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>

diff --git a/arch/metag/include/asm/processor.h b/arch/metag/include/asm/processor.h
index 3be8581af4956ad7bd559c2c314450eadf7f9750..a8a37477c66e22a8e3c29ba2402ff6559a35bf27 100644 (file)
--- a/arch/metag/include/asm/processor.h
+++ b/arch/metag/include/asm/processor.h
@@ -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.

diff --git a/arch/parisc/include/asm/processor.h b/arch/parisc/include/asm/processor.h
index 86522ef09d524b73475821eaceb30094d3cf3d1c..d951c9681ab316aa2be88cd65b4d18ae62f958cb 100644 (file)
--- a/arch/parisc/include/asm/processor.h
+++ b/arch/parisc/include/asm/processor.h
@@ -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
 

diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_parisc.c
index 31ffa9b5532216620d9a6106d2d4b76e7501ee0b..e1ffea2f9a0b05ccda844969dcb7c519ab17077a 100644 (file)
--- a/arch/parisc/kernel/sys_parisc.c
+++ b/arch/parisc/kernel/sys_parisc.c
@@ -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);
 }

diff --git a/mm/Kconfig b/mm/Kconfig
index ebe5880c29d6cbe2306054f19bda87ffb3daa59a..1b5a95f0fa013ca428e877ae39d6f0148a49cd61 100644 (file)
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -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.