Add documentation on using coresight during panic
and watchdog.
Signed-off-by: Linu Cherian <lcherian@marvell.com>
---
Changelog from v9:
This patch has been newly introduced.
Documentation/trace/coresight/panic.rst | 356 ++++++++++++++++++++++++
1 file changed, 356 insertions(+)
create mode 100644 Documentation/trace/coresight/panic.rst
diff --git a/Documentation/trace/coresight/panic.rst b/Documentation/trace/coresight/panic.rst
new file mode 100644
index 000000000000..3b53d91cace8
--- /dev/null
+++ b/Documentation/trace/coresight/panic.rst
@@ -0,0 +1,356 @@
+===================================================
+Using Coresight for Kernel panic and Watchdog reset
+===================================================
+
+Introduction
+------------
+This documentation is about using Linux coresight trace support to
+debug kernel panic and watchdog reset scenarios.
+
+Coresight trace during Kernel panic
+-----------------------------------
+From the coresight driver point of view, addressing the kernel panic
+situation has four main requirements.
+
+a. Support for allocation of trace buffer pages from reserved memory area.
+ Platform can advertise this using a new device tree property added to
+ relevant coresight nodes.
+
+b. Support for stopping coresight blocks at the time of panic
+
+c. Saving required metadata in the specified format
+
+d. Support for reading trace data captured at the time of panic
+
+Allocation of trace buffer pages from reserved RAM
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+A new optional device tree property "memory-region" is added to the
+ETR/ETF device nodes, that would give the base address and size of trace
+buffer.
+
+Static allocation of trace buffers would ensure that both IOMMU enabled
+and disabled cases are handled. Also, platforms that support persistent
+RAM will allow users to read trace data in the subsequent boot without
+booting the crashdump kernel.
+
+Note:
+For ETR sink devices, this reserved region will be used for both trace
+capture and trace data retrieval.
+For ETF sink devices, internal SRAM would be used for trace capture,
+and they would be synced to reserved region for retrieval.
+
+
+Disabling coresight blocks at the time of panic
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+In order to avoid the situation of losing relevant trace data after a
+kernel panic, it would be desirable to stop the coresight blocks at the
+time of panic.
+
+This can be achieved by configuring the comparator, CTI and sink
+devices as below::
+
+ Trigger on panic
+ Comparator --->External out --->CTI -->External In---->ETR/ETF stop
+
+Saving metadata at the time of kernel panic
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Coresight metadata involves all additional data that are required for a
+successful trace decode in addition to the trace data. This involves
+ETR/ETF, ETE register snapshot etc.
+
+A new optional device property "memory-region" is added to
+the ETR/ETF/ETE device nodes for this.
+
+Reading trace data captured at the time of panic
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Trace data captured at the time of panic, can be read from rebooted kernel
+or from crashdump kernel using a special device file /dev/crash_tmc_xxx.
+This device file is created only when there is a valid crashdata available.
+
+General flow of trace capture and decode incase of kernel panic
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+1. Enable source and sink on all the cores using the sysfs interface.
+ ETR sinks should have trace buffers allocated from reserved memory,
+ by selecting "resrv" buffer mode from sysfs.
+
+2. Run relevant tests.
+
+3. On a kernel panic, all coresight blocks are disabled, necessary
+ metadata is synced by kernel panic handler.
+
+ System would eventually reboot or boot a crashdump kernel.
+
+4. For platforms that supports crashdump kernel, raw trace data can be
+ dumped using the coresight sysfs interface from the crashdump kernel
+ itself. Persistent RAM is not a requirement in this case.
+
+5. For platforms that supports persistent RAM, trace data can be dumped
+ using the coresight sysfs interface in the subsequent Linux boot.
+ Crashdump kernel is not a requirement in this case. Persistent RAM
+ ensures that trace data is intact across reboot.
+
+Coresight trace during Watchdog reset
+-------------------------------------
+The main difference between addressing the watchdog reset and kernel panic
+case are below,
+
+a. Saving coresight metadata need to be taken care by the
+ SCP(system control processor) firmware in the specified format,
+ instead of kernel.
+
+b. Reserved memory region given by firmware for trace buffer and metadata
+ has to be in persistent RAM.
+ Note: This is a requirement for watchdog reset case but optional
+ in kernel panic case.
+
+Watchdog reset can be supported only on platforms that meet the above
+two requirements.
+
+Sample commands for testing a Kernel panic case with ETR sink
+-------------------------------------------------------------
+
+1. Boot Linux kernel with "crash_kexec_post_notifiers" added to the kernel
+ bootargs. This is mandatory if the user would like to read the tracedata
+ from the crashdump kernel.
+
+2. Enable the preloaded ETM configuration
+
+ #echo 1 > /sys/kernel/config/cs-syscfg/configurations/panicstop/enable
+
+3. Configure CTI using sysfs interface::
+
+ #./cti_setup.sh
+
+ #cat cti_setup.sh
+
+
+ cd /sys/bus/coresight/devices/
+
+ ap_cti_config () {
+ #ETM trig out[0] trigger to Channel 0
+ echo 0 4 > channels/trigin_attach
+ }
+
+ etf_cti_config () {
+ #ETF Flush in trigger from Channel 0
+ echo 0 1 > channels/trigout_attach
+ echo 1 > channels/trig_filter_enable
+ }
+
+ etr_cti_config () {
+ #ETR Flush in from Channel 0
+ echo 0 1 > channels/trigout_attach
+ echo 1 > channels/trig_filter_enable
+ }
+
+ ctidevs=`find . -name "cti*"`
+
+ for i in $ctidevs
+ do
+ cd $i
+
+ connection=`find . -name "ete*"`
+ if [ ! -z "$connection" ]
+ then
+ echo "AP CTI config for $i"
+ ap_cti_config
+ fi
+
+ connection=`find . -name "tmc_etf*"`
+ if [ ! -z "$connection" ]
+ then
+ echo "ETF CTI config for $i"
+ etf_cti_config
+ fi
+
+ connection=`find . -name "tmc_etr*"`
+ if [ ! -z "$connection" ]
+ then
+ echo "ETR CTI config for $i"
+ etr_cti_config
+ fi
+
+ cd ..
+ done
+
+Note: CTI connections are SOC specific and hence the above script is
+added just for reference.
+
+4. Choose reserved buffer mode for ETR buffer
+ #echo "resrv" > /sys/bus/coresight/devices/tmc_etr0/buf_mode_preferred
+
+5. Enable stop on flush trigger configuration
+ #echo 1 > /sys/bus/coresight/devices/tmc_etr0/stop_on_flush
+
+6. Start Coresight tracing on cores 1 and 2 using sysfs interface
+
+7. Run some application on core 1
+ #taskset -c 1 dd if=/dev/urandom of=/dev/null &
+
+8. Invoke kernel panic on core 2
+ #echo 1 > /proc/sys/kernel/panic
+ #taskset -c 2 echo c > /proc/sysrq-trigger
+
+9. From rebooted kernel or crashdump kernel, read crashdata
+
+ #dd if=/dev/crash_tmc_etr0 of=/trace/cstrace.bin
+
+10. Run opencsd decoder tools/scripts to generate the instruction trace.
+
+Sample instruction trace dump
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Core1 dump::
+
+ A etm4_enable_hw: ffff800008ae1dd4
+ CONTEXT EL2 etm4_enable_hw: ffff800008ae1dd4
+ I etm4_enable_hw: ffff800008ae1dd4:
+ d503201f nop
+ I etm4_enable_hw: ffff800008ae1dd8:
+ d503201f nop
+ I etm4_enable_hw: ffff800008ae1ddc:
+ d503201f nop
+ I etm4_enable_hw: ffff800008ae1de0:
+ d503201f nop
+ I etm4_enable_hw: ffff800008ae1de4:
+ d503201f nop
+ I etm4_enable_hw: ffff800008ae1de8:
+ d503233f paciasp
+ I etm4_enable_hw: ffff800008ae1dec:
+ a9be7bfd stp x29, x30, [sp, #-32]!
