kernel/linux.git/Documentation/ABI/testing/dev-kmsg, branch v6.6.132

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

2020-10-30T12:07:01+00:00

Some files over there won't parse well by Sphinx. Fix them. Acked-by: Jonathan Cameron # for IIO Acked-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.org Signed-off-by: Greg Kroah-Hartman

Merge tag 'printk-for-5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

2020-08-05T05:22:25+00:00

Pull printk updates from Petr Mladek: - Herbert Xu made printk header file self-contained. - Andy Shevchenko and Sergey Senozhatsky cleaned up console->setup() error handling. - Andy Shevchenko did some cleanups (e.g. sparse warning) in vsprintf code. - Minor documentation updates. * tag 'printk-for-5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: lib/vsprintf: Force type of flags value for gfp_t lib/vsprintf: Replace custom spec to print decimals with generic one lib/vsprintf: Replace hidden BUILD_BUG_ON() with static_assert() printk: Make linux/printk.h self-contained doc:kmsg: explicitly state the return value in case of SEEK_CUR Replace HTTP links with HTTPS ones: vsprintf hvc: unify console setup naming console: Fix trivia typo 'change' -> 'chance' console: Propagate error code from console ->setup() tty: hvc: Return proper error code from console ->setup() hook serial: sunzilog: Return proper error code from console ->setup() hook serial: sunsab: Return proper error code from console ->setup() hook mips: Return proper error code from console ->setup() hook

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

2020-07-13T13:07:45+00:00

The commit 625d3449788f ("Revert "kernel/printk: add kmsg SEEK_CUR handling"") reverted a change done to the return value in case a SEEK_CUR operation was performed for kmsg buffer based on the fact that different userspace apps were handling the new return value (-ESPIPE) in different ways, 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 was decided to keep this way to avoid more userspace breakage. This patch adds an official statement to the kmsg documentation pointing to the current return value for SEEK_CUR, -EINVAL, thus userspace libraries and 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

Revert "kernel/printk: add kmsg SEEK_CUR handling"

2020-06-22T03:47:20+00:00

This reverts commit 8ece3b3eb576a78d2e67ad4c3a80a39fa6708809. This commit broke userspace. Bash uses ESPIPE to determine whether or not the file should be read using "unbuffered I/O", which means reading 1 byte at a time instead of 128 bytes at a time. I used to use bash to read 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/kmsg This will show all lines that can fit into the 128 byte buffer, and skip lines 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 it skips all the lines, which is worse than before. Now, I don't really care very much about this, and I'm already look for a workaround. But I did just spend an hour trying to figure out why my scripts were broken. Either way, it makes no difference to me personally whether this is reverted, but it might be something to consider. If you declare that "trying to read /dev/kmsg with bash is terminally stupid anyway," I might be inclined to agree with you. But do note that bash uses lseek(fd, 0, SEEK_CUR)==>ESPIPE to determine whether or not it's reading 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

kernel/printk: add kmsg SEEK_CUR handling

2020-05-21T11:32:25+00:00

Userspace libraries, e.g. glibc's dprintf(), perform a SEEK_CUR operation over any file descriptor requested to make sure the current position isn't pointing to junk due to previous manipulation of that same fd. And whenever that 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, the current kernel code state returns -EINVAL instead, causing an unexpected behavior in userspace: in the case of glibc, when -ESPIPE is returned it gets ignored and the call completes successfully, while returning -EINVAL forces 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 is requested over kmsg and also add some kernel doc information to formalize this behavior. Link: https://lore.kernel.org/r/20200317103344.574277-1-bmeneg@redhat.com Cc: linux-kernel@vger.kernel.org Cc: rostedt@goodmis.org, Cc: David.Laight@ACULAB.COM Signed-off-by: Bruno Meneguele Acked-by: Sergey Senozhatsky Signed-off-by: Petr Mladek

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

2019-09-06T14:26:36+00:00

Commit 5aa068ea4082 ("printk: remove games with previous record flags") abolished the practice of setting the log flag to 'c' for the first continuation line and '+' for subsequent lines. Now all continuation lines are flagged with 'c' and '+' is never used. Update the 'dev-kmsg' documentation to remove the reference to the obsolete '+' 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.com Cc: Steven Rostedt Cc: linux-kernel@vger.kernel.org Signed-off-by: James Byrne Reviewed-by: Sergey Senozhatsky Signed-off-by: Petr Mladek

printk: implement support for extended console drivers

2015-06-26T00:00:38+00:00

printk log_buf keeps various metadata for each message including its sequence number and timestamp. The metadata is currently available only through /dev/kmsg and stripped out before passed onto console drivers. We want this metadata to be available to console drivers too so that console consumers can get full information including the metadata and dictionary, which among other things can be used to detect whether messages got lost in transit. This patch implements support for extended console drivers. Consoles can indicate that they want extended messages by setting the new CON_EXTENDED flag and they'll be fed messages formatted the same way as /dev/kmsg. ",,,;\n" If extended consoles exist, in-kernel fragment assembly is disabled. This ensures that all messages emitted to consoles have full metadata including sequence number. The contflag carries enough information to reassemble the fragments from the reader side trivially. Note that this only affects /dev/kmsg. Regular console and /proc/kmsg outputs are not affected by this 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

doc: fix quite a few typos within Documentation

2012-11-19T13:28:24+00:00

Correct spelling typo in Documentations Signed-off-by: Jiri Kosina

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

2012-07-17T01:35:30+00:00

In some cases we are forced to store individual records for a continuation line print. Export a flag to allow the external re-construction of the line. The flag allows us to apply a similar logic externally which is used internally when the 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] enabled Signed-off-by: Kay Sievers Signed-off-by: Greg Kroah-Hartman

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

2012-05-08T17:44:25+00:00

Signed-off-by: Kay Sievers Signed-off-by: Greg Kroah-Hartman