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Commit aadb178c authored by Tomislav Novak's avatar Tomislav Novak Committed by Greg Kroah-Hartman
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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: default avatarTomislav Novak <tnovak@meta.com>
Tested-by: Samuel Gosselin <sgosselin@google.com> # arm64
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/linux-arm-kernel/20220923203644.2731604-1-tnovak@fb.com/
Link: https://lore.kernel.org/r/20230605191923.1219974-1-tnovak@meta.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent cb37e7fa

arch/arm/kernel/hw_breakpoint.c

+4 −4
Original line number Diff line number Diff line
@@ -623,7 +623,7 @@ 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.
@@ -795,7 +795,7 @@ 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));
@@ -808,7 +808,7 @@ 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));

	}
@@ -883,7 +883,7 @@ 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;

		}

arch/arm64/kernel/hw_breakpoint.c

+2 −2
Original line number Diff line number Diff line
@@ -654,7 +654,7 @@ static int breakpoint_handler(unsigned long unused, unsigned int 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;

include/linux/perf_event.h

+19 −3
Original line number Diff line number Diff line
@@ -1018,15 +1018,31 @@ 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,