+ I etm4_enable_hw: ffff800008ae1df0:
+ 910003fd mov x29, sp
+ I etm4_enable_hw: ffff800008ae1df4:
+ a90153f3 stp x19, x20, [sp, #16]
+ I etm4_enable_hw: ffff800008ae1df8:
+ 2a0003f4 mov w20, w0
+ I etm4_enable_hw: ffff800008ae1dfc:
+ 900085b3 adrp x19, ffff800009b95000 <reserved_mem+0xc48>
+ I etm4_enable_hw: ffff800008ae1e00:
+ 910f4273 add x19, x19, #0x3d0
+ I etm4_enable_hw: ffff800008ae1e04:
+ f8747a60 ldr x0, [x19, x20, lsl #3]
+ E etm4_enable_hw: ffff800008ae1e08:
+ b4000140 cbz x0, ffff800008ae1e30 <etm4_starting_cpu+0x50>
+ I 149.039572921 etm4_enable_hw: ffff800008ae1e30:
+ a94153f3 ldp x19, x20, [sp, #16]
+ I 149.039572921 etm4_enable_hw: ffff800008ae1e34:
+ 52800000 mov w0, #0x0 // #0
+ I 149.039572921 etm4_enable_hw: ffff800008ae1e38:
+ a8c27bfd ldp x29, x30, [sp], #32
+
+ ..snip
+
+ 149.052324811 chacha_block_generic: ffff800008642d80:
+ 9100a3e0 add x0,
+ I 149.052324811 chacha_block_generic: ffff800008642d84:
+ b86178a2 ldr w2, [x5, x1, lsl #2]
+ I 149.052324811 chacha_block_generic: ffff800008642d88:
+ 8b010803 add x3, x0, x1, lsl #2
+ I 149.052324811 chacha_block_generic: ffff800008642d8c:
+ b85fc063 ldur w3, [x3, #-4]
+ I 149.052324811 chacha_block_generic: ffff800008642d90:
+ 0b030042 add w2, w2, w3
+ I 149.052324811 chacha_block_generic: ffff800008642d94:
+ b8217882 str w2, [x4, x1, lsl #2]
+ I 149.052324811 chacha_block_generic: ffff800008642d98:
+ 91000421 add x1, x1, #0x1
+ I 149.052324811 chacha_block_generic: ffff800008642d9c:
+ f100443f cmp x1, #0x11
+
+
+Core 2 dump::
+
+ A etm4_enable_hw: ffff800008ae1dd4
+ CONTEXT EL2 etm4_enable_hw: ffff800008ae1dd4
+ I etm4_enable_hw: ffff800008ae1dd4:
+ d503201f nop
+ I etm4_enable_hw: ffff800008ae1dd8:
+ d503201f nop
+ I etm4_enable_hw: ffff800008ae1ddc:
+ d503201f nop
+ I etm4_enable_hw: ffff800008ae1de0:
+ d503201f nop
+ I etm4_enable_hw: ffff800008ae1de4:
+ d503201f nop
+ I etm4_enable_hw: ffff800008ae1de8:
+ d503233f paciasp
+ I etm4_enable_hw: ffff800008ae1dec:
+ a9be7bfd stp x29, x30, [sp, #-32]!
+ I etm4_enable_hw: ffff800008ae1df0:
+ 910003fd mov x29, sp
+ I etm4_enable_hw: ffff800008ae1df4:
+ a90153f3 stp x19, x20, [sp, #16]
+ I etm4_enable_hw: ffff800008ae1df8:
+ 2a0003f4 mov w20, w0
+ I etm4_enable_hw: ffff800008ae1dfc:
+ 900085b3 adrp x19, ffff800009b95000 <reserved_mem+0xc48>
+ I etm4_enable_hw: ffff800008ae1e00:
+ 910f4273 add x19, x19, #0x3d0
+ I etm4_enable_hw: ffff800008ae1e04:
+ f8747a60 ldr x0, [x19, x20, lsl #3]
+ E etm4_enable_hw: ffff800008ae1e08:
+ b4000140 cbz x0, ffff800008ae1e30 <etm4_starting_cpu+0x50>
+ I 149.046243445 etm4_enable_hw: ffff800008ae1e30:
+ a94153f3 ldp x19, x20, [sp, #16]
+ I 149.046243445 etm4_enable_hw: ffff800008ae1e34:
+ 52800000 mov w0, #0x0 // #0
+ I 149.046243445 etm4_enable_hw: ffff800008ae1e38:
+ a8c27bfd ldp x29, x30, [sp], #32
+ I 149.046243445 etm4_enable_hw: ffff800008ae1e3c:
+ d50323bf autiasp
+ E 149.046243445 etm4_enable_hw: ffff800008ae1e40:
+ d65f03c0 ret
+ A ete_sysreg_write: ffff800008adfa18
+
+ ..snip
+
+ I 149.05422547 panic: ffff800008096300:
+ a90363f7 stp x23, x24, [sp, #48]
+ I 149.05422547 panic: ffff800008096304:
+ 6b00003f cmp w1, w0
+ I 149.05422547 panic: ffff800008096308:
+ 3a411804 ccmn w0, #0x1, #0x4, ne // ne = any
+ N 149.05422547 panic: ffff80000809630c:
+ 540001e0 b.eq ffff800008096348 <panic+0xe0> // b.none
+ I 149.05422547 panic: ffff800008096310:
+ f90023f9 str x25, [sp, #64]
+ E 149.05422547 panic: ffff800008096314:
+ 97fe44ef bl ffff8000080276d0 <panic_smp_self_stop>
+ A panic: ffff80000809634c
+ I 149.05422547 panic: ffff80000809634c:
+ 910102d5 add x21, x22, #0x40
+ I 149.05422547 panic: ffff800008096350:
+ 52800020 mov w0, #0x1 // #1
+ E 149.05422547 panic: ffff800008096354:
+ 94166b8b bl ffff800008631180 <bust_spinlocks>
+ N 149.054225518 bust_spinlocks: ffff800008631180:
+ 340000c0 cbz w0, ffff800008631198 <bust_spinlocks+0x18>
+ I 149.054225518 bust_spinlocks: ffff800008631184:
+ f000a321 adrp x1, ffff800009a98000 <pbufs.0+0xbb8>
+ I 149.054225518 bust_spinlocks: ffff800008631188:
+ b9405c20 ldr w0, [x1, #92]
+ I 149.054225518 bust_spinlocks: ffff80000863118c:
+ 11000400 add w0, w0, #0x1
+ I 149.054225518 bust_spinlocks: ffff800008631190:
+ b9005c20 str w0, [x1, #92]
+ E 149.054225518 bust_spinlocks: ffff800008631194:
+ d65f03c0 ret
+ A panic: ffff800008096358
+
+Perf based testing
+------------------
+
+Starting perf session
+~~~~~~~~~~~~~~~~~~~~~
+ETF:
+perf record -e cs_etm/panicstop,@tmc_etf1/ -C 1
+perf record -e cs_etm/panicstop,@tmc_etf2/ -C 2
+
+ETR:
+perf record -e cs_etm/panicstop,@tmc_etr0/ -C 1,2
+
+Reading trace data after panic
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Same sysfs based method explained above can be used to retrieve and
+decode the trace data after the reboot on kernel panic.
