On Tue, Apr 23, 2013 at 03:18:44PM +0200, Oleg Nesterov wrote:
> On 04/23, Jacob Shin wrote:
> >
> > +__weak int arch_validate_hwbkpt_addr_mask(struct perf_event *bp)
> > +{
> > + return bp->attr.bp_addr_mask == 0;
> > +}
> > +
> > static int validate_hw_breakpoint(struct perf_event *bp)
> > {
> > int ret;
> > @@ -393,6 +398,10 @@ static int validate_hw_breakpoint(struct perf_event
> > *bp)
> > if (ret)
> > return ret;
> >
> > + ret = arch_validate_hwbkpt_addr_mask(bp);
> > + if (ret)
> > + return ret;
>
> Well, this looks obviously wrong?
>
> arch_validate_hwbkpt_addr_mask() fails if bp_addr_mask == 0? and returns
> "1" as the error code.
>
> Either it should returns something like "bp_addr_mask ? -ENOTSUPP : 0"
> or the caller should do "if (!validate_hw_breakpoint()) return -ERR".
You are absolutely right. I have mixed up "does this arch support address
masks?" vs "is this a valid address mask?" So sorry about that.
Here is the corrected patch:
>From f2054e8af979f024aa2da93f80646db18492479e Mon Sep 17 00:00:00 2001
From: Jacob Shin <jacob.s...@amd.com>
Date: Mon, 22 Apr 2013 17:02:37 -0500
Subject: [PATCH 1/4] perf: Add hardware breakpoint address mask
Some architectures (for us, AMD Family 16h) allow for "don't care" bit
mask to further qualify a hardware breakpoint address, in order to
trap on range of addresses. Update perf uapi to add bp_addr_mask field.
Signed-off-by: Jacob Shin <jacob.s...@amd.com>
---
include/uapi/linux/perf_event.h | 5 ++++-
kernel/events/hw_breakpoint.c | 9 +++++++++
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index fb104e5..e22e1d1 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -286,7 +286,10 @@ struct perf_event_attr {
__u64 config1; /* extension of config */
};
union {
- __u64 bp_len;
+ struct {
+ __u32 bp_len;
+ __u32 bp_addr_mask;
+ };
__u64 config2; /* extension of config1 */
};
__u64 branch_sample_type; /* enum perf_branch_sample_type */
diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index a64f8ae..dde8273 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -385,6 +385,11 @@ int dbg_release_bp_slot(struct perf_event *bp)
return 0;
}
+__weak int arch_validate_hwbkpt_addr_mask(struct perf_event *bp)
+{
+ return bp->attr.bp_addr_mask ? -EOPNOTSUPP : 0;
+}
+
static int validate_hw_breakpoint(struct perf_event *bp)
{
int ret;
@@ -393,6 +398,10 @@ static int validate_hw_breakpoint(struct perf_event *bp)
if (ret)
return ret;
+ ret = arch_validate_hwbkpt_addr_mask(bp);
+ if (ret)
+ return ret;
+
if (arch_check_bp_in_kernelspace(bp)) {
if (bp->attr.exclude_kernel)
return -EINVAL;
--
1.7.9.5
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