This is a note to let you know that I've just added the patch titled
hw_breakpoint: fix single-stepping when using bpf_overflow_handler
to the 6.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
hw_breakpoint-fix-single-stepping-when-using-bpf_ove.patch
and it can be found in the queue-6.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 579f7fbb827f60efe1e46a663b5803d61b534523
Author: Tomislav Novak <tnovak@xxxxxxxx>
Date: Mon Jun 5 12:19:23 2023 -0700
hw_breakpoint: fix single-stepping when using bpf_overflow_handler
[ Upstream commit d11a69873d9a7435fe6a48531e165ab80a8b1221 ]
Arm platforms use is_default_overflow_handler() to determine if the
hw_breakpoint code should single-step over the breakpoint trigger or
let the custom handler deal with it.
Since bpf_overflow_handler() currently isn't recognized as a default
handler, attaching a BPF program to a PERF_TYPE_BREAKPOINT event causes
it to keep firing (the instruction triggering the data abort exception
is never skipped). For example:
# bpftrace -e 'watchpoint:0x10000:4:w { print("hit") }' -c ./test
Attaching 1 probe...
hit
hit
[...]
^C
(./test performs a single 4-byte store to 0x10000)
This patch replaces the check with uses_default_overflow_handler(),
which accounts for the bpf_overflow_handler() case by also testing
if one of the perf_event_output functions gets invoked indirectly,
via orig_default_handler.
Signed-off-by: Tomislav Novak <tnovak@xxxxxxxx>
Tested-by: Samuel Gosselin <sgosselin@xxxxxxxxxx> # arm64
Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Acked-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Link: https://lore.kernel.org/linux-arm-kernel/20220923203644.2731604-1-tnovak@xxxxxx/
Link: https://lore.kernel.org/r/20230605191923.1219974-1-tnovak@xxxxxxxx
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index 054e9199f30db..dc0fb7a813715 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -626,7 +626,7 @@ int hw_breakpoint_arch_parse(struct perf_event *bp,
hw->address &= ~alignment_mask;
hw->ctrl.len <<= offset;
- if (is_default_overflow_handler(bp)) {
+ if (uses_default_overflow_handler(bp)) {
/*
* Mismatch breakpoints are required for single-stepping
* breakpoints.
@@ -798,7 +798,7 @@ static void watchpoint_handler(unsigned long addr, unsigned int fsr,
* Otherwise, insert a temporary mismatch breakpoint so that
* we can single-step over the watchpoint trigger.
*/
- if (!is_default_overflow_handler(wp))
+ if (!uses_default_overflow_handler(wp))
continue;
step:
enable_single_step(wp, instruction_pointer(regs));
@@ -811,7 +811,7 @@ static void watchpoint_handler(unsigned long addr, unsigned int fsr,
info->trigger = addr;
pr_debug("watchpoint fired: address = 0x%x\n", info->trigger);
perf_bp_event(wp, regs);
- if (is_default_overflow_handler(wp))
+ if (uses_default_overflow_handler(wp))
enable_single_step(wp, instruction_pointer(regs));
}
@@ -886,7 +886,7 @@ static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
info->trigger = addr;
pr_debug("breakpoint fired: address = 0x%x\n", addr);
perf_bp_event(bp, regs);
- if (is_default_overflow_handler(bp))
+ if (uses_default_overflow_handler(bp))
enable_single_step(bp, addr);
goto unlock;
}
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index db2a1861bb978..35225632d70ad 100644
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -654,7 +654,7 @@ static int breakpoint_handler(unsigned long unused, unsigned long esr,
perf_bp_event(bp, regs);
/* Do we need to handle the stepping? */
- if (is_default_overflow_handler(bp))
+ if (uses_default_overflow_handler(bp))
step = 1;
unlock:
rcu_read_unlock();
@@ -733,7 +733,7 @@ static u64 get_distance_from_watchpoint(unsigned long addr, u64 val,
static int watchpoint_report(struct perf_event *wp, unsigned long addr,
struct pt_regs *regs)
{
- int step = is_default_overflow_handler(wp);
+ int step = uses_default_overflow_handler(wp);
struct arch_hw_breakpoint *info = counter_arch_bp(wp);
info->trigger = addr;
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 2166a69e3bf2e..e657916c9509c 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1316,15 +1316,31 @@ extern int perf_event_output(struct perf_event *event,
struct pt_regs *regs);
static inline bool
-is_default_overflow_handler(struct perf_event *event)
+__is_default_overflow_handler(perf_overflow_handler_t overflow_handler)
{
- if (likely(event->overflow_handler == perf_event_output_forward))
+ if (likely(overflow_handler == perf_event_output_forward))
return true;
- if (unlikely(event->overflow_handler == perf_event_output_backward))
+ if (unlikely(overflow_handler == perf_event_output_backward))
return true;
return false;
}
+#define is_default_overflow_handler(event) \
+ __is_default_overflow_handler((event)->overflow_handler)
+
+#ifdef CONFIG_BPF_SYSCALL
+static inline bool uses_default_overflow_handler(struct perf_event *event)
+{
+ if (likely(is_default_overflow_handler(event)))
+ return true;
+
+ return __is_default_overflow_handler(event->orig_overflow_handler);
+}
+#else
+#define uses_default_overflow_handler(event) \
+ is_default_overflow_handler(event)
+#endif
+
extern void
perf_event_header__init_id(struct perf_event_header *header,
struct perf_sample_data *data,