--
2.34.1Hi Linu
On 16/09/2024 11:34, Linu Cherian wrote:
> Add documentation on using coresight during panic
> and watchdog.
Thank you so much for the documentation, this will be quite useful !
Some minor comments below.
>
> Signed-off-by: Linu Cherian <lcherian@marvell.com>
> ---
> Changelog from v9:
> This patch has been newly introduced.
>
> Documentation/trace/coresight/panic.rst | 356 ++++++++++++++++++++++++
> 1 file changed, 356 insertions(+)
> create mode 100644 Documentation/trace/coresight/panic.rst
>
> diff --git a/Documentation/trace/coresight/panic.rst b/Documentation/trace/coresight/panic.rst
> new file mode 100644
> index 000000000000..3b53d91cace8
> --- /dev/null
> +++ b/Documentation/trace/coresight/panic.rst
> @@ -0,0 +1,356 @@
> +===================================================
> +Using Coresight for Kernel panic and Watchdog reset
> +===================================================
> +
> +Introduction
> +------------
> +This documentation is about using Linux coresight trace support to
> +debug kernel panic and watchdog reset scenarios.
> +
> +Coresight trace during Kernel panic
> +-----------------------------------
> +From the coresight driver point of view, addressing the kernel panic
> +situation has four main requirements.
> +
> +a. Support for allocation of trace buffer pages from reserved memory area.
> + Platform can advertise this using a new device tree property added to
> + relevant coresight nodes.
> +
> +b. Support for stopping coresight blocks at the time of panic
> +
> +c. Saving required metadata in the specified format
> +
> +d. Support for reading trace data captured at the time of panic
> +
> +Allocation of trace buffer pages from reserved RAM
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +A new optional device tree property "memory-region" is added to the
> +ETR/ETF device nodes, that would give the base address and size of trace
ETR/ETF => CoreSight TMC
> +buffer.
> +
> +Static allocation of trace buffers would ensure that both IOMMU enabled
> +and disabled cases are handled. Also, platforms that support persistent
> +RAM will allow users to read trace data in the subsequent boot without
> +booting the crashdump kernel.
> +
> +Note:
> +For ETR sink devices, this reserved region will be used for both trace
> +capture and trace data retrieval.
> +For ETF sink devices, internal SRAM would be used for trace capture,
> +and they would be synced to reserved region for retrieval.
> +
> +
> +Disabling coresight blocks at the time of panic
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +In order to avoid the situation of losing relevant trace data after a
> +kernel panic, it would be desirable to stop the coresight blocks at the
> +time of panic.
> +
> +This can be achieved by configuring the comparator, CTI and sink
> +devices as below::
> +
> + Trigger on panic
> + Comparator --->External out --->CTI -->External In---->ETR/ETF stop
> +
> +Saving metadata at the time of kernel panic
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +Coresight metadata involves all additional data that are required for a
> +successful trace decode in addition to the trace data. This involves
> +ETR/ETF, ETE register snapshot etc.
s/ETE/ETB ?
> +
> +A new optional device property "memory-region" is added to
> +the ETR/ETF/ETE device nodes for this.
same here ^^
> +
> +Reading trace data captured at the time of panic
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +Trace data captured at the time of panic, can be read from rebooted kernel
> +or from crashdump kernel using a special device file /dev/crash_tmc_xxx.
> +This device file is created only when there is a valid crashdata available.
> +
> +General flow of trace capture and decode incase of kernel panic
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +1. Enable source and sink on all the cores using the sysfs interface.
> + ETR sinks should have trace buffers allocated from reserved memory,
> + by selecting "resrv" buffer mode from sysfs.
> +
> +2. Run relevant tests.
> +
> +3. On a kernel panic, all coresight blocks are disabled, necessary
> + metadata is synced by kernel panic handler.
> +
> + System would eventually reboot or boot a crashdump kernel.
> +
> +4. For platforms that supports crashdump kernel, raw trace data can be
> + dumped using the coresight sysfs interface from the crashdump kernel
> + itself. Persistent RAM is not a requirement in this case.
> +
> +5. For platforms that supports persistent RAM, trace data can be dumped
> + using the coresight sysfs interface in the subsequent Linux boot.
> + Crashdump kernel is not a requirement in this case. Persistent RAM
> + ensures that trace data is intact across reboot.
> +
> +Coresight trace during Watchdog reset
> +-------------------------------------
> +The main difference between addressing the watchdog reset and kernel panic
> +case are below,
> +
> +a. Saving coresight metadata need to be taken care by the
> + SCP(system control processor) firmware in the specified format,
> + instead of kernel.
> +
> +b. Reserved memory region given by firmware for trace buffer and metadata
> + has to be in persistent RAM.
> + Note: This is a requirement for watchdog reset case but optional
> + in kernel panic case.
> +
> +Watchdog reset can be supported only on platforms that meet the above
> +two requirements.
> +
> +Sample commands for testing a Kernel panic case with ETR sink
> +-------------------------------------------------------------
> +
> +1. Boot Linux kernel with "crash_kexec_post_notifiers" added to the kernel
> + bootargs. This is mandatory if the user would like to read the tracedata
> + from the crashdump kernel.
> +
> +2. Enable the preloaded ETM configuration
> +
> + #echo 1 > /sys/kernel/config/cs-syscfg/configurations/panicstop/enable
> +
> +3. Configure CTI using sysfs interface::
> +
> + #./cti_setup.sh
> +
> + #cat cti_setup.sh
> +
> +
> + cd /sys/bus/coresight/devices/
> +
> + ap_cti_config () {
> + #ETM trig out[0] trigger to Channel 0
> + echo 0 4 > channels/trigin_attach
> + }
> +
> + etf_cti_config () {
> + #ETF Flush in trigger from Channel 0
> + echo 0 1 > channels/trigout_attach
> + echo 1 > channels/trig_filter_enable
> + }
> +
> + etr_cti_config () {
> + #ETR Flush in from Channel 0
> + echo 0 1 > channels/trigout_attach
> + echo 1 > channels/trig_filter_enable
> + }
> +
> + ctidevs=`find . -name "cti*"`
> +
> + for i in $ctidevs
> + do
> + cd $i
> +
> + connection=`find . -name "ete*"`
minor nit: this could be ete or etm
> + if [ ! -z "$connection" ]
> + then
> + echo "AP CTI config for $i"
> + ap_cti_config
> + fi
> +
> + connection=`find . -name "tmc_etf*"`
> + if [ ! -z "$connection" ]
> + then
> + echo "ETF CTI config for $i"
> + etf_cti_config
> + fi
> +
> + connection=`find . -name "tmc_etr*"`
> + if [ ! -z "$connection" ]
> + then
> + echo "ETR CTI config for $i"
> + etr_cti_config
> + fi
> +
> + cd ..
> + done
> +
> +Note: CTI connections are SOC specific and hence the above script is
> +added just for reference.
> +
> +4. Choose reserved buffer mode for ETR buffer
> + #echo "resrv" > /sys/bus/coresight/devices/tmc_etr0/buf_mode_preferred
> +
> +5. Enable stop on flush trigger configuration
> + #echo 1 > /sys/bus/coresight/devices/tmc_etr0/stop_on_flush
> +
> +6. Start Coresight tracing on cores 1 and 2 using sysfs interface
> +
> +7. Run some application on core 1
> + #taskset -c 1 dd if=/dev/urandom of=/dev/null &
> +
> +8. Invoke kernel panic on core 2
> + #echo 1 > /proc/sys/kernel/panic
> + #taskset -c 2 echo c > /proc/sysrq-trigger
> +
> +9. From rebooted kernel or crashdump kernel, read crashdata
> +
> + #dd if=/dev/crash_tmc_etr0 of=/trace/cstrace.bin
> +
> +10. Run opencsd decoder tools/scripts to generate the instruction trace.
