| #include <linux/mm.h> |
| #include <linux/slab.h> |
| #include <linux/string.h> |
| #include <linux/compiler.h> |
| #include <linux/export.h> |
| #include <linux/err.h> |
| #include <linux/sched.h> |
| #include <linux/sched/mm.h> |
| #include <linux/sched/task_stack.h> |
| #include <linux/security.h> |
| #include <linux/swap.h> |
| #include <linux/swapops.h> |
| #include <linux/mman.h> |
| #include <linux/hugetlb.h> |
| #include <linux/vmalloc.h> |
| #include <linux/userfaultfd_k.h> |
| #include <linux/random.h> |
| |
| #include <asm/sections.h> |
| #include <linux/uaccess.h> |
| |
| #include "internal.h" |
| |
| static inline int is_kernel_rodata(unsigned long addr) |
| { |
| return addr >= (unsigned long)__start_rodata && |
| addr < (unsigned long)__end_rodata; |
| } |
| |
| /** |
| * kfree_const - conditionally free memory |
| * @x: pointer to the memory |
| * |
| * Function calls kfree only if @x is not in .rodata section. |
| */ |
| void kfree_const(const void *x) |
| { |
| if (!is_kernel_rodata((unsigned long)x)) |
| kfree(x); |
| } |
| EXPORT_SYMBOL(kfree_const); |
| |
| /** |
| * kstrdup - allocate space for and copy an existing string |
| * @s: the string to duplicate |
| * @gfp: the GFP mask used in the kmalloc() call when allocating memory |
| */ |
| char *kstrdup(const char *s, gfp_t gfp) |
| { |
| size_t len; |
| char *buf; |
| |
| if (!s) |
| return NULL; |
| |
| len = strlen(s) + 1; |
| buf = kmalloc_track_caller(len, gfp); |
| if (buf) |
| memcpy(buf, s, len); |
| return buf; |
| } |
| EXPORT_SYMBOL(kstrdup); |
| |
| /** |
| * kstrdup_const - conditionally duplicate an existing const string |
| * @s: the string to duplicate |
| * @gfp: the GFP mask used in the kmalloc() call when allocating memory |
| * |
| * Function returns source string if it is in .rodata section otherwise it |
| * fallbacks to kstrdup. |
| * Strings allocated by kstrdup_const should be freed by kfree_const. |
| */ |
| const char *kstrdup_const(const char *s, gfp_t gfp) |
| { |
| if (is_kernel_rodata((unsigned long)s)) |
| return s; |
| |
| return kstrdup(s, gfp); |
| } |
| EXPORT_SYMBOL(kstrdup_const); |
| |
| /** |
| * kstrndup - allocate space for and copy an existing string |
| * @s: the string to duplicate |
| * @max: read at most @max chars from @s |
| * @gfp: the GFP mask used in the kmalloc() call when allocating memory |
| * |
| * Note: Use kmemdup_nul() instead if the size is known exactly. |
| */ |
| char *kstrndup(const char *s, size_t max, gfp_t gfp) |
| { |
| size_t len; |
| char *buf; |
| |
| if (!s) |
| return NULL; |
| |
| len = strnlen(s, max); |
| buf = kmalloc_track_caller(len+1, gfp); |
| if (buf) { |
| memcpy(buf, s, len); |
| buf[len] = '\0'; |
| } |
| return buf; |
| } |
| EXPORT_SYMBOL(kstrndup); |
| |
| /** |
| * kmemdup - duplicate region of memory |
| * |
| * @src: memory region to duplicate |
| * @len: memory region length |
| * @gfp: GFP mask to use |
| */ |
| void *kmemdup(const void *src, size_t len, gfp_t gfp) |
| { |
| void *p; |
| |
| p = kmalloc_track_caller(len, gfp); |
| if (p) |
| memcpy(p, src, len); |
| return p; |
| } |
| EXPORT_SYMBOL(kmemdup); |
| |
| /** |
| * kmemdup_nul - Create a NUL-terminated string from unterminated data |
| * @s: The data to stringify |
| * @len: The size of the data |
| * @gfp: the GFP mask used in the kmalloc() call when allocating memory |
| */ |
| char *kmemdup_nul(const char *s, size_t len, gfp_t gfp) |
| { |
| char *buf; |
| |
| if (!s) |
| return NULL; |
| |
| buf = kmalloc_track_caller(len + 1, gfp); |
| if (buf) { |
| memcpy(buf, s, len); |
| buf[len] = '\0'; |
| } |
| return buf; |
| } |
| EXPORT_SYMBOL(kmemdup_nul); |
| |
| /** |
| * memdup_user - duplicate memory region from user space |
| * |
| * @src: source address in user space |
