Hi all,
In v4: - A few cosmetic changes in func_set_flag(), as suggested by Steven Rostedt. Firstly, in the patch that adds pstore option, I use 'else if' for the new bit (it keeps changes minimal), but then there is a new separate patch (the last in the series) that converts the whole thing into a switch construction.
In v3: - Make traces versioned, as suggested by Steven, Tony and Colin. (The version tag is stored in the PRZ signature, see the last patch for the implementation details). - Add Steven's Ack on the first patch.
In v2: - Do not introduce a separate 'persistent' tracer, but introduce an option to the existing 'function' tracer.
Rationale for this patch set:
With this support kernel can save functions call chain log into a persistent ram buffer that can be decoded and dumped after reboot through pstore filesystem. It can be used to determine what function was last called before a hang or an unexpected reset (caused by, for example, a buggy driver that abuses HW).
Here's a "nano howto", to get the idea:
# mount -t debugfs debugfs /sys/kernel/debug/ # cd /sys/kernel/debug/tracing # echo function > current_tracer # echo 1 > options/func_pstore # 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
Mostly the code comes from trace_persistent.c driver found in the Android git tree, written by Colin Cross ccross@android.com (according to sign-off history). I reworked the driver a little bit, and ported it to pstore subsystem.
--- Documentation/ramoops.txt | 25 +++++++++ fs/pstore/Kconfig | 13 +++++ fs/pstore/Makefile | 1 + fs/pstore/ftrace.c | 35 +++++++++++++ fs/pstore/inode.c | 111 ++++++++++++++++++++++++++++++++++++++-- fs/pstore/internal.h | 43 ++++++++++++++++ fs/pstore/platform.c | 12 ++++- fs/pstore/ram.c | 65 +++++++++++++++++------ fs/pstore/ram_core.c | 12 +++-- include/linux/pstore.h | 13 +++++ include/linux/pstore_ram.h | 3 +- kernel/trace/trace.c | 7 +-- kernel/trace/trace_functions.c | 36 +++++++++---- 13 files changed, 337 insertions(+), 39 deletions(-)