From 2425ce84026c385b73ae72039f90d042d49e0394 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Thu, 8 May 2014 15:51:37 -0400 Subject: [PATCH 1/5] metag: fix memory barriers Volatile access doesn't really imply the compiler barrier. Volatile access is only ordered with respect to other volatile accesses, it isn't ordered with respect to general memory accesses. Gcc may reorder memory accesses around volatile access, as we can see in this simple example (if we compile it with optimization, both increments of *b will be collapsed to just one): void fn(volatile int *a, long *b) { (*b)++; *a = 10; (*b)++; } Consequently, we need the compiler barrier after a write to the volatile variable, to make sure that the compiler doesn't reorder the volatile write with something else. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Acked-by: Peter Zijlstra Signed-off-by: James Hogan --- arch/metag/include/asm/barrier.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/metag/include/asm/barrier.h b/arch/metag/include/asm/barrier.h index 5d6b4b407dda..2d6f0de77325 100644 --- a/arch/metag/include/asm/barrier.h +++ b/arch/metag/include/asm/barrier.h @@ -15,6 +15,7 @@ static inline void wr_fence(void) volatile int *flushptr = (volatile int *) LINSYSEVENT_WR_FENCE; barrier(); *flushptr = 0; + barrier(); } #else /* CONFIG_METAG_META21 */ @@ -35,6 +36,7 @@ static inline void wr_fence(void) *flushptr = 0; *flushptr = 0; *flushptr = 0; + barrier(); } #endif /* !CONFIG_METAG_META21 */ @@ -68,6 +70,7 @@ static inline void fence(void) volatile int *flushptr = (volatile int *) LINSYSEVENT_WR_ATOMIC_UNLOCK; barrier(); *flushptr = 0; + barrier(); } #define smp_mb() fence() #define smp_rmb() fence() From d71f290b4e98a39f49f2595a13be3b4d5ce8e1f1 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Tue, 13 May 2014 23:58:24 +0100 Subject: [PATCH 2/5] metag: Reduce maximum stack size to 256MB Specify the maximum stack size for arches where the stack grows upward (parisc and metag) in asm/processor.h rather than hard coding in fs/exec.c so that metag can specify a smaller value of 256MB rather than 1GB. This fixes a BUG on metag if the RLIMIT_STACK hard limit is increased beyond a safe value by root. E.g. when starting a process after running "ulimit -H -s unlimited" it will then attempt to use a stack size of the maximum 1GB which is far too big for metag's limited user virtual address space (stack_top is usually 0x3ffff000): BUG: failure at fs/exec.c:589/shift_arg_pages()! Signed-off-by: James Hogan Cc: Helge Deller Cc: "James E.J. Bottomley" Cc: linux-parisc@vger.kernel.org Cc: linux-metag@vger.kernel.org Cc: John David Anglin Cc: stable@vger.kernel.org # only needed for >= v3.9 (arch/metag) --- arch/metag/include/asm/processor.h | 2 ++ arch/parisc/include/asm/processor.h | 2 ++ fs/exec.c | 6 +++--- 3 files changed, 7 insertions(+), 3 deletions(-) diff --git a/arch/metag/include/asm/processor.h b/arch/metag/include/asm/processor.h index f16477d1f571..3be8581af495 100644 --- a/arch/metag/include/asm/processor.h +++ b/arch/metag/include/asm/processor.h @@ -22,6 +22,8 @@ /* Add an extra page of padding at the top of the stack for the guard page. */ #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 */ /* 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 198a86feb574..86522ef09d52 100644 --- a/arch/parisc/include/asm/processor.h +++ b/arch/parisc/include/asm/processor.h @@ -55,6 +55,8 @@ #define STACK_TOP TASK_SIZE #define STACK_TOP_MAX DEFAULT_TASK_SIZE +#define STACK_SIZE_MAX (1 << 30) /* 1 GB */ + #endif #ifndef __ASSEMBLY__ diff --git a/fs/exec.c b/fs/exec.c index 476f3ebf437e..238b7aa26f68 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -657,10 +657,10 @@ int setup_arg_pages(struct linux_binprm *bprm, unsigned long rlim_stack; #ifdef CONFIG_STACK_GROWSUP - /* Limit stack size to 1GB */ + /* Limit stack size */ 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; /* Make sure we didn't let the argument array grow too large. */ if (vma->vm_end - vma->vm_start > stack_base) From 042d27acb64924a0e8a43e972485913a32407beb Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Wed, 30 Apr 2014 23:26:02 +0200 Subject: [PATCH 3/5] 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 Signed-off-by: James Hogan Cc: "James E.J. Bottomley" Cc: linux-parisc@vger.kernel.org Cc: linux-metag@vger.kernel.org Cc: John David Anglin --- arch/metag/include/asm/processor.h | 2 +- arch/parisc/include/asm/processor.h | 5 ++++- arch/parisc/kernel/sys_parisc.c | 6 +++--- mm/Kconfig | 15 +++++++++++++++ 4 files changed, 23 insertions(+), 5 deletions(-) diff --git a/arch/metag/include/asm/processor.h b/arch/metag/include/asm/processor.h index 3be8581af495..a8a37477c66e 100644 --- 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 86522ef09d52..d951c9681ab3 100644 --- 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 31ffa9b55322..e1ffea2f9a0b 100644 --- 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 ebe5880c29d6..1b5a95f0fa01 100644 --- 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. From c70458f50cd4271410aa75011f56ffabc0e2d34a Mon Sep 17 00:00:00 2001 From: James Hogan Date: Thu, 1 May 2014 12:31:14 +0100 Subject: [PATCH 4/5] metag: Remove _STK_LIM_MAX override Meta overrode _STK_LIM_MAX (the default RLIMIT_STACK hard limit) to 256MB, apparently in an attempt to prevent setup_arg_pages's STACK_GROWSUP code from choosing the maximum stack size of 1GB, which is far too large for Meta's limited virtual address space and hits a BUG_ON (stack_top is usually 0x3ffff000). However the commit "metag: Reduce maximum stack size to 256MB" reduces the absolute stack size limit to a safe value for metag. This allows the default _STK_LIM_MAX override to be removed, bringing the default behaviour in line with all other architectures. Parisc in particular recently removed their override of _STK_LIMT_MAX in commit e0d8898d76a7 (parisc: remove _STK_LIM_MAX override) since it subtly affects stack allocation semantics in userland. Meta's uapi/asm/resource.h can now be removed and switch to using generic-y. Suggested-by: Helge Deller Signed-off-by: James Hogan Cc: linux-metag@vger.kernel.org Cc: John David Anglin --- arch/metag/include/uapi/asm/Kbuild | 2 +- arch/metag/include/uapi/asm/resource.h | 7 ------- 2 files changed, 1 insertion(+), 8 deletions(-) delete mode 100644 arch/metag/include/uapi/asm/resource.h diff --git a/arch/metag/include/uapi/asm/Kbuild b/arch/metag/include/uapi/asm/Kbuild index 84e09feb4d54..ab78be2b6eb0 100644 --- a/arch/metag/include/uapi/asm/Kbuild +++ b/arch/metag/include/uapi/asm/Kbuild @@ -4,11 +4,11 @@ include include/uapi/asm-generic/Kbuild.asm header-y += byteorder.h header-y += ech.h header-y += ptrace.h -header-y += resource.h header-y += sigcontext.h header-y += siginfo.h header-y += swab.h header-y += unistd.h generic-y += mman.h +generic-y += resource.h generic-y += setup.h diff --git a/arch/metag/include/uapi/asm/resource.h b/arch/metag/include/uapi/asm/resource.h deleted file mode 100644 index 526d23cc3054..000000000000 --- a/arch/metag/include/uapi/asm/resource.h +++ /dev/null @@ -1,7 +0,0 @@ -#ifndef _UAPI_METAG_RESOURCE_H -#define _UAPI_METAG_RESOURCE_H - -#define _STK_LIM_MAX (1 << 28) -#include - -#endif /* _UAPI_METAG_RESOURCE_H */ From ffe6902b66aaa4ca6694bc19639259c16d84ddb1 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Thu, 1 May 2014 15:05:07 +0100 Subject: [PATCH 5/5] asm-generic: remove _STK_LIM_MAX _STK_LIM_MAX could be used to override the RLIMIT_STACK hard limit from an arch's include/uapi/asm-generic/resource.h file, but is no longer used since both parisc and metag removed the override. Therefore remove it entirely, setting the hard RLIMIT_STACK limit to RLIM_INFINITY directly in include/asm-generic/resource.h. Signed-off-by: James Hogan Cc: Arnd Bergmann Cc: linux-arch@vger.kernel.org Cc: Helge Deller Cc: John David Anglin --- include/asm-generic/resource.h | 2 +- include/uapi/asm-generic/resource.h | 7 ------- 2 files changed, 1 insertion(+), 8 deletions(-) diff --git a/include/asm-generic/resource.h b/include/asm-generic/resource.h index b4ea8f50fc65..5e752b959054 100644 --- a/include/asm-generic/resource.h +++ b/include/asm-generic/resource.h @@ -12,7 +12,7 @@ [RLIMIT_CPU] = { RLIM_INFINITY, RLIM_INFINITY }, \ [RLIMIT_FSIZE] = { RLIM_INFINITY, RLIM_INFINITY }, \ [RLIMIT_DATA] = { RLIM_INFINITY, RLIM_INFINITY }, \ - [RLIMIT_STACK] = { _STK_LIM, _STK_LIM_MAX }, \ + [RLIMIT_STACK] = { _STK_LIM, RLIM_INFINITY }, \ [RLIMIT_CORE] = { 0, RLIM_INFINITY }, \ [RLIMIT_RSS] = { RLIM_INFINITY, RLIM_INFINITY }, \ [RLIMIT_NPROC] = { 0, 0 }, \ diff --git a/include/uapi/asm-generic/resource.h b/include/uapi/asm-generic/resource.h index f863428796d5..c6d10af50123 100644 --- a/include/uapi/asm-generic/resource.h +++ b/include/uapi/asm-generic/resource.h @@ -57,12 +57,5 @@ # define RLIM_INFINITY (~0UL) #endif -/* - * RLIMIT_STACK default maximum - some architectures override it: - */ -#ifndef _STK_LIM_MAX -# define _STK_LIM_MAX RLIM_INFINITY -#endif - #endif /* _UAPI_ASM_GENERIC_RESOURCE_H */