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From 5ed7d8c8905e639e711f1a21e5f978fc21585f8c Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 3 Nov 2020 10:27:17 +0100
Subject: [PATCH 028/323] asm-generic: Provide kmap_size.h
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
kmap_types.h is a misnomer because the old atomic MAP based array does not
exist anymore and the whole indirection of architectures including
kmap_types.h is inconinstent and does not allow to provide guard page
debugging for this misfeature.
Add a common header file which defines the mapping stack size for all
architectures. Will be used when converting architectures over to a
generic kmap_local/atomic implementation.
The array size is chosen with the following constraints in mind:
- The deepest nest level in one context is 3 according to code
inspection.
- The worst case nesting for the upcoming reemptible version would be:
2 maps in task context and a fault inside
2 maps in the fault handler
3 maps in softirq
2 maps in interrupt
So a total of 16 is sufficient and probably overestimated.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
include/asm-generic/Kbuild | 1 +
include/asm-generic/kmap_size.h | 12 ++++++++++++
2 files changed, 13 insertions(+)
create mode 100644 include/asm-generic/kmap_size.h
diff --git a/include/asm-generic/Kbuild b/include/asm-generic/Kbuild
index d1300c6e0a47..3114a6da7e56 100644
--- a/include/asm-generic/Kbuild
+++ b/include/asm-generic/Kbuild
@@ -31,6 +31,7 @@ mandatory-y += irq_regs.h
mandatory-y += irq_work.h
mandatory-y += kdebug.h
mandatory-y += kmap_types.h
+mandatory-y += kmap_size.h
mandatory-y += kprobes.h
mandatory-y += linkage.h
mandatory-y += local.h
diff --git a/include/asm-generic/kmap_size.h b/include/asm-generic/kmap_size.h
new file mode 100644
index 000000000000..9d6c7786a645
--- /dev/null
+++ b/include/asm-generic/kmap_size.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_KMAP_SIZE_H
+#define _ASM_GENERIC_KMAP_SIZE_H
+
+/* For debug this provides guard pages between the maps */
+#ifdef CONFIG_DEBUG_HIGHMEM
+# define KM_MAX_IDX 33
+#else
+# define KM_MAX_IDX 16
+#endif
+
+#endif
--
2.43.0
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