Commit 370d8419 authored by Christophe Leroy's avatar Christophe Leroy Committed by Madhavan Srinivasan
Browse files

powerpc/32: Automatically adapt TASK_SIZE based on constraints 



At the time being, TASK_SIZE can be customized by the user via Kconfig
but it is not possible to check all constraints in Kconfig. Impossible
setups are detected at compile time with BUILD_BUG() but that leads
to build failure when setting crazy values. It is not a problem on its
own because the user will usually either use the default value or set
a well thought value. However build robots generate crazy random
configs that lead to build failures, and build robots see it as a
regression every time a patch adds such a constraint.

So instead of failing the build when the custom TASK_SIZE is too
big, just adjust it to the maximum possible value matching the setup.

Several architectures already calculate TASK_SIZE based on other
parameters and options.

In order to do so, move MODULES_VADDR calculation into task_size_32.h
and ensure that:
- On book3s/32, userspace and module area have their own segments (256M)
- On 8xx, userspace has its own full PGDIR entries (4M)

Then TASK_SIZE is guaranteed to be correct so remove related
BUILD_BUG()s.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMadhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/6a2575420770d075cd090b5a316730a2ffafdee4.1766574657.git.chleroy@kernel.org
parent fb790377

arch/powerpc/Kconfig

+1 −2
Original line number Diff line number Diff line
@@ -1293,9 +1293,8 @@ config TASK_SIZE_BOOL 
	  Say N here unless you know what you are doing.



config TASK_SIZE

	hex "Size of user task space" if TASK_SIZE_BOOL

	hex "Size of maximum user task space" if TASK_SIZE_BOOL

	default "0x80000000" if PPC_8xx

	default "0xb0000000" if PPC_BOOK3S_32 && EXECMEM

	default "0xc0000000"



config MODULES_SIZE_BOOL

arch/powerpc/include/asm/book3s/32/pgtable.h

+0 −4
Original line number Diff line number Diff line
@@ -195,10 +195,6 @@ void unmap_kernel_page(unsigned long va); 
#define VMALLOC_END	ioremap_bot

#endif



#define MODULES_END	ALIGN_DOWN(PAGE_OFFSET, SZ_256M)

#define MODULES_SIZE	(CONFIG_MODULES_SIZE * SZ_1M)

#define MODULES_VADDR	(MODULES_END - MODULES_SIZE)



#ifndef __ASSEMBLER__

#include <linux/sched.h>

#include <linux/threads.h>

arch/powerpc/include/asm/nohash/32/mmu-8xx.h

+0 −4
Original line number Diff line number Diff line
@@ -170,10 +170,6 @@ 


#define mmu_linear_psize	MMU_PAGE_8M



#define MODULES_END	PAGE_OFFSET

#define MODULES_SIZE	(CONFIG_MODULES_SIZE * SZ_1M)

#define MODULES_VADDR	(MODULES_END - MODULES_SIZE)



#ifndef __ASSEMBLER__



#include <linux/mmdebug.h>

arch/powerpc/include/asm/task_size_32.h

+26 −0
Original line number Diff line number Diff line
@@ -2,11 +2,37 @@ 
#ifndef _ASM_POWERPC_TASK_SIZE_32_H

#define _ASM_POWERPC_TASK_SIZE_32_H



#include <linux/sizes.h>



#if CONFIG_TASK_SIZE > CONFIG_KERNEL_START

#error User TASK_SIZE overlaps with KERNEL_START address

#endif



#ifdef CONFIG_PPC_8xx

#define MODULES_END	ASM_CONST(CONFIG_PAGE_OFFSET)

#define MODULES_SIZE	(CONFIG_MODULES_SIZE * SZ_1M)

#define MODULES_VADDR	(MODULES_END - MODULES_SIZE)

#define MODULES_BASE	(MODULES_VADDR & ~(UL(SZ_4M) - 1))

#define USER_TOP	MODULES_BASE

#endif



#ifdef CONFIG_PPC_BOOK3S_32

#define MODULES_END	(ASM_CONST(CONFIG_PAGE_OFFSET) & ~(UL(SZ_256M) - 1))

#define MODULES_SIZE	(CONFIG_MODULES_SIZE * SZ_1M)

#define MODULES_VADDR	(MODULES_END - MODULES_SIZE)

#define MODULES_BASE	(MODULES_VADDR & ~(UL(SZ_256M) - 1))

#define USER_TOP	MODULES_BASE

#endif



#ifndef USER_TOP

#define USER_TOP	ASM_CONST(CONFIG_PAGE_OFFSET)

#endif



#if CONFIG_TASK_SIZE < USER_TOP

#define TASK_SIZE ASM_CONST(CONFIG_TASK_SIZE)

#else

#define TASK_SIZE USER_TOP

#endif



/*

 * This decides where the kernel will search for a free chunk of vm space during

arch/powerpc/mm/book3s32/mmu.c

+0 −2
Original line number Diff line number Diff line
@@ -223,8 +223,6 @@ int mmu_mark_initmem_nx(void) 


	update_bats();



	BUILD_BUG_ON(ALIGN_DOWN(MODULES_VADDR, SZ_256M) < TASK_SIZE);



	for (i = ALIGN(TASK_SIZE, SZ_256M) >> 28; i < 16; i++) {

		/* Do not set NX on VM space for modules */

		if (is_module_segment(i << 28))