linux-kernel - [PATCH 10/14] powerpc/32s: Reduce default size of module/execmem area

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Message-ID: <c1f6a4e47f177d919561c6e97d31af5564923cf6.1724173828.git.christophe.leroy@csgroup.eu>
Date: Tue, 20 Aug 2024 19:23:54 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: CASAUBON Jean Michel <jean-michel.casaubon@...soprasteria.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Naveen N Rao <naveen@...nel.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 10/14] powerpc/32s: Reduce default size of module/execmem area

book3s/32 platforms have usually more memory than 8xx, but it is still
not worth reserving a full segment (256 Mbytes) for module text.
64Mbytes should be far enough.

Also fix TASK_SIZE when EXECMEM is not selected, and add a build
verification for overlap of module execmem space with user segments.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/Kconfig                         | 7 ++++---
 arch/powerpc/include/asm/book3s/32/pgtable.h | 3 ++-
 arch/powerpc/mm/book3s32/mmu.c               | 2 ++
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index f050a37aa857..b9f11c262582 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -1269,23 +1269,24 @@ config TASK_SIZE_BOOL
 config TASK_SIZE
 	hex "Size of user task space" if TASK_SIZE_BOOL
 	default "0x80000000" if PPC_8xx
-	default "0xb0000000" if PPC_BOOK3S_32
+	default "0xb0000000" if PPC_BOOK3S_32 && EXECMEM
 	default "0xc0000000"
 
 config MODULES_SIZE_BOOL
 	bool "Set custom size for modules/execmem area"
 	depends on EXECMEM && ADVANCED_OPTIONS
-	depends on PPC_8xx
 	help
 	  This option allows you to set the size of kernel virtual address
 	  space dedicated for modules/execmem.
-	  For the time being it is only for 8xx.
+	  For the time being it is only for 8xx and book3s/32. Other
+	  platform share it with vmalloc space.
 
 	  Say N here unless you know what you are doing.
 
 config MODULES_SIZE
 	int "Size of modules/execmem area (In Mbytes)" if MODULES_SIZE_BOOL
 	range 1 256 if EXECMEM
+	default 64 if EXECMEM && PPC_BOOK3S_32
 	default 32 if EXECMEM && PPC_8xx
 	default 0
 
diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
index 52971ee30717..42c3af90d1f0 100644
--- a/arch/powerpc/include/asm/book3s/32/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
@@ -196,7 +196,8 @@ void unmap_kernel_page(unsigned long va);
 #endif
 
 #define MODULES_END	ALIGN_DOWN(PAGE_OFFSET, SZ_256M)
-#define MODULES_VADDR	(MODULES_END - SZ_256M)
+#define MODULES_SIZE	(CONFIG_MODULES_SIZE * SZ_1M)
+#define MODULES_VADDR	(MODULES_END - MODULES_SIZE)
 
 #ifndef __ASSEMBLY__
 #include <linux/sched.h>
diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c
index 625fe7d08e06..2db167f4233f 100644
--- a/arch/powerpc/mm/book3s32/mmu.c
+++ b/arch/powerpc/mm/book3s32/mmu.c
@@ -223,6 +223,8 @@ int mmu_mark_initmem_nx(void)
 
 	update_bats();
 
+	BUILD_BUG_ON(ALIGN_DOWN(MODULES_VADDR, SZ_256M) < TASK_SIZE);
+
 	for (i = TASK_SIZE >> 28; i < 16; i++) {
 		/* Do not set NX on VM space for modules */
 		if (is_module_segment(i << 28))
-- 
2.44.0