Changes in dev-kmsg

34433332 - docs: ABI: testing: make the files compatible with ReST output

Fri, 30 Oct 2020 07:40:39 +0000

docs: ABI: testing: make the files compatible with ReST outputSome files over there won't parse well by Sphinx.Fix them.Acked-by: Jonathan Cameron # for IIOAcked-by: Fabrice Gasnier Acked-by: Jonathan Corbet Signed-off-by: Mauro Carvalho Chehab Link: https://lore.kernel.org/r/58cf3c2d611e0197fb215652719ebd82ca2658db.1604042072.git.mchehab+huawei@kernel.orgSigned-off-by: Greg Kroah-Hartman List of files: /linux-6.15/Documentation/ABI/testing/dev-kmsg

bc885f1a - doc:kmsg: explicitly state the return value in case of SEEK_CUR

Fri, 10 Jul 2020 17:44:23 +0000

doc:kmsg: explicitly state the return value in case of SEEK_CURThe commit 625d3449788f ("Revert "kernel/printk: add kmsg SEEK_CURhandling"") reverted a change done to the return value in case a SEEK_CURoperation was performed for kmsg buffer based on the fact that differentuserspace apps were handling the new return value (-ESPIPE) in differentways, breaking them.At the same time -ESPIPE was the wrong decision because kmsg /does support/seek() but doesn't follow the "normal" behavior userspace is used to.Because of that and also considering the time -EINVAL has been used, it wasdecided to keep this way to avoid more userspace breakage.This patch adds an official statement to the kmsg documentation pointing tothe current return value for SEEK_CUR, -EINVAL, thus userspace librariesand apps can refer to it for a definitive guide on what to expect.Signed-off-by: Bruno Meneguele Reviewed-by: Sergey Senozhatsky Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20200710174423.10480-1-bmeneg@redhat.com List of files: /linux-6.15/Documentation/ABI/testing/dev-kmsg

625d3449 - Revert "kernel/printk: add kmsg SEEK_CUR handling"

Mon, 22 Jun 2020 03:02:22 +0000

Revert "kernel/printk: add kmsg SEEK_CUR handling"This reverts commit 8ece3b3eb576a78d2e67ad4c3a80a39fa6708809.This commit broke userspace. Bash uses ESPIPE to determine whether ornot the file should be read using "unbuffered I/O", which means reading1 byte at a time instead of 128 bytes at a time. I used to use bash toread through kmsg in a really quite nasty way: while read -t 0.1 -r line 2>/dev/null || [[ $? -ne 142 ]]; do echo "SARU $line" done < /dev/kmsgThis will show all lines that can fit into the 128 byte buffer, and skiplines that don't. That's pretty awful, but at least it worked.With this change, bash now tries to do 1-byte reads, which means itskips all the lines, which is worse than before.Now, I don't really care very much about this, and I'm already look fora workaround. But I did just spend an hour trying to figure out why myscripts were broken. Either way, it makes no difference to me personallywhether this is reverted, but it might be something to consider. If youdeclare that "trying to read /dev/kmsg with bash is terminally stupidanyway," I might be inclined to agree with you. But do note that bashuses lseek(fd, 0, SEEK_CUR)==>ESPIPE to determine whether or not it'sreading from a pipe.Cc: Bruno Meneguele Cc: Sergey Senozhatsky Cc: Steven Rostedt Cc: David Laight Cc: Sergey Senozhatsky Cc: Petr Mladek Signed-off-by: Jason A. Donenfeld Signed-off-by: Linus Torvalds List of files: /linux-6.15/Documentation/ABI/testing/dev-kmsg

8ece3b3e - kernel/printk: add kmsg SEEK_CUR handling

Tue, 17 Mar 2020 10:33:44 +0000

kernel/printk: add kmsg SEEK_CUR handlingUserspace libraries, e.g. glibc's dprintf(), perform a SEEK_CUR operationover any file descriptor requested to make sure the current position isn'tpointing to junk due to previous manipulation of that same fd. And wheneverthat fd doesn't have support for such operation, the userspace code expects-ESPIPE to be returned.However, when the fd in question references the /dev/kmsg interface, thecurrent kernel code state returns -EINVAL instead, causing an unexpectedbehavior in userspace: in the case of glibc, when -ESPIPE is returned itgets ignored and the call completes successfully, while returning -EINVALforces dprintf to fail without performing any action over that fd: if (_IO_SEEKOFF (fp, (off64_t)0, _IO_seek_cur, _IOS_INPUT|_IOS_OUTPUT) == _IO_pos_BAD && errno != ESPIPE) return NULL;With this patch we make sure to return the correct value when SEEK_CUR isrequested over kmsg and also add some kernel doc information to formalizethis behavior.Link: https://lore.kernel.org/r/20200317103344.574277-1-bmeneg@redhat.comCc: linux-kernel@vger.kernel.orgCc: rostedt@goodmis.org,Cc: David.Laight@ACULAB.COMSigned-off-by: Bruno Meneguele Acked-by: Sergey Senozhatsky Signed-off-by: Petr Mladek List of files: /linux-6.15/Documentation/ABI/testing/dev-kmsg

