| Message ID | 20200509214159.19680-4-liwei391@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: kgdb/kdb: Fix single-step debugging issues | expand |
Hi, On Sat, May 9, 2020 at 6:49 AM Wei Li <liwei391@huawei.com> 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 <cpu_ops+1288> > 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 <liwei391@huawei.com> > --- > 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
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); kernel_disable_single_step(); + } err = 0; break; @@ -221,8 +226,12 @@ int kgdb_arch_handle_exception(int exception_vector, int signo, /* * Enable single step handling */ - if (!kernel_active_single_step()) + if (!kernel_active_single_step()) { + kernel_prepare_single_step(&per_cpu(kgdb_ss_flags, + raw_smp_processor_id()), linux_regs); kernel_enable_single_step(linux_regs); + } + err = 0; break; default:
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 <cpu_ops+1288> 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 <liwei391@huawei.com> --- arch/arm64/kernel/kgdb.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)