x86 -tip: entry_64.S cleanup series

x86 -tip: entry_64.S cleanup series

[gorcunov]

  Hi, here is a trivial cleanups for entry_64.S,
please review. The dangerous one is patch 2: get rid
of back jump -- check it twice.

Alexander, I hope it doesn't interfere with the stuff
you are working on?

		- Cyrill -

[PATCH 1/5] x86: entry_64.S - use ENTRY to define child_rip

[gorcunov]

From: Cyrill Gorcunov <gorcunov@gmail.com>

child_rip is called not by its name but indirectly
rather so make it global and aligned.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
 arch/x86/kernel/entry_64.S |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 64688db..098ba0b 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1322,7 +1322,7 @@ ENTRY(kernel_thread)
 	CFI_ENDPROC
 END(kernel_thread)
 
-child_rip:
+ENTRY(child_rip)
 	pushq $0		# fake return address
 	CFI_STARTPROC
 	/*
-- 
1.6.0.4.603.gbc9c0

[PATCH 2/5] x86: ret_from_fork - get rid of jump back

[gorcunov]

From: Cyrill Gorcunov <gorcunov@gmail.com>

Impact: cleanup, microoptimization

Use straightforward jumping if possible, cpu like it.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
 arch/x86/kernel/entry_64.S |   10 ++++------
 1 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 098ba0b..7b52b0f 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -379,7 +379,10 @@ ENTRY(ret_from_fork)
 	GET_THREAD_INFO(%rcx)
 	testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT),TI_flags(%rcx)
 	CFI_REMEMBER_STATE
-	jnz rff_trace
+	jz rff_action
+	movq %rsp,%rdi
+	call syscall_trace_leave
+	GET_THREAD_INFO(%rcx)
 rff_action:
 	RESTORE_REST
 	testl $3,CS-ARGOFFSET(%rsp)	# from kernel_thread?
@@ -389,11 +392,6 @@ rff_action:
 	RESTORE_TOP_OF_STACK %rdi, -ARGOFFSET
 	jmp ret_from_sys_call
 	CFI_RESTORE_STATE
-rff_trace:
-	movq %rsp,%rdi
-	call syscall_trace_leave
-	GET_THREAD_INFO(%rcx)
-	jmp rff_action
 	CFI_ENDPROC
 END(ret_from_fork)
 
-- 
1.6.0.4.603.gbc9c0

[PATCH 3/5] x86: entry_64.S - use X86_EFLAGS_IF instead of hardcoded number

[gorcunov]

From: Cyrill Gorcunov <gorcunov@gmail.com>

Impact: cleanup

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
 arch/x86/kernel/entry_64.S |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 7b52b0f..c409f73 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -199,7 +199,7 @@ ENTRY(native_usergs_sysret64)
 	pushq %rax /* rsp */
 	CFI_ADJUST_CFA_OFFSET	8
 	CFI_REL_OFFSET	rsp,0
-	pushq $(1<<9) /* eflags - interrupts on */
+	pushq $X86_EFLAGS_IF /* eflags - interrupts on */
 	CFI_ADJUST_CFA_OFFSET	8
 	/*CFI_REL_OFFSET	rflags,0*/
 	pushq $__KERNEL_CS /* cs */
-- 
1.6.0.4.603.gbc9c0

[PATCH 4/5] x86: ret_from_fork - add CFI proc annotation

[gorcunov]

From: Cyrill Gorcunov <gorcunov@gmail.com>

ret_from_fork is definitly procedure so mark it as that.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
 arch/x86/kernel/entry_64.S |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index c409f73..a21be86 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -370,6 +370,7 @@ END(save_paranoid)
  */
 /* rdi:	prev */
 ENTRY(ret_from_fork)
+	CFI_STARTPROC
 	DEFAULT_FRAME
 	push kernel_eflags(%rip)
 	CFI_ADJUST_CFA_OFFSET 8
-- 
1.6.0.4.603.gbc9c0

[PATCH 5/5] x86: entry_64.S - trivial: space, comments fixup

[gorcunov]

From: Cyrill Gorcunov <gorcunov@gmail.com>

Impact: cleanup

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
 arch/x86/kernel/entry_64.S |   92 ++++++++++++++++++++++---------------------
 1 files changed, 47 insertions(+), 45 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index a21be86..5ccf410 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1119,8 +1119,8 @@ paranoidzeroentry machine_check do_machine_check
 zeroentry simd_coprocessor_error do_simd_coprocessor_error
 
 	/*
- 	 * "Paranoid" exit path from exception stack.
-  	 * Paranoid because this is used by NMIs and cannot take
+	 * "Paranoid" exit path from exception stack.
+	 * Paranoid because this is used by NMIs and cannot take
 	 * any kernel state for granted.
 	 * We don't do kernel preemption checks here, because only
 	 * NMI should be common and it does not enable IRQs and
@@ -1225,7 +1225,7 @@ error_kernelspace:
 	cmpq %rcx,RIP+8(%rsp)
 	je error_swapgs
 	cmpq $gs_change,RIP+8(%rsp)
-        je error_swapgs
+	je error_swapgs
 	jmp error_sti
 KPROBE_END(error_entry)
 
@@ -1249,36 +1249,36 @@ KPROBE_ENTRY(error_exit)
 	CFI_ENDPROC
 KPROBE_END(error_exit)
 
-       /* Reload gs selector with exception handling */
-       /* edi:  new selector */
+	/* Reload gs selector with exception handling */
+	/* edi:  new selector */
 ENTRY(native_load_gs_index)
 	CFI_STARTPROC
 	pushf
 	CFI_ADJUST_CFA_OFFSET 8
 	DISABLE_INTERRUPTS(CLBR_ANY | ~(CLBR_RDI))
-        SWAPGS
+	SWAPGS
 gs_change:
-        movl %edi,%gs
+	movl %edi,%gs
 2:	mfence		/* workaround */
 	SWAPGS
-        popf
+	popf
 	CFI_ADJUST_CFA_OFFSET -8
-        ret
+	ret
 	CFI_ENDPROC
 END(native_load_gs_index)
 
-        .section __ex_table,"a"
-        .align 8
-        .quad gs_change,bad_gs
-        .previous
-        .section .fixup,"ax"
+	.section __ex_table,"a"
+	.align 8
+	.quad gs_change,bad_gs
+	.previous
+	.section .fixup,"ax"
 	/* running with kernelgs */
 bad_gs:
 	SWAPGS			/* switch back to user gs */
 	xorl %eax,%eax
-        movl %eax,%gs
-        jmp  2b
-        .previous
+	movl %eax,%gs
+	jmp  2b
+	.previous
 
 /*
  * Create a kernel thread.
@@ -1313,7 +1313,7 @@ ENTRY(kernel_thread)
 	 * so internally to the x86_64 port you can rely on kernel_thread()
 	 * not to reschedule the child before returning, this avoids the need
 	 * of hacks for example to fork off the per-CPU idle tasks.
-         * [Hopefully no generic code relies on the reschedule -AK]
+	 * [Hopefully no generic code relies on the reschedule -AK]
 	 */
 	RESTORE_ALL
 	UNFAKE_STACK_FRAME
@@ -1420,7 +1420,7 @@ nmi_schedule:
 	CFI_ENDPROC
 #else
 	jmp paranoid_exit
- 	CFI_ENDPROC
+	CFI_ENDPROC
 #endif
 KPROBE_END(nmi)
 
@@ -1455,22 +1455,24 @@ KPROBE_END(ignore_sysret)
 zeroentry xen_hypervisor_callback xen_do_hypervisor_callback
 
