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hw_breakpoint: fix single-stepping when using bpf_overflow_handler 

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@meta.com>
Tested-by: Samuel Gosselin <sgosselin@google.com> # arm64
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Alexei 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: Will Deacon <will@kernel.org>
This commit is contained in:
Tomislav Novak 2023-06-05 12:19:23 -07:00 committed by Will Deacon
parent f4e2bd91dd
commit d11a69873d
3 changed files with 25 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
arch/arm/kernel/hw_breakpoint.c
View File

@ -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;
}

4
arch/arm64/kernel/hw_breakpoint.c
View File

@ -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;

22
include/linux/perf_event.h
View File

@ -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,