| * @len: number of bytes to copy |
| * |
| * Returns an ERR_PTR() on failure. |
| */ |
| void *memdup_user(const void __user *src, size_t len) |
| { |
| void *p; |
| |
| /* |
| * Always use GFP_KERNEL, since copy_from_user() can sleep and |
| * cause pagefault, which makes it pointless to use GFP_NOFS |
| * or GFP_ATOMIC. |
| */ |
| p = kmalloc_track_caller(len, GFP_KERNEL); |
| if (!p) |
| return ERR_PTR(-ENOMEM); |
| |
| if (copy_from_user(p, src, len)) { |
| kfree(p); |
| return ERR_PTR(-EFAULT); |
| } |
| |
| return p; |
| } |
| EXPORT_SYMBOL(memdup_user); |
| |
| /* |
| * strndup_user - duplicate an existing string from user space |
| * @s: The string to duplicate |
| * @n: Maximum number of bytes to copy, including the trailing NUL. |
| */ |
| char *strndup_user(const char __user *s, long n) |
| { |
| char *p; |
| long length; |
| |
| length = strnlen_user(s, n); |
| |
| if (!length) |
| return ERR_PTR(-EFAULT); |
| |
| if (length > n) |
| return ERR_PTR(-EINVAL); |
| |
| p = memdup_user(s, length); |
| |
| if (IS_ERR(p)) |
| return p; |
| |
| p[length - 1] = '\0'; |
| |
| return p; |
| } |
| EXPORT_SYMBOL(strndup_user); |
| |
| /** |
| * memdup_user_nul - duplicate memory region from user space and NUL-terminate |
| * |
| * @src: source address in user space |
| * @len: number of bytes to copy |
| * |
| * Returns an ERR_PTR() on failure. |
| */ |
| void *memdup_user_nul(const void __user *src, size_t len) |
| { |
| char *p; |
| |
| /* |
| * Always use GFP_KERNEL, since copy_from_user() can sleep and |
| * cause pagefault, which makes it pointless to use GFP_NOFS |
| * or GFP_ATOMIC. |
| */ |
| p = kmalloc_track_caller(len + 1, GFP_KERNEL); |
| if (!p) |
| return ERR_PTR(-ENOMEM); |
| |
| if (copy_from_user(p, src, len)) { |
| kfree(p); |
| return ERR_PTR(-EFAULT); |
| } |
| p[len] = '\0'; |
| |
| return p; |
| } |
| EXPORT_SYMBOL(memdup_user_nul); |
| |
| void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma, |
| struct vm_area_struct *prev, struct rb_node *rb_parent) |
| { |
| struct vm_area_struct *next; |
| |
| vma->vm_prev = prev; |
| if (prev) { |
| next = prev->vm_next; |
| prev->vm_next = vma; |
| } else { |
| mm->mmap = vma; |
| if (rb_parent) |
| next = rb_entry(rb_parent, |
| struct vm_area_struct, vm_rb); |
| else |
| next = NULL; |
| } |
| vma->vm_next = next; |
| if (next) |
| next->vm_prev = vma; |
| } |
| |
| /* Check if the vma is being used as a stack by this task */ |
| int vma_is_stack_for_current(struct vm_area_struct *vma) |
| { |
| struct task_struct * __maybe_unused t = current; |
| |
| return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t)); |
| } |
| |
| /** |
| * randomize_page - Generate a random, page aligned address |
| * @start: The smallest acceptable address the caller will take. |
| * @range: The size of the area, starting at @start, within which the |
| * random address must fall. |
| * |
| * If @start + @range would overflow, @range is capped. |
| * |
| * NOTE: Historical use of randomize_range, which this replaces, presumed that |
| * @start was already page aligned. We now align it regardless. |
| * |
| * Return: A page aligned address within [start, start + range). On error, |
| * @start is returned. |
| */ |
| unsigned long randomize_page(unsigned long start, unsigned long range) |
| { |
| if (!PAGE_ALIGNED(start)) { |
| range -= PAGE_ALIGN(start) - start; |
| start = PAGE_ALIGN(start); |
| } |
| |
| if (start > ULONG_MAX - range) |
| range = ULONG_MAX - start; |
| |
| range >>= PAGE_SHIFT; |
| |
| if (range == 0) |
| return start; |
| |
| return start + (get_random_long() % range << PAGE_SHIFT); |
| } |
| |
| #if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT) |
| void arch_pick_mmap_layout(struct mm_struct *mm) |
| { |
| mm->mmap_base = TASK_UNMAPPED_BASE; |