 /*
-# A note on the "critical region" in our callback handler.
-# We want to avoid stacking callback handlers due to events occurring
-# during handling of the last event. To do this, we keep events disabled
-# until we've done all processing. HOWEVER, we must enable events before
-# popping the stack frame (can't be done atomically) and so it would still
-# be possible to get enough handler activations to overflow the stack.
-# Although unlikely, bugs of that kind are hard to track down, so we'd
-# like to avoid the possibility.
-# So, on entry to the handler we detect whether we interrupted an
-# existing activation in its critical region -- if so, we pop the current
-# activation and restart the handler using the previous one.
-*/
+ * A note on the "critical region" in our callback handler.
+ * We want to avoid stacking callback handlers due to events occurring
+ * during handling of the last event. To do this, we keep events disabled
+ * until we've done all processing. HOWEVER, we must enable events before
+ * popping the stack frame (can't be done atomically) and so it would still
+ * be possible to get enough handler activations to overflow the stack.
+ * Although unlikely, bugs of that kind are hard to track down, so we'd
+ * like to avoid the possibility.
+ * So, on entry to the handler we detect whether we interrupted an
+ * existing activation in its critical region -- if so, we pop the current
+ * activation and restart the handler using the previous one.
+ */
 ENTRY(xen_do_hypervisor_callback)   # do_hypervisor_callback(struct *pt_regs)
 	CFI_STARTPROC
-/* Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will
-   see the correct pointer to the pt_regs */
+/*
+ * Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will
+ * see the correct pointer to the pt_regs
+ */
 	movq %rdi, %rsp            # we don't return, adjust the stack frame
 	CFI_ENDPROC
 	DEFAULT_FRAME
@@ -1488,18 +1490,18 @@ ENTRY(xen_do_hypervisor_callback)   # do_hypervisor_callback(struct *pt_regs)
 END(do_hypervisor_callback)
 
 /*
-# Hypervisor uses this for application faults while it executes.
-# We get here for two reasons:
-#  1. Fault while reloading DS, ES, FS or GS
-#  2. Fault while executing IRET
-# Category 1 we do not need to fix up as Xen has already reloaded all segment
-# registers that could be reloaded and zeroed the others.
-# Category 2 we fix up by killing the current process. We cannot use the
-# normal Linux return path in this case because if we use the IRET hypercall
-# to pop the stack frame we end up in an infinite loop of failsafe callbacks.
-# We distinguish between categories by comparing each saved segment register
-# with its current contents: any discrepancy means we in category 1.
-*/
+ * Hypervisor uses this for application faults while it executes.
+ * We get here for two reasons:
+ *  1. Fault while reloading DS, ES, FS or GS
+ *  2. Fault while executing IRET
+ * Category 1 we do not need to fix up as Xen has already reloaded all segment
+ * registers that could be reloaded and zeroed the others.
+ * Category 2 we fix up by killing the current process. We cannot use the
+ * normal Linux return path in this case because if we use the IRET hypercall
+ * to pop the stack frame we end up in an infinite loop of failsafe callbacks.
+ * We distinguish between categories by comparing each saved segment register
+ * with its current contents: any discrepancy means we in category 1.
+ */
 ENTRY(xen_failsafe_callback)
 	INTR_FRAME 1 (6*8)
 	/*CFI_REL_OFFSET gs,GS*/
-- 
1.6.0.4.603.gbc9c0

Re: [PATCH 2/5] x86: ret_from_fork - get rid of jump back

[Cyrill Gorcunov]

[gorcunov@gmail.com - Wed, Nov 26, 2008 at 10:17:01PM +0300]
| From: Cyrill Gorcunov <gorcunov@gmail.com>
| 
| Impact: cleanup, microoptimization
| 
| Use straightforward jumping if possible, cpu like it.

Wrong word, not _straight_ forward but forward branch target
in this case.

| 
| Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
| ---
|  arch/x86/kernel/entry_64.S |   10 ++++------
|  1 files changed, 4 insertions(+), 6 deletions(-)
| 
		- Cyrill -

Re: [PATCH 2/5] x86: ret_from_fork - get rid of jump back

[Andi Kleen]

gorcunov@gmail.com writes:
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -379,7 +379,10 @@ ENTRY(ret_from_fork)
>  	GET_THREAD_INFO(%rcx)
>  	testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT),TI_flags(%rcx)
>  	CFI_REMEMBER_STATE
> -	jnz rff_trace
> +	jz rff_action
> +	movq %rsp,%rdi
> +	call syscall_trace_leave
> +	GET_THREAD_INFO(%rcx)

The uncommon path is supposed to be out of line. I don't think
the CPU will like that.

-Andi

>  rff_action:

-- 
ak@linux.intel.com

Re: [PATCH 2/5] x86: ret_from_fork - get rid of jump back

[Cyrill Gorcunov]

[Andi Kleen - Wed, Nov 26, 2008 at 09:04:33PM +0100]
| gorcunov@gmail.com writes:
| > --- a/arch/x86/kernel/entry_64.S
| > +++ b/arch/x86/kernel/entry_64.S
| > @@ -379,7 +379,10 @@ ENTRY(ret_from_fork)
| >  	GET_THREAD_INFO(%rcx)
| >  	testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT),TI_flags(%rcx)
| >  	CFI_REMEMBER_STATE
| > -	jnz rff_trace
| > +	jz rff_action
| > +	movq %rsp,%rdi
| > +	call syscall_trace_leave
| > +	GET_THREAD_INFO(%rcx)
| 
| The uncommon path is supposed to be out of line. I don't think
| the CPU will like that.
| 
| -Andi
| 
| >  rff_action:
| 
| -- 
| ak@linux.intel.com
| 

Aha! Thanks Andi for review.

		- Cyrill -

Re: [PATCH 2/5] x86: ret_from_fork - get rid of jump back

[Cyrill Gorcunov]

[Cyrill Gorcunov - Wed, Nov 26, 2008 at 11:10:54PM +0300]
...
| | 
| | The uncommon path is supposed to be out of line. I don't think
| | the CPU will like that.
| | 
| | -Andi
| | 
| | >  rff_action:
| | 
| | -- 
| | ak@linux.intel.com
| | 
| 
| Aha! Thanks Andi for review.
| 
| 		- Cyrill -

And if I would be tracing all and everywhere would it be
common then? :)

		- Cyrill -

Re: [PATCH 4/5] x86: ret_from_fork - add CFI proc annotation

[Alexander van Heukelum]

On Wed, 26 Nov 2008 22:17:03 +0300, gorcunov@gmail.com said:
> From: Cyrill Gorcunov <gorcunov@gmail.com>
> 
> ret_from_fork is definitly procedure so mark it as that.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
> ---
>  arch/x86/kernel/entry_64.S |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
> index c409f73..a21be86 100644
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -370,6 +370,7 @@ END(save_paranoid)
>   */
>  /* rdi:	prev */
>  ENTRY(ret_from_fork)
> +	CFI_STARTPROC
>  	DEFAULT_FRAME
>  	push kernel_eflags(%rip)
>  	CFI_ADJUST_CFA_OFFSET 8

This is not needed/wanted. DEFAULT_FRAME includes "CFI_STARTPROC simple"
already.