> +
> +Sample instruction trace dump
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +Core1 dump::
> +
> + A etm4_enable_hw: ffff800008ae1dd4
> + CONTEXT EL2 etm4_enable_hw: ffff800008ae1dd4
> + I etm4_enable_hw: ffff800008ae1dd4:
> + d503201f nop
> + I etm4_enable_hw: ffff800008ae1dd8:
> + d503201f nop
> + I etm4_enable_hw: ffff800008ae1ddc:
> + d503201f nop
> + I etm4_enable_hw: ffff800008ae1de0:
> + d503201f nop
> + I etm4_enable_hw: ffff800008ae1de4:
> + d503201f nop
> + I etm4_enable_hw: ffff800008ae1de8:
> + d503233f paciasp
> + I etm4_enable_hw: ffff800008ae1dec:
> + a9be7bfd stp x29, x30, [sp, #-32]!
> + I etm4_enable_hw: ffff800008ae1df0:
> + 910003fd mov x29, sp
> + I etm4_enable_hw: ffff800008ae1df4:
> + a90153f3 stp x19, x20, [sp, #16]
> + I etm4_enable_hw: ffff800008ae1df8:
> + 2a0003f4 mov w20, w0
> + I etm4_enable_hw: ffff800008ae1dfc:
> + 900085b3 adrp x19, ffff800009b95000 <reserved_mem+0xc48>
> + I etm4_enable_hw: ffff800008ae1e00:
> + 910f4273 add x19, x19, #0x3d0
> + I etm4_enable_hw: ffff800008ae1e04:
> + f8747a60 ldr x0, [x19, x20, lsl #3]
> + E etm4_enable_hw: ffff800008ae1e08:
> + b4000140 cbz x0, ffff800008ae1e30 <etm4_starting_cpu+0x50>
> + I 149.039572921 etm4_enable_hw: ffff800008ae1e30:
> + a94153f3 ldp x19, x20, [sp, #16]
> + I 149.039572921 etm4_enable_hw: ffff800008ae1e34:
> + 52800000 mov w0, #0x0 // #0
> + I 149.039572921 etm4_enable_hw: ffff800008ae1e38:
> + a8c27bfd ldp x29, x30, [sp], #32
> +
> + ..snip
> +
> + 149.052324811 chacha_block_generic: ffff800008642d80:
> + 9100a3e0 add x0,
> + I 149.052324811 chacha_block_generic: ffff800008642d84:
> + b86178a2 ldr w2, [x5, x1, lsl #2]
> + I 149.052324811 chacha_block_generic: ffff800008642d88:
> + 8b010803 add x3, x0, x1, lsl #2
> + I 149.052324811 chacha_block_generic: ffff800008642d8c:
> + b85fc063 ldur w3, [x3, #-4]
> + I 149.052324811 chacha_block_generic: ffff800008642d90:
> + 0b030042 add w2, w2, w3
> + I 149.052324811 chacha_block_generic: ffff800008642d94:
> + b8217882 str w2, [x4, x1, lsl #2]
> + I 149.052324811 chacha_block_generic: ffff800008642d98:
> + 91000421 add x1, x1, #0x1
> + I 149.052324811 chacha_block_generic: ffff800008642d9c:
> + f100443f cmp x1, #0x11
> +
> +
> +Core 2 dump::
> +
> + A etm4_enable_hw: ffff800008ae1dd4
> + CONTEXT EL2 etm4_enable_hw: ffff800008ae1dd4
> + I etm4_enable_hw: ffff800008ae1dd4:
> + d503201f nop
> + I etm4_enable_hw: ffff800008ae1dd8:
> + d503201f nop
> + I etm4_enable_hw: ffff800008ae1ddc:
> + d503201f nop
> + I etm4_enable_hw: ffff800008ae1de0:
> + d503201f nop
> + I etm4_enable_hw: ffff800008ae1de4:
> + d503201f nop
> + I etm4_enable_hw: ffff800008ae1de8:
> + d503233f paciasp
> + I etm4_enable_hw: ffff800008ae1dec:
> + a9be7bfd stp x29, x30, [sp, #-32]!
> + I etm4_enable_hw: ffff800008ae1df0:
> + 910003fd mov x29, sp
> + I etm4_enable_hw: ffff800008ae1df4:
> + a90153f3 stp x19, x20, [sp, #16]
> + I etm4_enable_hw: ffff800008ae1df8:
> + 2a0003f4 mov w20, w0
> + I etm4_enable_hw: ffff800008ae1dfc:
> + 900085b3 adrp x19, ffff800009b95000 <reserved_mem+0xc48>
> + I etm4_enable_hw: ffff800008ae1e00:
> + 910f4273 add x19, x19, #0x3d0
> + I etm4_enable_hw: ffff800008ae1e04:
> + f8747a60 ldr x0, [x19, x20, lsl #3]
> + E etm4_enable_hw: ffff800008ae1e08:
> + b4000140 cbz x0, ffff800008ae1e30 <etm4_starting_cpu+0x50>
> + I 149.046243445 etm4_enable_hw: ffff800008ae1e30:
> + a94153f3 ldp x19, x20, [sp, #16]
> + I 149.046243445 etm4_enable_hw: ffff800008ae1e34:
> + 52800000 mov w0, #0x0 // #0
> + I 149.046243445 etm4_enable_hw: ffff800008ae1e38:
> + a8c27bfd ldp x29, x30, [sp], #32
> + I 149.046243445 etm4_enable_hw: ffff800008ae1e3c:
> + d50323bf autiasp
> + E 149.046243445 etm4_enable_hw: ffff800008ae1e40:
> + d65f03c0 ret
> + A ete_sysreg_write: ffff800008adfa18
> +
> + ..snip
> +
> + I 149.05422547 panic: ffff800008096300:
> + a90363f7 stp x23, x24, [sp, #48]
> + I 149.05422547 panic: ffff800008096304:
> + 6b00003f cmp w1, w0
> + I 149.05422547 panic: ffff800008096308:
> + 3a411804 ccmn w0, #0x1, #0x4, ne // ne = any
> + N 149.05422547 panic: ffff80000809630c:
> + 540001e0 b.eq ffff800008096348 <panic+0xe0> // b.none
> + I 149.05422547 panic: ffff800008096310:
> + f90023f9 str x25, [sp, #64]
> + E 149.05422547 panic: ffff800008096314:
> + 97fe44ef bl ffff8000080276d0 <panic_smp_self_stop>
> + A panic: ffff80000809634c
> + I 149.05422547 panic: ffff80000809634c:
> + 910102d5 add x21, x22, #0x40
> + I 149.05422547 panic: ffff800008096350:
> + 52800020 mov w0, #0x1 // #1
> + E 149.05422547 panic: ffff800008096354:
> + 94166b8b bl ffff800008631180 <bust_spinlocks>
> + N 149.054225518 bust_spinlocks: ffff800008631180:
> + 340000c0 cbz w0, ffff800008631198 <bust_spinlocks+0x18>
> + I 149.054225518 bust_spinlocks: ffff800008631184:
> + f000a321 adrp x1, ffff800009a98000 <pbufs.0+0xbb8>
> + I 149.054225518 bust_spinlocks: ffff800008631188:
> + b9405c20 ldr w0, [x1, #92]
> + I 149.054225518 bust_spinlocks: ffff80000863118c:
> + 11000400 add w0, w0, #0x1
> + I 149.054225518 bust_spinlocks: ffff800008631190:
> + b9005c20 str w0, [x1, #92]
> + E 149.054225518 bust_spinlocks: ffff800008631194:
> + d65f03c0 ret
> + A panic: ffff800008096358
> +
> +Perf based testing
> +------------------
> +
> +Starting perf session
> +~~~~~~~~~~~~~~~~~~~~~
> +ETF:
> +perf record -e cs_etm/panicstop,@tmc_etf1/ -C 1
> +perf record -e cs_etm/panicstop,@tmc_etf2/ -C 2
> +
> +ETR:
> +perf record -e cs_etm/panicstop,@tmc_etr0/ -C 1,2
> +
> +Reading trace data after panic
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +Same sysfs based method explained above can be used to retrieve and
> +decode the trace data after the reboot on kernel panic.
