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[209.85.217.44]) by smtp.gmail.com with ESMTPSA id v16sm340442vsq.18.2020.05.13.17.22.09 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 13 May 2020 17:22:09 -0700 (PDT) Received: by mail-vs1-f44.google.com with SMTP id 62so963607vsi.2 for ; Wed, 13 May 2020 17:22:09 -0700 (PDT) X-Received: by 2002:a67:f5d6:: with SMTP id t22mr1506572vso.73.1589415729146; Wed, 13 May 2020 17:22:09 -0700 (PDT) MIME-Version: 1.0 References: <20200509214159.19680-1-liwei391@huawei.com> <20200509214159.19680-4-liwei391@huawei.com> In-Reply-To: <20200509214159.19680-4-liwei391@huawei.com> From: Doug Anderson Date: Wed, 13 May 2020 17:21:58 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 3/4] arm64: kgdb: Fix single-stepping into the irq handler wrongly To: Wei Li Cc: Daniel Thompson , Jason Wessel , Marc Zyngier , Mark Rutland , Masami Hiramatsu , David Miller , Will Deacon , Catalin Marinas , Linux ARM , LKML , liwei1412@163.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Sat, May 9, 2020 at 6:49 AM Wei Li wrote: > > After the single-step exception handling oops is fixed, when we execute > single-step in kdb/kgdb, we may see it jumps to the irq_handler (where > PSTATE.D is cleared) instead of the next instruction. > > Add the prepare and cleanup work for single-step when enabling and > disabling to maintain the PSTATE.I and PSTATE.D carefully. > > Before this patch: > * kdb: > Entering kdb (current=0xffff8000119e2dc0, pid 0) on processor 0 due to Keyboard Entry > [0]kdb> bp printk > Instruction(i) BP #0 at 0xffff8000101486cc (printk) > is enabled addr at ffff8000101486cc, hardtype=0 installed=0 > > [0]kdb> g > > / # echo h > /proc/sysrq-trigger > > Entering kdb (current=0xffff0000fada65c0, pid 267) on processor 0 due to Breakpoint @ 0xffff8000101486cc > [0]kdb> ss > > Entering kdb (current=0xffff0000fada65c0, pid 267) on processor 0 due to SS trap @ 0xffff800010082ab8 > [0]kdb> 0xffff800010082ab8 > 0xffff800010082ab8 = 0xffff800010082ab8 (el1_irq+0x78) > [0]kdb> > > 0xffff800010082ab0 <+112>: nop > 0xffff800010082ab4 <+116>: msr daifclr, #0xd > 0xffff800010082ab8 <+120>: adrp x1, 0xffff8000113a7000 > 0xffff800010082abc <+124>: ldr x1, [x1, #1408] > > * kgdb: > (gdb) target remote 127.1:23002 > Remote debugging using 127.1:23002 > arch_kgdb_breakpoint () at /home/liwei/main_code/linux/arch/arm64/include/asm/kgdb.h:21 > 21 asm ("brk %0" : : "I" (KGDB_COMPILED_DBG_BRK_IMM)); > (gdb) b printk > Breakpoint 1 at 0xffff8000101486cc: file /home/liwei/main_code/linux/kernel/printk/printk.c, line 2076. > (gdb) c > Continuing. > [New Thread 287] > [Switching to Thread 283] > > Thread 177 hit Breakpoint 1, printk (fmt=0xffff80001130c9d8 "\001\066sysrq: HELP : ") > at /home/liwei/main_code/linux/kernel/printk/printk.c:2076 > 2076 { > (gdb) stepi > el1_irq () at /home/liwei/main_code/linux/arch/arm64/kernel/entry.S:608 > 608 irq_handler > (gdb) > > After this patch: > * kdb: > Entering kdb (current=0xffff8000119d2dc0, pid 0) on processor 0 due to Keyboard Entry > [0]kdb> bp printk > Instruction(i) BP #0 at 0xffff80001014874c (printk) > is enabled addr at ffff80001014874c, hardtype=0 installed=0 > > [0]kdb> g > > / # echo h > /proc/sysrq-trigger > > Entering kdb (current=0xffff0000fa6948c0, pid 265) on processor 0 due to Breakpoint @ 0xffff80001014874c > [0]kdb> ss > > Entering kdb (current=0xffff0000fa6948c0, pid 265) on processor 0 due to SS trap @ 0xffff800010148750 > [0]kdb> > > * kgdb: > (gdb) target remote 127.1:23002 > Remote debugging using 127.1:23002 > arch_kgdb_breakpoint () at /home/liwei/main_code/linux/arch/arm64/include/asm/kgdb.h:21 > 21 asm ("brk %0" : : "I" (KGDB_COMPILED_DBG_BRK_IMM)); > (gdb) b printk > Breakpoint 1 at 0xffff80001014874c: file /home/liwei/main_code/linux/kernel/printk/printk.c, line 2076. > (gdb) c > Continuing. > [New Thread 277] > [Switching to Thread 276] > > Thread 171 hit Breakpoint 1, printk (fmt=0xffff8000112fc130 "\001\066sysrq: HELP : ") > at /home/liwei/main_code/linux/kernel/printk/printk.c:2076 > 2076 { > (gdb) stepi > 0xffff800010148750 2076 { > (gdb) > > Fixes: 44679a4f142b ("arm64: KGDB: Add step debugging support") > Signed-off-by: Wei Li > --- > arch/arm64/kernel/kgdb.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c > index 1a157ca33262..3910ac06c261 100644 > --- a/arch/arm64/kernel/kgdb.c > +++ b/arch/arm64/kernel/kgdb.c > @@ -100,6 +100,8 @@ struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = { > { "fpcr", 4, -1 }, > }; > > +static DEFINE_PER_CPU(unsigned long, kgdb_ss_flags); > + > char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs) > { > if (regno >= DBG_MAX_REG_NUM || regno < 0) > @@ -200,8 +202,11 @@ int kgdb_arch_handle_exception(int exception_vector, int signo, > /* > * Received continue command, disable single step > */ > - if (kernel_active_single_step()) > + if (kernel_active_single_step()) { > + kernel_cleanup_single_step(per_cpu(kgdb_ss_flags, > + raw_smp_processor_id()), linux_regs); I don't think you need the raw_ version of smp_processor_id(), do you? -Doug