Alexander

> 1.6.0.4.603.gbc9c0
> 
-- 
  Alexander van Heukelum
  heukelum@fastmail.fm

-- 
http://www.fastmail.fm - The professional email service

Re: [PATCH 1/5] x86: entry_64.S - use ENTRY to define child_rip

[Alexander van Heukelum]

On Wed, 26 Nov 2008 22:17:00 +0300, gorcunov@gmail.com said:
> From: Cyrill Gorcunov <gorcunov@gmail.com>
> 
> child_rip is called not by its name but indirectly
> rather so make it global and aligned.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
> ---
>  arch/x86/kernel/entry_64.S |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
> index 64688db..098ba0b 100644
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -1322,7 +1322,7 @@ ENTRY(kernel_thread)
>  	CFI_ENDPROC
>  END(kernel_thread)
>  
> -child_rip:
> +ENTRY(child_rip)
>  	pushq $0		# fake return address
>  	CFI_STARTPROC
>  	/*

Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>

> 1.6.0.4.603.gbc9c0
> 
-- 
  Alexander van Heukelum
  heukelum@fastmail.fm

-- 
http://www.fastmail.fm - Accessible with your email software
                          or over the web

Re: [PATCH 3/5] x86: entry_64.S - use X86_EFLAGS_IF instead of hardcoded number

[Alexander van Heukelum]

On Wed, 26 Nov 2008 22:17:02 +0300, gorcunov@gmail.com said:
> From: Cyrill Gorcunov <gorcunov@gmail.com>
> 
> Impact: cleanup
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>

Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>


>  arch/x86/kernel/entry_64.S |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
> index 7b52b0f..c409f73 100644
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -199,7 +199,7 @@ ENTRY(native_usergs_sysret64)
>  	pushq %rax /* rsp */
>  	CFI_ADJUST_CFA_OFFSET	8
>  	CFI_REL_OFFSET	rsp,0
> -	pushq $(1<<9) /* eflags - interrupts on */
> +	pushq $X86_EFLAGS_IF /* eflags - interrupts on */
>  	CFI_ADJUST_CFA_OFFSET	8
>  	/*CFI_REL_OFFSET	rflags,0*/
>  	pushq $__KERNEL_CS /* cs */
> 
> 1.6.0.4.603.gbc9c0
> 
-- 
  Alexander van Heukelum
  heukelum@fastmail.fm

-- 
http://www.fastmail.fm - A no graphics, no pop-ups email service

Re: [PATCH 5/5] x86: entry_64.S - trivial: space, comments fixup

[Alexander van Heukelum]

On Wed, 26 Nov 2008 22:17:04 +0300, gorcunov@gmail.com said:
> From: Cyrill Gorcunov <gorcunov@gmail.com>
> 
> Impact: cleanup
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>

Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>


>  arch/x86/kernel/entry_64.S |   92
>  ++++++++++++++++++++++---------------------
>  1 files changed, 47 insertions(+), 45 deletions(-)
> 
> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
> index a21be86..5ccf410 100644
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -1119,8 +1119,8 @@ paranoidzeroentry machine_check do_machine_check
>  zeroentry simd_coprocessor_error do_simd_coprocessor_error
>  
>  	/*
> - 	 * "Paranoid" exit path from exception stack.
> -  	 * Paranoid because this is used by NMIs and cannot take
> +	 * "Paranoid" exit path from exception stack.
> +	 * Paranoid because this is used by NMIs and cannot take
>  	 * any kernel state for granted.
>  	 * We don't do kernel preemption checks here, because only
>  	 * NMI should be common and it does not enable IRQs and
> @@ -1225,7 +1225,7 @@ error_kernelspace:
>  	cmpq %rcx,RIP+8(%rsp)
>  	je error_swapgs
>  	cmpq $gs_change,RIP+8(%rsp)
> -        je error_swapgs
> +	je error_swapgs
>  	jmp error_sti
>  KPROBE_END(error_entry)
>  
> @@ -1249,36 +1249,36 @@ KPROBE_ENTRY(error_exit)
>  	CFI_ENDPROC
>  KPROBE_END(error_exit)
>  
> -       /* Reload gs selector with exception handling */
> -       /* edi:  new selector */
> +	/* Reload gs selector with exception handling */
> +	/* edi:  new selector */
>  ENTRY(native_load_gs_index)
>  	CFI_STARTPROC
>  	pushf
>  	CFI_ADJUST_CFA_OFFSET 8
>  	DISABLE_INTERRUPTS(CLBR_ANY | ~(CLBR_RDI))
> -        SWAPGS
> +	SWAPGS
>  gs_change:
> -        movl %edi,%gs
> +	movl %edi,%gs
>  2:	mfence		/* workaround */
>  	SWAPGS
> -        popf
> +	popf
>  	CFI_ADJUST_CFA_OFFSET -8
> -        ret
> +	ret
>  	CFI_ENDPROC
>  END(native_load_gs_index)
>  
> -        .section __ex_table,"a"
> -        .align 8
> -        .quad gs_change,bad_gs
> -        .previous
> -        .section .fixup,"ax"
> +	.section __ex_table,"a"
> +	.align 8
> +	.quad gs_change,bad_gs
> +	.previous
> +	.section .fixup,"ax"
>  	/* running with kernelgs */
>  bad_gs:
>  	SWAPGS			/* switch back to user gs */
>  	xorl %eax,%eax
> -        movl %eax,%gs
> -        jmp  2b
> -        .previous
> +	movl %eax,%gs
> +	jmp  2b
> +	.previous
>  
>  /*
>   * Create a kernel thread.
> @@ -1313,7 +1313,7 @@ ENTRY(kernel_thread)
>  	 * so internally to the x86_64 port you can rely on kernel_thread()
>  	 * not to reschedule the child before returning, this avoids the need
>  	 * of hacks for example to fork off the per-CPU idle tasks.
> -         * [Hopefully no generic code relies on the reschedule -AK]
> +	 * [Hopefully no generic code relies on the reschedule -AK]
>  	 */
>  	RESTORE_ALL
>  	UNFAKE_STACK_FRAME
> @@ -1420,7 +1420,7 @@ nmi_schedule:
>  	CFI_ENDPROC
>  #else
>  	jmp paranoid_exit
> - 	CFI_ENDPROC
> +	CFI_ENDPROC
>  #endif
>  KPROBE_END(nmi)
>  
> @@ -1455,22 +1455,24 @@ KPROBE_END(ignore_sysret)
>  zeroentry xen_hypervisor_callback xen_do_hypervisor_callback
>  
>  /*
> -# A note on the "critical region" in our callback handler.
> -# We want to avoid stacking callback handlers due to events occurring
> -# during handling of the last event. To do this, we keep events disabled
> -# until we've done all processing. HOWEVER, we must enable events before
> -# popping the stack frame (can't be done atomically) and so it would
> still
> -# be possible to get enough handler activations to overflow the stack.
> -# Although unlikely, bugs of that kind are hard to track down, so we'd
> -# like to avoid the possibility.
> -# So, on entry to the handler we detect whether we interrupted an
> -# existing activation in its critical region -- if so, we pop the
> current
> -# activation and restart the handler using the previous one.
> -*/
> + * A note on the "critical region" in our callback handler.
> + * We want to avoid stacking callback handlers due to events occurring
> + * during handling of the last event. To do this, we keep events
> disabled
> + * until we've done all processing. HOWEVER, we must enable events
> before
> + * popping the stack frame (can't be done atomically) and so it would
> still
> + * be possible to get enough handler activations to overflow the stack.
> + * Although unlikely, bugs of that kind are hard to track down, so we'd
> + * like to avoid the possibility.
> + * So, on entry to the handler we detect whether we interrupted an
> + * existing activation in its critical region -- if so, we pop the
> current
> + * activation and restart the handler using the previous one.
> + */
>  ENTRY(xen_do_hypervisor_callback)   # do_hypervisor_callback(struct
>  *pt_regs)
>  	CFI_STARTPROC
> -/* Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will
> -   see the correct pointer to the pt_regs */
> +/*
> + * Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will
> + * see the correct pointer to the pt_regs
> + */
>  	movq %rdi, %rsp            # we don't return, adjust the stack frame
>  	CFI_ENDPROC
>  	DEFAULT_FRAME
> @@ -1488,18 +1490,18 @@ ENTRY(xen_do_hypervisor_callback)   #
> do_hypervisor_callback(struct *pt_regs)
>  END(do_hypervisor_callback)
>  
>  /*
> -# Hypervisor uses this for application faults while it executes.
> -# We get here for two reasons:
> -#  1. Fault while reloading DS, ES, FS or GS
> -#  2. Fault while executing IRET
> -# Category 1 we do not need to fix up as Xen has already reloaded all
> segment
> -# registers that could be reloaded and zeroed the others.
> -# Category 2 we fix up by killing the current process. We cannot use the
> -# normal Linux return path in this case because if we use the IRET
> hypercall
> -# to pop the stack frame we end up in an infinite loop of failsafe
> callbacks.
> -# We distinguish between categories by comparing each saved segment
> register
> -# with its current contents: any discrepancy means we in category 1.
> -*/
> + * Hypervisor uses this for application faults while it executes.
> + * We get here for two reasons:
> + *  1. Fault while reloading DS, ES, FS or GS
> + *  2. Fault while executing IRET
> + * Category 1 we do not need to fix up as Xen has already reloaded all
> segment
> + * registers that could be reloaded and zeroed the others.
> + * Category 2 we fix up by killing the current process. We cannot use
> the
> + * normal Linux return path in this case because if we use the IRET
> hypercall
> + * to pop the stack frame we end up in an infinite loop of failsafe
> callbacks.
> + * We distinguish between categories by comparing each saved segment
> register
> + * with its current contents: any discrepancy means we in category 1.
> + */
>  ENTRY(xen_failsafe_callback)
>  	INTR_FRAME 1 (6*8)
>  	/*CFI_REL_OFFSET gs,GS*/
> -- 
> 1.6.0.4.603.gbc9c0
> 
-- 
  Alexander van Heukelum
  heukelum@fastmail.fm