On 2024-10-03 at 19:13:10, Suzuki K Poulose (suzuki.poulose@arm.com) wrote:
> Hi Linu
>
> On 16/09/2024 11:34, Linu Cherian wrote:
> > Add documentation on using coresight during panic
> > and watchdog.
>
> Thank you so much for the documentation, this will be quite useful !
>
> Some minor comments below.
>
> >
> > Signed-off-by: Linu Cherian <lcherian@marvell.com>
> > ---
> > Changelog from v9:
> > This patch has been newly introduced.
> >
> > Documentation/trace/coresight/panic.rst | 356 ++++++++++++++++++++++++
> > 1 file changed, 356 insertions(+)
> > create mode 100644 Documentation/trace/coresight/panic.rst
> >
> > diff --git a/Documentation/trace/coresight/panic.rst b/Documentation/trace/coresight/panic.rst
> > new file mode 100644
> > index 000000000000..3b53d91cace8
> > --- /dev/null
> > +++ b/Documentation/trace/coresight/panic.rst
> > @@ -0,0 +1,356 @@
> > +===================================================
> > +Using Coresight for Kernel panic and Watchdog reset
> > +===================================================
> > +
> > +Introduction
> > +------------
> > +This documentation is about using Linux coresight trace support to
> > +debug kernel panic and watchdog reset scenarios.
> > +
> > +Coresight trace during Kernel panic
> > +-----------------------------------
> > +From the coresight driver point of view, addressing the kernel panic
> > +situation has four main requirements.
> > +
> > +a. Support for allocation of trace buffer pages from reserved memory area.
> > + Platform can advertise this using a new device tree property added to
> > + relevant coresight nodes.
> > +
> > +b. Support for stopping coresight blocks at the time of panic
> > +
> > +c. Saving required metadata in the specified format
> > +
> > +d. Support for reading trace data captured at the time of panic
> > +
> > +Allocation of trace buffer pages from reserved RAM
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +A new optional device tree property "memory-region" is added to the
> > +ETR/ETF device nodes, that would give the base address and size of trace
>
> ETR/ETF => CoreSight TMC
Ack.
>
> > +buffer.
> > +
> > +Static allocation of trace buffers would ensure that both IOMMU enabled
> > +and disabled cases are handled. Also, platforms that support persistent
> > +RAM will allow users to read trace data in the subsequent boot without
> > +booting the crashdump kernel.
> > +
> > +Note:
> > +For ETR sink devices, this reserved region will be used for both trace
> > +capture and trace data retrieval.
> > +For ETF sink devices, internal SRAM would be used for trace capture,
> > +and they would be synced to reserved region for retrieval.
> > +
> > +
> > +Disabling coresight blocks at the time of panic
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +In order to avoid the situation of losing relevant trace data after a
> > +kernel panic, it would be desirable to stop the coresight blocks at the
> > +time of panic.
> > +
> > +This can be achieved by configuring the comparator, CTI and sink
> > +devices as below::
> > +
> > + Trigger on panic
> > + Comparator --->External out --->CTI -->External In---->ETR/ETF stop
> > +
> > +Saving metadata at the time of kernel panic
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +Coresight metadata involves all additional data that are required for a
> > +successful trace decode in addition to the trace data. This involves
> > +ETR/ETF, ETE register snapshot etc.
>
> s/ETE/ETB ?
Ack.
>
> > +
> > +A new optional device property "memory-region" is added to
> > +the ETR/ETF/ETE device nodes for this.
>
> same here ^^
Ack.
>
>
> > +
> > +Reading trace data captured at the time of panic
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +Trace data captured at the time of panic, can be read from rebooted kernel
> > +or from crashdump kernel using a special device file /dev/crash_tmc_xxx.
> > +This device file is created only when there is a valid crashdata available.
> > +
> > +General flow of trace capture and decode incase of kernel panic
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +1. Enable source and sink on all the cores using the sysfs interface.
> > + ETR sinks should have trace buffers allocated from reserved memory,
> > + by selecting "resrv" buffer mode from sysfs.
> > +
> > +2. Run relevant tests.
> > +
> > +3. On a kernel panic, all coresight blocks are disabled, necessary
> > + metadata is synced by kernel panic handler.
> > +
> > + System would eventually reboot or boot a crashdump kernel.
> > +
> > +4. For platforms that supports crashdump kernel, raw trace data can be
> > + dumped using the coresight sysfs interface from the crashdump kernel
> > + itself. Persistent RAM is not a requirement in this case.
> > +
> > +5. For platforms that supports persistent RAM, trace data can be dumped
> > + using the coresight sysfs interface in the subsequent Linux boot.
> > + Crashdump kernel is not a requirement in this case. Persistent RAM
> > + ensures that trace data is intact across reboot.
> > +
> > +Coresight trace during Watchdog reset
> > +-------------------------------------
> > +The main difference between addressing the watchdog reset and kernel panic
> > +case are below,
> > +
> > +a. Saving coresight metadata need to be taken care by the
> > + SCP(system control processor) firmware in the specified format,
> > + instead of kernel.
> > +
> > +b. Reserved memory region given by firmware for trace buffer and metadata
> > + has to be in persistent RAM.
> > + Note: This is a requirement for watchdog reset case but optional
> > + in kernel panic case.
> > +
> > +Watchdog reset can be supported only on platforms that meet the above
> > +two requirements.
> > +
> > +Sample commands for testing a Kernel panic case with ETR sink
> > +-------------------------------------------------------------
> > +
> > +1. Boot Linux kernel with "crash_kexec_post_notifiers" added to the kernel
> > + bootargs. This is mandatory if the user would like to read the tracedata
> > + from the crashdump kernel.
> > +
> > +2. Enable the preloaded ETM configuration
> > +
> > + #echo 1 > /sys/kernel/config/cs-syscfg/configurations/panicstop/enable
> > +
> > +3. Configure CTI using sysfs interface::
> > +
> > + #./cti_setup.sh
> > +
> > + #cat cti_setup.sh
> > +
> > +
> > + cd /sys/bus/coresight/devices/
> > +
> > + ap_cti_config () {
> > + #ETM trig out[0] trigger to Channel 0
> > + echo 0 4 > channels/trigin_attach
> > + }
> > +
> > + etf_cti_config () {
> > + #ETF Flush in trigger from Channel 0
> > + echo 0 1 > channels/trigout_attach
> > + echo 1 > channels/trig_filter_enable
> > + }
> > +
> > + etr_cti_config () {
> > + #ETR Flush in from Channel 0
> > + echo 0 1 > channels/trigout_attach
> > + echo 1 > channels/trig_filter_enable
> > + }
> > +
> > + ctidevs=`find . -name "cti*"`
> > +
> > + for i in $ctidevs
> > + do
> > + cd $i
> > +
> > + connection=`find . -name "ete*"`
>
> minor nit: this could be ete or etm
Ack.
