Hi Neil, Thank you for a kernel patch and a makedumpfile patch.
Neil Horman wrote: >> That aside we aren't currently exporting log_buf_len, so I don't >> think this code works actually works. >> >> Neil can you add a comment in kernel/printk.c of the algorithm >> necessary for external tools to decode the ring buffer? >> >> We need the comment because people working on kernel/printk.c >> need to know what is happening and without having to review lots >> of user space code, and we need the comment to verify that we >> are exporting the right things. >> > > Ok, as per Erics comment, I've written this. It applies on top of whats > already > in your tree Andrew. It adds some comments on the function in question so > that > anyone working on printk.c will know why we're exporting their symbols. It > also > modifies slightly the symbols we are exporting so that we can handle dmesg > buffers that are longer than the standard PAGE_SIZE configuration, and lets us > detect and handle buffer wraps. > > Thanks! > > printk.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > Signed-off-by: Neil Horman <[email protected]> > > diff --git a/kernel/printk.c b/kernel/printk.c > index dd5cc7b..6a1163b 100644 > --- a/kernel/printk.c > +++ b/kernel/printk.c > @@ -138,10 +138,20 @@ static int log_buf_len = __LOG_BUF_LEN; > static unsigned logged_chars; /* Number of chars produced since last > read+clear operation */ > > #ifdef CONFIG_KEXEC > +/* > + * This appends the listed symbols to /proc/vmcoreinfo > + * /proc/vmcoreinfo is used by various utiilties, like > + * crash and makedumpfile to obtain access to symbols that > + * are otherwise very difficult to locate. These symbols > + * are specifically used so that utilities > + * can access and extract the dmesg log from a vmcore file > + * after a crash > + */ > void log_buf_kexec_setup(void) > { > VMCOREINFO_SYMBOL(log_buf); > - VMCOREINFO_SYMBOL(log_end); > + VMCOREINFO_SYMBOL(log_buf_len); > + VMCOREINFO_SYMBOL(logged_chars) > } > #endif Please do not remove VMCOREINFO_SYMBOL(log_end), because makedumpfile needs it for knowing the latest log offset in ring buffer of dmesg. I updated a makedumpfile patch for handling ring buffer, and it is possible to download the latest patch from the following site: https://sourceforge.net/tracker2/download.php?group_id=178938&atid=887142&file_id=312113&aid=2521075 Thanks Ken'ichi Ohmichi
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