lib/posix-poll: Make epoll_ctl identify files by (fd + file description) #1198
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Previously, when compiling without CONFIG_LIBVFSCORE, epoll_ctl would fail to lookup the file descriptor, leading to the use of uninitialized memory. This change fixes this omission, adding lookup code for pure newvfs configurations. Signed-off-by: Andrei Tatar <andrei@unikraft.io>
Previously epoll_ctl would identify epoll entries by fd alone, in accordance with published documentation (see epoll_ctl(2)). However, the Linux kernel actually identifies entries by a tuple of (fd, file description) instead, a behavior on which some applications mistakenly depend. In order to support these applications we have to mimic this behavior. This change implements the above described identification of files, along with relevant cleanup of epoll_ctl-related code. Signed-off-by: Andrei Tatar <andrei@unikraft.io>
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Reviewed-by: Razvan Deaconescu razvand@unikraft.io
Approved-by: Razvan Deaconescu razvand@unikraft.io
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Previously, when compiling without CONFIG_LIBVFSCORE, epoll_ctl would fail to lookup the file descriptor, leading to the use of uninitialized memory. This change fixes this omission, adding lookup code for pure newvfs configurations. Signed-off-by: Andrei Tatar <andrei@unikraft.io> Reviewed-by: Razvan Deaconescu <razvand@unikraft.io> Approved-by: Razvan Deaconescu <razvand@unikraft.io> GitHub-Closes: #1198
razvand
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Dec 13, 2023
Previously epoll_ctl would identify epoll entries by fd alone, in accordance with published documentation (see epoll_ctl(2)). However, the Linux kernel actually identifies entries by a tuple of (fd, file description) instead, a behavior on which some applications mistakenly depend. In order to support these applications we have to mimic this behavior. This change implements the above described identification of files, along with relevant cleanup of epoll_ctl-related code. Signed-off-by: Andrei Tatar <andrei@unikraft.io> Reviewed-by: Razvan Deaconescu <razvand@unikraft.io> Approved-by: Razvan Deaconescu <razvand@unikraft.io> GitHub-Closes: #1198
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Description of changes
Previously epoll_ctl would identify epoll entries by fd alone, in accordance with published documentation (see
epoll_ctl(2)).However, the Linux kernel actually identifies entries by a tuple of (fd, file description) instead, a behavior on which some applications mistakenly depend.
In order to support these applications we have to mimic this behavior.
This changeset implements the above described identification of files, along with relevant cleanup of epoll_ctl-related code.
In addition, the first commit in the PR fixes an omission whereby
epoll_ctlwould fail to lookup thefdwhen Unikraft is configured without the legacy vfscore.Prerequisite checklist
checkpatch.ukon your commit series before opening this PR;Base target
Additional configuration
Should work with or without
CONFIG_LIBVFSCORE.