Decoding the binary trace w/ a different kernel might be troublesome since we convert addresses to symbols. For kernels with minimal changes, the mappings would probably match, but it's not guaranteed at all. (But still we could convert the addresses by hand, since we do print raw addresses.)
If we use modules, the symbols could be loaded at different addresses from the previously booted kernel, and so this would also fail, but there's nothing we can do about it.
Also, the binary data format that pstore/ram is using in its ringbuffer may change between the kernels, so here we too must ensure that we're running the same kernel.
So, there are two questions really:
1. How to compute the unique kernel tag; 2. Where to store it.
In this patch we're just passing linux_banner through CRC32. This way we are protecting from the kernel version mismatch, making sure that we're running the same image. We could also add CRC of a symbol table (as suggested by Tony Luck), but for now let's not be that strict.
And as for storing, we are using a small trick here. Instead of allocating a dedicated buffer for the tag (i.e. another prz), or hacking ram_core routines to "reserve" some control data in the buffer, we are just encoding the tag into the buffer signature (and XOR'ing it with the actual signature value, so that buffers not needing a tag can just pass zero, which will result into the plain old PRZ signature).
Suggested-by: Steven Rostedt rostedt@goodmis.org Suggested-by: Tony Luck tony.luck@intel.com Suggested-by: Colin Cross ccross@android.com Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org --- fs/pstore/Kconfig | 1 + fs/pstore/ram.c | 13 ++++++++----- fs/pstore/ram_core.c | 12 +++++++----- include/linux/pstore_ram.h | 2 +- 4 files changed, 17 insertions(+), 11 deletions(-)
diff --git a/fs/pstore/Kconfig b/fs/pstore/Kconfig index d39bb5c..a123754 100644 --- a/fs/pstore/Kconfig +++ b/fs/pstore/Kconfig @@ -36,6 +36,7 @@ config PSTORE_RAM depends on PSTORE depends on HAS_IOMEM depends on HAVE_MEMBLOCK + select CRC32 select REED_SOLOMON select REED_SOLOMON_ENC8 select REED_SOLOMON_DEC8 diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c index 1dd108e..a7610a1 100644 --- a/fs/pstore/ram.c +++ b/fs/pstore/ram.c @@ -31,6 +31,7 @@ #include <linux/ioport.h> #include <linux/platform_device.h> #include <linux/slab.h> +#include <linux/crc32.h> #include <linux/pstore_ram.h>
#define RAMOOPS_KERNMSG_HDR "====" @@ -309,7 +310,7 @@ static int ramoops_init_przs(struct device *dev, struct ramoops_context *cxt, for (i = 0; i < cxt->max_dump_cnt; i++) { size_t sz = cxt->record_size;
- cxt->przs[i] = persistent_ram_new(*paddr, sz, cxt->ecc_size); + cxt->przs[i] = persistent_ram_new(*paddr, sz, 0, cxt->ecc_size); if (IS_ERR(cxt->przs[i])) { err = PTR_ERR(cxt->przs[i]); dev_err(dev, "failed to request mem region (0x%zx@0x%llx): %d\n", @@ -327,7 +328,7 @@ fail_prz:
static int ramoops_init_prz(struct device *dev, struct ramoops_context *cxt, struct persistent_ram_zone **prz, - phys_addr_t *paddr, size_t sz) + phys_addr_t *paddr, size_t sz, u32 sig) { if (!sz) return 0; @@ -335,7 +336,7 @@ static int ramoops_init_prz(struct device *dev, struct ramoops_context *cxt, if (*paddr + sz > *paddr + cxt->size) return -ENOMEM;
- *prz = persistent_ram_new(*paddr, sz, cxt->ecc_size); + *prz = persistent_ram_new(*paddr, sz, sig, cxt->ecc_size); if (IS_ERR(*prz)) { int err = PTR_ERR(*prz);
@@ -394,11 +395,13 @@ static int __devinit ramoops_probe(struct platform_device *pdev) if (err) goto fail_out;
- err = ramoops_init_prz(dev, cxt, &cxt->cprz, &paddr, cxt->console_size); + err = ramoops_init_prz(dev, cxt, &cxt->cprz, &paddr, + cxt->console_size, 0); if (err) goto fail_init_cprz;
- err = ramoops_init_prz(dev, cxt, &cxt->fprz, &paddr, cxt->ftrace_size); + err = ramoops_init_prz(dev, cxt, &cxt->fprz, &paddr, cxt->ftrace_size, + crc32_le(0, linux_banner, strlen(linux_banner))); if (err) goto fail_init_fprz;
diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c index 4dabbb8..eecd2a8 100644 --- a/fs/pstore/ram_core.c +++ b/fs/pstore/ram_core.c @@ -391,7 +391,7 @@ static int persistent_ram_buffer_map(phys_addr_t start, phys_addr_t size, }
static int __devinit persistent_ram_post_init(struct persistent_ram_zone *prz, - int ecc_size) + u32 sig, int ecc_size) { int ret;
@@ -399,7 +399,9 @@ static int __devinit persistent_ram_post_init(struct persistent_ram_zone *prz, if (ret) return ret;
- if (prz->buffer->sig == PERSISTENT_RAM_SIG) { + sig ^= PERSISTENT_RAM_SIG; + + if (prz->buffer->sig == sig) { if (buffer_size(prz) > prz->buffer_size || buffer_start(prz) > buffer_size(prz)) pr_info("persistent_ram: found existing invalid buffer," @@ -417,7 +419,7 @@ static int __devinit persistent_ram_post_init(struct persistent_ram_zone *prz, " (sig = 0x%08x)\n", prz->buffer->sig); }
- prz->buffer->sig = PERSISTENT_RAM_SIG; + prz->buffer->sig = sig; persistent_ram_zap(prz);
return 0; @@ -442,7 +444,7 @@ void persistent_ram_free(struct persistent_ram_zone *prz) }
struct persistent_ram_zone * __devinit persistent_ram_new(phys_addr_t start, - size_t size, + size_t size, u32 sig, int ecc_size) { struct persistent_ram_zone *prz; @@ -458,7 +460,7 @@ struct persistent_ram_zone * __devinit persistent_ram_new(phys_addr_t start, if (ret) goto err;
- ret = persistent_ram_post_init(prz, ecc_size); + ret = persistent_ram_post_init(prz, sig, ecc_size); if (ret) goto err;
diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h index af848e1..1d779c4 100644 --- a/include/linux/pstore_ram.h +++ b/include/linux/pstore_ram.h @@ -46,7 +46,7 @@ struct persistent_ram_zone { };
struct persistent_ram_zone * __devinit persistent_ram_new(phys_addr_t start, - size_t size, + size_t size, u32 sig, int ecc_size); void persistent_ram_free(struct persistent_ram_zone *prz); void persistent_ram_zap(struct persistent_ram_zone *prz);