| mm->get_unmapped_area = arch_get_unmapped_area; |
| } |
| #endif |
| |
| /* |
| * Like get_user_pages_fast() except its IRQ-safe in that it won't fall |
| * back to the regular GUP. |
| * If the architecture not support this function, simply return with no |
| * page pinned |
| */ |
| int __weak __get_user_pages_fast(unsigned long start, |
| int nr_pages, int write, struct page **pages) |
| { |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(__get_user_pages_fast); |
| |
| /** |
| * get_user_pages_fast() - pin user pages in memory |
| * @start: starting user address |
| * @nr_pages: number of pages from start to pin |
| * @write: whether pages will be written to |
| * @pages: array that receives pointers to the pages pinned. |
| * Should be at least nr_pages long. |
| * |
| * Returns number of pages pinned. This may be fewer than the number |
| * requested. If nr_pages is 0 or negative, returns 0. If no pages |
| * were pinned, returns -errno. |
| * |
| * get_user_pages_fast provides equivalent functionality to get_user_pages, |
| * operating on current and current->mm, with force=0 and vma=NULL. However |
| * unlike get_user_pages, it must be called without mmap_sem held. |
| * |
| * get_user_pages_fast may take mmap_sem and page table locks, so no |
| * assumptions can be made about lack of locking. get_user_pages_fast is to be |
| * implemented in a way that is advantageous (vs get_user_pages()) when the |
| * user memory area is already faulted in and present in ptes. However if the |
| * pages have to be faulted in, it may turn out to be slightly slower so |
| * callers need to carefully consider what to use. On many architectures, |
| * get_user_pages_fast simply falls back to get_user_pages. |
| */ |
| int __weak get_user_pages_fast(unsigned long start, |
| int nr_pages, int write, struct page **pages) |
| { |
| return get_user_pages_unlocked(start, nr_pages, pages, |
| write ? FOLL_WRITE : 0); |
| } |
| EXPORT_SYMBOL_GPL(get_user_pages_fast); |
| |
| unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr, |
| unsigned long len, unsigned long prot, |
| unsigned long flag, unsigned long pgoff) |
| { |
| unsigned long ret; |
| struct mm_struct *mm = current->mm; |
| unsigned long populate; |
| LIST_HEAD(uf); |
| |
| ret = security_mmap_file(file, prot, flag); |
| if (!ret) { |
| if (down_write_killable(&mm->mmap_sem)) |
| return -EINTR; |
| ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff, |
| &populate, &uf); |
| up_write(&mm->mmap_sem); |
| userfaultfd_unmap_complete(mm, &uf); |
| if (populate) |
| mm_populate(ret, populate); |
| } |
| return ret; |
| } |
| |
| unsigned long vm_mmap(struct file *file, unsigned long addr, |
| unsigned long len, unsigned long prot, |
| unsigned long flag, unsigned long offset) |
| { |
| if (unlikely(offset + PAGE_ALIGN(len) < offset)) |
| return -EINVAL; |
| if (unlikely(offset_in_page(offset))) |
| return -EINVAL; |
| |
| return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT); |
| } |
| EXPORT_SYMBOL(vm_mmap); |
| |
| /** |
| * kvmalloc_node - attempt to allocate physically contiguous memory, but upon |
| * failure, fall back to non-contiguous (vmalloc) allocation. |
| * @size: size of the request. |
| * @flags: gfp mask for the allocation - must be compatible (superset) with GFP_KERNEL. |
| * @node: numa node to allocate from |
| * |
| * Uses kmalloc to get the memory but if the allocation fails then falls back |
| * to the vmalloc allocator. Use kvfree for freeing the memory. |
| * |
| * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported. |
| * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is |
| * preferable to the vmalloc fallback, due to visible performance drawbacks. |
| * |
