mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-24 21:24:00 +08:00
65f8c95e46
With this patch we no longer reuse function tracer infrastructure, now we register our own tracer back-end via a debugfs knob. It's a bit more code, but that is the only downside. On the bright side we have: - Ability to make persistent_ram module removable (when needed, we can move ftrace_ops struct into a module). Note that persistent_ram is still not removable for other reasons, but with this patch it's just one thing less to worry about; - Pstore part is more isolated from the generic function tracer. We tried it already by registering our own tracer in available_tracers, but that way we're loosing ability to see the traces while we record them to pstore. This solution is somewhere in the middle: we only register "internal ftracer" back-end, but not the "front-end"; - When there is only pstore tracing enabled, the kernel will only write to the pstore buffer, omitting function tracer buffer (which, of course, still can be enabled via 'echo function > current_tracer'). Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
120 lines
4.6 KiB
Plaintext
120 lines
4.6 KiB
Plaintext
Ramoops oops/panic logger
|
|
=========================
|
|
|
|
Sergiu Iordache <sergiu@chromium.org>
|
|
|
|
Updated: 17 November 2011
|
|
|
|
0. Introduction
|
|
|
|
Ramoops is an oops/panic logger that writes its logs to RAM before the system
|
|
crashes. It works by logging oopses and panics in a circular buffer. Ramoops
|
|
needs a system with persistent RAM so that the content of that area can
|
|
survive after a restart.
|
|
|
|
1. Ramoops concepts
|
|
|
|
Ramoops uses a predefined memory area to store the dump. The start and size of
|
|
the memory area are set using two variables:
|
|
* "mem_address" for the start
|
|
* "mem_size" for the size. The memory size will be rounded down to a
|
|
power of two.
|
|
|
|
The memory area is divided into "record_size" chunks (also rounded down to
|
|
power of two) and each oops/panic writes a "record_size" chunk of
|
|
information.
|
|
|
|
Dumping both oopses and panics can be done by setting 1 in the "dump_oops"
|
|
variable while setting 0 in that variable dumps only the panics.
|
|
|
|
The module uses a counter to record multiple dumps but the counter gets reset
|
|
on restart (i.e. new dumps after the restart will overwrite old ones).
|
|
|
|
Ramoops also supports software ECC protection of persistent memory regions.
|
|
This might be useful when a hardware reset was used to bring the machine back
|
|
to life (i.e. a watchdog triggered). In such cases, RAM may be somewhat
|
|
corrupt, but usually it is restorable.
|
|
|
|
2. Setting the parameters
|
|
|
|
Setting the ramoops parameters can be done in 2 different manners:
|
|
1. Use the module parameters (which have the names of the variables described
|
|
as before).
|
|
For quick debugging, you can also reserve parts of memory during boot
|
|
and then use the reserved memory for ramoops. For example, assuming a machine
|
|
with > 128 MB of memory, the following kernel command line will tell the
|
|
kernel to use only the first 128 MB of memory, and place ECC-protected ramoops
|
|
region at 128 MB boundary:
|
|
"mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1"
|
|
2. Use a platform device and set the platform data. The parameters can then
|
|
be set through that platform data. An example of doing that is:
|
|
|
|
#include <linux/pstore_ram.h>
|
|
[...]
|
|
|
|
static struct ramoops_platform_data ramoops_data = {
|
|
.mem_size = <...>,
|
|
.mem_address = <...>,
|
|
.record_size = <...>,
|
|
.dump_oops = <...>,
|
|
.ecc = <...>,
|
|
};
|
|
|
|
static struct platform_device ramoops_dev = {
|
|
.name = "ramoops",
|
|
.dev = {
|
|
.platform_data = &ramoops_data,
|
|
},
|
|
};
|
|
|
|
[... inside a function ...]
|
|
int ret;
|
|
|
|
ret = platform_device_register(&ramoops_dev);
|
|
if (ret) {
|
|
printk(KERN_ERR "unable to register platform device\n");
|
|
return ret;
|
|
}
|
|
|
|
You can specify either RAM memory or peripheral devices' memory. However, when
|
|
specifying RAM, be sure to reserve the memory by issuing memblock_reserve()
|
|
very early in the architecture code, e.g.:
|
|
|
|
#include <linux/memblock.h>
|
|
|
|
memblock_reserve(ramoops_data.mem_address, ramoops_data.mem_size);
|
|
|
|
3. Dump format
|
|
|
|
The data dump begins with a header, currently defined as "====" followed by a
|
|
timestamp and a new line. The dump then continues with the actual data.
|
|
|
|
4. Reading the data
|
|
|
|
The dump data can be read from the pstore filesystem. The format for these
|
|
files is "dmesg-ramoops-N", where N is the record number in memory. To delete
|
|
a stored record from RAM, simply unlink the respective pstore file.
|
|
|
|
5. Persistent function tracing
|
|
|
|
Persistent function tracing might be useful for debugging software or hardware
|
|
related hangs. The functions call chain log is stored in a "ftrace-ramoops"
|
|
file. Here is an example of usage:
|
|
|
|
# mount -t debugfs debugfs /sys/kernel/debug/
|
|
# echo 1 > /sys/kernel/debug/pstore/record_ftrace
|
|
# reboot -f
|
|
[...]
|
|
# mount -t pstore pstore /mnt/
|
|
# tail /mnt/ftrace-ramoops
|
|
0 ffffffff8101ea64 ffffffff8101bcda native_apic_mem_read <- disconnect_bsp_APIC+0x6a/0xc0
|
|
0 ffffffff8101ea44 ffffffff8101bcf6 native_apic_mem_write <- disconnect_bsp_APIC+0x86/0xc0
|
|
0 ffffffff81020084 ffffffff8101a4b5 hpet_disable <- native_machine_shutdown+0x75/0x90
|
|
0 ffffffff81005f94 ffffffff8101a4bb iommu_shutdown_noop <- native_machine_shutdown+0x7b/0x90
|
|
0 ffffffff8101a6a1 ffffffff8101a437 native_machine_emergency_restart <- native_machine_restart+0x37/0x40
|
|
0 ffffffff811f9876 ffffffff8101a73a acpi_reboot <- native_machine_emergency_restart+0xaa/0x1e0
|
|
0 ffffffff8101a514 ffffffff8101a772 mach_reboot_fixups <- native_machine_emergency_restart+0xe2/0x1e0
|
|
0 ffffffff811d9c54 ffffffff8101a7a0 __const_udelay <- native_machine_emergency_restart+0x110/0x1e0
|
|
0 ffffffff811d9c34 ffffffff811d9c80 __delay <- __const_udelay+0x30/0x40
|
|
0 ffffffff811d9d14 ffffffff811d9c3f delay_tsc <- __delay+0xf/0x20
|