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parisc,metag: Do not hardcode maximum userspace stack size

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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 <[email protected]>
Signed-off-by: James Hogan <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: John David Anglin <[email protected]>
This commit is contained in:
Helge Deller 2014-04-30 23:26:02 +02:00 • committed by James Hogan
commit 042d27acb6
4 changed files with 23 additions and 5 deletions
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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);
}