I am sponsoring this fast-track case for myself.
No external/ABI interfaces are changing, so there is no documentation change.
The release binding is "minor",
so it can be done in solaris_nevada (Solaris Next, OpenSolaris)
(this will never be back-ported).
DISCUSSION:
Over the years, a number of system call traps have fallen
into an unused/obsolete state. These are never called
from libc, as in the case of:
/*
* Obsolete lwp_mutex_lock() interface, no longer called from libc.
* libc now calls lwp_mutex_timedlock(lp, NULL, NULL).
* This system call trap continues to exist solely for the benefit
* of old statically-linked binaries from Solaris 9 and before.
* It should be removed from the system when we no longer care
* about such applications.
*/
int
lwp_mutex_lock(lwp_mutex_t *lp)
{
return (lwp_mutex_timedlock(lp, NULL, NULL));
}
There are cases where two traps do the same thing.
For example:
dup(fd)
is exactly the same as:
fcntl(fd, F_DUPFD, 0)
The dup() syscall trap can be eliminated in favor of
fcntl(fd, F_DUPFD, 0) (in dup() as implemented in libc).
PROPOSAL:
The time has come to actually delete these obsolete/redundant
system call traps from the kernel and free their system call
numbers for reuse by future, yet-to-be-invented system calls.
The *at() system calls were introduced in Solaris 9:
openat()
openat64()
fstatat()
fstatat64()
fchownat()
unlinkat()
renameat()
accessat()
These functions are a super-set of the corresponding traps:
open()
open64()
fstat()
fstat64()
fchown()
unlink()
rename()
access()
all of which can be implemented in libc using calls to the
corresponding *at() system call traps. There is no need
to have such duplicate functionality in the system call traps.
Aside: There is a bug fix in the libc open() function that
did not get implemented in the libc openat() function.
Such errors are a consequence of having two system call traps
that perform esentially the same operation. A bug fix in one
can be neglected in the other. There should be only one.
Finally, the *at() system calls were implemented as subcodes
of a single trap number, SYS_fsat. These system calls are
important enough for each to have its own system call trap number.
These old system call traps are already never called from libc.
They can just be deleted from the kernel:
fork()
forkall()
utime()
utimes()
futimesat()
poll()
lwp_mutex_lock()
lwp_sema_wait()
wait()
These system call wrapper functions can be reimplemented in libc as shown
amd then the old system call traps can be deleted from the kernel:
open(path, flag, ...) openat(AT_FDCWD, path, flag, ...)
creat(path, ...) open(path, O_WRONLY | O_CREAT | O_TRUNC, ...)
open64(path, flag, ...) openat64(AT_FDCWD, path, flag, ...)
creat64(path, mode) open64(path, O_WRONLY | O_CREAT | O_TRUNC, mode)
unlink(path) unlinkat(AT_FDCWD, path, 0)
rmdir(path) unlinkat(AT_FDCWD, path, AT_REMOVEDIR)
chown(path, uid, gid) fchownat(AT_FDCWD, path, uid, gid, 0)
lchown(path, uid, gid) fchownat(AT_FDCWD, path, uid, gid, AT_SYMLINK_NOFOLLOW)
fchown(fd, uid, gid) fchownat(fd, NULL, uid, gid, 0)
stat(path, &sb) fstatat(AT_FDCWD, path, &sb, 0)
lstat(path, &sb) fstatat(AT_FDCWD, path, &sb, AT_SYMLINK_NOFOLLOW)
fstat(fd, &sb) fstatat(fd, NULL, &sb, 0)
stat64(path, &sb) fstatat64(AT_FDCWD, path, &sb, 0)
lstat64(path, &sb) fstatat64(AT_FDCWD, path, &sb, AT_SYMLINK_NOFOLLOW)
fstat64(fd, &sb) fstatat64(fd, NULL, &sb, 0)
xstat(vers, path, &sb) stat(path, &sb)
lxstat(vers, path, &sb) lstat(path, &sb)
fxstat(vers, path, &sb) fstat(path, &sb)
xmknod(vers, path, ...) mknod(path, ...)
dup(fd) fcntl(fd, F_DUPFD, 0)
rename(oldnam, newnam) renameat(AT_FDCWD, oldnam, AT_FDCWD, newnam)
access(fname, amode) faccessat(AT_FDCWD, fname, amode, 0)
All of this is possible without sacrificing any part of binary
compatibility due to the Solaris 10 Branded Zone project,
integrated into onnv-gate in build snv_127. See:
PSARC 2009/253 S10C
6666646 Solaris 10 zones on OpenSolaris binary (supported) distributions
http://hub.opensolaris.org/bin/view/Community+Group+zones/s10brand_dev_guide
As part of deleting old system call traps from the kernel,
changes must be made to:
usr/src/lib/brand/solaris10
and:
usr/src/uts/common/brand/solaris10
to emulate the deleted system call traps.
Any process running in a Solaris 10 branded zone will see
a kernel interface identical to that of Solaris 10 itself.
There will be an impact on dtrace(1M) in scripts that assume
knowledge of the details of the system call trap interfaces.
For example, instead of:
syscall::open
syscall::open64
you have to type:
syscall::openat
syscall::openat64
and you also have to change 'arg0' to 'arg1' (for ::openat:entry).
See the bugid:
6906485 delete obsolete system call traps
Roger Faulkner