>
> > + if [ ! -z "$connection" ]
> > + then
> > + echo "AP CTI config for $i"
> > + ap_cti_config
> > + fi
> > +
> > + connection=`find . -name "tmc_etf*"`
> > + if [ ! -z "$connection" ]
> > + then
> > + echo "ETF CTI config for $i"
> > + etf_cti_config
> > + fi
> > +
> > + connection=`find . -name "tmc_etr*"`
> > + if [ ! -z "$connection" ]
> > + then
> > + echo "ETR CTI config for $i"
> > + etr_cti_config
> > + fi
> > +
> > + cd ..
> > + done
> > +
> > +Note: CTI connections are SOC specific and hence the above script is
> > +added just for reference.
> > +
> > +4. Choose reserved buffer mode for ETR buffer
> > + #echo "resrv" > /sys/bus/coresight/devices/tmc_etr0/buf_mode_preferred
> > +
> > +5. Enable stop on flush trigger configuration
> > + #echo 1 > /sys/bus/coresight/devices/tmc_etr0/stop_on_flush
> > +
> > +6. Start Coresight tracing on cores 1 and 2 using sysfs interface
> > +
> > +7. Run some application on core 1
> > + #taskset -c 1 dd if=/dev/urandom of=/dev/null &
> > +
> > +8. Invoke kernel panic on core 2
> > + #echo 1 > /proc/sys/kernel/panic
> > + #taskset -c 2 echo c > /proc/sysrq-trigger
> > +
> > +9. From rebooted kernel or crashdump kernel, read crashdata
> > +
> > + #dd if=/dev/crash_tmc_etr0 of=/trace/cstrace.bin
> > +
> > +10. Run opencsd decoder tools/scripts to generate the instruction trace.
> > +
> > +Sample instruction trace dump
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +
> > +Core1 dump::
> > +
> > + A etm4_enable_hw: ffff800008ae1dd4
> > + CONTEXT EL2 etm4_enable_hw: ffff800008ae1dd4
> > + I etm4_enable_hw: ffff800008ae1dd4:
> > + d503201f nop
> > + I etm4_enable_hw: ffff800008ae1dd8:
> > + d503201f nop
> > + I etm4_enable_hw: ffff800008ae1ddc:
> > + d503201f nop
> > + I etm4_enable_hw: ffff800008ae1de0:
> > + d503201f nop
> > + I etm4_enable_hw: ffff800008ae1de4:
> > + d503201f nop
> > + I etm4_enable_hw: ffff800008ae1de8:
> > + d503233f paciasp
> > + I etm4_enable_hw: ffff800008ae1dec:
> > + a9be7bfd stp x29, x30, [sp, #-32]!
> > + I etm4_enable_hw: ffff800008ae1df0:
> > + 910003fd mov x29, sp
> > + I etm4_enable_hw: ffff800008ae1df4:
> > + a90153f3 stp x19, x20, [sp, #16]
> > + I etm4_enable_hw: ffff800008ae1df8:
> > + 2a0003f4 mov w20, w0
> > + I etm4_enable_hw: ffff800008ae1dfc:
> > + 900085b3 adrp x19, ffff800009b95000 <reserved_mem+0xc48>
> > + I etm4_enable_hw: ffff800008ae1e00:
> > + 910f4273 add x19, x19, #0x3d0
> > + I etm4_enable_hw: ffff800008ae1e04:
> > + f8747a60 ldr x0, [x19, x20, lsl #3]
> > + E etm4_enable_hw: ffff800008ae1e08:
> > + b4000140 cbz x0, ffff800008ae1e30 <etm4_starting_cpu+0x50>
> > + I 149.039572921 etm4_enable_hw: ffff800008ae1e30:
> > + a94153f3 ldp x19, x20, [sp, #16]
> > + I 149.039572921 etm4_enable_hw: ffff800008ae1e34:
> > + 52800000 mov w0, #0x0 // #0
> > + I 149.039572921 etm4_enable_hw: ffff800008ae1e38:
> > + a8c27bfd ldp x29, x30, [sp], #32
> > +
> > + ..snip
> > +
> > + 149.052324811 chacha_block_generic: ffff800008642d80:
> > + 9100a3e0 add x0,
> > + I 149.052324811 chacha_block_generic: ffff800008642d84:
> > + b86178a2 ldr w2, [x5, x1, lsl #2]
> > + I 149.052324811 chacha_block_generic: ffff800008642d88:
> > + 8b010803 add x3, x0, x1, lsl #2
> > + I 149.052324811 chacha_block_generic: ffff800008642d8c:
> > + b85fc063 ldur w3, [x3, #-4]
> > + I 149.052324811 chacha_block_generic: ffff800008642d90:
> > + 0b030042 add w2, w2, w3
> > + I 149.052324811 chacha_block_generic: ffff800008642d94:
> > + b8217882 str w2, [x4, x1, lsl #2]
> > + I 149.052324811 chacha_block_generic: ffff800008642d98:
> > + 91000421 add x1, x1, #0x1
> > + I 149.052324811 chacha_block_generic: ffff800008642d9c:
> > + f100443f cmp x1, #0x11
> > +
> > +
> > +Core 2 dump::
> > +
> > + A etm4_enable_hw: ffff800008ae1dd4
> > + CONTEXT EL2 etm4_enable_hw: ffff800008ae1dd4
> > + I etm4_enable_hw: ffff800008ae1dd4:
> > + d503201f nop
> > + I etm4_enable_hw: ffff800008ae1dd8:
> > + d503201f nop
> > + I etm4_enable_hw: ffff800008ae1ddc:
> > + d503201f nop
> > + I etm4_enable_hw: ffff800008ae1de0:
> > + d503201f nop
> > + I etm4_enable_hw: ffff800008ae1de4:
> > + d503201f nop
> > + I etm4_enable_hw: ffff800008ae1de8:
> > + d503233f paciasp
> > + I etm4_enable_hw: ffff800008ae1dec:
> > + a9be7bfd stp x29, x30, [sp, #-32]!
