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Subject[PATCH 5/5] pstore/ram: Add ftrace messages handling
Date
The ftrace log size is configurable via ramoops.ftrace_size
module option, and the log itself is available via
<pstore-mount>/ftrace-ramoops file.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
---
Documentation/ramoops.txt | 24 ++++++++++++++++++++++++
fs/pstore/ram.c | 37 +++++++++++++++++++++++++++++++++----
include/linux/pstore_ram.h | 1 +
3 files changed, 58 insertions(+), 4 deletions(-)
diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt
index 59a74a8..dee307b 100644
--- a/Documentation/ramoops.txt
+++ b/Documentation/ramoops.txt
@@ -94,3 +94,27 @@ timestamp and a new line. The dump then continues with the actual 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/
+ # cd /sys/kernel/debug/tracing
+ # echo persistent > current_tracer
+ # 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
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 96dbd1e..018d895 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -45,6 +45,10 @@ static ulong ramoops_console_size = MIN_MEM_SIZE;
module_param_named(console_size, ramoops_console_size, ulong, 0400);
MODULE_PARM_DESC(console_size, "size of kernel console log");

+static ulong ramoops_ftrace_size = MIN_MEM_SIZE;
+module_param_named(ftrace_size, ramoops_ftrace_size, ulong, 0400);
+MODULE_PARM_DESC(ftrace_size, "size of ftrace log");
+
static ulong mem_address;
module_param(mem_address, ulong, 0400);
MODULE_PARM_DESC(mem_address,
@@ -68,16 +72,19 @@ MODULE_PARM_DESC(ramoops_ecc,
struct ramoops_context {
struct persistent_ram_zone **przs;
struct persistent_ram_zone *cprz;
+ struct persistent_ram_zone *fprz;
phys_addr_t phys_addr;
unsigned long size;
size_t record_size;
size_t console_size;
+ size_t ftrace_size;
int dump_oops;
bool ecc;
unsigned int max_dump_cnt;
unsigned int dump_write_cnt;
unsigned int dump_read_cnt;
unsigned int console_read_cnt;
+ unsigned int ftrace_read_cnt;
struct pstore_info pstore;
};

@@ -136,6 +143,9 @@ static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
prz = ramoops_get_next_prz(&cxt->cprz, &cxt->console_read_cnt,
1, id, type, PSTORE_TYPE_CONSOLE, 0);
if (!prz)
+ prz = ramoops_get_next_prz(&cxt->fprz, &cxt->ftrace_read_cnt,
+ 1, id, type, PSTORE_TYPE_FTRACE, 0);
+ if (!prz)
return 0;

/* TODO(kees): Bogus time for the moment. */
@@ -184,6 +194,11 @@ static int ramoops_pstore_write_buf(enum pstore_type_id type,
return -ENOMEM;
persistent_ram_write(cxt->cprz, buf, size);
return 0;
+ } else if (type == PSTORE_TYPE_FTRACE) {
+ if (!cxt->fprz)
+ return -ENOMEM;
+ persistent_ram_write(cxt->fprz, buf, size);
+ return 0;
}

if (type != PSTORE_TYPE_DMESG)
@@ -233,6 +248,9 @@ static int ramoops_pstore_erase(enum pstore_type_id type, u64 id,
case PSTORE_TYPE_CONSOLE:
prz = cxt->cprz;
break;
+ case PSTORE_TYPE_FTRACE:
+ prz = cxt->fprz;
+ break;
default:
return -EINVAL;
}
@@ -346,7 +364,8 @@ static int __init ramoops_probe(struct platform_device *pdev)
if (cxt->max_dump_cnt)
goto fail_out;

- if (!pdata->mem_size || (!pdata->record_size && !pdata->console_size)) {
+ if (!pdata->mem_size || (!pdata->record_size && !pdata->console_size &&
+ !pdata->ftrace_size)) {
pr_err("The memory size and the record/console size must be "
"non-zero\n");
goto fail_out;
@@ -355,18 +374,20 @@ static int __init ramoops_probe(struct platform_device *pdev)
pdata->mem_size = rounddown_pow_of_two(pdata->mem_size);
pdata->record_size = rounddown_pow_of_two(pdata->record_size);
pdata->console_size = rounddown_pow_of_two(pdata->console_size);
+ pdata->ftrace_size = rounddown_pow_of_two(pdata->ftrace_size);

cxt->dump_read_cnt = 0;
cxt->size = pdata->mem_size;
cxt->phys_addr = pdata->mem_address;
cxt->record_size = pdata->record_size;
cxt->console_size = pdata->console_size;
+ cxt->ftrace_size = pdata->ftrace_size;
cxt->dump_oops = pdata->dump_oops;
cxt->ecc = pdata->ecc;

paddr = cxt->phys_addr;

- dump_mem_sz = cxt->size - cxt->console_size;
+ dump_mem_sz = cxt->size - cxt->console_size - cxt->ftrace_size;
err = ramoops_init_przs(dev, cxt, &paddr, dump_mem_sz);
if (err)
goto fail_out;
@@ -375,9 +396,14 @@ static int __init ramoops_probe(struct platform_device *pdev)
if (err)
goto fail_init_cprz;

- if (!cxt->przs && !cxt->cprz) {
+ err = ramoops_init_prz(dev, cxt, &cxt->fprz, &paddr, cxt->ftrace_size);
+ if (err)
+ goto fail_init_fprz;
+
+ if (!cxt->przs && !cxt->cprz && !cxt->fprz) {
pr_err("memory size too small, minimum is %lu\n",
- cxt->console_size + cxt->record_size);
+ cxt->console_size + cxt->record_size +
+ cxt->ftrace_size);
goto fail_cnt;
}

@@ -424,6 +450,8 @@ fail_clear:
cxt->pstore.bufsize = 0;
cxt->max_dump_cnt = 0;
fail_cnt:
+ kfree(cxt->fprz);
+fail_init_fprz:
kfree(cxt->cprz);
fail_init_cprz:
ramoops_free_przs(cxt);
@@ -478,6 +506,7 @@ static int __init ramoops_init(void)
dummy_data->mem_address = mem_address;
dummy_data->record_size = record_size;
dummy_data->console_size = ramoops_console_size;
+ dummy_data->ftrace_size = ramoops_ftrace_size;
dummy_data->dump_oops = dump_oops;
dummy_data->ecc = ramoops_ecc;
dummy = platform_create_bundle(&ramoops_driver, ramoops_probe,
diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h
index 2470bb5..368da13 100644
--- a/include/linux/pstore_ram.h
+++ b/include/linux/pstore_ram.h
@@ -75,6 +75,7 @@ struct ramoops_platform_data {
unsigned long mem_address;
unsigned long record_size;
unsigned long console_size;
+ unsigned long ftrace_size;
int dump_oops;
bool ecc;
};
--
1.7.9.2


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