path: root/guts/README
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authorPeter Seebach <seebs@eee12.(none)>2010-03-16 19:26:24 -0500
committerPeter Seebach <seebs@eee12.(none)>2010-03-16 19:26:24 -0500
commit33d9386e8d818860ce603356eee074d2a2849085 (patch)
tree185f2c14b86df39403971f0651f4b6136dda147f /guts/README
initial public release
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+The files in this directory are partially machine-generated, and are
+all covered by the COPYRIGHT file in this directory.
+The set of functions covered here may seem surprising. For instance,
+obviously, fopen(3) simply calls the underlying open(2) syscall. But...
+There is a problem. In a few places in glibc, the syscalls are inlined
+such that there is no actual call to the C function open(2), just a raw
+call. So there are a couple of functions (fopen, freopen) which are
+wrapped with intent only to detect the possible creation of files.
+Many of these functions are closely related. Some programs may have
+calls to openat(), while others have calls to __openat_2(). To reduce
+code duplication, a number of functions are implemented purely as calls
+to other functions.
+When a *at() function exists, the regular function is implemented
+as *at() with AT_FDCWD as the directory fd (see the dummy #define of
+this in pseudo_client.h, used for systems which lack these.) On systems
+where AT_NOFOLLOW_SYMLINKS is not defined, the underlying *at() functions
+don't exist, so we provide a bare implementation which works only when
+the fd is AT_FDCWD...
+The creat64 and open64 families are equivalent to the plain versions with
+O_LARGEFILE in mode bits. (Again, there's a suitable dummy #define
+in pseudo_client.h.) By contrast, the stat64 functions actually do have
+some difference -- the structure they manipulate is not the same.
+The following table shows which functions are merely wrappers around
+other functions:
+ chmod: fchmodat
+ chown: fchownat
+ creat64: openat
+ creat: openat
+ __fxstatat: __fxstatat64
+ __fxstat: __fxstat64
+ __lxstat64: __fxstatat64
+ __lxstat: __fxstatat
+ mkdir: mkdirat
+ open64: openat
+ __openat_2: openat
+ __openat64_2: openat
+ openat64: openat
+ open: openat
+ rename: renameat
+ symlink: symlinkat
+ unlink: unlinkat
+ __xmknod: __xmknodat
+ __xstat64: __fxstatat64
+ __xstat: __fxstatat
+The following functions are full implementations:
+ chdir
+ fchdir
+ fchmod
+ fchmodat
+ fchown
+ fchownat
+ __fxstat64
+ __fxstatat64
+ lchown
+ mkdirat
+ openat
+ renameat
+ rmdir
+ symlinkat
+ unlinkat
+ __xmknodat
+The following functions provide only partial implementations, to trap special
+cases, to track internal data structures (for instance, close() is tracked so
+that the path to a file descriptor can be dropped when the file descriptor
+is closed), or to handle functions which may not use the underlying syscall
+ close
+ dup
+ dup2
+ fclose
+ fopen
+ fopen64
+ freopen
+ mkstemp
+ fcntl
+ fork
+ link
+ vfork
+The following functions don't have any direct database interactions,
+but are used to simulate the permissions system:
+ getegid
+ getuid
+ setgid
+ setreuid
+ geteuid
+ setegid
+ setgroups
+ setuid
+ getgid
+ seteuid
+ setregid
+ getresgid
+ setfsgid
+ setresgid
+ getresuid
+ setfsuid
+ setresuid