-- 
http://www.fastmail.fm - The way an email service should be

Re: [PATCH 4/5] x86: ret_from_fork - add CFI proc annotation

[Cyrill Gorcunov]

On Thu, Nov 27, 2008 at 1:15 PM, Alexander van Heukelum
<heukelum@fastmail.fm> wrote:
>
> On Wed, 26 Nov 2008 22:17:03 +0300, gorcunov@gmail.com said:
>> From: Cyrill Gorcunov <gorcunov@gmail.com>
>>
>> ret_from_fork is definitly procedure so mark it as that.
>>
>> Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
>> ---
>>  arch/x86/kernel/entry_64.S |    1 +
>>  1 files changed, 1 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
>> index c409f73..a21be86 100644
>> --- a/arch/x86/kernel/entry_64.S
>> +++ b/arch/x86/kernel/entry_64.S
>> @@ -370,6 +370,7 @@ END(save_paranoid)
>>   */
>>  /* rdi:      prev */
>>  ENTRY(ret_from_fork)
>> +     CFI_STARTPROC
>>       DEFAULT_FRAME
>>       push kernel_eflags(%rip)
>>       CFI_ADJUST_CFA_OFFSET 8
>
> This is not needed/wanted. DEFAULT_FRAME includes "CFI_STARTPROC simple"
> already.
>
> Alexander
>
>> 1.6.0.4.603.gbc9c0
>>
> --
>  Alexander van Heukelum
>  heukelum@fastmail.fm
>
> --
> http://www.fastmail.fm - The professional email service
>
>

Indeed, thanks (such an indirect and nested definition sometime confusing)

Re: [PATCH 3/5] x86: entry_64.S - use X86_EFLAGS_IF instead of hardcoded number

[Ingo Molnar]

* Alexander van Heukelum <heukelum@fastmail.fm> wrote:

> On Wed, 26 Nov 2008 22:17:02 +0300, gorcunov@gmail.com said:
> > From: Cyrill Gorcunov <gorcunov@gmail.com>
> > 
> > Impact: cleanup
> > 
> > Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
> 
> Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>

applied, thanks guys!

	Ingo

Re: [PATCH 5/5] x86: entry_64.S - trivial: space, comments fixup

[Ingo Molnar]

* Alexander van Heukelum <heukelum@fastmail.fm> wrote:

> On Wed, 26 Nov 2008 22:17:04 +0300, gorcunov@gmail.com said:
> > From: Cyrill Gorcunov <gorcunov@gmail.com>
> > 
> > Impact: cleanup
> > 
> > Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
> 
> Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>

Cyrill, could you please rework the still relevant bits against latest 
tip/master? Alexander's wider patch got in the way.

Thanks,

	Ingo

Re: [PATCH 1/5] x86: entry_64.S - use ENTRY to define child_rip

[Ingo Molnar]

* Alexander van Heukelum <heukelum@fastmail.fm> wrote:

> 
> On Wed, 26 Nov 2008 22:17:00 +0300, gorcunov@gmail.com said:
> > From: Cyrill Gorcunov <gorcunov@gmail.com>
> > 
> > child_rip is called not by its name but indirectly
> > rather so make it global and aligned.
> > 
> > Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
> > ---
> >  arch/x86/kernel/entry_64.S |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
> > index 64688db..098ba0b 100644
> > --- a/arch/x86/kernel/entry_64.S
> > +++ b/arch/x86/kernel/entry_64.S
> > @@ -1322,7 +1322,7 @@ ENTRY(kernel_thread)
> >  	CFI_ENDPROC
> >  END(kernel_thread)
> >  
> > -child_rip:
> > +ENTRY(child_rip)
> >  	pushq $0		# fake return address
> >  	CFI_STARTPROC
> >  	/*
> 
> Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>

applied to tip/x86/irq, thanks!

	Ingo

Re: [PATCH 5/5] x86: entry_64.S - trivial: space, comments fixup

[Cyrill Gorcunov]

On Thu, Nov 27, 2008 at 3:02 PM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Alexander van Heukelum <heukelum@fastmail.fm> wrote:
>
>> On Wed, 26 Nov 2008 22:17:04 +0300, gorcunov@gmail.com said:
>> > From: Cyrill Gorcunov <gorcunov@gmail.com>
>> >
>> > Impact: cleanup
>> >
>> > Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
>>
>> Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>
>
> Cyrill, could you please rework the still relevant bits against latest
> tip/master? Alexander's wider patch got in the way.
>
> Thanks,
>
>        Ingo
>

yep, no problem (wait 'till evening please)

Re: [PATCH 2/5] x86: ret_from_fork - get rid of jump back

[Ingo Molnar]

* Cyrill Gorcunov <gorcunov@gmail.com> wrote:

> [Andi Kleen - Wed, Nov 26, 2008 at 09:04:33PM +0100]
> | gorcunov@gmail.com writes:
> | > --- a/arch/x86/kernel/entry_64.S
> | > +++ b/arch/x86/kernel/entry_64.S
> | > @@ -379,7 +379,10 @@ ENTRY(ret_from_fork)
> | >  	GET_THREAD_INFO(%rcx)
> | >  	testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT),TI_flags(%rcx)
> | >  	CFI_REMEMBER_STATE
> | > -	jnz rff_trace
> | > +	jz rff_action
> | > +	movq %rsp,%rdi
> | > +	call syscall_trace_leave
> | > +	GET_THREAD_INFO(%rcx)
> | 
> | The uncommon path is supposed to be out of line. I don't think
> | the CPU will like that.
> | 
> | -Andi
> | 
> | >  rff_action:
> | 
> | -- 
> | ak@linux.intel.com
> | 
> 
> Aha! Thanks Andi for review.

Unfortunately that review got you off the right track ...

The principle you applied was good: entry_64.S is murky, and we want 
to simplify the current overcomplicated assembly code flow spaghetti 
there.

Note that if you take a closer look at rff_trace/rff_action 
ret_from_fork code here, you'll realize that it does all the wrong 
things: for example it checks the TIF flag - while later on jumping 
back to the ret-from-syscall path - duplicating the check needlessly.

But it gets worse than that: checking for _TIF_SYSCALL_TRACE is 
completely unnecessary here because we clear that flag for every 
freshly forked task. So the whole "tracing" code here, for which there 
is this "out of line jump optimization" is in reality completely dead 
code in the ptrace case...

