On 02/06/2022 00:20, David Malcolm wrote:
(2) find a list of system calls (e.g. those implemented on Linux), and
see which ones relate to file descriptors e.g. acquiring them, using
them, releasing them, and duplicating them. Look for patterns of usage
that could be expressed using function attributes. Probably ignore
"ioctl" for now.
(3) probably talk to glibc's developers about this, since glibc
provides headers that wrap system calls, which would want to use the
attributes if we provide them
There are a significant number of interfaces that use file descriptors,
not just limited to syscall interfaces. Another area I can think of is
stdio, i.e. FILE interfaces. There are interfaces (e.g. fdopen) that
interact with file descriptors and they may require some special handling.
(4) implement the attributes, so that the analyzer doesn't have
hardcoded function names, and can instead rely on function attributes.
GCC's attributes are implemented in gcc/c-family/c-attribs.cc; see the
big c_common_attribute_table array, which associates the string names
of the attrbutes with properties, including a handler callback. These
either set flags of a decl, or the attribute itself is appended to a
singly-linked list on that decl (for those things that don't directly
relate to fields of a decl).
I believe Siddhesh Poyarekar has been looking at attributes from the
glibc side of things, so I'm CCing him in case he has input on this.
I'm wondering if other people on this list have ideas for projects that
make heavy use of syscalls/file-descriptors that would benefit from
having this analyzer feature. Maybe systemd?
Systemd AFAIK doesn't bypass glibc's syscall interfaces, so annotating
glibc headers ought to be good start for a GSoC project. If this is
done before time we can explore server software, e.g. sshd, httpd, etc.
to see if there's scope for additional annotations there. I'll be happy
to help on the glibc and interfaces front.
Siddhesh
