[PATCH v2] x86, kasan, ftrace: Put APIC interrupt handlers into .irqentry.text

[Alexander Potapenko]

When building with CONFIG_FUNCTION_GRAPH_TRACER or CONFIG_KASAN, put the
APIC interrupt handlers into the .irqentry.text section. This is needed
because both KASAN and function graph tracer use __irqentry_text_start and
__irqentry_text_end to determine whether a function is an IRQ entry point.

Dmitry Vyukov has reported unexpected KASAN stackdepot growth
(https://github.com/google/kasan/issues/36), which had been caused by
the APIC handlers not being present in .irqentry.text.

Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
---
v2: - fixed kbuild warning (incorrect #if directive)
---
 arch/x86/entry/entry_64.S | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 9ee0da1..2ef4f0b 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -601,9 +601,20 @@ apicinterrupt3 \num trace(\sym) smp_trace(\sym)
 .endm
 #endif
 
+/* Make sure APIC interrupt handlers end up in the irqentry section. */
+#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
+#define PUSH_SECTION_IRQENTRY	.pushsection .irqentry.text, "ax"
+#define POP_SECTION_IRQENTRY	.popsection
+#else
+#define PUSH_SECTION_IRQENTRY
+#define POP_SECTION_IRQENTRY
+#endif
+
 .macro apicinterrupt num sym do_sym
+PUSH_SECTION_IRQENTRY
 apicinterrupt3 \num \sym \do_sym
 trace_apicinterrupt \num \sym
+POP_SECTION_IRQENTRY
 .endm
 
 #ifdef CONFIG_SMP
-- 
2.8.0.rc3.226.g39d4020