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Subject[RFC][PATCH] kmsg_dumper for NVRAM
Hi,

This prototype patch introduces kmsg_dumper for NVRAM(Non-Volatile RAM).

[Purpose]
My purpose is developing reliable logging feature for enterprise use.
I plan to realize it by using NVRAM equipped with some enterprise servers.

[Solution]
There are following enterprise servers equipped with NVRAM.
1. Supporting UEFI
2. Not supporting UEFI

At first, I suggest kmsg_dumper with UEFI because customers will have advantage as follows.

- UEFI is tolerant of memory corruption because kernel can't access to UEFI area.
In other words, Kernel messages are gotten reliably.

- Kernel messages are gotten at a very early stage of boot process.
So we can investigate root cause of a problem even if kdump isn't enabled.

[Patch Description]
This patch adds following boot paremeters.

- nvram_kmsg_dump_enable
Enable kmsg_dumper for NVRAM with UEFI.

- nvram_kmsg_dump_len
Size of kernel messages dumped to NVRAM.
default size is 1KB.(because I would like to use efivars for reading them from userspace.)
Maximum size is 32KB.

On the next boot, sysfs files are created as follows and through these files we can see
the kernel messages stored in NVRAM.

/sys/firmware/efi/vars/LinuxKmsgDump001-8be4df61-93ca-11d2-aa0d-00e098032b8c/data
/sys/firmware/efi/vars/LinuxKmsgDump002-8be4df61-93ca-11d2-aa0d-00e098032b8c/data
.
.
/sys/firmware/efi/vars/LinuxKmsgDump032-8be4df61-93ca-11d2-aa0d-00e098032b8c/data

  - Size of each entry is 1KB. 32 entries are created at a maximum.
  - "8be4df61-93ca-11d2-aa0d-00e098032b8c" is EFI_GLOBAL_VARIABLE which is defined in
UEFI specification.

[Test]
I tested this feature with x86_64.

This is a prototype patch.
So, any comments are welcome.

Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>

---
Documentation/kernel-parameters.txt | 9 +++
arch/ia64/kernel/efi.c | 4 +
arch/x86/platform/efi/efi.c | 135 +++++++++++++++++++++++++++++++++++
include/linux/efi.h | 4 +
init/main.c | 5 +-
5 files changed, 156 insertions(+), 1 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index b72e071..10212a9 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1778,6 +1778,15 @@ and is between 256 and 4096 characters. It is defined in the file
This can be set from sysctl after boot.
See Documentation/sysctl/vm.txt for details.

+ nvram_kmsg_dump_enable [X86]
+ Enable kmsg_dump for NVRAM
+
+ nvram_kmsg_dump_len=n [X86]
+ Sets the buffer size of kmsg_dump for NVRAM, in bytes.
+ Format: { n | nk | nM }
+ n must be a power of two. The default size
+ is 1024.
+
ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
See Documentation/debugging-via-ohci1394.txt for more
info.
diff --git a/arch/ia64/kernel/efi.c b/arch/ia64/kernel/efi.c
index a0f0019..6ba22aa 100644
--- a/arch/ia64/kernel/efi.c
+++ b/arch/ia64/kernel/efi.c
@@ -1366,3 +1366,7 @@ vmcore_find_descriptor_size (unsigned long address)
return ret;
}
#endif
+
+void nvram_kmsg_dump_init(void)
+{
+}
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 0fe27d7..1499fb6 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -37,6 +37,10 @@
#include <linux/io.h>
#include <linux/reboot.h>
#include <linux/bcd.h>
+#include <linux/kmsg_dump.h>
+#include <linux/nls.h>
+#include <linux/slab_def.h>
+#include <linux/gfp.h>

#include <asm/setup.h>
#include <asm/efi.h>
@@ -59,6 +63,18 @@ struct efi_memory_map memmap;
static struct efi efi_phys __initdata;
static efi_system_table_t efi_systab __initdata;

