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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: Helge Deller <deller@gmx.de>
Signed-off-by: James 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>
This commit is contained in:
Helge Deller 2014-04-30 23:26:02 +02:00 committed by James Hogan
parent d71f290b4e
commit 042d27acb6
4 changed files with 23 additions and 5 deletions
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2
arch/metag/include/asm/processor.h
View File

@ -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.

5
arch/parisc/include/asm/processor.h
View File

@ -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

6
arch/parisc/kernel/sys_parisc.c
View File

@ -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);
}

15
mm/Kconfig
View File

@ -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.