Could you test something like the patch attached below, which cleans 
up this code and applies the code reduction and speedup? Warning: 
completely untested! Please check that things like strace -f and gdb 
attaching to forked tasks still works fine. (it should by all means)

Thanks,

	Ingo

---
 arch/x86/kernel/entry_64.S |   31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

Index: linux/arch/x86/kernel/entry_64.S
===================================================================
--- linux.orig/arch/x86/kernel/entry_64.S
+++ linux/arch/x86/kernel/entry_64.S
@@ -366,34 +366,35 @@ ENTRY(save_paranoid)
 END(save_paranoid)
 
 /*
- * A newly forked process directly context switches into this.
+ * A newly forked process directly context switches into this address.
+ *
+ * rdi: prev task we switched from
  */
-/* rdi:	prev */
 ENTRY(ret_from_fork)
 	DEFAULT_FRAME
+
 	push kernel_eflags(%rip)
 	CFI_ADJUST_CFA_OFFSET 8
-	popf				# reset kernel eflags
+	popf					# reset kernel eflags
 	CFI_ADJUST_CFA_OFFSET -8
-	call schedule_tail
+
+	call schedule_tail			# rdi: 'prev' task parameter
+
 	GET_THREAD_INFO(%rcx)
-	testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT),TI_flags(%rcx)
+
 	CFI_REMEMBER_STATE
-	jnz rff_trace
-rff_action:
 	RESTORE_REST
-	testl $3,CS-ARGOFFSET(%rsp)	# from kernel_thread?
+
+	testl $3, CS-ARGOFFSET(%rsp)		# from kernel_thread?
 	je   int_ret_from_sys_call
-	testl $_TIF_IA32,TI_flags(%rcx)
+
+	testl $_TIF_IA32, TI_flags(%rcx)	# 32-bit compat task needs IRET
 	jnz  int_ret_from_sys_call
+
 	RESTORE_TOP_OF_STACK %rdi, -ARGOFFSET
-	jmp ret_from_sys_call
+	jmp ret_from_sys_call			# go to the SYSRET fastpath
+
 	CFI_RESTORE_STATE
-rff_trace:
-	movq %rsp,%rdi
-	call syscall_trace_leave
-	GET_THREAD_INFO(%rcx)
-	jmp rff_action
 	CFI_ENDPROC
 END(ret_from_fork)
 

Re: [PATCH 2/5] x86: ret_from_fork - get rid of jump back

[Andi Kleen]

> But it gets worse than that: checking for _TIF_SYSCALL_TRACE is 
> completely unnecessary here because we clear that flag for every 

That's true. I found your 2005 changeset which did that, although
it seems to have been written before meaningful changelogs
became en vogue so it's unclear why. But assuming strace/gdb
always reattach it's probably ok.

But _TIF_SYSCALL_AUDIT for which it also checks is not always cleared so 
it's not completely dead. 

That said in theory the ret_from_sys checks should handle those too, 
so it might be unnecessary (I don't remember why I added the additional
check here).  Still removing it  would change the order
of signal checks versus trace checks and since signal
handling is always hairy one would need to be very careful
when changing it to not break anything.

-Andi

Re: [PATCH 2/5] x86: ret_from_fork - get rid of jump back

[Cyrill Gorcunov]

[Ingo Molnar - Thu, Nov 27, 2008 at 02:41:21PM +0100]
...
| 
| Could you test something like the patch attached below, which cleans 
| up this code and applies the code reduction and speedup? Warning: 
| completely untested! Please check that things like strace -f and gdb 
| attaching to forked tasks still works fine. (it should by all means)
|
...

Thanks for explanation Ingo! Will try to test this but I will require
some time.

		- Cyrill -

Re: [PATCH 5/5] x86: entry_64.S - trivial: space, comments fixup

[Cyrill Gorcunov]

[Ingo Molnar - Thu, Nov 27, 2008 at 01:02:34PM +0100]
| > > From: Cyrill Gorcunov <gorcunov@gmail.com>
| > > 
| > > Impact: cleanup
| > > 
| > > Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
| > 
| > Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>
| 
| Cyrill, could you please rework the still relevant bits against latest 
| tip/master? Alexander's wider patch got in the way.
| 
| Thanks,
| 
| 	Ingo
| 

Here is an updated version
---
From: Cyrill Gorcunov <gorcunov@gmail.com>
Subject: x86: entry_64.S - trivial: space, comments fixup

Impact: cleanup

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
 arch/x86/kernel/entry_64.S |   94 ++++++++++++++++++++++-----------------------
 1 file changed, 48 insertions(+), 46 deletions(-)

Index: linux-2.6.git/arch/x86/kernel/entry_64.S
===================================================================
--- linux-2.6.git.orig/arch/x86/kernel/entry_64.S
+++ linux-2.6.git/arch/x86/kernel/entry_64.S
@@ -1027,7 +1027,7 @@ END(\sym)
 
 .macro paranoidzeroentry_ist sym do_sym ist
 ENTRY(\sym)
- 	INTR_FRAME
+	INTR_FRAME
 	PARAVIRT_ADJUST_EXCEPTION_FRAME
 	pushq $-1		/* ORIG_RAX: no syscall to restart */
 	CFI_ADJUST_CFA_OFFSET 8
@@ -1095,36 +1095,36 @@ zeroentry coprocessor_error do_coprocess
 errorentry alignment_check do_alignment_check
 zeroentry simd_coprocessor_error do_simd_coprocessor_error
 
-       /* Reload gs selector with exception handling */
-       /* edi:  new selector */
+	/* Reload gs selector with exception handling */
+	/* edi:  new selector */
 ENTRY(native_load_gs_index)
 	CFI_STARTPROC
 	pushf
 	CFI_ADJUST_CFA_OFFSET 8
 	DISABLE_INTERRUPTS(CLBR_ANY | ~(CLBR_RDI))
-        SWAPGS
+	SWAPGS
 gs_change:
-        movl %edi,%gs
+	movl %edi,%gs
 2:	mfence		/* workaround */
 	SWAPGS
-        popf
+	popf
 	CFI_ADJUST_CFA_OFFSET -8
-        ret
+	ret
 	CFI_ENDPROC
 END(native_load_gs_index)
 
-        .section __ex_table,"a"
-        .align 8
-        .quad gs_change,bad_gs
-        .previous
-        .section .fixup,"ax"
+	.section __ex_table,"a"
+	.align 8
+	.quad gs_change,bad_gs
+	.previous
+	.section .fixup,"ax"
 	/* running with kernelgs */
 bad_gs:
 	SWAPGS			/* switch back to user gs */
 	xorl %eax,%eax
-        movl %eax,%gs
-        jmp  2b
-        .previous
+	movl %eax,%gs
+	jmp  2b
+	.previous
 
 /*
  * Create a kernel thread.
@@ -1159,7 +1159,7 @@ ENTRY(kernel_thread)
 	 * so internally to the x86_64 port you can rely on kernel_thread()
 	 * not to reschedule the child before returning, this avoids the need
 	 * of hacks for example to fork off the per-CPU idle tasks.
-         * [Hopefully no generic code relies on the reschedule -AK]
+	 * [Hopefully no generic code relies on the reschedule -AK]
 	 */
 	RESTORE_ALL
 	UNFAKE_STACK_FRAME
@@ -1239,22 +1239,24 @@ END(call_softirq)
 zeroentry xen_hypervisor_callback xen_do_hypervisor_callback
 
 /*
-# A note on the "critical region" in our callback handler.
-# We want to avoid stacking callback handlers due to events occurring
-# during handling of the last event. To do this, we keep events disabled
-# until we've done all processing. HOWEVER, we must enable events before
-# popping the stack frame (can't be done atomically) and so it would still
-# be possible to get enough handler activations to overflow the stack.
-# Although unlikely, bugs of that kind are hard to track down, so we'd
-# like to avoid the possibility.
-# So, on entry to the handler we detect whether we interrupted an
-# existing activation in its critical region -- if so, we pop the current
-# activation and restart the handler using the previous one.
-*/
+ * A note on the "critical region" in our callback handler.
+ * We want to avoid stacking callback handlers due to events occurring
+ * during handling of the last event. To do this, we keep events disabled
+ * until we've done all processing. HOWEVER, we must enable events before
+ * popping the stack frame (can't be done atomically) and so it would still
+ * be possible to get enough handler activations to overflow the stack.
+ * Although unlikely, bugs of that kind are hard to track down, so we'd
+ * like to avoid the possibility.
+ * So, on entry to the handler we detect whether we interrupted an
+ * existing activation in its critical region -- if so, we pop the current
+ * activation and restart the handler using the previous one.
+ */
 ENTRY(xen_do_hypervisor_callback)   # do_hypervisor_callback(struct *pt_regs)
 	CFI_STARTPROC
-/* Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will
-   see the correct pointer to the pt_regs */
+/*
+ * Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will
+ * see the correct pointer to the pt_regs
+ */
 	movq %rdi, %rsp            # we don't return, adjust the stack frame
 	CFI_ENDPROC
 	DEFAULT_FRAME
@@ -1272,18 +1274,18 @@ ENTRY(xen_do_hypervisor_callback)   # do
 END(do_hypervisor_callback)
 
