Commit 042d27ac authored by Helge Deller's avatar Helge Deller Committed by James Hogan
Browse files

parisc,metag: Do not hardcode maximum userspace stack size 



This patch affects only architectures where the stack grows upwards
(currently parisc and metag only). On those do not hardcode the maximum
initial stack size to 1GB for 32-bit processes, but make it configurable
via a config option.

The main problem with the hardcoded stack size is, that we have two
memory regions which grow upwards: stack and heap. To keep most of the
memory available for heap in a flexmap memory layout, it makes no sense
to hard allocate up to 1GB of the memory for stack which can't be used
as heap then.

This patch makes the stack size for 32-bit processes configurable and
uses 80MB as default value which has been in use during the last few
years on parisc and which hasn't showed any problems yet.

Signed-off-by: default avatarHelge Deller <deller@gmx.de>
Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: linux-parisc@vger.kernel.org
Cc: linux-metag@vger.kernel.org
Cc: John David Anglin <dave.anglin@bell.net>
parent d71f290b

arch/metag/include/asm/processor.h

+1 −1
Original line number Diff line number Diff line
@@ -23,7 +23,7 @@ 
#define STACK_TOP	(TASK_SIZE - PAGE_SIZE)

#define STACK_TOP_MAX	STACK_TOP

/* Maximum virtual space for stack */

#define STACK_SIZE_MAX	(1 << 28)	/* 256 MB */

#define STACK_SIZE_MAX	(CONFIG_MAX_STACK_SIZE_MB*1024*1024)



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

 * space during mmap's.

arch/parisc/include/asm/processor.h

+4 −1
Original line number Diff line number Diff line
@@ -55,7 +55,10 @@ 
#define STACK_TOP	TASK_SIZE

#define STACK_TOP_MAX	DEFAULT_TASK_SIZE



#define STACK_SIZE_MAX	(1 << 30)	/* 1 GB */

/* Allow bigger stacks for 64-bit processes */

#define STACK_SIZE_MAX	(USER_WIDE_MODE					\

			 ? (1 << 30)	/* 1 GB */			\

			 : (CONFIG_MAX_STACK_SIZE_MB*1024*1024))



#endif

arch/parisc/kernel/sys_parisc.c

+3 −3
Original line number Diff line number Diff line
@@ -72,10 +72,10 @@ static unsigned long mmap_upper_limit(void) 
{

	unsigned long stack_base;



	/* Limit stack size to 1GB - see setup_arg_pages() in fs/exec.c */

	/* Limit stack size - see setup_arg_pages() in fs/exec.c */

	stack_base = rlimit_max(RLIMIT_STACK);

	if (stack_base > (1 << 30))

		stack_base = 1 << 30;

	if (stack_base > STACK_SIZE_MAX)

		stack_base = STACK_SIZE_MAX;



	return PAGE_ALIGN(STACK_TOP - stack_base);

}

mm/Kconfig

+15 −0
Original line number Diff line number Diff line
@@ -581,3 +581,18 @@ config PGTABLE_MAPPING 


config GENERIC_EARLY_IOREMAP

	bool



config MAX_STACK_SIZE_MB

	int "Maximum user stack size for 32-bit processes (MB)"

	default 80

	range 8 256 if METAG

	range 8 2048

	depends on STACK_GROWSUP && (!64BIT || COMPAT)

	help

	  This is the maximum stack size in Megabytes in the VM layout of 32-bit

	  user processes when the stack grows upwards (currently only on parisc

	  and metag arch). The stack will be located at the highest memory

	  address minus the given value, unless the RLIMIT_STACK hard limit is

	  changed to a smaller value in which case that is used.



	  A sane initial value is 80 MB.

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