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| author | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2013-09-24 07:17:21 +0200 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2013-09-25 06:15:51 +0200 |
| commit | cbc9565ee82694dec31d8137dec975b83175183b (patch) | |
| tree | 7740d7f8f0372e80c067ee2e867bb69ab7b15eec /arch/powerpc/kernel/misc_32.S | |
| parent | powerpc/irq: Run softirqs off the top of the irq stack (diff) | |
| download | linux-cbc9565ee82694dec31d8137dec975b83175183b.tar.xz linux-cbc9565ee82694dec31d8137dec975b83175183b.zip | |
powerpc: Remove ksp_limit on ppc64
We've been keeping that field in thread_struct for a while, it contains
the "limit" of the current stack pointer and is meant to be used for
detecting stack overflows.
It has a few problems however:
- First, it was never actually *used* on 64-bit. Set and updated but
not actually exploited
- When switching stack to/from irq and softirq stacks, it's update
is racy unless we hard disable interrupts, which is costly. This
is fine on 32-bit as we don't soft-disable there but not on 64-bit.
Thus rather than fixing 2 in order to implement 1 in some hypothetical
future, let's remove the code completely from 64-bit. In order to avoid
a clutter of ifdef's, we remove the updates from C code completely
during interrupt stack switching, and instead maintain it from the
asm helper that is used to do the stack switching in the first place.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/kernel/misc_32.S')
| -rw-r--r-- | arch/powerpc/kernel/misc_32.S | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S index 7da3882a3622..2b0ad9845363 100644 --- a/arch/powerpc/kernel/misc_32.S +++ b/arch/powerpc/kernel/misc_32.S @@ -36,25 +36,41 @@ .text +/* + * We store the saved ksp_limit in the unused part + * of the STACK_FRAME_OVERHEAD + */ _GLOBAL(call_do_softirq) mflr r0 stw r0,4(r1) + lwz r10,THREAD+KSP_LIMIT(r2) + addi r11,r3,THREAD_INFO_GAP stwu r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r3) mr r1,r3 + stw r10,8(r1) + stw r11,THREAD+KSP_LIMIT(r2) bl __do_softirq + lwz r10,8(r1) lwz r1,0(r1) lwz r0,4(r1) + stw r10,THREAD+KSP_LIMIT(r2) mtlr r0 blr _GLOBAL(call_do_irq) mflr r0 stw r0,4(r1) + lwz r10,THREAD+KSP_LIMIT(r2) + addi r11,r3,THREAD_INFO_GAP stwu r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r4) mr r1,r4 + stw r10,8(r1) + stw r11,THREAD+KSP_LIMIT(r2) bl __do_irq + lwz r10,8(r1) lwz r1,0(r1) lwz r0,4(r1) + stw r10,THREAD+KSP_LIMIT(r2) mtlr r0 blr |