 /*
-# Hypervisor uses this for application faults while it executes.
-# We get here for two reasons:
-#  1. Fault while reloading DS, ES, FS or GS
-#  2. Fault while executing IRET
-# Category 1 we do not need to fix up as Xen has already reloaded all segment
-# registers that could be reloaded and zeroed the others.
-# Category 2 we fix up by killing the current process. We cannot use the
-# normal Linux return path in this case because if we use the IRET hypercall
-# to pop the stack frame we end up in an infinite loop of failsafe callbacks.
-# We distinguish between categories by comparing each saved segment register
-# with its current contents: any discrepancy means we in category 1.
-*/
+ * Hypervisor uses this for application faults while it executes.
+ * We get here for two reasons:
+ *  1. Fault while reloading DS, ES, FS or GS
+ *  2. Fault while executing IRET
+ * Category 1 we do not need to fix up as Xen has already reloaded all segment
+ * registers that could be reloaded and zeroed the others.
+ * Category 2 we fix up by killing the current process. We cannot use the
+ * normal Linux return path in this case because if we use the IRET hypercall
+ * to pop the stack frame we end up in an infinite loop of failsafe callbacks.
+ * We distinguish between categories by comparing each saved segment register
+ * with its current contents: any discrepancy means we in category 1.
+ */
 ENTRY(xen_failsafe_callback)
 	INTR_FRAME 1 (6*8)
 	/*CFI_REL_OFFSET gs,GS*/
@@ -1347,8 +1349,8 @@ paranoidzeroentry machine_check do_machi
 #endif
 
 	/*
- 	 * "Paranoid" exit path from exception stack.
-  	 * Paranoid because this is used by NMIs and cannot take
+	 * "Paranoid" exit path from exception stack.
+	 * Paranoid because this is used by NMIs and cannot take
 	 * any kernel state for granted.
 	 * We don't do kernel preemption checks here, because only
 	 * NMI should be common and it does not enable IRQs and
@@ -1453,7 +1455,7 @@ error_kernelspace:
 	cmpq %rcx,RIP+8(%rsp)
 	je error_swapgs
 	cmpq $gs_change,RIP+8(%rsp)
-        je error_swapgs
+	je error_swapgs
 	jmp error_sti
 END(error_entry)
 
@@ -1529,7 +1531,7 @@ nmi_schedule:
 	CFI_ENDPROC
 #else
 	jmp paranoid_exit
- 	CFI_ENDPROC
+	CFI_ENDPROC
 #endif
 END(nmi)
 

Re: [PATCH 2/5] x86: ret_from_fork - get rid of jump back

[Cyrill Gorcunov]

[Ingo Molnar - Thu, Nov 27, 2008 at 02:41:21PM +0100]
| 
| * Cyrill Gorcunov <gorcunov@gmail.com> wrote:
| 
...
| 
| Could you test something like the patch attached below, which cleans 
| up this code and applies the code reduction and speedup? Warning: 
| completely untested! Please check that things like strace -f and gdb 
| attaching to forked tasks still works fine. (it should by all means)
| 
| Thanks,
| 
| 	Ingo

Ingo, I found 2.6.26 test machine where I've patched the entry_64.S
in a manner you pointed. So here is a test program and strace output.
Seems all works fine. Didn't check "audit" code which I simply don't
know how to be done.
 
		- Cyrill -
---

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
	int pid;

	pid = fork();

	if (pid < 0) {
		fprintf(stderr, "Fork failed!\n");
		exit(-1);
	}

	else if (pid == 0) {
		printf("I am the child, return from fork=%d\n", pid);
	} else {
	  printf("I am the parent, return from fork, child pid=%d\n", pid);
	  printf("Parent exiting!\n");
	  exit(0);
	}
}
---

5897  execve("./main", ["./main"], [/* 18 vars */]) = 0
5897  brk(0)                            = 0x2514000
5897  mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa0e517f000
5897  access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
5897  mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa0e517d000
5897  access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
5897  open("/etc/ld.so.cache", O_RDONLY) = 3
5897  fstat(3, {st_mode=S_IFREG|0644, st_size=48530, ...}) = 0
5897  mmap(NULL, 48530, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fa0e5171000
5897  close(3)                          = 0
5897  access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
5897  open("/lib/libc.so.6", O_RDONLY)  = 3
5897  read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\220\345"..., 832) = 832
5897  fstat(3, {st_mode=S_IFREG|0755, st_size=1502520, ...}) = 0
5897  mmap(NULL, 3609304, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fa0e4bf0000
5897  mprotect(0x7fa0e4d59000, 2093056, PROT_NONE) = 0
5897  mmap(0x7fa0e4f58000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x168000) = 0x7fa0e4f58000
5897  mmap(0x7fa0e4f5d000, 17112, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fa0e4f5d000
5897  close(3)                          = 0
5897  mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa0e5170000
5897  mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa0e516f000
5897  arch_prctl(ARCH_SET_FS, 0x7fa0e516f6e0) = 0
5897  mprotect(0x7fa0e4f58000, 16384, PROT_READ) = 0
5897  mprotect(0x7fa0e5180000, 4096, PROT_READ) = 0
5897  munmap(0x7fa0e5171000, 48530)     = 0
5897  clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7fa0e516f770) = 5898
5897  fstat(1, {st_mode=S_IFCHR|0600, st_rdev=makedev(5, 1), ...}) = 0
5898  fstat(1,  <unfinished ...>
5897  ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS <unfinished ...>
5898  <... fstat resumed> {st_mode=S_IFCHR|0600, st_rdev=makedev(5, 1), ...}) = 0
5897  <... ioctl resumed> , {B38400 opost isig icanon echo ...}) = 0
5897  mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0 <unfinished ...>
5898  ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS <unfinished ...>
5897  <... mmap resumed> )              = 0x7fa0e517c000
5898  <... ioctl resumed> , {B38400 opost isig icanon echo ...}) = 0
5897  write(1, "I am the parent, return from for"..., 50 <unfinished ...>
5898  mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0 <unfinished ...>
5897  <... write resumed> )             = 50
5898  <... mmap resumed> )              = 0x7fa0e517c000
5897  write(1, "Parent exiting!\n", 16 <unfinished ...>
5898  write(1, "I am the child, return from fork"..., 35 <unfinished ...>
5897  <... write resumed> )             = 16
5898  <... write resumed> )             = 35
5897  exit_group(0)                     = ?
5898  exit_group(0)                     = ?
---

Re: [PATCH 2/5] x86: ret_from_fork - get rid of jump back

[Ingo Molnar]

* Andi Kleen <andi@firstfloor.org> wrote:

> > But it gets worse than that: checking for _TIF_SYSCALL_TRACE is 
> > completely unnecessary here because we clear that flag for every 
> 
> That's true. I found your 2005 changeset which did that, [...]

that's irrelevant, because all the necessary TIF_ flag processing is 
already done in ret_from_sys_call.

