[Adeos-main] Re: tracer broken on 2.6.20-i386

[Jan Kiszka <jan.kiszka@domain.hid>]

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Philippe Gerum wrote:

> On Sat, 2007-02-10 at 14:20 +0100, Jan Kiszka wrote:
>   
>> Jan Kiszka wrote:
>>     
>>> Jan Kiszka wrote:
>>>
>>>       
>>>> Philippe,
>>>>
>>>> have you had to adopt any tracer-related code while switching to 2.6.20?
>>>> The same .config that worked fine for 2.6.19 doesn't boot here on
>>>> 2.6.20. The kernel hangs during or after decompression. Disabling the
>>>> tracer resolves this.
>>>>   
>>>>         
>>> I had a look at latest -rt and found some new change (which turned out
>>> to be a hack). Playing with it, I understood its motivation (avoid
>>> instrumentation of the decompressor). Here comes a cleaner variant for
>>> 2.6.20 (all archs). Tracer boots fine again. :)
>>>       
>>           ^^^^^^^^^
>> Strike that, I lost the overview for a while. It remains an i386 issue.
>>
>>     
>
> The tracer still has a problem when booting 2.6.20 here (UP, LAPIC,
> static Xenomai build, default configuration for both Xeno and the
> pipeline+tracer, your latest patch against boot/compressed/Makefile
> applied).
>
> __ipipe_trace seems to be called before the trace log has been setup,
> hence the box jumps out of the window upon an invalid data reference
> when storing some mcount data. Enabling the VMALLOC log option clears
> the issue.
>   
CONFIG_REGPARM passed away. It became default in fact. The following patch
removes the remainders from the tracer:

---
 arch/i386/kernel/entry.S  |   11 -----------
 arch/i386/kernel/mcount.S |   13 +------------
 2 files changed, 1 insertion(+), 23 deletions(-)

Index: linux-2.6.20/arch/i386/kernel/entry.S
===================================================================
--- linux-2.6.20.orig/arch/i386/kernel/entry.S
+++ linux-2.6.20/arch/i386/kernel/entry.S
@@ -105,25 +105,14 @@ VM_MASK		= 0x00020000
 				jnz restore_nocheck_notrace
 
 #ifdef CONFIG_IPIPE_TRACE_IRQSOFF
-# ifdef CONFIG_REGPARM
-#  define LOAD_ARG
-#  define REMOVE_ARG
-# else  /* !CONFIG_REGPARM */
-#  define LOAD_ARG      pushl %eax
-#  define REMOVE_ARG    addl $4, %esp
-# endif /* CONFIG_REGPARM */
 # define IPIPE_TRACE_IRQ_ENTER \
 	lea PT_EIP-4(%esp), %ebp; \
 	movl PT_ORIG_EAX(%esp), %eax; \
-	LOAD_ARG; \
 	call ipipe_trace_begin; \
-	REMOVE_ARG
 # define IPIPE_TRACE_IRQ_EXIT \
 	pushl %eax; \
 	movl PT_ORIG_EAX+4(%esp), %eax; \
-	LOAD_ARG; \
 	call ipipe_trace_end; \
-	REMOVE_ARG; \
 	popl %eax
 #else  /* !CONFIG_IPIPE_TRACE_IRQSOFF */
 #define IPIPE_TRACE_IRQ_ENTER
Index: linux-2.6.20/arch/i386/kernel/mcount.S
===================================================================
--- linux-2.6.20.orig/arch/i386/kernel/mcount.S
+++ linux-2.6.20/arch/i386/kernel/mcount.S
@@ -1,7 +1,7 @@
 /*
  *  linux/arch/i386/mcount.S
  *
- *  Copyright (C) 2005 Jan Kiszka
+ *  Copyright (C) 2005, 2007 Jan Kiszka
  */
 
 .globl mcount
@@ -17,23 +17,12 @@ mcount:
 	pushl %edx
 
 	pushl $0		# no additional value (v)
-#ifdef CONFIG_REGPARM
 	movl (%ebp),%eax
 	movl 0x4(%ebp),%edx	# __CALLER_ADDR0
 	movl 0x4(%eax),%ecx	# __CALLER_ADDR1
 	movl $0,%eax		# IPIPE_TRACE_FUNC
 	call __ipipe_trace
 	popl %eax
-#else /* !CONFIG_REGPARM */
-	movl (%ebp),%eax
-	movl 0x4(%eax),%eax
-	pushl %eax		# __CALLER_ADDR1
-	movl 0x4(%ebp),%eax
-	pushl %eax		# __CALLER_ADDR0
-	pushl $0		# IPIPE_TRACE_FUNC
-	call __ipipe_trace
-	addl $0x10,%esp
-#endif /* CONFIG_REGPARM */
 
 	popl %edx
 	popl %ecx


Looking at the tracer enable code made me wonder why it didn't look like
it should do. Some patch obviously dropped on the floor:

https://mail.gna.org/public/adeos-main/2006-12/msg00037.html

Please apply now as well.

Jan



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