| * Please note that any use of gfp flags outside of GFP_KERNEL is careful to not |
| * fall back to vmalloc. |
| */ |
| void *kvmalloc_node(size_t size, gfp_t flags, int node) |
| { |
| gfp_t kmalloc_flags = flags; |
| void *ret; |
| |
| /* |
| * vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables) |
| * so the given set of flags has to be compatible. |
| */ |
| if ((flags & GFP_KERNEL) != GFP_KERNEL) |
| return kmalloc_node(size, flags, node); |
| |
| /* |
| * We want to attempt a large physically contiguous block first because |
| * it is less likely to fragment multiple larger blocks and therefore |
| * contribute to a long term fragmentation less than vmalloc fallback. |
| * However make sure that larger requests are not too disruptive - no |
| * OOM killer and no allocation failure warnings as we have a fallback. |
| */ |
| if (size > PAGE_SIZE) { |
| kmalloc_flags |= __GFP_NOWARN; |
| |
| if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL)) |
| kmalloc_flags |= __GFP_NORETRY; |
| } |
| |
| ret = kmalloc_node(size, kmalloc_flags, node); |
| |
| /* |
| * It doesn't really make sense to fallback to vmalloc for sub page |
| * requests |
| */ |
| if (ret || size <= PAGE_SIZE) |
| return ret; |
| |
| return __vmalloc_node_flags_caller(size, node, flags, |
| __builtin_return_address(0)); |
| } |
| EXPORT_SYMBOL(kvmalloc_node); |
| |
| void kvfree(const void *addr) |
| { |
| if (is_vmalloc_addr(addr)) |
| vfree(addr); |
| else |
| kfree(addr); |
| } |
| EXPORT_SYMBOL(kvfree); |
| |
| /** |
| * kvfree_sensitive - Free a data object containing sensitive information. |
| * @addr: address of the data object to be freed. |
| * @len: length of the data object. |
| * |
| * Use the special memzero_explicit() function to clear the content of a |
| * kvmalloc'ed object containing sensitive data to make sure that the |
| * compiler won't optimize out the data clearing. |
| */ |
| void kvfree_sensitive(const void *addr, size_t len) |
| { |
| if (likely(!ZERO_OR_NULL_PTR(addr))) { |
| memzero_explicit((void *)addr, len); |
| kvfree(addr); |
| } |
| } |
| EXPORT_SYMBOL(kvfree_sensitive); |
| |
| static inline void *__page_rmapping(struct page *page) |
| { |
| unsigned long mapping; |
| |
| mapping = (unsigned long)page->mapping; |
| mapping &= ~PAGE_MAPPING_FLAGS; |
| |
| return (void *)mapping; |
| } |
| |
| /* Neutral page->mapping pointer to address_space or anon_vma or other */ |
| void *page_rmapping(struct page *page) |
| { |
| page = compound_head(page); |
| return __page_rmapping(page); |
| } |
| |
| /* |
| * Return true if this page is mapped into pagetables. |
| * For compound page it returns true if any subpage of compound page is mapped. |
| */ |
| bool page_mapped(struct page *page) |
| { |
| int i; |
| |
| if (likely(!PageCompound(page))) |
| return atomic_read(&page->_mapcount) >= 0; |
| page = compound_head(page); |
| if (atomic_read(compound_mapcount_ptr(page)) >= 0) |
| return true; |
| if (PageHuge(page)) |
| return false; |
| for (i = 0; i < (1 << compound_order(page)); i++) { |
| if (atomic_read(&page[i]._mapcount) >= 0) |
| return true; |
| } |
| return false; |
| } |
| EXPORT_SYMBOL(page_mapped); |
| |
| struct anon_vma *page_anon_vma(struct page *page) |
| { |
| unsigned long mapping; |
| |
| page = compound_head(page); |
| mapping = (unsigned long)page->mapping; |
| if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) |
| return NULL; |
| return __page_rmapping(page); |
| } |
| |
| struct address_space *page_mapping(struct page *page) |
| { |
| struct address_space *mapping; |
| |
| page = compound_head(page); |
| |
| /* This happens if someone calls flush_dcache_page on slab page */ |
| if (unlikely(PageSlab(page))) |
| return NULL; |
| |
| if (unlikely(PageSwapCache(page))) { |
| swp_entry_t entry; |
| |