The unnecessary TIF_SYSCALL_TRACE code in the 64-bit ret_from_fork was 
apparently added by you in 2002:

  +ENTRY(ret_from_fork)
  +       movq %rbx, %rdi
  +       call schedule_tail
  +       GET_THREAD_INFO(%rcx)
  +       bt $TIF_SYSCALL_TRACE,threadinfo_flags(%rcx)
  +       jc rff_trace

when you added it to x86_64 via the changeset quoted below.

at that time the 32-bit code (from which you copied the x86_64 tree, 
creating the whole split x86 trees approach) had this simple and 
straightforward ret_from_fork implementation:

  ENTRY(ret_from_fork)
  #if CONFIG_SMP
        pushl %ebx
        call SYMBOL_NAME(schedule_tail)
        addl $4, %esp
  #endif
        GET_THREAD_INFO(%ebx)
        jmp syscall_exit

so by all means the rff_trace/rff_action hack came from you.

	Ingo

------------------>
>From 0457d99a336be658cea1a5bdb689de5adb3b382d Mon Sep 17 00:00:00 2001
From: Andi Kleen <ak@muc.de>
Date: Tue, 12 Feb 2002 20:17:35 -0800
Subject: [PATCH] [PATCH] x86_64 merge: arch + asm

This adds the x86_64 arch and asm directories and a Documentation/x86_64.

It took a bit longer because I first had to make preemption and thread_info
work and also found some other bugs while doing this. The port has been
tested for a long time on UP.

I'm not sure what I should describe.  A lot is based on i386 with
a lot of cleanups. I wrote a paper about it for last year's OLS that describes
most of the changes (ftp://ftp.firstfloor.org/pub/ak/x86_64.ps.gz). It is
a bit outdated now, but should give a good overview.

It currently has a completely cut'n'pasted from others+hacked 32bit
emulation. I hope to clean that up in the future by merging the generic
core of this with other 64bit archs.

Thanks,
-Andi
---
 Documentation/x86_64/mm.txt             |  148 ++
 arch/x86_64/Config.help                 |  531 +++++
 arch/x86_64/Makefile                    |  130 ++
 arch/x86_64/boot/Makefile               |   92 +
 arch/x86_64/boot/bootsect.S             |  416 ++++
 arch/x86_64/boot/compressed/Makefile    |   43 +
 arch/x86_64/boot/compressed/head.S      |  142 ++
 arch/x86_64/boot/compressed/misc.c      |  431 ++++
 arch/x86_64/boot/compressed/miscsetup.h |   39 +
 arch/x86_64/boot/install.sh             |   39 +
 arch/x86_64/boot/setup.S                |  955 ++++++++
 arch/x86_64/boot/tools/build.c          |  189 ++
 arch/x86_64/boot/video.S                | 1934 ++++++++++++++++
 arch/x86_64/config.in                   |  240 ++
 arch/x86_64/defconfig                   |  568 +++++
 arch/x86_64/ia32/Makefile               |   18 +
 arch/x86_64/ia32/ia32_binfmt.c          |  165 ++
 arch/x86_64/ia32/ia32_ioctl.c           | 3843 +++++++++++++++++++++++++++++++
 arch/x86_64/ia32/ia32_signal.c          |  489 ++++
 arch/x86_64/ia32/ia32entry.S            |  365 +++
 arch/x86_64/ia32/ptrace32.c             |  312 +++
 arch/x86_64/ia32/socket32.c             |  686 ++++++
 arch/x86_64/ia32/sys_ia32.c             | 2788 ++++++++++++++++++++++
 arch/x86_64/kernel/Makefile             |   38 +
 arch/x86_64/kernel/apic.c               | 1160 ++++++++++
 arch/x86_64/kernel/bluesmoke.c          |  174 ++
 arch/x86_64/kernel/cpuid.c              |  177 ++
 arch/x86_64/kernel/early_printk.c       |   77 +
 arch/x86_64/kernel/entry.S              |  640 +++++
 arch/x86_64/kernel/head.S               |  342 +++
 arch/x86_64/kernel/head64.c             |   85 +
 arch/x86_64/kernel/i387.c               |  439 ++++
 arch/x86_64/kernel/i8259.c              |  485 ++++
 arch/x86_64/kernel/init_task.c          |   42 +
 arch/x86_64/kernel/io_apic.c            | 1617 +++++++++++++
 arch/x86_64/kernel/ioport.c             |  114 +
 arch/x86_64/kernel/irq.c                | 1198 ++++++++++
 arch/x86_64/kernel/ldt.c                |  177 ++
 arch/x86_64/kernel/mpparse.c            |  670 ++++++
 arch/x86_64/kernel/msr.c                |  279 +++
 arch/x86_64/kernel/mtrr.c               | 2310 +++++++++++++++++++
 arch/x86_64/kernel/nmi.c                |  272 +++
 arch/x86_64/kernel/pci-dma.c            |   33 +
 arch/x86_64/kernel/pci-irq.c            |  753 ++++++
 arch/x86_64/kernel/pci-pc.c             |  438 ++++
 arch/x86_64/kernel/pci-x86_64.c         |  384 +++
 arch/x86_64/kernel/pci-x86_64.h         |   72 +
 arch/x86_64/kernel/process.c            |  756 ++++++
 arch/x86_64/kernel/ptrace.c             |  435 ++++
 arch/x86_64/kernel/semaphore.c          |  225 ++
 arch/x86_64/kernel/setup.c              | 1128 +++++++++
 arch/x86_64/kernel/setup64.c            |  142 ++
 arch/x86_64/kernel/signal.c             |  591 +++++
 arch/x86_64/kernel/smp.c                |  584 +++++
 arch/x86_64/kernel/smpboot.c            | 1023 ++++++++
 arch/x86_64/kernel/sys_x86_64.c         |  113 +
 arch/x86_64/kernel/syscall.c            |   25 +
 arch/x86_64/kernel/time.c               |  494 ++++
 arch/x86_64/kernel/trampoline.S         |   72 +
 arch/x86_64/kernel/traps.c              |  771 +++++++
 arch/x86_64/kernel/vsyscall.c           |  190 ++
 arch/x86_64/kernel/x8664_ksyms.c        |  162 ++
 arch/x86_64/lib/Makefile                |   17 +
 arch/x86_64/lib/checksum_copy.S         |  142 ++
 arch/x86_64/lib/dec_and_lock.c          |   40 +
 arch/x86_64/lib/delay.c                 |   45 +
 arch/x86_64/lib/generic-checksum.c      |  124 +
 arch/x86_64/lib/getuser.S               |   90 +
 arch/x86_64/lib/iodebug.c               |   11 +
 arch/x86_64/lib/mmx.c                   |  377 +++
 arch/x86_64/lib/old-checksum.c          |   33 +
 arch/x86_64/lib/putuser.S               |   88 +
 arch/x86_64/lib/rwsem_thunk.S           |   27 +
 arch/x86_64/lib/usercopy.c              |  147 ++
 arch/x86_64/mm/Makefile                 |   13 +
 arch/x86_64/mm/extable.c                |   62 +
 arch/x86_64/mm/fault.c                  |  324 +++
 arch/x86_64/mm/init.c                   |  387 ++++
 arch/x86_64/mm/ioremap.c                |  163 ++
 arch/x86_64/tools/Makefile              |   31 +
 arch/x86_64/tools/offset.c              |   70 +
 arch/x86_64/tools/offset.sed            |    7 +
 arch/x86_64/vmlinux.lds                 |  112 +
 include/asm-x86_64/a.out.h              |   30 +
 include/asm-x86_64/apic.h               |  103 +
 include/asm-x86_64/apicdef.h            |  363 +++
 include/asm-x86_64/atomic.h             |  206 ++
 include/asm-x86_64/bitops.h             |  465 ++++
 include/asm-x86_64/boot.h               |   15 +
 include/asm-x86_64/bootsetup.h          |   34 +
 include/asm-x86_64/bugs.h               |   42 +
 include/asm-x86_64/byteorder.h          |   32 +
 include/asm-x86_64/cache.h              |   13 +
 include/asm-x86_64/calling.h            |  100 +
 include/asm-x86_64/checksum.h           |  158 ++
 include/asm-x86_64/cpufeature.h         |   73 +
 include/asm-x86_64/current.h            |   29 +
 include/asm-x86_64/debugreg.h           |   65 +
 include/asm-x86_64/delay.h              |   20 +
 include/asm-x86_64/desc.h               |  187 ++
 include/asm-x86_64/div64.h              |   14 +
 include/asm-x86_64/dma.h                |  298 +++
 include/asm-x86_64/e820.h               |   40 +
 include/asm-x86_64/elf.h                |  120 +
 include/asm-x86_64/errno.h              |  132 ++
 include/asm-x86_64/fcntl.h              |   79 +
 include/asm-x86_64/fixmap.h             |  105 +
 include/asm-x86_64/floppy.h             |  286 +++
 include/asm-x86_64/hardirq.h            |   93 +
 include/asm-x86_64/hdreg.h              |   12 +
 include/asm-x86_64/hw_irq.h             |  210 ++
 include/asm-x86_64/i387.h               |   87 +
 include/asm-x86_64/ia32.h               |  274 +++
 include/asm-x86_64/ia32_unistd.h        |  251 ++
 include/asm-x86_64/ide.h                |  128 +
 include/asm-x86_64/init.h               |    1 +
 include/asm-x86_64/io.h                 |  270 +++
 include/asm-x86_64/io_apic.h            |  148 ++
 include/asm-x86_64/ioctl.h              |   75 +
 include/asm-x86_64/ioctls.h             |   82 +
 include/asm-x86_64/ipc.h                |   32 +
 include/asm-x86_64/ipcbuf.h             |   29 +
 include/asm-x86_64/irq.h                |   35 +
 include/asm-x86_64/kdebug.h             |   23 +
 include/asm-x86_64/keyboard.h           |   71 +
 include/asm-x86_64/kmap_types.h         |   14 +
 include/asm-x86_64/ldt.h                |   37 +
 include/asm-x86_64/linux_logo.h         |   29 +
 include/asm-x86_64/locks.h              |  135 ++
 include/asm-x86_64/mc146818rtc.h        |   29 +
 include/asm-x86_64/mman.h               |   39 +
 include/asm-x86_64/mmu.h                |   13 +
 include/asm-x86_64/mmu_context.h        |   95 +
 include/asm-x86_64/mmx.h                |   14 +
 include/asm-x86_64/module.h             |   12 +
 include/asm-x86_64/mpspec.h             |  188 ++
 include/asm-x86_64/msgbuf.h             |   27 +
 include/asm-x86_64/msr.h                |  140 ++
 include/asm-x86_64/mtrr.h               |  127 +
 include/asm-x86_64/namei.h              |   17 +
 include/asm-x86_64/page.h               |  118 +
 include/asm-x86_64/param.h              |   24 +
 include/asm-x86_64/parport.h            |   18 +
 include/asm-x86_64/pci.h                |  273 +++
 include/asm-x86_64/pda.h                |   79 +
 include/asm-x86_64/pgalloc.h            |  258 +++
 include/asm-x86_64/pgtable.h            |  399 ++++
 include/asm-x86_64/poll.h               |   25 +
 include/asm-x86_64/posix_types.h        |  116 +
 include/asm-x86_64/prctl.h              |   10 +
 include/asm-x86_64/processor.h          |  463 ++++
 include/asm-x86_64/ptrace.h             |  114 +
 include/asm-x86_64/resource.h           |   47 +
 include/asm-x86_64/rwlock.h             |   84 +
 include/asm-x86_64/rwsem.h              |  217 ++
 include/asm-x86_64/scatterlist.h        |   13 +
 include/asm-x86_64/segment.h            |   19 +
 include/asm-x86_64/semaphore.h          |  216 ++
 include/asm-x86_64/sembuf.h             |   25 +
 include/asm-x86_64/serial.h             |  133 ++
 include/asm-x86_64/setup.h              |   10 +
 include/asm-x86_64/shmbuf.h             |   38 +
 include/asm-x86_64/shmparam.h           |    6 +
 include/asm-x86_64/sigcontext.h         |   97 +
 include/asm-x86_64/siginfo.h            |  232 ++
 include/asm-x86_64/signal.h             |  205 ++
 include/asm-x86_64/smp.h                |   98 +
 include/asm-x86_64/smplock.h            |   95 +
 include/asm-x86_64/socket.h             |   64 +
 include/asm-x86_64/socket32.h           |   70 +
 include/asm-x86_64/sockios.h            |   12 +
 include/asm-x86_64/softirq.h            |   34 +
 include/asm-x86_64/spinlock.h           |  181 ++
 include/asm-x86_64/stat.h               |   27 +
 include/asm-x86_64/statfs.h             |   25 +
 include/asm-x86_64/string.h             |   38 +
 include/asm-x86_64/system.h             |  283 +++
 include/asm-x86_64/termbits.h           |  172 ++
 include/asm-x86_64/termios.h            |  106 +
 include/asm-x86_64/thread_info.h        |  116 +
 include/asm-x86_64/timex.h              |   51 +
 include/asm-x86_64/tlb.h                |    1 +
 include/asm-x86_64/types.h              |   47 +
 include/asm-x86_64/uaccess.h            |  373 +++
 include/asm-x86_64/ucontext.h           |   12 +
 include/asm-x86_64/unaligned.h          |   37 +
 include/asm-x86_64/unistd.h             |  653 ++++++
 include/asm-x86_64/user.h               |  113 +
 include/asm-x86_64/user32.h             |   58 +
 include/asm-x86_64/vga.h                |   20 +
 include/asm-x86_64/vsyscall.h           |   48 +
 include/asm-x86_64/xor.h                |  859 +++++++
 192 files changed, 48138 insertions(+), 0 deletions(-)

