[PATCH] boot/common/util.S: Put flush_{instruction, data}_cache back in .relocate_code section

[PATCH] boot/common/util.S: Put flush_{instruction, data}_cache back in .relocate_code section

[Paul Janzen]

In 2.6.14, we had the following definition of _GLOBAL() in
include/asm-ppc/processor.h:

#define _GLOBAL(n)\
        .stabs __stringify(n:F-1),N_FUN,0,0,n;\
        .globl n;\
n:

In 2.6.15, as part of the great powerpc merge, we moved this definition to
include/asm-powerpc/ppc_asm.h, where it appears (to 32-bit code) as: 

#define _GLOBAL(n)      \
        .text;          \
        .stabs __stringify(n:F-1),N_FUN,0,0,n;\
        .globl n;       \
n:

Mostly, this is fine.  However, we also have the following, in
arch/ppc/boot/common/util.S:

        .section ".relocate_code","xa"
[...]
_GLOBAL(flush_instruction_cache)
[...]
_GLOBAL(flush_data_cache)
[...]

The addition of the .text section definition in the definition of
_GLOBAL overrides the .relocate_code section definition.  As a result,
these two functions don't end up in .relocate_code, so they don't get
relocated correctly, and the boot fails.

There's another suspicious-looking usage at kernel/swsusp.S:37 that
someone should look into.  I did not exhaustively search the source
tree, though.

The following is the minimal patch that fixes the immediate problem.
I could easily be convinced that the _GLOBAL definition should be
modified to remove the ".text;" line either instead of, or in addition
to, this fix.

Signed-off-by: Paul Janzen <pcj@linux.sez.to>

--- arch/ppc/boot/common/util.S~	2005-12-24 15:47:48.000000000 -0800
+++ arch/ppc/boot/common/util.S 	2006-01-04 14:07:12.000000000 -0800
@@ -234,7 +234,8 @@ udelay:
  * First, flush the data cache in case it was enabled and may be
  * holding instructions for copy back.
  */
-_GLOBAL(flush_instruction_cache)
+        .globl flush_instruction_cache
+flush_instruction_cache:        
 	mflr	r6
 	bl	flush_data_cache
 
@@ -279,7 +280,8 @@ _GLOBAL(flush_instruction_cache)
  * Flush data cache
  * Do this by just reading lots of stuff into the cache.
  */
-_GLOBAL(flush_data_cache)
+        .globl flush_data_cache
+flush_data_cache:       
 	lis	r3,cache_flush_buffer@h
 	ori	r3,r3,cache_flush_buffer@l
 	li	r4,NUM_CACHE_LINES

-- Paul

Re: [PATCH] boot/common/util.S: Put flush_{instruction, data}_cache back in .relocate_code section

[Tom Rini]

On Wed, Jan 04, 2006 at 09:40:48PM -0800, Paul Janzen wrote:

> In 2.6.14, we had the following definition of _GLOBAL() in
> include/asm-ppc/processor.h:
> 
> #define _GLOBAL(n)\
>         .stabs __stringify(n:F-1),N_FUN,0,0,n;\
>         .globl n;\
> n:
> 
> In 2.6.15, as part of the great powerpc merge, we moved this definition to
> include/asm-powerpc/ppc_asm.h, where it appears (to 32-bit code) as: 
> 
> #define _GLOBAL(n)      \
>         .text;          \
>         .stabs __stringify(n:F-1),N_FUN,0,0,n;\
>         .globl n;       \
> n:
> 
> Mostly, this is fine.  However, we also have the following, in
> arch/ppc/boot/common/util.S:
> 
>         .section ".relocate_code","xa"
> [...]
> _GLOBAL(flush_instruction_cache)
> [...]
> _GLOBAL(flush_data_cache)
> [...]
> 
> The addition of the .text section definition in the definition of
> _GLOBAL overrides the .relocate_code section definition.  As a result,
> these two functions don't end up in .relocate_code, so they don't get
> relocated correctly, and the boot fails.
> 
> There's another suspicious-looking usage at kernel/swsusp.S:37 that
> someone should look into.  I did not exhaustively search the source
> tree, though.
> 
> The following is the minimal patch that fixes the immediate problem.
> I could easily be convinced that the _GLOBAL definition should be
> modified to remove the ".text;" line either instead of, or in addition
> to, this fix.
> 
> Signed-off-by: Paul Janzen <pcj@linux.sez.to>

Thanks for tracking this one down.  Paul, can you please make sure this
gets to Linus and the stable team?  Thanks.

Acked-by: Tom Rini <trini@kernel.crashing.org>

> --- arch/ppc/boot/common/util.S~	2005-12-24 15:47:48.000000000 -0800
> +++ arch/ppc/boot/common/util.S 	2006-01-04 14:07:12.000000000 -0800
> @@ -234,7 +234,8 @@ udelay:
>   * First, flush the data cache in case it was enabled and may be
>   * holding instructions for copy back.
>   */
> -_GLOBAL(flush_instruction_cache)
> +        .globl flush_instruction_cache
> +flush_instruction_cache:        
>  	mflr	r6
>  	bl	flush_data_cache
>  
> @@ -279,7 +280,8 @@ _GLOBAL(flush_instruction_cache)
>   * Flush data cache
>   * Do this by just reading lots of stuff into the cache.
>   */
> -_GLOBAL(flush_data_cache)
> +        .globl flush_data_cache
> +flush_data_cache:       
>  	lis	r3,cache_flush_buffer@h
>  	ori	r3,r3,cache_flush_buffer@l
>  	li	r4,NUM_CACHE_LINES
> 
> -- Paul

-- 
Tom Rini
http://gate.crashing.org/~trini/