Re: [PATCH 2.6.27] [POWERPC] Invalidate all TLB entries in a specified range

2008-08-14 Thread Benjamin Herrenschmidt 
On Thu, 2008-08-14 at 07:11 -0600, Rocky Craig wrote:
 From: Rocky Craig [EMAIL PROTECTED]
 
 The apparent intent of flush_tlbs is to invalidate TLB entries that
 might match in the address range 0 to 0x0040.  A loop counter is 
 set up at the high value and decremented by page size.  However, the 
 loop is only done once as the sense of the conditional branch at the
 loop end does not match the setup/decrement.
 
 Signed-off-by: Rocky Craig [EMAIL PROTECTED]
 ---
 
 Source is from 2.6.27 development, but the bug appears as far back as 2.4.0.
 The small user-space program below demonstrates the loop behavior.  It was
 compiled via crosstool gcc 3.4.5 / glibc 2.3.6 for an MPC8347 target.

Heh nice, that's a bug as old as the port I would say :-)

Ben.
 
 int main()
 {
   long endval;// 16(r31)
 
   __asm__ __volatile__(
  lis 10,0x40\n
   1: addic. 10,10,-0x1000\n
  bgt 1b\n
  stw 10,16(31)\n);  // endval
 
   printf(end value = 0x%08lx\n, endval);
 }
 
 This might win the prize for Smallest actual code patch ever.
 
 --- a/arch/powerpc/kernel/head_32.S.orig  2008-07-24 19:25:09.0 
 -0600
 +++ a/arch/powerpc/kernel/head_32.S   2008-07-24 19:25:22.0 -0600
 @@ -1155,7 +1155,7 @@ flush_tlbs:
   lis r10, 0x40
  1:   addic.  r10, r10, -0x1000
   tlbie   r10
 - blt 1b
 + bgt 1b
   sync
   blr
  
 
 

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[PATCH 2.6.27] [POWERPC] Invalidate all TLB entries in a specified range

2008-08-14 Thread Rocky Craig 
From: Rocky Craig [EMAIL PROTECTED]

The apparent intent of flush_tlbs is to invalidate TLB entries that
might match in the address range 0 to 0x0040.  A loop counter is 
set up at the high value and decremented by page size.  However, the 
loop is only done once as the sense of the conditional branch at the
loop end does not match the setup/decrement.

Signed-off-by: Rocky Craig [EMAIL PROTECTED]
---

Source is from 2.6.27 development, but the bug appears as far back as 2.4.0.
The small user-space program below demonstrates the loop behavior.  It was
compiled via crosstool gcc 3.4.5 / glibc 2.3.6 for an MPC8347 target.

int main()
{
long endval;// 16(r31)

__asm__ __volatile__(
   lis 10,0x40\n
1: addic. 10,10,-0x1000\n
   bgt 1b\n
   stw 10,16(31)\n);  // endval

printf(end value = 0x%08lx\n, endval);
}

This might win the prize for Smallest actual code patch ever.

--- a/arch/powerpc/kernel/head_32.S.orig2008-07-24 19:25:09.0 
-0600
+++ a/arch/powerpc/kernel/head_32.S 2008-07-24 19:25:22.0 -0600
@@ -1155,7 +1155,7 @@ flush_tlbs:
lis r10, 0x40
 1: addic.  r10, r10, -0x1000
tlbie   r10
-   blt 1b
+   bgt 1b
sync
blr
 



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