Dec 2022 15:54:52 +0530 Message-Id: <20221219102452.2860088-3-sumit.garg@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20221219102452.2860088-1-sumit.garg@linaro.org> References: <20221219102452.2860088-1-sumit.garg@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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=3D1 should be set at each step before transferring the PE to the 'Active-not-pending' state. The problem here is PSTATE.SS=3D1 is not set since the second single-step. After the first single-step, the PE transferes to the 'Inactive' state, with PSTATE.SS=3D0 and MDSCR.SS=3D1, thus PSTATE.SS won't be set to 1 due to kernel_active_single_step()=3Dtrue. Then the PE transferes to the 'Active-pending' state when ERET and returns to the debugger by step exception. Before this patch: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Entering kdb (current=3D0xffff3376039f0000, pid 1) on processor 0 due to Ke= yboard 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=3D0 installed=3D0 [0]kdb> go $ echo h > /proc/sysrq-trigger Entering kdb (current=3D0xffff4f7e453f8000, pid 175) on processor 1 due to = Breakpoint @ 0xffffad651a309290 [1]kdb> ss Entering kdb (current=3D0xffff4f7e453f8000, pid 175) on processor 1 due to = SS trap @ 0xffffad651a309294 [1]kdb> ss Entering kdb (current=3D0xffff4f7e453f8000, pid 175) on processor 1 due to = SS trap @ 0xffffad651a309294 [1]kdb> After this patch: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Entering kdb (current=3D0xffff6851c39f0000, pid 1) on processor 0 due to Ke= yboard Entry [0]kdb> bp write_sysrq_trigger Instruction(i) BP #0 at 0xffffc02d2dd09290 (write_sysrq_trigger) is enabled addr at ffffc02d2dd09290, hardtype=3D0 installed=3D0 [0]kdb> go $ echo h > /proc/sysrq-trigger Entering kdb (current=3D0xffff6851c53c1840, pid 174) on processor 1 due to = Breakpoint @ 0xffffc02d2dd09290 [1]kdb> ss Entering kdb (current=3D0xffff6851c53c1840, pid 174) on processor 1 due to = SS trap @ 0xffffc02d2dd09294 [1]kdb> ss Entering kdb (current=3D0xffff6851c53c1840, pid 174) on processor 1 due to = SS trap @ 0xffffc02d2dd09298 [1]kdb> ss Entering kdb (current=3D0xffff6851c53c1840, 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 --- 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/a= sm/debug-monitors.h index 7b7e05c02691..ce3875ad5cd3 100644 --- a/arch/arm64/include/asm/debug-monitors.h +++ b/arch/arm64/include/asm/debug-monitors.h @@ -104,6 +104,7 @@ void user_regs_reset_single_step(struct user_pt_regs *r= egs, void kernel_enable_single_step(struct pt_regs *regs); void kernel_disable_single_step(void); int kernel_active_single_step(void); +void kernel_regs_reset_single_step(struct pt_regs *regs); =20 #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-m= onitors.c index 3da09778267e..9af898b22ed4 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -438,6 +438,11 @@ int kernel_active_single_step(void) } NOKPROBE_SYMBOL(kernel_active_single_step); =20 +void kernel_regs_reset_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 cda9c1e9864f..51f204bbcf87 100644 --- a/arch/arm64/kernel/kgdb.c +++ b/arch/arm64/kernel/kgdb.c @@ -224,6 +224,8 @@ int kgdb_arch_handle_exception(int exception_vector, in= t signo, */ if (!kernel_active_single_step()) kernel_enable_single_step(linux_regs); + else + kernel_regs_reset_single_step(linux_regs); err =3D 0; break; default: --=20 2.34.1