[PATCH v2 2/2] mm: adds NOSIGBUS extension to mmap()
From: Ming Lin <mlin@kernel.org>
Date: 2021-06-04 07:43:37
Also in:
linux-fsdevel, linux-mm, lkml
Subsystem:
generic include/asm header files, memory management, memory management - core, memory mapping, memory mapping - madvise (memory advice), parisc architecture, the rest · Maintainers:
Arnd Bergmann, Andrew Morton, David Hildenbrand, Liam R. Howlett, Lorenzo Stoakes, "James E.J. Bottomley", Helge Deller, Linus Torvalds
Adds new flag MAP_NOSIGBUS of mmap() to specify the behavior of "don't SIGBUS on fault". Right now, this flag is only allowed for private mapping. For MAP_NOSIGBUS mapping, map in the zero page on read fault or fill a freshly allocated page with zeroes on write fault. Signed-off-by: Ming Lin <mlin@kernel.org> --- arch/parisc/include/uapi/asm/mman.h | 1 + include/linux/mm.h | 2 ++ include/linux/mman.h | 1 + include/uapi/asm-generic/mman-common.h | 1 + mm/memory.c | 11 +++++++++++ mm/mmap.c | 4 ++++ tools/include/uapi/asm-generic/mman-common.h | 1 + 7 files changed, 21 insertions(+)
diff --git a/arch/parisc/include/uapi/asm/mman.h b/arch/parisc/include/uapi/asm/mman.h
index ab78cba..eecf9af 100644
--- a/arch/parisc/include/uapi/asm/mman.h
+++ b/arch/parisc/include/uapi/asm/mman.h@@ -25,6 +25,7 @@ #define MAP_STACK 0x40000 /* give out an address that is best suited for process/thread stacks */ #define MAP_HUGETLB 0x80000 /* create a huge page mapping */ #define MAP_FIXED_NOREPLACE 0x100000 /* MAP_FIXED which doesn't unmap underlying mapping */ +#define MAP_NOSIGBUS 0x200000 /* do not SIGBUS on fault */ #define MAP_UNINITIALIZED 0 /* uninitialized anonymous mmap */ #define MS_SYNC 1 /* synchronous memory sync */
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 9e86ca1..100d122 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h@@ -373,6 +373,8 @@ int __add_to_page_cache_locked(struct page *page, struct address_space *mapping, # define VM_UFFD_MINOR VM_NONE #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */ +#define VM_NOSIGBUS VM_FLAGS_BIT(38) /* Do not SIGBUS on fault */ + /* Bits set in the VMA until the stack is in its final location */ #define VM_STACK_INCOMPLETE_SETUP (VM_RAND_READ | VM_SEQ_READ)
diff --git a/include/linux/mman.h b/include/linux/mman.h
index b2cbae9..c966b08 100644
--- a/include/linux/mman.h
+++ b/include/linux/mman.h@@ -154,6 +154,7 @@ static inline bool arch_validate_flags(unsigned long flags) _calc_vm_trans(flags, MAP_DENYWRITE, VM_DENYWRITE ) | _calc_vm_trans(flags, MAP_LOCKED, VM_LOCKED ) | _calc_vm_trans(flags, MAP_SYNC, VM_SYNC ) | + _calc_vm_trans(flags, MAP_NOSIGBUS, VM_NOSIGBUS ) | arch_calc_vm_flag_bits(flags); }
diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h
index f94f65d..a2a5333 100644
--- a/include/uapi/asm-generic/mman-common.h
+++ b/include/uapi/asm-generic/mman-common.h@@ -29,6 +29,7 @@ #define MAP_HUGETLB 0x040000 /* create a huge page mapping */ #define MAP_SYNC 0x080000 /* perform synchronous page faults for the mapping */ #define MAP_FIXED_NOREPLACE 0x100000 /* MAP_FIXED which doesn't unmap underlying mapping */ +#define MAP_NOSIGBUS 0x200000 /* do not SIGBUS on fault */ #define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be * uninitialized */
diff --git a/mm/memory.c b/mm/memory.c
index 8d5e583..6b5a897 100644
--- a/mm/memory.c
+++ b/mm/memory.c@@ -3676,6 +3676,17 @@ static vm_fault_t __do_fault(struct vm_fault *vmf) } ret = vma->vm_ops->fault(vmf); + if (unlikely(ret & VM_FAULT_SIGBUS) && (vma->vm_flags & VM_NOSIGBUS)) { + /* + * For MAP_NOSIGBUS mapping, map in the zero page on read fault + * or fill a freshly allocated page with zeroes on write fault + */ + ret = do_anonymous_page(vmf); + if (!ret) + ret = VM_FAULT_NOPAGE; + return ret; + } + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY | VM_FAULT_DONE_COW))) return ret;
diff --git a/mm/mmap.c b/mm/mmap.c
index 8bed547..d5c9fb5 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c@@ -1419,6 +1419,10 @@ unsigned long do_mmap(struct file *file, unsigned long addr, if (!len) return -EINVAL; + /* Restrict MAP_NOSIGBUS to MAP_PRIVATE mapping */ + if ((flags & MAP_NOSIGBUS) && !(flags & MAP_PRIVATE)) + return -EINVAL; + /* * Does the application expect PROT_READ to imply PROT_EXEC? *
diff --git a/tools/include/uapi/asm-generic/mman-common.h b/tools/include/uapi/asm-generic/mman-common.h
index f94f65d..a2a5333 100644
--- a/tools/include/uapi/asm-generic/mman-common.h
+++ b/tools/include/uapi/asm-generic/mman-common.h@@ -29,6 +29,7 @@ #define MAP_HUGETLB 0x040000 /* create a huge page mapping */ #define MAP_SYNC 0x080000 /* perform synchronous page faults for the mapping */ #define MAP_FIXED_NOREPLACE 0x100000 /* MAP_FIXED which doesn't unmap underlying mapping */ +#define MAP_NOSIGBUS 0x200000 /* do not SIGBUS on fault */ #define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be * uninitialized */
--
1.8.3.1