[PATCH v4 3/5] signal: Factor force_sig_perf out of perf_sigtrap

[Eric W. Beiderman]

From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>

Separate filling in siginfo for TRAP_PERF from deciding that
siginal needs to be sent.

There are enough little details that need to be correct when
properly filling in siginfo_t that it is easy to make mistakes
if filling in the siginfo_t is in the same function with other
logic.  So factor out force_sig_perf to reduce the cognative
load of on reviewers, maintainers and implementors.

v1: https://lkml.kernel.org/r/m17dkjqqxz.fsf_-_@xxxxxxxxxxxxxxxxx
v2: https://lkml.kernel.org/r/20210505141101.11519-10-ebiederm@xxxxxxxxxxxx
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
 include/linux/sched/signal.h |  1 +
 kernel/events/core.c         | 11 ++---------
 kernel/signal.c              | 13 +++++++++++++
 3 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 3f6a0fcaa10c..7f4278fa21fe 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -326,6 +326,7 @@ int send_sig_mceerr(int code, void __user *, short, struct task_struct *);
 
 int force_sig_bnderr(void __user *addr, void __user *lower, void __user *upper);
 int force_sig_pkuerr(void __user *addr, u32 pkey);
+int force_sig_perf(void __user *addr, u32 type, u64 sig_data);
 
 int force_sig_ptrace_errno_trap(int errno, void __user *addr);
 
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 928b166d888e..48ea8863183b 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6394,8 +6394,6 @@ void perf_event_wakeup(struct perf_event *event)
 
 static void perf_sigtrap(struct perf_event *event)
 {
-	struct kernel_siginfo info;
-
 	/*
 	 * We'd expect this to only occur if the irq_work is delayed and either
 	 * ctx->task or current has changed in the meantime. This can be the
@@ -6410,13 +6408,8 @@ static void perf_sigtrap(struct perf_event *event)
 	if (current->flags & PF_EXITING)
 		return;
 
-	clear_siginfo(&info);
-	info.si_signo = SIGTRAP;
-	info.si_code = TRAP_PERF;
-	info.si_errno = event->attr.type;
-	info.si_perf = event->attr.sig_data;
-	info.si_addr = (void __user *)event->pending_addr;
-	force_sig_info(&info);
+	force_sig_perf((void __user *)event->pending_addr,
+		       event->attr.type, event->attr.sig_data);
 }
 
 static void perf_pending_event_disable(struct perf_event *event)
diff --git a/kernel/signal.c b/kernel/signal.c
index 597594ee72de..3a18d13c39b2 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1763,6 +1763,19 @@ int force_sig_pkuerr(void __user *addr, u32 pkey)
 }
 #endif
 
+int force_sig_perf(void __user *addr, u32 type, u64 sig_data)
+{
+	struct kernel_siginfo info;
+
+	clear_siginfo(&info);
+	info.si_signo = SIGTRAP;
+	info.si_errno = type;
+	info.si_code  = TRAP_PERF;
+	info.si_addr  = addr;
+	info.si_perf  = sig_data;
+	return force_sig_info(&info);
+}
+
 /* For the crazy architectures that include trap information in
  * the errno field, instead of an actual errno value.
  */
-- 
2.30.1