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SubjectRe: [update] Re: new execve/kernel_thread design
On Mon, Oct 29, 2012 at 08:53:39AM +0100, Martin Schwidefsky wrote:

> Oops, sorry. I tested this weeks ago but it seems I never wrote a mail to
> indicate success. The current git kernel works just fine.

"Current git" being what? Linus' tree? linux-next? signal.git#arch-s390?
FWIW, the relevant diff against mainline is below, linux-next already
contains it.

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 3f3d9ca..3cdc0f1 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -136,6 +136,7 @@ config S390
select KTIME_SCALAR if 32BIT
select HAVE_ARCH_SECCOMP_FILTER
select GENERIC_KERNEL_THREAD
+ select GENERIC_KERNEL_EXECVE
select HAVE_MOD_ARCH_SPECIFIC
select MODULES_USE_ELF_RELA

diff --git a/arch/s390/include/asm/unistd.h b/arch/s390/include/asm/unistd.h
index bbbae41..ccbcab7 100644
--- a/arch/s390/include/asm/unistd.h
+++ b/arch/s390/include/asm/unistd.h
@@ -54,7 +54,6 @@
# define __ARCH_WANT_COMPAT_SYS_RT_SIGSUSPEND
# endif
#define __ARCH_WANT_SYS_EXECVE
-#define __ARCH_WANT_KERNEL_EXECVE

/*
* "Conditional" syscalls
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index ef46f66..aa8f2ba 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -330,40 +330,18 @@ ENTRY(ret_from_fork)
la %r11,STACK_FRAME_OVERHEAD(%r15)
l %r12,__LC_THREAD_INFO
l %r13,__LC_SVC_NEW_PSW+4
- tm __PT_PSW+1(%r11),0x01 # forking a kernel thread ?
- je 1f
l %r1,BASED(.Lschedule_tail)
basr %r14,%r1 # call schedule_tail
TRACE_IRQS_ON
ssm __LC_SVC_NEW_PSW # reenable interrupts
- j sysc_tracenogo
-
-1: # it's a kernel thread
- st %r15,__PT_R15(%r11) # store stack pointer for new kthread
- l %r1,BASED(.Lschedule_tail)
- basr %r14,%r1 # call schedule_tail
- TRACE_IRQS_ON
- ssm __LC_SVC_NEW_PSW # reenable interrupts
- lm %r9,%r11,__PT_R9(%r11) # load gprs
+ tm __PT_PSW+1(%r11),0x01 # forking a kernel thread ?
+ jne sysc_tracenogo
+ # it's a kernel thread
+ lm %r9,%r10,__PT_R9(%r11) # load gprs
ENTRY(kernel_thread_starter)
la %r2,0(%r10)
basr %r14,%r9
- la %r2,0
- br %r11 # do_exit
-
-#
-# kernel_execve function needs to deal with pt_regs that is not
-# at the usual place
-#
-ENTRY(ret_from_kernel_execve)
- ssm __LC_PGM_NEW_PSW # disable I/O and ext. interrupts
- lr %r15,%r2
- lr %r11,%r2
- ahi %r15,-STACK_FRAME_OVERHEAD
- xc __SF_BACKCHAIN(4,%r15),__SF_BACKCHAIN(%r15)
- l %r12,__LC_THREAD_INFO
- ssm __LC_SVC_NEW_PSW # reenable interrupts
- j sysc_return
+ j sysc_tracenogo

/*
* Program check handler routine
diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index 07d8de3..499e95e 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -352,33 +352,17 @@ sysc_tracenogo:
ENTRY(ret_from_fork)
la %r11,STACK_FRAME_OVERHEAD(%r15)
lg %r12,__LC_THREAD_INFO
- tm __PT_PSW+1(%r11),0x01 # forking a kernel thread ?
- je 1f
brasl %r14,schedule_tail
TRACE_IRQS_ON
ssm __LC_SVC_NEW_PSW # reenable interrupts
- j sysc_tracenogo
-1: # it's a kernel thread
- stg %r15,__PT_R15(%r11) # store stack pointer for new kthread
- brasl %r14,schedule_tail
- TRACE_IRQS_ON
- ssm __LC_SVC_NEW_PSW # reenable interrupts
- lmg %r9,%r11,__PT_R9(%r11) # load gprs
+ tm __PT_PSW+1(%r11),0x01 # forking a kernel thread ?
+ jne sysc_tracenogo
+ # it's a kernel thread
+ lmg %r9,%r10,__PT_R9(%r11) # load gprs
ENTRY(kernel_thread_starter)
la %r2,0(%r10)
basr %r14,%r9
- la %r2,0
- br %r11 # do_exit
-
-ENTRY(ret_from_kernel_execve)
- ssm __LC_PGM_NEW_PSW # disable I/O and ext. interrupts
- lgr %r15,%r2
- lgr %r11,%r2
- aghi %r15,-STACK_FRAME_OVERHEAD
- xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
- lg %r12,__LC_THREAD_INFO
- ssm __LC_SVC_NEW_PSW # reenable interrupts
- j sysc_return
+ j sysc_tracenogo

/*
* Program check handler routine

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