| entry.val = page_private(page); |
| return swap_address_space(entry); |
| } |
| |
| mapping = page->mapping; |
| if ((unsigned long)mapping & PAGE_MAPPING_ANON) |
| return NULL; |
| |
| return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS); |
| } |
| EXPORT_SYMBOL(page_mapping); |
| |
| /* Slow path of page_mapcount() for compound pages */ |
| int __page_mapcount(struct page *page) |
| { |
| int ret; |
| |
| ret = atomic_read(&page->_mapcount) + 1; |
| /* |
| * For file THP page->_mapcount contains total number of mapping |
| * of the page: no need to look into compound_mapcount. |
| */ |
| if (!PageAnon(page) && !PageHuge(page)) |
| return ret; |
| page = compound_head(page); |
| ret += atomic_read(compound_mapcount_ptr(page)) + 1; |
| if (PageDoubleMap(page)) |
| ret--; |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(__page_mapcount); |
| |
| int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS; |
| int sysctl_overcommit_ratio __read_mostly = 50; |
| unsigned long sysctl_overcommit_kbytes __read_mostly; |
| int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT; |
| unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */ |
| unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */ |
| |
| int overcommit_ratio_handler(struct ctl_table *table, int write, |
| void __user *buffer, size_t *lenp, |
| loff_t *ppos) |
| { |
| int ret; |
| |
| ret = proc_dointvec(table, write, buffer, lenp, ppos); |
| if (ret == 0 && write) |
| sysctl_overcommit_kbytes = 0; |
| return ret; |
| } |
| |
| int overcommit_kbytes_handler(struct ctl_table *table, int write, |
| void __user *buffer, size_t *lenp, |
| loff_t *ppos) |
| { |
| int ret; |
| |
| ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
| if (ret == 0 && write) |
| sysctl_overcommit_ratio = 0; |
| return ret; |
| } |
| |
| /* |
| * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used |
| */ |
| unsigned long vm_commit_limit(void) |
| { |
| unsigned long allowed; |
| |
| if (sysctl_overcommit_kbytes) |
| allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10); |
| else |
| allowed = ((totalram_pages - hugetlb_total_pages()) |
| * sysctl_overcommit_ratio / 100); |
| allowed += total_swap_pages; |
| |
| return allowed; |
| } |
| |
| /* |
| * Make sure vm_committed_as in one cacheline and not cacheline shared with |
| * other variables. It can be updated by several CPUs frequently. |
| */ |
| struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp; |
| |
| /* |
| * The global memory commitment made in the system can be a metric |
| * that can be used to drive ballooning decisions when Linux is hosted |
| * as a guest. On Hyper-V, the host implements a policy engine for dynamically |
| * balancing memory across competing virtual machines that are hosted. |
| * Several metrics drive this policy engine including the guest reported |
| * memory commitment. |
| */ |
| unsigned long vm_memory_committed(void) |
| { |
| return percpu_counter_read_positive(&vm_committed_as); |
| } |
| EXPORT_SYMBOL_GPL(vm_memory_committed); |
| |
| /* |
| * Check that a process has enough memory to allocate a new virtual |
| * mapping. 0 means there is enough memory for the allocation to |
| * succeed and -ENOMEM implies there is not. |
| * |
| * We currently support three overcommit policies, which are set via the |
| * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting |
| * |
| * Strict overcommit modes added 2002 Feb 26 by Alan Cox. |
| * Additional code 2002 Jul 20 by Robert Love. |
| * |
| * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise. |
| * |
| * Note this is a helper function intended to be used by LSMs which |
| * wish to use this logic. |
| */ |
| int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) |
| { |
| long free, allowed, reserve; |
