On Thu, Aug 08, 2013 at 08:15:21PM +0200, Oleg Nesterov wrote:
> On 08/08, Frederic Weisbecker wrote:
> >
> > I'm all for fixing this. May be we can start by backporting a patch that
> > ignores the value of gen_len for instruction breakpoints in x86?
>
> Or perhaps we can start with the something like below.
(commented on the diff below)
>
> But probably we should move "attr.bp_len == HW_BREAKPOINT_LEN_1" check
> from arch_build_bp_info() to its caller, arch_validate_hwbkpt_settings().
>
> Because:
>
> > But this bp_len
> > should rather be used for range breakpoints on archs that support it.
>
> Yes, exactly, and we already have the patches for amd, so bp->len can
> be actually != 1 but currently we can't support because it is checked
> in arch_build_bp_info().
Hmm, but how moving that to arch_validate_hwbkpt_seetings() would solve
the issue?
>
> Oleg.
>
> --- x/arch/x86/kernel/hw_breakpoint.c
> +++ x/arch/x86/kernel/hw_breakpoint.c
> @@ -208,19 +208,16 @@ int arch_bp_generic_fields(int x86_len,
> {
> /* Type */
> switch (x86_type) {
> - case X86_BREAKPOINT_EXECUTE:
> - if (x86_len != X86_BREAKPOINT_LEN_X)
> - return -EINVAL;
> -
> - *gen_type = HW_BREAKPOINT_X;
> - *gen_len = sizeof(long);
> - return 0;
> case X86_BREAKPOINT_WRITE:
> *gen_type = HW_BREAKPOINT_W;
> break;
> case X86_BREAKPOINT_RW:
> *gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
> break;
> + case X86_BREAKPOINT_EXECUTE:
> + *gen_type = HW_BREAKPOINT_X;
> + if (x86_len == X86_BREAKPOINT_LEN_1)
> +
> break;
> default:
> return -EINVAL;
> }
> @@ -265,15 +262,11 @@ static int arch_build_bp_info(struct per
> break;
> case HW_BREAKPOINT_X:
> info->type = X86_BREAKPOINT_EXECUTE;
> - /*
> - * x86 inst breakpoints need to have a specific undefined len.
> - * But we still need to check userspace is not trying to setup
> - * an unsupported length, to get a range breakpoint for example.
> - */
> - if (bp->attr.bp_len == sizeof(long)) {
> - info->len = X86_BREAKPOINT_LEN_X;
> - return 0;
> - }
> + /* until we change tools/perf */
> + if (bp->attr.bp_len == sizeof(long))
> + bp->attr.bp_len = HW_BREAKPOINT_LEN_1;
Too bad we need to keep that compatibility around. Do you think this could be
a problem for AMD range breakpoints?
We can also fix the tools, then may be we'll be able to remove the kernel hack
compatibility in a few years.
Oh I need to check other archs as well.
thanks.
> + if (bp->attr.bp_len == HW_BREAKPOINT_LEN_1)
> + break;
> default:
> return -EINVAL;
> }
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
