On 26/07/2019 14:05, Will Deacon wrote:
On Fri, Jul 26, 2019 at 01:38:24PM +0100, Robin Murphy wrote:
On 26/07/2019 13:27, Will Deacon wrote:
On Fri, Jul 26, 2019 at 01:13:54PM +0100, Mark Rutland wrote:
On Fri, Jul 26, 2019 at 01:10:57PM +0100, Mark Rutland wrote:
On Fri, Jul 26, 2019 at 01:27:16PM +0200, Anders Roxell wrote:
When fall-through warnings was enabled by default, commit d93512ef0f0e ("Makefile: Globally enable fall-through warning"), the following warnings was starting to show up:
../arch/arm64/kernel/hw_breakpoint.c: In function ‘hw_breakpoint_arch_parse’: ../arch/arm64/kernel/hw_breakpoint.c:540:7: warning: this statement may fall through [-Wimplicit-fallthrough=] if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1) ^ ../arch/arm64/kernel/hw_breakpoint.c:542:3: note: here case 2: ^~~~ ../arch/arm64/kernel/hw_breakpoint.c:544:7: warning: this statement may fall through [-Wimplicit-fallthrough=] if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2) ^ ../arch/arm64/kernel/hw_breakpoint.c:546:3: note: here default: ^~~~~~~
Rework so that the compiler doesn't warn about fall-through. Rework so the code looks like the arm code. Since the comment in the function indicates taht this is supposed to behave the same way as arm32 because
Typo: s/taht/that/
it handles 32-bit tasks also.
Cc: stable@vger.kernel.org # v3.16+ Fixes: 6ee33c2712fc ("ARM: hw_breakpoint: correct and simplify alignment fixup code") Signed-off-by: Anders Roxell anders.roxell@linaro.org
The patch itself looks fine, but I don't think this needs a CC to stable, nor does it require that fixes tag, as there's no functional problem.
Hmm... I now see I spoke too soon, and this is making the 1-byte breakpoint work at a 3-byte offset.
I still don't think it's quite right though, since it forbids a 2-byte watchpoint on a byte-aligned address.
Plus, AFAICS, a 1-byte watchpoint on a 2-byte-aligned address.
[and of course, what I missed was that that's the case the fallthrough serves... yuck indeed]
Not that I know anything about this code, but it does start to look like it might want rewriting without the offending switch statement anyway. At a glance, it looks like the intended semantic might boil down to:
if (hw->ctrl.len > offset) return -EINVAL;
Given that it's compat code, I think it's worth staying as close to the arch/arm/ implementation as we can.
Right, I also misread the accompanying arch/arm/ patch and got the impression that 32-bit also had a problem such that any fix would happen in parallel - on closer inspection the current arch/arm/ code does actually seem to make sense, even if it is horribly subtle.
Also, beware that the ARM_BREAKPOINT_LEN_* definitions are masks because of the BAS fields in the debug architecture.
Fun... Clearly it's a bit too Friday for me to be useful here, so apologies for the confusion :)
Robin.