> > + I etm4_enable_hw: ffff800008ae1df0:
> > + 910003fd mov x29, sp
> > + I etm4_enable_hw: ffff800008ae1df4:
> > + a90153f3 stp x19, x20, [sp, #16]
> > + I etm4_enable_hw: ffff800008ae1df8:
> > + 2a0003f4 mov w20, w0
> > + I etm4_enable_hw: ffff800008ae1dfc:
> > + 900085b3 adrp x19, ffff800009b95000 <reserved_mem+0xc48>
> > + I etm4_enable_hw: ffff800008ae1e00:
> > + 910f4273 add x19, x19, #0x3d0
> > + I etm4_enable_hw: ffff800008ae1e04:
> > + f8747a60 ldr x0, [x19, x20, lsl #3]
> > + E etm4_enable_hw: ffff800008ae1e08:
> > + b4000140 cbz x0, ffff800008ae1e30 <etm4_starting_cpu+0x50>
> > + I 149.046243445 etm4_enable_hw: ffff800008ae1e30:
> > + a94153f3 ldp x19, x20, [sp, #16]
> > + I 149.046243445 etm4_enable_hw: ffff800008ae1e34:
> > + 52800000 mov w0, #0x0 // #0
> > + I 149.046243445 etm4_enable_hw: ffff800008ae1e38:
> > + a8c27bfd ldp x29, x30, [sp], #32
> > + I 149.046243445 etm4_enable_hw: ffff800008ae1e3c:
> > + d50323bf autiasp
> > + E 149.046243445 etm4_enable_hw: ffff800008ae1e40:
> > + d65f03c0 ret
> > + A ete_sysreg_write: ffff800008adfa18
> > +
> > + ..snip
> > +
> > + I 149.05422547 panic: ffff800008096300:
> > + a90363f7 stp x23, x24, [sp, #48]
> > + I 149.05422547 panic: ffff800008096304:
> > + 6b00003f cmp w1, w0
> > + I 149.05422547 panic: ffff800008096308:
> > + 3a411804 ccmn w0, #0x1, #0x4, ne // ne = any
> > + N 149.05422547 panic: ffff80000809630c:
> > + 540001e0 b.eq ffff800008096348 <panic+0xe0> // b.none
> > + I 149.05422547 panic: ffff800008096310:
> > + f90023f9 str x25, [sp, #64]
> > + E 149.05422547 panic: ffff800008096314:
> > + 97fe44ef bl ffff8000080276d0 <panic_smp_self_stop>
> > + A panic: ffff80000809634c
> > + I 149.05422547 panic: ffff80000809634c:
> > + 910102d5 add x21, x22, #0x40
> > + I 149.05422547 panic: ffff800008096350:
> > + 52800020 mov w0, #0x1 // #1
> > + E 149.05422547 panic: ffff800008096354:
> > + 94166b8b bl ffff800008631180 <bust_spinlocks>
> > + N 149.054225518 bust_spinlocks: ffff800008631180:
> > + 340000c0 cbz w0, ffff800008631198 <bust_spinlocks+0x18>
> > + I 149.054225518 bust_spinlocks: ffff800008631184:
> > + f000a321 adrp x1, ffff800009a98000 <pbufs.0+0xbb8>
> > + I 149.054225518 bust_spinlocks: ffff800008631188:
> > + b9405c20 ldr w0, [x1, #92]
> > + I 149.054225518 bust_spinlocks: ffff80000863118c:
> > + 11000400 add w0, w0, #0x1
> > + I 149.054225518 bust_spinlocks: ffff800008631190:
> > + b9005c20 str w0, [x1, #92]
> > + E 149.054225518 bust_spinlocks: ffff800008631194:
> > + d65f03c0 ret
> > + A panic: ffff800008096358
> > +
> > +Perf based testing
> > +------------------
> > +
> > +Starting perf session
> > +~~~~~~~~~~~~~~~~~~~~~
> > +ETF:
> > +perf record -e cs_etm/panicstop,@tmc_etf1/ -C 1
> > +perf record -e cs_etm/panicstop,@tmc_etf2/ -C 2
> > +
> > +ETR:
> > +perf record -e cs_etm/panicstop,@tmc_etr0/ -C 1,2
> > +
> > +Reading trace data after panic
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +Same sysfs based method explained above can be used to retrieve and
> > +decode the trace data after the reboot on kernel panic.
>
>
Linu Cherian
On Mon, Sep 16, 2024 at 04:04:37PM +0530, Linu Cherian wrote:
> +3. On a kernel panic, all coresight blocks are disabled, necessary
> + metadata is synced by kernel panic handler.
"... and necessary metadata ..."
> +
> + System would eventually reboot or boot a crashdump kernel.
> +
> +4. For platforms that supports crashdump kernel, raw trace data can be
> + dumped using the coresight sysfs interface from the crashdump kernel
> + itself. Persistent RAM is not a requirement in this case.
> +
> +5. For platforms that supports persistent RAM, trace data can be dumped
> + using the coresight sysfs interface in the subsequent Linux boot.
> + Crashdump kernel is not a requirement in this case. Persistent RAM
> + ensures that trace data is intact across reboot.
> +
> +Coresight trace during Watchdog reset
> +-------------------------------------
> +The main difference between addressing the watchdog reset and kernel panic
> +case are below,
"... are:"
> +Sample commands for testing a Kernel panic case with ETR sink
> +-------------------------------------------------------------
> +
> +1. Boot Linux kernel with "crash_kexec_post_notifiers" added to the kernel
> + bootargs. This is mandatory if the user would like to read the tracedata
> + from the crashdump kernel.
> +
> +2. Enable the preloaded ETM configuration
> +
> + #echo 1 > /sys/kernel/config/cs-syscfg/configurations/panicstop/enable
> +
> +3. Configure CTI using sysfs interface::
> +
> + #./cti_setup.sh
> +
> + #cat cti_setup.sh
> +
> +
> + cd /sys/bus/coresight/devices/
> +
> + ap_cti_config () {
> + #ETM trig out[0] trigger to Channel 0
> + echo 0 4 > channels/trigin_attach
> + }
> +
> + etf_cti_config () {
> + #ETF Flush in trigger from Channel 0
> + echo 0 1 > channels/trigout_attach
> + echo 1 > channels/trig_filter_enable
> + }
> +
> + etr_cti_config () {
> + #ETR Flush in from Channel 0
> + echo 0 1 > channels/trigout_attach
> + echo 1 > channels/trig_filter_enable
> + }
> +
> + ctidevs=`find . -name "cti*"`
> +
> + for i in $ctidevs
> + do
> + cd $i
> +
> + connection=`find . -name "ete*"`
> + if [ ! -z "$connection" ]
> + then
> + echo "AP CTI config for $i"
> + ap_cti_config
> + fi
> +
> + connection=`find . -name "tmc_etf*"`
> + if [ ! -z "$connection" ]
> + then
> + echo "ETF CTI config for $i"
> + etf_cti_config
> + fi
> +
> + connection=`find . -name "tmc_etr*"`
> + if [ ! -z "$connection" ]
> + then
> + echo "ETR CTI config for $i"
> + etr_cti_config
> + fi
> +
> + cd ..
> + done
> +
> +Note: CTI connections are SOC specific and hence the above script is
> +added just for reference.
> +
> +4. Choose reserved buffer mode for ETR buffer
> + #echo "resrv" > /sys/bus/coresight/devices/tmc_etr0/buf_mode_preferred
> +
> +5. Enable stop on flush trigger configuration
> + #echo 1 > /sys/bus/coresight/devices/tmc_etr0/stop_on_flush
> +
> +6. Start Coresight tracing on cores 1 and 2 using sysfs interface
> +
> +7. Run some application on core 1
> + #taskset -c 1 dd if=/dev/urandom of=/dev/null &
> +
> +8. Invoke kernel panic on core 2
> + #echo 1 > /proc/sys/kernel/panic
> + #taskset -c 2 echo c > /proc/sysrq-trigger
> +
> +9. From rebooted kernel or crashdump kernel, read crashdata
> +
> + #dd if=/dev/crash_tmc_etr0 of=/trace/cstrace.bin
> +
> +10. Run opencsd decoder tools/scripts to generate the instruction trace.
Format all command lines as literal code blocks to be consistent:
---- >8 ----
diff --git a/Documentation/trace/coresight/panic.rst b/Documentation/trace/coresight/panic.rst
index 3b53d91cace8fd..864f6c05b3f7af 100644
--- a/Documentation/trace/coresight/panic.rst
+++ b/Documentation/trace/coresight/panic.rst
@@ -113,7 +113,7 @@ Sample commands for testing a Kernel panic case with ETR sink
bootargs. This is mandatory if the user would like to read the tracedata
from the crashdump kernel.
-2. Enable the preloaded ETM configuration
+2. Enable the preloaded ETM configuration::
#echo 1 > /sys/kernel/config/cs-syscfg/configurations/panicstop/enable
@@ -176,22 +176,26 @@ Sample commands for testing a Kernel panic case with ETR sink
Note: CTI connections are SOC specific and hence the above script is
added just for reference.
