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From: Frederic Weisbecker on 24 Jun 2010 17:50
Instruction breakpoints need to have a specific length of 0 to
be working. Bring this support but also take care the user is not
trying to set an unsupported length, like a range breakpoint for
example.

Signed-off-by: Frederic Weisbecker <fweisbec(a)gmail.com>
Cc: Ingo Molnar <mingo(a)elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra(a)chello.nl>
Cc: Arnaldo Carvalho de Melo <acme(a)redhat.com>
Cc: Paul Mackerras <paulus(a)samba.org>
Cc: Prasad <prasad(a)linux.vnet.ibm.com>
Cc: Mahesh Salgaonkar <mahesh(a)linux.vnet.ibm.com>
Cc: Will Deacon <will.deacon(a)arm.com>
Cc: Jason Wessel <jason.wessel(a)windriver.com>
---
arch/x86/include/asm/hw_breakpoint.h | 2 +-
arch/x86/kernel/hw_breakpoint.c | 44 ++++++++++++++++++++++-----------
2 files changed, 30 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/hw_breakpoint.h b/arch/x86/include/asm/hw_breakpoint.h
index 9422553..528a11e 100644
--- a/arch/x86/include/asm/hw_breakpoint.h
+++ b/arch/x86/include/asm/hw_breakpoint.h
@@ -20,10 +20,10 @@ struct arch_hw_breakpoint {
#include <linux/list.h>

/* Available HW breakpoint length encodings */
+#define X86_BREAKPOINT_LEN_X 0x00
#define X86_BREAKPOINT_LEN_1 0x40
#define X86_BREAKPOINT_LEN_2 0x44
#define X86_BREAKPOINT_LEN_4 0x4c
-#define X86_BREAKPOINT_LEN_EXECUTE 0x40

#ifdef CONFIG_X86_64
#define X86_BREAKPOINT_LEN_8 0x48
diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
index eaa6ae2..a474ec3 100644
--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -208,6 +208,9 @@ int arch_bp_generic_fields(int x86_len, int x86_type,
{
/* Len */
switch (x86_len) {
+ case X86_BREAKPOINT_LEN_X:
+ *gen_len = sizeof(long);
+ break;
case X86_BREAKPOINT_LEN_1:
*gen_len = HW_BREAKPOINT_LEN_1;
break;
@@ -251,6 +254,29 @@ static int arch_build_bp_info(struct perf_event *bp)

info->address = bp->attr.bp_addr;

+ /* Type */
+ switch (bp->attr.bp_type) {
+ case HW_BREAKPOINT_W:
+ info->type = X86_BREAKPOINT_WRITE;
+ break;
+ case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
+ info->type = X86_BREAKPOINT_RW;
+ 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;
+ }
+ default:
+ return -EINVAL;
+ }
+
/* Len */
switch (bp->attr.bp_len) {
case HW_BREAKPOINT_LEN_1:
@@ -271,21 +297,6 @@ static int arch_build_bp_info(struct perf_event *bp)
return -EINVAL;
}

- /* Type */
- switch (bp->attr.bp_type) {
- case HW_BREAKPOINT_W:
- info->type = X86_BREAKPOINT_WRITE;
- break;
- case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
- info->type = X86_BREAKPOINT_RW;
- break;
- case HW_BREAKPOINT_X:
- info->type = X86_BREAKPOINT_EXECUTE;
- break;
- default:
- return -EINVAL;
- }
-
return 0;
}
/*
@@ -305,6 +316,9 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp)
ret = -EINVAL;

switch (info->len) {
+ case X86_BREAKPOINT_LEN_X:
+ align = sizeof(long) -1;
+ break;
case X86_BREAKPOINT_LEN_1:
align = 0;
break;
--
1.6.2.3

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Prev: [PATCH 6/7] perf: Don't print traces when debugging ordering
Next: [PATCH 2/7] perf: Fix argument of perf_arch_fetch_caller_regs