linux-kernel - [PATCH 1/1] exception/stackdepot: add irqentry section in case of STACKDEPOT

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Date:   Wed, 18 Aug 2021 12:45:43 +0530
From:   Maninder Singh <maninder1.s@...sung.com>
To:     linux@...linux.org.uk, catalin.marinas@....com, will@...nel.org,
        mark.rutland@....com, joey.gouly@....com, maz@...nel.org,
        pcc@...gle.com, amit.kachhap@....com, ryabinin.a.a@...il.com,
        dvyukov@...gle.com, akpm@...ux-foundation.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, v.narang@...sung.com,
        a.sahrawat@...sung.com, Maninder Singh <maninder1.s@...sung.com>
Subject: [PATCH 1/1] exception/stackdepot: add irqentry section in case of
 STACKDEPOT

As of now if CONFIG_FUNCTION_GRAPH_TRACER is disabled some functions
like gic_handle_irq will not be added in irqentry text section.

which leads to adding more stacks in stackdepot as frames below IRQ
will not be filtered with filter_irq_stack() function.

checked with debug interface for satckdepot:
https://lkml.org/lkml/2017/11/22/242

e.g. (ARM)
stack count 23188 backtrace
 prep_new_page+0x14c/0x160
 get_page_from_freelist+0x1258/0x1350
...
 __handle_domain_irq+0x1ac/0x4ac
 gic_handle_irq+0x44/0x80
 __irq_svc+0x5c/0x98
 __slab_alloc.constprop.0+0x84/0xac
 __kmalloc+0x31c/0x340
 sf_malloc+0x14/0x18

and for same _irq_svc there were 25000 calls which was causing
memory pressure of 2MB more on satckdepot, which will keep increasing.

Before patch memory consumption on ARM target after 2 hours:
Memory consumed by Stackdepot:3600 KB

After change:
============
Memory consumed by Stackdepot:1744 KB

 prep_new_page+0x14c/0x160
 get_page_from_freelist+0x2e4/0x1350
...
 __handle_domain_irq+0x1ac/0x4ac
 gic_handle_irq+0x44/0x80

^^^^^ no frames below this.

Signed-off-by: Maninder Singh <maninder1.s@...sung.com>
Signed-off-by: Vaneet Narang <v.narang@...sung.com>
---
 arch/arm/include/asm/exception.h   | 2 +-
 arch/arm64/include/asm/exception.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/exception.h b/arch/arm/include/asm/exception.h
index 58e039a851af..3f4534cccc0f 100644
--- a/arch/arm/include/asm/exception.h
+++ b/arch/arm/include/asm/exception.h
@@ -10,7 +10,7 @@
 
 #include <linux/interrupt.h>
 
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_STACKDEPOT)
 #define __exception_irq_entry	__irq_entry
 #else
 #define __exception_irq_entry
diff --git a/arch/arm64/include/asm/exception.h b/arch/arm64/include/asm/exception.h
index 339477dca551..ef2581b63405 100644
--- a/arch/arm64/include/asm/exception.h
+++ b/arch/arm64/include/asm/exception.h
@@ -13,7 +13,7 @@
 
 #include <linux/interrupt.h>
 
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_STACKDEPOT)
 #define __exception_irq_entry	__irq_entry
 #else
 #define __exception_irq_entry	__kprobes
-- 
2.17.1