Messages in this thread | | | Date | Fri, 20 Mar 2020 11:45:08 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [PATCH v2] kernel/printk: add kmsg SEEK_CUR handling |
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On (20/03/17 07:33), Bruno Meneguele wrote: > 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. > > Signed-off-by: Bruno Meneguele <bmeneg@redhat.com>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
-ss
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