Re: [PATCH 5/5] x86: entry_64.S - trivial: space, comments fixup

[Ingo Molnar]

* Cyrill Gorcunov <gorcunov@gmail.com> wrote:

> [Ingo Molnar - Thu, Nov 27, 2008 at 01:02:34PM +0100]
> | > > From: Cyrill Gorcunov <gorcunov@gmail.com>
> | > > 
> | > > Impact: cleanup
> | > > 
> | > > Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
> | > 
> | > Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>
> | 
> | Cyrill, could you please rework the still relevant bits against latest 
> | tip/master? Alexander's wider patch got in the way.
> | 
> | Thanks,
> | 
> | 	Ingo
> | 
> 
> Here is an updated version
> ---
> From: Cyrill Gorcunov <gorcunov@gmail.com>
> Subject: x86: entry_64.S - trivial: space, comments fixup
> 
> Impact: cleanup

applied, thanks Cyrill!

	Ingo

Re: [PATCH 2/5] x86: ret_from_fork - get rid of jump back

[Andi Kleen]

On Fri, Nov 28, 2008 at 02:47:54PM +0100, Ingo Molnar wrote:

Hi Ingo,

> 
> * Andi Kleen <andi@firstfloor.org> wrote:
> 
> > > But it gets worse than that: checking for _TIF_SYSCALL_TRACE is 
> > > completely unnecessary here because we clear that flag for every 
> > 
> > That's true. I found your 2005 changeset which did that, [...]
> 
> that's irrelevant, because all the necessary TIF_ flag processing is 
> already done in ret_from_sys_call.

Yes, that's true (as I wrote in my email), but it's just not dead because 
the audit code will take it (or used to handle both audit and fork before 
2005), just unnecessary because the later code checks it as well@). Ok it's
only a very subtle difference given.

It would have been nice if you had pruned at least the fork case
when you changed fork.c to always clear it, but that can be also
done now.

> 
> The unnecessary TIF_SYSCALL_TRACE code in the 64-bit ret_from_fork was 
> apparently added by you in 2002:

Yes, to be honest I don't remember why I did it this way. Most likely
the additional check was needed in some earlier iteration and then not pruned 
away when it became unnecessary. I remember I had some ordering problems
with strace very early on it might have been related to that. Or perhaps 
I just goofed up. In the current form it's certainly not great code.

Anyways I have no objections to removing it now, just one has to be
careful that the changed processing order (signals vs trace) -- which
is likely user visible -- won't break anything.

-Andi