085a3a8f - ABI: Update dev-kmsg documentation to match current kernel behaviour

Mon, 02 Sep 2019 11:18:16 +0000

ABI: Update dev-kmsg documentation to match current kernel behaviourCommit 5aa068ea4082 ("printk: remove games with previous record flags")abolished the practice of setting the log flag to 'c' for the firstcontinuation line and '+' for subsequent lines. Now all continuationlines are flagged with 'c' and '+' is never used.Update the 'dev-kmsg' documentation to remove the reference to theobsolete '+' flag. In addition, state explicitly that only 8 bits of the syslog prefix are used for the facility number when writing to/dev/kmsg.Link: http://lkml.kernel.org/r/0102016cf1b26630-8e9b337b-da49-43c6-b028-4250c2fac3ef-000000@eu-west-1.amazonses.comCc: Steven Rostedt Cc: linux-kernel@vger.kernel.orgSigned-off-by: James Byrne Reviewed-by: Sergey Senozhatsky Signed-off-by: Petr Mladek List of files: /linux-6.15/Documentation/ABI/testing/dev-kmsg

6fe29354 - printk: implement support for extended console drivers

Thu, 25 Jun 2015 22:01:30 +0000

printk: implement support for extended console driversprintk log_buf keeps various metadata for each message including itssequence number and timestamp. The metadata is currently available onlythrough /dev/kmsg and stripped out before passed onto console drivers. Wewant this metadata to be available to console drivers too so that consoleconsumers can get full information including the metadata and dictionary,which among other things can be used to detect whether messages got lostin transit.This patch implements support for extended console drivers. Consoles canindicate that they want extended messages by setting the new CON_EXTENDEDflag and they'll be fed messages formatted the same way as /dev/kmsg. ",,,;\n"If extended consoles exist, in-kernel fragment assembly is disabled. Thisensures that all messages emitted to consoles have full metadata includingsequence number. The contflag carries enough information to reassemblethe fragments from the reader side trivially. Note that this only affects/dev/kmsg. Regular console and /proc/kmsg outputs are not affected bythis change.* Extended message formatting for console drivers is enabled iff there are registered extended consoles.* Comment describing /dev/kmsg message format updated to add missing contflag field and help distinguishing variable from verbatim terms.Signed-off-by: Tejun Heo Cc: David Miller Cc: Kay Sievers Reviewed-by: Petr Mladek Cc: Tetsuo Handa Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds List of files: /linux-6.15/Documentation/ABI/testing/dev-kmsg

4e79162a - doc: fix quite a few typos within Documentation

Thu, 08 Nov 2012 12:57:35 +0000

doc: fix quite a few typos within DocumentationCorrect spelling typo in DocumentationsSigned-off-by: Jiri Kosina List of files: /linux-6.15/Documentation/ABI/testing/dev-kmsg

d39f3d77 - kmsg - export "continuation record" flag to /dev/kmsg

Tue, 17 Jul 2012 01:35:30 +0000

kmsg - export "continuation record" flag to /dev/kmsgIn some cases we are forced to store individual records for a continuationline print.Export a flag to allow the external re-construction of the line. The flagallows us to apply a similar logic externally which is used internally whenthe console, /proc/kmsg or the syslog() output is printed. $ cat /dev/kmsg 4,165,0,-;Free swap = 0kB 4,166,0,-;Total swap = 0kB 6,167,0,c;[ 4,168,0,+;0 4,169,0,+;1 4,170,0,+;2 4,171,0,+;3 4,172,0,+;] 6,173,0,-;[0 1 2 3 ] 6,174,0,-;Console: colour VGA+ 80x25 6,175,0,-;console [tty0] enabledSigned-off-by: Kay Sievers Signed-off-by: Greg Kroah-Hartman List of files: /linux-6.15/Documentation/ABI/testing/dev-kmsg

3b552b92 - kmsg - add Documentation/ABI/testing/dev-kmsg

Tue, 08 May 2012 16:50:50 +0000

kmsg - add Documentation/ABI/testing/dev-kmsgSigned-off-by: Kay Sievers Signed-off-by: Greg Kroah-Hartman List of files: /linux-6.15/Documentation/ABI/testing/dev-kmsg