3 files changed, 59 insertions, 4 deletions

diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt
index 59a74a8ee2e5..197ad59ab9bf 100644
--- a/Documentation/ramoops.txt
+++ b/Documentation/ramoops.txt
@@ -94,3 +94,28 @@ 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 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
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 74f4111bd0da..1dd108e0cc60 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,
@@ -70,16 +74,19 @@ 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;
         int ecc_size;
         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;
 };
 
@@ -138,6 +145,9 @@ 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. */
@@ -186,6 +196,11 @@ 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)
@@ -235,6 +250,9 @@ 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;
         }
@@ -348,7 +366,8 @@ static int __devinit 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;
@@ -357,18 +376,20 @@ static int __devinit 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_size = pdata->ecc_size;
 
         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;
@@ -377,9 +398,14 @@ static int __devinit 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;
         }
 
@@ -426,6 +452,8 @@ 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);
@@ -480,6 +508,7 @@ static void ramoops_register_dummy(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;
         /*
          * For backwards compatibility ramoops.ecc=1 means 16 bytes ECC
diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h
index dcf805f56bc6..af848e1593b9 100644
--- a/include/linux/pstore_ram.h
+++ b/include/linux/pstore_ram.h
@@ -72,6 +72,7 @@ struct ramoops_platform_data {
         unsigned long   mem_address;
         unsigned long   record_size;
         unsigned long   console_size;
+        unsigned long   ftrace_size;
         int             dump_oops;
         int             ecc_size;
 };