| |
| VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) < |
| -(s64)vm_committed_as_batch * num_online_cpus(), |
| "memory commitment underflow"); |
| |
| vm_acct_memory(pages); |
| |
| /* |
| * Sometimes we want to use more memory than we have |
| */ |
| if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS) |
| return 0; |
| |
| if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) { |
| free = global_zone_page_state(NR_FREE_PAGES); |
| free += global_node_page_state(NR_FILE_PAGES); |
| |
| /* |
| * shmem pages shouldn't be counted as free in this |
| * case, they can't be purged, only swapped out, and |
| * that won't affect the overall amount of available |
| * memory in the system. |
| */ |
| free -= global_node_page_state(NR_SHMEM); |
| |
| free += get_nr_swap_pages(); |
| |
| /* |
| * Any slabs which are created with the |
| * SLAB_RECLAIM_ACCOUNT flag claim to have contents |
| * which are reclaimable, under pressure. The dentry |
| * cache and most inode caches should fall into this |
| */ |
| free += global_node_page_state(NR_SLAB_RECLAIMABLE); |
| |
| /* |
| * Part of the kernel memory, which can be released |
| * under memory pressure. |
| */ |
| free += global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE); |
| |
| /* |
| * Leave reserved pages. The pages are not for anonymous pages. |
| */ |
| if (free <= totalreserve_pages) |
| goto error; |
| else |
| free -= totalreserve_pages; |
| |
| /* |
| * Reserve some for root |
| */ |
| if (!cap_sys_admin) |
| free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10); |
| |
| if (free > pages) |
| return 0; |
| |
| goto error; |
| } |
| |
| allowed = vm_commit_limit(); |
| /* |
| * Reserve some for root |
| */ |
| if (!cap_sys_admin) |
| allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10); |
| |
| /* |
| * Don't let a single process grow so big a user can't recover |
| */ |
| if (mm) { |
| reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10); |
| allowed -= min_t(long, mm->total_vm / 32, reserve); |
| } |
| |
| if (percpu_counter_read_positive(&vm_committed_as) < allowed) |
| return 0; |
| error: |
| vm_unacct_memory(pages); |
| |
| return -ENOMEM; |
| } |
| |
| /** |
| * get_cmdline() - copy the cmdline value to a buffer. |
| * @task: the task whose cmdline value to copy. |
| * @buffer: the buffer to copy to. |
| * @buflen: the length of the buffer. Larger cmdline values are truncated |
| * to this length. |
| * Returns the size of the cmdline field copied. Note that the copy does |
| * not guarantee an ending NULL byte. |
| */ |
| int get_cmdline(struct task_struct *task, char *buffer, int buflen) |
| { |
| int res = 0; |
| unsigned int len; |
| struct mm_struct *mm = get_task_mm(task); |
| unsigned long arg_start, arg_end, env_start, env_end; |
| if (!mm) |
| goto out; |
| if (!mm->arg_end) |
| goto out_mm; /* Shh! No looking before we're done */ |
| |
| down_read(&mm->mmap_sem); |
| arg_start = mm->arg_start; |
| arg_end = mm->arg_end; |
| env_start = mm->env_start; |
| env_end = mm->env_end; |
| up_read(&mm->mmap_sem); |
| |
| len = arg_end - arg_start; |
| |
| if (len > buflen) |
| len = buflen; |
| |
| res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE); |
| |
| /* |
| * If the nul at the end of args has been overwritten, then |
| * assume application is using setproctitle(3). |
| */ |
| if (res > 0 && buffer[res-1] != '\0' && len < buflen) { |
| len = strnlen(buffer, res); |
| if (len < res) { |
| res = len; |
| } else { |
| len = env_end - env_start; |
| if (len > buflen - res) |
| len = buflen - res; |
| res += access_process_vm(task, env_start, |
| buffer+res, len, |
| FOLL_FORCE); |
| res = strnlen(buffer, res); |
| } |
| } |
| out_mm: |
| mmput(mm); |
| out: |
| return res; |
| } |