+int nvram_kmsg_dump_enabled;
+#define LINUX_KMSG_DUMP_PREFIX "LinuxKmsgDump"
+#define LINUX_KMSG_DUMP_LEN 18
+#define MAX_ENTRY 32
+#define SET_VARIABLE_LEN 1024
+static char kmsg_dump_value[LINUX_KMSG_DUMP_LEN];
+static efi_char16_t kmsg_dump_value_utf16[MAX_ENTRY][LINUX_KMSG_DUMP_LEN];
+static char __nvram_kmsg_dump_buf[SET_VARIABLE_LEN];
+static char *nvram_kmsg_dump_buf = __nvram_kmsg_dump_buf;
+static int nvram_kmsg_dump_len = SET_VARIABLE_LEN;
+static struct kmsg_dumper nvram_kmsg_dumper;
+
static int __init setup_noefi(char *arg)
{
efi_enabled = 0;
@@ -611,3 +627,122 @@ u64 efi_mem_attributes(unsigned long phys_addr)
}
return 0;
}
+
+static int __init setup_nvram_kmsg_dump_enable(char *arg)
+{
+ nvram_kmsg_dump_enabled = 1;
+ return 0;
+}
+__setup("nvram_kmsg_dump_enable", setup_nvram_kmsg_dump_enable);
+
+static int __init setup_nvram_kmsg_dump_len(char *str)
+{
+ unsigned size = memparse(str, &str);
+
+ if (!efi_enabled) {
+ printk(KERN_INFO "setup_nvram_kmsg_dump_len: EFI is disabled\n");
+ return 1;
+ }
+
+ if (size)
+ size = roundup_pow_of_two(size);
+ if (size > nvram_kmsg_dump_len) {
+ char *new_nvram_kmsg_dump;
+
+ new_nvram_kmsg_dump = alloc_bootmem(size);
+ if (!new_nvram_kmsg_dump) {
+ printk(KERN_WARNING "nvram_kmsg_dump_len: \
+allocation failed\n");
+ return 1;
+ }
+ nvram_kmsg_dump_len = size;
+ nvram_kmsg_dump_buf = new_nvram_kmsg_dump;
+ }
+ printk(KERN_NOTICE "nvram_kmsg_dump_len: %d\n", nvram_kmsg_dump_len);
+
+ return 0;
+
+}
+__setup("nvram_kmsg_dump_len=", setup_nvram_kmsg_dump_len);
+
+static void nvram_do_kmsg_dump(struct kmsg_dumper *dumper,
+ enum kmsg_dump_reason reason, const char *s1, unsigned long l1,
+ const char *s2, unsigned long l2)
+{
+ unsigned long s1_start, s2_start, l1_cpy, l2_cpy;
+ unsigned long attribute = 0xf, total, tmp, cpy_size;
+ int i;
+ efi_status_t efi_status;
+ void *tmp_buf;
+
+ l2_cpy = min(l2, (unsigned long)nvram_kmsg_dump_len);
+ l1_cpy = min(l1, (unsigned long)nvram_kmsg_dump_len - l2_cpy);
+
+ s2_start = l2 - l2_cpy;
+ s1_start = l1 - l1_cpy;
+
+ memcpy(nvram_kmsg_dump_buf, s1 + s1_start, l1_cpy);
+ memcpy(nvram_kmsg_dump_buf + l1_cpy, s2 + s2_start, l2_cpy);
+
+ /* initialize */
+ for (i = 0; i < MAX_ENTRY; i++)
+ efi.set_variable(kmsg_dump_value_utf16[i],
+ &EFI_GLOBAL_VARIABLE_GUID,
+ attribute, 0, NULL);
+
+ /* write data */
+ total = l1_cpy + l2_cpy;
+ tmp_buf = (void *)nvram_kmsg_dump_buf + total;
+ cpy_size = 0;
+ for (i = 0; i < MAX_ENTRY; i++) {
+ tmp = min(total - cpy_size, (unsigned long)SET_VARIABLE_LEN);
+ tmp_buf -= tmp;
+ efi_status = efi.set_variable(kmsg_dump_value_utf16[i],
+ &EFI_GLOBAL_VARIABLE_GUID,
+ attribute, tmp, tmp_buf);
+ if (efi_status) {
+ printk(KERN_WARNING "nvram_do_kmsg_dump: \
+set_variable %d failed 0x%lx\n", i, efi_status);
+ efi.set_variable(kmsg_dump_value_utf16[i],
+ &EFI_GLOBAL_VARIABLE_GUID,
+ attribute, 0, NULL);
+ tmp_buf += tmp;
+ cpy_size -= tmp;
+ }
+ cpy_size += tmp;
+ if (cpy_size >= total)
+ break;
+ }
+}
+
+void nvram_kmsg_dump_init(void)
+{
+
+ int i, outlen, err;
+
+ for (i = 0; i < MAX_ENTRY; i++) {
+ snprintf(kmsg_dump_value, sizeof(kmsg_dump_value),
+ "%s%04d", LINUX_KMSG_DUMP_PREFIX, i + 1);
+ outlen = utf8s_to_utf16s((u8 *)kmsg_dump_value,
+ sizeof(kmsg_dump_value),
+ (wchar_t *)kmsg_dump_value_utf16[i]);
+ if (outlen != LINUX_KMSG_DUMP_LEN - 1) {
+ printk(KERN_ERR
+ "nvram_kmsg_dump_init: utf8s_to_utf16s %d\n",
+ outlen);
+ return;
+ }
+ }
+
+ memset(&nvram_kmsg_dumper, 0, sizeof(nvram_kmsg_dumper));
+ nvram_kmsg_dumper.dump = nvram_do_kmsg_dump;
+ err = kmsg_dump_register(&nvram_kmsg_dumper);
+ if (err) {
+ printk(KERN_ERR "nvram_kmsg_dump_init: kmsg_dump_register %d\n",
+ err);
+ return;
+ }
+ printk(KERN_NOTICE "nvram_kmsg_dump initialized\n");
+
+ return;
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index fb737bc..d0d1a3c 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -300,6 +300,7 @@ extern void efi_initialize_iomem_resources(struct resource *code_resource,
extern unsigned long efi_get_time(void);
extern int efi_set_rtc_mmss(unsigned long nowtime);
extern struct efi_memory_map memmap;
+extern void nvram_kmsg_dump_init(void);

/**
* efi_range_is_wc - check the WC bit on an address range
@@ -333,11 +334,14 @@ extern int __init efi_setup_pcdp_console(char *);
#ifdef CONFIG_EFI
# ifdef CONFIG_X86
extern int efi_enabled;
+ extern int nvram_kmsg_dump_enabled;
# else
# define efi_enabled 1
+# define nvram_kmsg_dump_enabled 1
# endif
#else
# define efi_enabled 0
+# define nvram_kmsg_dump_enabled 0
#endif

/*
diff --git a/init/main.c b/init/main.c
index 33c37c3..a8ee2bd 100644
--- a/init/main.c
+++ b/init/main.c
@@ -679,8 +679,11 @@ asmlinkage void __init start_kernel(void)
pidmap_init();
anon_vma_init();
#ifdef CONFIG_X86
- if (efi_enabled)
+ if (efi_enabled) {
efi_enter_virtual_mode();
+ if (nvram_kmsg_dump_enabled)
+ nvram_kmsg_dump_init();
+ }
#endif
thread_info_cache_init();
cred_init();
--
1.7.1

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