Hi Elliott, On Tue, Aug 27, 2024 at 03:07:54PM GMT, enh wrote: > oh, i can definitely make a start... > > (i was going to at least send you the easiest patch, but then i > realized even there there's a bit of a bikeshed opportunity, so i'll > just give you all the pieces and let you decide what to do with them!) Thanks! > > so i think we have these things to say: > > 1. AT_SYMLINK_NOFOLLOW _is_ supported for fchmodat(2). > 2. but only since Linux 6.6 (except see 4). > 3. there's no mention of lchmod(). > 4. that function is very old, but it doesn't actually work on glibc > until 2.32 (https://sourceware.org/bugzilla/show_bug.cgi?id=14578#c16) > where it uses the O_PATH trick that musl and bionic also use (and so > doesn't need Linux 6.6). > > heh, actually trying to write the bits down is probably easiest done > as a diff anyway... > > diff --git a/man/man2/chmod.2 b/man/man2/chmod.2 > index ae53fe3c9..c6c54eeca 100644 > --- a/man/man2/chmod.2 > +++ b/man/man2/chmod.2 > @@ -11,7 +11,7 @@ > .\" > .TH chmod 2 (date) "Linux man-pages (unreleased)" > .SH NAME > -chmod, fchmod, fchmodat \- change permissions of a file > +chmod, fchmod, lchown, fchmodat \- change permissions of a file > .SH LIBRARY > Standard C library > .RI ( libc ,\~ \-lc ) > @@ -21,6 +21,7 @@ Standard C library > .P > .BI "int chmod(const char *" pathname ", mode_t " mode ); > .BI "int fchmod(int " fd ", mode_t " mode ); > +.BI "int lchmod(const char *" pathname ", mode_t " mode ); Does lchmod() need any feature test macros? > .P > .BR "#include <fcntl.h>" " /* Definition of AT_* constants */" > .B #include <sys/stat.h> > @@ -60,9 +61,10 @@ Feature Test Macro Requirements for glibc (see > .fi > .SH DESCRIPTION > The > -.BR chmod () > -and > +.BR chmod (), > .BR fchmod () We use Oxford comma. > +and > +.BR lchmod () > system calls change a file's mode bits. > (The file mode consists of the file permission bits plus the set-user-ID, > set-group-ID, and sticky bits.) > @@ -76,6 +78,11 @@ which is dereferenced if it is a symbolic link. > .BR fchmod () > changes the mode of the file referred to by the open file descriptor > .IR fd . > +.IP \[bu] > +.BR lchmod () > +is like > +.BR chmod (), > +but does not dereference symbolic links. > .P > The new file mode is specified in > .IR mode , > @@ -203,8 +210,9 @@ can either be 0, or include the following flag: > If > .I pathname > is a symbolic link, do not dereference it: > -instead operate on the link itself. > -This flag is not currently implemented. > +instead operate on the link itself, > +like > +.BR lchmod (). > .P > See > .BR openat (2) > @@ -285,6 +293,7 @@ is a file descriptor referring to a file other Would you mind checking this?: $ head -n11 <CONTRIBUTING.d/git Name Git - instructions for configuring git(1) Description git-diff(1), gitattributes(5) To produce useful hunk contexts in manual pages, we need to hack git(1)'s idea of a function name, and also to tell git what is a manual page. $ git config --global diff.man.xfuncname '^\.S[SHsh] .*$'; $ echo '*.[0-9]* diff=man' >>~/.config/git/attributes; It helps reviewing diffs for manual pages. :) > than a directory. > specified > .BR AT_SYMLINK_NOFOLLOW , > which is not supported. > +(See C library/kernel differences.) > .TP > .B EPERM > The effective UID does not match the owner of the file, > @@ -310,12 +319,22 @@ This interface differs from the underlying Linux > system call, which does > have a > .I flags > argument. > +.P > +Linux 6.6 added the > +.BR fchmodat2 () > +system call with the POSIX flags argument. > .SS glibc notes > On older kernels where > -.BR fchmodat () > +.BR fchmodat2 () > is unavailable, the glibc wrapper function falls back to the use of > -.BR chmod (). > -When > +.BR fchmodat () > +when no flags are supplied, > +or to > +.BR chmod () > +otherwise. > +In the > +.BR chmod () > +fallback, if > .I pathname > is a relative pathname, > glibc constructs a pathname based on the symbolic link in > > something along those lines? Sounds good. I'd like to also add entries in HISTORY for lchmod() and fchmodat2(). And STANDARDS should also be updated. Have a lovely night! Alex -- <https://www.alejandro-colomar.es/>
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