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author | Eric W. Biederman <ebiederm@xmission.com> | 2021-12-07 16:42:35 -0600 |
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committer | Eric W. Biederman <ebiederm@xmission.com> | 2021-12-13 12:03:47 -0600 |
commit | 5e354747b2c91f64544b97760d38e2d3280307b2 (patch) | |
tree | 1beb86d3abc953a99d2ee996f820a0e0c8affc02 /arch/s390 | |
parent | 9d3f401c52e3eeeb6cf2c642a8d17879b0e1a3d3 (diff) | |
download | linux-5e354747b2c91f64544b97760d38e2d3280307b2.tar.gz linux-5e354747b2c91f64544b97760d38e2d3280307b2.tar.bz2 linux-5e354747b2c91f64544b97760d38e2d3280307b2.zip |
exit/s390: Remove dead reference to do_exit from copy_thread
My s390 assembly is not particularly good so I have read the history
of the reference to do_exit copy_thread and have been able to
verify that do_exit is not used.
The general argument is that s390 has been changed to use the generic
kernel_thread and kernel_execve and the generic versions do not call
do_exit. So it is strange to see a do_exit reference sitting there.
The history of the do_exit reference in s390's version of copy_thread
seems conclusive that the do_exit reference is something that lingers
and should have been removed several years ago.
Up through 8d19f15a60be ("[PATCH] s390 update (1/27): arch.") the
s390 code made a call to the exit(2) system call when a kernel thread
finished. Then kernel_thread_starter was added which branched
directly to the value in register 11 when the kernel thread finshed.
The value in register 11 was set in kernel_thread to
"regs.gprs[11] = (unsigned long) do_exit"
In commit 37fe5d41f640 ("s390: fold kernel_thread_helper() into
ret_from_fork()") kernel_thread_starter was moved into entry.S and
entry64.S unchanged (except for the syntax differences between inline
assemly and in the assembly file).
In commit f9a7e025dfc2 ("s390: switch to generic kernel_thread()") the
assignment to "gprs[11]" was moved into copy_thread from the old
kernel_thread. The helper kernel_thread_starter was still being used
and was still branching to "%r11" at the end.
In commit 30dcb0996e40 ("s390: switch to saner kernel_execve()
semantics") kernel_thread_starter was changed to unconditionally
branch to sysc_tracenogo instead to %r11 which held the value of
do_exit. Unfortunately copy_thread was not updated to stop passing
do_exit in "gprs[11]".
In commit 56e62a737028 ("s390: convert to generic entry")
kernel_thread_starter was replaced by __ret_from_fork. And the code
still continued to pass do_exit in "gprs[11]" despite __ret_from_fork
not caring in the slightest.
Remove this dead reference to do_exit to make it clear that s390 is
not doing anything with do_exit in copy_thread.
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Fixes: 30dcb0996e40 ("s390: switch to saner kernel_execve() semantics")
History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'arch/s390')
-rw-r--r-- | arch/s390/kernel/process.c | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c index e8858b2de24b..71d86f73b02c 100644 --- a/arch/s390/kernel/process.c +++ b/arch/s390/kernel/process.c @@ -139,7 +139,6 @@ int copy_thread(unsigned long clone_flags, unsigned long new_stackp, (unsigned long)__ret_from_fork; frame->childregs.gprs[9] = new_stackp; /* function */ frame->childregs.gprs[10] = arg; - frame->childregs.gprs[11] = (unsigned long)do_exit; frame->childregs.orig_gpr2 = -1; frame->childregs.last_break = 1; return 0; |