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diff --git a/guts/README b/guts/README new file mode 100644 index 0000000..be00d30 --- /dev/null +++ b/guts/README @@ -0,0 +1,109 @@ +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 +wrappers: + + 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 |