Invalidate all TLB entries in a specified range
PATCH 1/1 Invalidate all TLB entries in a specified range
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 0x00400000. 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.
---
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".
arch/powerpc/kernel/head_32.S renamed from arch/powerpc/kernel/head_32.S.orig +1 -1
@@ -1155,7 +1155,7 @@ flush_tlbs: lis r10, 0x40 1: addic. r10, r10, -0x1000 tlbie r10 - blt 1b + bgt 1b sync blr
Quoted 8 lines · 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 to0x00400000. 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.
Quoted 6 lines
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.
Quoted 28 lines
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".
arch/powerpc/kernel/head_32.S renamed from arch/powerpc/kernel/head_32.S.orig +1
-1@@ -1155,7 +1155,7 @@ flush_tlbs: lis r10, 0x40 1: addic. r10, r10, -0x1000 tlbie r10 - blt 1b + bgt 1b sync blr