[PATCH v3 07/16] perf: Add wrappers for invoking guest callbacks

Sean Christopherson
2021-09-22T00:06:15Z

Add helpers for the guest callbacks to prepare for burying the callbacks
behind a Kconfig (it's a lot easier to provide a few stubs than to #ifdef
piles of code), and also to prepare for converting the callbacks to
static_call(). perf_instruction_pointer() in particular will have subtle
semantics with static_call(), as the "no callbacks" case will return 0 if
the callbacks are unregistered between querying guest state and getting
the IP. Implement the change now to avoid a functional change when adding
static_call() support, and because the new helper needs to return
_something_ in this case.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/arm64/kernel/perf_callchain.c | 16 +++++-----------
arch/x86/events/core.c | 15 +++++----------
arch/x86/events/intel/core.c | 5 +----
include/linux/perf_event.h | 24 ++++++++++++++++++++++++
4 files changed, 35 insertions(+), 25 deletions(-)

diff --git a/arch/arm64/kernel/perf_callchain.c b/arch/arm64/kernel/perf_callchain.c
index 274dc3e11b6d..db04a55cee7e 100644
--- a/arch/arm64/kernel/perf_callchain.c
+++ b/arch/arm64/kernel/perf_callchain.c
@@ -102,9 +102,7 @@ compat_user_backtrace(struct compat_frame_tail __user *tail,
void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
struct pt_regs *regs)
{
- struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
-
- if (guest_cbs && guest_cbs->state()) {
+ if (perf_guest_state()) {
/* We don't support guest os callchain now */
return;
}
@@ -149,10 +147,9 @@ static bool callchain_trace(void *data, unsigned long pc)
void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
struct pt_regs *regs)
{
- struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
struct stackframe frame;

- if (guest_cbs && guest_cbs->state()) {
+ if (perf_guest_state()) {
/* We don't support guest os callchain now */
return;
}
@@ -163,18 +160,15 @@ void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,

unsigned long perf_instruction_pointer(struct pt_regs *regs)
{
- struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
-
- if (guest_cbs && guest_cbs->state())
- return guest_cbs->get_ip();
+ if (perf_guest_state())
+ return perf_guest_get_ip();

return instruction_pointer(regs);
}

unsigned long perf_misc_flags(struct pt_regs *regs)
{
- struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
- unsigned int guest_state = guest_cbs ? guest_cbs->state() : 0;
+ unsigned int guest_state = perf_guest_state();
int misc = 0;

if (guest_state) {
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 3a7630fdd340..d20e4f8d1aef 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2761,11 +2761,10 @@ static bool perf_hw_regs(struct pt_regs *regs)
void
perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
{
- struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
struct unwind_state state;
unsigned long addr;

- if (guest_cbs && guest_cbs->state()) {
+ if (perf_guest_state()) {
/* TODO: We don't support guest os callchain now */
return;
}
@@ -2865,11 +2864,10 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry_ctx *ent
void
perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
{
- struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
struct stack_frame frame;
const struct stack_frame __user *fp;

- if (guest_cbs && guest_cbs->state()) {
+ if (perf_guest_state()) {
/* TODO: We don't support guest os callchain now */
return;
}
@@ -2946,18 +2944,15 @@ static unsigned long code_segment_base(struct pt_regs *regs)

unsigned long perf_instruction_pointer(struct pt_regs *regs)
{
- struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
-
- if (guest_cbs && guest_cbs->state())
- return guest_cbs->get_ip();
+ if (perf_guest_state())
+ return perf_guest_get_ip();

return regs->ip + code_segment_base(regs);
}

unsigned long perf_misc_flags(struct pt_regs *regs)
{
- struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
- unsigned int guest_state = guest_cbs ? guest_cbs->state() : 0;
+ unsigned int guest_state = perf_guest_state();
int misc = 0;

if (guest_state) {
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 524ad1f747bd..f5b02017ba16 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -2786,7 +2786,6 @@ static int handle_pmi_common(struct pt_regs *regs, u64 status)
{
struct perf_sample_data data;
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
- struct perf_guest_info_callbacks *guest_cbs;
int bit;
int handled = 0;
u64 intel_ctrl = hybrid(cpuc->pmu, intel_ctrl);
@@ -2853,9 +2852,7 @@ static int handle_pmi_common(struct pt_regs *regs, u64 status)
*/
if (__test_and_clear_bit(GLOBAL_STATUS_TRACE_TOPAPMI_BIT, (unsigned long *)&status)) {
handled++;
-
- guest_cbs = perf_get_guest_cbs();
- if (likely(!guest_cbs || !guest_cbs->handle_intel_pt_intr()))
+ if (!perf_guest_handle_intel_pt_intr())
intel_pt_interrupt();
}

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index f9be88a47434..c0a6eaf55fb1 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1247,6 +1247,30 @@ static inline struct perf_guest_info_callbacks *perf_get_guest_cbs(void)
/* Prevent reloading between a !NULL check and dereferences. */
return READ_ONCE(perf_guest_cbs);
}
+static inline unsigned int perf_guest_state(void)
+{
+ struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
+
+ return guest_cbs ? guest_cbs->state() : 0;
+}
+static inline unsigned long perf_guest_get_ip(void)
+{
+ struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
+
+ /*
+ * Arbitrarily return '0' in the unlikely scenario that the callbacks
+ * are unregistered between checking guest state and getting the IP.
+ */
+ return guest_cbs ? guest_cbs->get_ip() : 0;
+}
+static inline unsigned int perf_guest_handle_intel_pt_intr(void)
+{
+ struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
+
+ if (guest_cbs && guest_cbs->handle_intel_pt_intr)
+ return guest_cbs->handle_intel_pt_intr();
+ return 0;
+}
extern void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs);
extern void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs);

--
2.33.0.464.g1972c5931b-goog