Re: [PATCH 6 of 8] Xen: remove run_in_exception_handler() and recode its only caller

[Keir Fraser <keir.xen@gmail.com>]

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On 07/03/2011 15:05, "Keir Fraser" <keir.xen@gmail.com> wrote:

> On 07/03/2011 11:26, "Tim Deegan" <Tim.Deegan@citrix.com> wrote:
> 
>> (dump_execution_state()) as its own bug-trap.
>> 
>> This is needed to compile xen with clang, which can't handle using a
>> function name in an asm immediate.
> 
> Actually run_in_exception_handler() does have another user, in ns16550.c.
> Although non-essential, it makes the 'd' debug key much more useful when
> running the UART in polled mode.
> 
> So I suggest we keep run_in_exception_handler but modify it to pass the
> function pointer in (say) rAX.

Like the attached patch (against latest tip).

 -- Keir

> I think we won't easily be able to use
> BUG_STR() logic but r_i_e_h is only used (directly or indirectly) in a few
> places so the BUG_STR optimisation is unimportant. The only other
> disadvantage is that rAX is less interesting in the state dump, but any
> value the function pointer displaces can still be found in the stack dump,
> albeit with likely a little extra effort.
> 
> Sound good?
> 
>  -- Keir 
> 
>> Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>
>> 
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xensource.com
>> http://lists.xensource.com/xen-devel
> 
> 


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diff -r 076b63b74cf6 xen/arch/x86/traps.c
--- a/xen/arch/x86/traps.c	Mon Mar 07 11:34:09 2011 +0000
+++ b/xen/arch/x86/traps.c	Mon Mar 07 15:14:22 2011 +0000
@@ -909,9 +909,10 @@
 
     id = bug.id & 3;
 
-    if ( id == BUGFRAME_state )
+    if ( id == BUGFRAME_run_fn )
     {
-        show_execution_state(regs);
+        void (*fn)(struct cpu_user_regs *) = (void *)regs->eax;
+        (*fn)(regs);
         regs->eip = (unsigned long)eip;
         return;
     }
diff -r 076b63b74cf6 xen/include/asm-x86/bug.h
--- a/xen/include/asm-x86/bug.h	Mon Mar 07 11:34:09 2011 +0000
+++ b/xen/include/asm-x86/bug.h	Mon Mar 07 15:14:22 2011 +0000
@@ -13,15 +13,16 @@
     unsigned short id; /* BUGFRAME_??? */
 } __attribute__((packed));
 
-#define BUGFRAME_state  0
+#define BUGFRAME_run_fn 0
 #define BUGFRAME_warn   1
 #define BUGFRAME_bug    2
 #define BUGFRAME_assert 3
 
-#define dump_execution_state()                     \
+#define run_in_exception_handler(fn)               \
     asm volatile (                                 \
         "ud2 ; ret %0"                             \
-        : : "i" (BUGFRAME_state) )
+        : : "i" (BUGFRAME_run_fn),                 \
+            "a" (fn) )
 
 #define WARN()                                     \
     asm volatile (                                 \
diff -r 076b63b74cf6 xen/include/asm-x86/processor.h
--- a/xen/include/asm-x86/processor.h	Mon Mar 07 11:34:09 2011 +0000
+++ b/xen/include/asm-x86/processor.h	Mon Mar 07 15:14:22 2011 +0000
@@ -542,6 +542,7 @@
 void show_stack_overflow(unsigned int cpu, unsigned long esp);
 void show_registers(struct cpu_user_regs *regs);
 void show_execution_state(struct cpu_user_regs *regs);
+#define dump_execution_state() run_in_exception_handler(show_execution_state)
 void show_page_walk(unsigned long addr);
 asmlinkage void fatal_trap(int trapnr, struct cpu_user_regs *regs);
 

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