-4. Choose reserved buffer mode for ETR buffer
+4. Choose reserved buffer mode for ETR buffer::
+
#echo "resrv" > /sys/bus/coresight/devices/tmc_etr0/buf_mode_preferred
-5. Enable stop on flush trigger configuration
+5. Enable stop on flush trigger configuration::
+
#echo 1 > /sys/bus/coresight/devices/tmc_etr0/stop_on_flush
6. Start Coresight tracing on cores 1 and 2 using sysfs interface
-7. Run some application on core 1
+7. Run some application on core 1::
+
#taskset -c 1 dd if=/dev/urandom of=/dev/null &
-8. Invoke kernel panic on core 2
+8. Invoke kernel panic on core 2::
+
#echo 1 > /proc/sys/kernel/panic
#taskset -c 2 echo c > /proc/sysrq-trigger
-9. From rebooted kernel or crashdump kernel, read crashdata
+9. From rebooted kernel or crashdump kernel, read crashdata::
#dd if=/dev/crash_tmc_etr0 of=/trace/cstrace.bin
Thanks.
--
An old man doll... just what I always wanted! - Clara
Hi,
On 2024-09-17 at 07:16:46, Bagas Sanjaya (bagasdotme@gmail.com) wrote:
> On Mon, Sep 16, 2024 at 04:04:37PM +0530, Linu Cherian wrote:
> > +3. On a kernel panic, all coresight blocks are disabled, necessary
> > + metadata is synced by kernel panic handler.
> "... and necessary metadata ..."
> > +
> > + System would eventually reboot or boot a crashdump kernel.
> > +
> > +4. For platforms that supports crashdump kernel, raw trace data can be
> > + dumped using the coresight sysfs interface from the crashdump kernel
> > + itself. Persistent RAM is not a requirement in this case.
> > +
> > +5. For platforms that supports persistent RAM, trace data can be dumped
> > + using the coresight sysfs interface in the subsequent Linux boot.
> > + Crashdump kernel is not a requirement in this case. Persistent RAM
> > + ensures that trace data is intact across reboot.
> > +
> > +Coresight trace during Watchdog reset
> > +-------------------------------------
> > +The main difference between addressing the watchdog reset and kernel panic
> > +case are below,
> "... are:"
> > +Sample commands for testing a Kernel panic case with ETR sink
> > +-------------------------------------------------------------
> > +
> > +1. Boot Linux kernel with "crash_kexec_post_notifiers" added to the kernel
> > + bootargs. This is mandatory if the user would like to read the tracedata
> > + from the crashdump kernel.
> > +
> > +2. Enable the preloaded ETM configuration
> > +
> > + #echo 1 > /sys/kernel/config/cs-syscfg/configurations/panicstop/enable
> > +
> > +3. Configure CTI using sysfs interface::
> > +
> > + #./cti_setup.sh
> > +
> > + #cat cti_setup.sh
> > +
> > +
> > + cd /sys/bus/coresight/devices/
> > +
> > + ap_cti_config () {
> > + #ETM trig out[0] trigger to Channel 0
> > + echo 0 4 > channels/trigin_attach
> > + }
> > +
> > + etf_cti_config () {
> > + #ETF Flush in trigger from Channel 0
> > + echo 0 1 > channels/trigout_attach
> > + echo 1 > channels/trig_filter_enable
> > + }
> > +
> > + etr_cti_config () {
> > + #ETR Flush in from Channel 0
> > + echo 0 1 > channels/trigout_attach
> > + echo 1 > channels/trig_filter_enable
> > + }
> > +
> > + ctidevs=`find . -name "cti*"`
> > +
> > + for i in $ctidevs
> > + do
> > + cd $i
> > +
> > + connection=`find . -name "ete*"`
> > + if [ ! -z "$connection" ]
> > + then
> > + echo "AP CTI config for $i"
> > + ap_cti_config
> > + fi
> > +
> > + connection=`find . -name "tmc_etf*"`
> > + if [ ! -z "$connection" ]
> > + then
> > + echo "ETF CTI config for $i"
> > + etf_cti_config
> > + fi
> > +
> > + connection=`find . -name "tmc_etr*"`
> > + if [ ! -z "$connection" ]
> > + then
> > + echo "ETR CTI config for $i"
> > + etr_cti_config
> > + fi
> > +
> > + cd ..
> > + done
> > +
> > +Note: CTI connections are SOC specific and hence the above script is
> > +added just for reference.
> > +
> > +4. Choose reserved buffer mode for ETR buffer
> > + #echo "resrv" > /sys/bus/coresight/devices/tmc_etr0/buf_mode_preferred
> > +
> > +5. Enable stop on flush trigger configuration
> > + #echo 1 > /sys/bus/coresight/devices/tmc_etr0/stop_on_flush
> > +
> > +6. Start Coresight tracing on cores 1 and 2 using sysfs interface
> > +
> > +7. Run some application on core 1
> > + #taskset -c 1 dd if=/dev/urandom of=/dev/null &
> > +
> > +8. Invoke kernel panic on core 2
> > + #echo 1 > /proc/sys/kernel/panic
> > + #taskset -c 2 echo c > /proc/sysrq-trigger
> > +
> > +9. From rebooted kernel or crashdump kernel, read crashdata
> > +
> > + #dd if=/dev/crash_tmc_etr0 of=/trace/cstrace.bin
> > +
> > +10. Run opencsd decoder tools/scripts to generate the instruction trace.
>
> Format all command lines as literal code blocks to be consistent:
>
> ---- >8 ----
> diff --git a/Documentation/trace/coresight/panic.rst b/Documentation/trace/coresight/panic.rst
> index 3b53d91cace8fd..864f6c05b3f7af 100644
> --- a/Documentation/trace/coresight/panic.rst
> +++ b/Documentation/trace/coresight/panic.rst
> @@ -113,7 +113,7 @@ Sample commands for testing a Kernel panic case with ETR sink
> bootargs. This is mandatory if the user would like to read the tracedata
> from the crashdump kernel.
>
> -2. Enable the preloaded ETM configuration
> +2. Enable the preloaded ETM configuration::
>
> #echo 1 > /sys/kernel/config/cs-syscfg/configurations/panicstop/enable
>
> @@ -176,22 +176,26 @@ Sample commands for testing a Kernel panic case with ETR sink
> Note: CTI connections are SOC specific and hence the above script is
> added just for reference.
>
> -4. Choose reserved buffer mode for ETR buffer
> +4. Choose reserved buffer mode for ETR buffer::
> +
> #echo "resrv" > /sys/bus/coresight/devices/tmc_etr0/buf_mode_preferred
>
> -5. Enable stop on flush trigger configuration
> +5. Enable stop on flush trigger configuration::
> +
> #echo 1 > /sys/bus/coresight/devices/tmc_etr0/stop_on_flush
>
> 6. Start Coresight tracing on cores 1 and 2 using sysfs interface
>
> -7. Run some application on core 1
> +7. Run some application on core 1::
> +
> #taskset -c 1 dd if=/dev/urandom of=/dev/null &
>
> -8. Invoke kernel panic on core 2
> +8. Invoke kernel panic on core 2::
> +
> #echo 1 > /proc/sys/kernel/panic
> #taskset -c 2 echo c > /proc/sysrq-trigger
>
> -9. From rebooted kernel or crashdump kernel, read crashdata
> +9. From rebooted kernel or crashdump kernel, read crashdata::
>
> #dd if=/dev/crash_tmc_etr0 of=/trace/cstrace.bin
Ack.
>
> Thanks.
>
> --
> An old man doll... just what I always wanted! - Clara
Linu Cherian.
© 2016 - 2024 Red Hat, Inc.