On Tue, Nov 1, 2022 at 4:54 AM Uladzislau Rezki <urezki@xxxxxxxxx> wrote: > > On Mon, Oct 31, 2022 at 02:58:30PM -0700, Song Liu wrote: > > vmalloc_exec is used to allocate memory to host dynamic kernel text > > (modules, BPF programs, etc.) with huge pages. This is similar to the > > proposal by Peter in [1]. > > > > A new tree of vmap_area, free_text_area_* tree, is introduced in addition > > to free_vmap_area_* and vmap_area_*. vmalloc_exec allocates pages from > > free_text_area_*. When there isn't enough space left in free_text_area_*, > > new PMD_SIZE page(s) is allocated from free_vmap_area_* and added to > > free_text_area_*. To be more accurate, the vmap_area is first added to > > vmap_area_* tree and then moved to free_text_area_*. This extra move > > simplifies the logic of vmalloc_exec. > > > > vmap_area in free_text_area_* tree are backed with memory, but we need > > subtree_max_size for tree operations. Therefore, vm_struct for these > > vmap_area are stored in a separate list, all_text_vm. > > > > The new tree allows separate handling of < PAGE_SIZE allocations, as > > current vmalloc code mostly assumes PAGE_SIZE aligned allocations. This > > version of vmalloc_exec can handle bpf programs, which uses 64 byte > > aligned allocations), and modules, which uses PAGE_SIZE aligned > > allocations. > > > > Memory allocated by vmalloc_exec() is set to RO+X before returning to the > > caller. Therefore, the caller cannot write directly write to the memory. > > Instead, the caller is required to use vcopy_exec() to update the memory. > > For the safety and security of X memory, vcopy_exec() checks the data > > being updated always in the memory allocated by one vmalloc_exec() call. > > vcopy_exec() uses text_poke like mechanism and requires arch support. > > Specifically, the arch need to implement arch_vcopy_exec(). > > > > In vfree_exec(), the memory is first erased with arch_invalidate_exec(). > > Then, the memory is added to free_text_area_*. If this free creates big > > enough continuous free space (> PMD_SIZE), vfree_exec() will try to free > > the backing vm_struct. > > > > [1] https://lore.kernel.org/bpf/Ys6cWUMHO8XwyYgr@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > > > > Signed-off-by: Song Liu <song@xxxxxxxxxx> > > --- > > include/linux/vmalloc.h | 5 + > > mm/nommu.c | 12 ++ > > mm/vmalloc.c | 318 ++++++++++++++++++++++++++++++++++++++++ > > 3 files changed, 335 insertions(+) > > > > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h > > index 096d48aa3437..9b2042313c12 100644 > > --- a/include/linux/vmalloc.h > > +++ b/include/linux/vmalloc.h > > @@ -154,6 +154,11 @@ extern void *__vmalloc_node_range(unsigned long size, unsigned long align, > > void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask, > > int node, const void *caller) __alloc_size(1); > > void *vmalloc_huge(unsigned long size, gfp_t gfp_mask) __alloc_size(1); > > +void *vmalloc_exec(unsigned long size, unsigned long align) __alloc_size(1); > > +void *vcopy_exec(void *dst, void *src, size_t len); > > +void vfree_exec(void *addr); > > +void *arch_vcopy_exec(void *dst, void *src, size_t len); > > +int arch_invalidate_exec(void *ptr, size_t len); > > > > extern void *__vmalloc_array(size_t n, size_t size, gfp_t flags) __alloc_size(1, 2); > > extern void *vmalloc_array(size_t n, size_t size) __alloc_size(1, 2); > > diff --git a/mm/nommu.c b/mm/nommu.c > > index 214c70e1d059..8a1317247ef0 100644 > > --- a/mm/nommu.c > > +++ b/mm/nommu.c > > @@ -371,6 +371,18 @@ int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages, > > } > > EXPORT_SYMBOL(vm_map_pages_zero); > > > > +void *vmalloc_exec(unsigned long size, unsigned long align) > > +{ > > + return NULL; > > +} > > + > > +void *vcopy_exec(void *dst, void *src, size_t len) > > +{ > > + return ERR_PTR(-EOPNOTSUPP); > > +} > > + > > +void vfree_exec(const void *addr) { } > > + > > /* > > * sys_brk() for the most part doesn't need the global kernel > > * lock, except when an application is doing something nasty > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index ccaa461998f3..6f4c73e67191 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -72,6 +72,9 @@ early_param("nohugevmalloc", set_nohugevmalloc); > > static const bool vmap_allow_huge = false; > > #endif /* CONFIG_HAVE_ARCH_HUGE_VMALLOC */ > > > > +#define PMD_ALIGN(addr) ALIGN(addr, PMD_SIZE) > > +#define PMD_ALIGN_DOWN(addr) ALIGN_DOWN(addr, PMD_SIZE) > > + > > bool is_vmalloc_addr(const void *x) > > { > > unsigned long addr = (unsigned long)kasan_reset_tag(x); > > @@ -769,6 +772,38 @@ static LIST_HEAD(free_vmap_area_list); > > */ > > static struct rb_root free_vmap_area_root = RB_ROOT; > > > > +/* > > + * free_text_area for vmalloc_exec() > > + */ > > +static DEFINE_SPINLOCK(free_text_area_lock); > > +/* > > + * This linked list is used in pair with free_text_area_root. > > + * It gives O(1) access to prev/next to perform fast coalescing. > > + */ > > +static LIST_HEAD(free_text_area_list); > > + > > +/* > > + * This augment red-black tree represents the free text space. > > + * All vmap_area objects in this tree are sorted by va->va_start > > + * address. It is used for allocation and merging when a vmap > > + * object is released. > > + * > > + * Each vmap_area node contains a maximum available free block > > + * of its sub-tree, right or left. Therefore it is possible to > > + * find a lowest match of free area. > > + * > > + * vmap_area in this tree are backed by RO+X memory, but they do > > + * not have valid vm pointer (because we need subtree_max_size). > > + * The vm for these vmap_area are stored in all_text_vm. > > + */ > > +static struct rb_root free_text_area_root = RB_ROOT; > > + > > +/* > > + * List of vm_struct for free_text_area_root. This list is rarely > > + * accessed, so the O(N) complexity is not likely a real issue. > > + */ > > +struct vm_struct *all_text_vm; > > + > > /* > > * Preload a CPU with one object for "no edge" split case. The > > * aim is to get rid of allocations from the atomic context, thus > > @@ -3313,6 +3348,289 @@ void *vmalloc(unsigned long size) > > } > > EXPORT_SYMBOL(vmalloc); > > > > +#if defined(CONFIG_MODULES) && defined(MODULES_VADDR) > > +#define VMALLOC_EXEC_START MODULES_VADDR > > +#define VMALLOC_EXEC_END MODULES_END > > +#else > > +#define VMALLOC_EXEC_START VMALLOC_START > > +#define VMALLOC_EXEC_END VMALLOC_END > > +#endif > > + > > +static void move_vmap_to_free_text_tree(void *addr) > > +{ > > + struct vmap_area *va; > > + > > + /* remove from vmap_area_root */ > > + spin_lock(&vmap_area_lock); > > + va = __find_vmap_area((unsigned long)addr, &vmap_area_root); > > + if (WARN_ON_ONCE(!va)) { > > + spin_unlock(&vmap_area_lock); > > + return; > > + } > > + unlink_va(va, &vmap_area_root); > > + spin_unlock(&vmap_area_lock); > > + > > + /* make the memory RO+X */ > > + memset(addr, 0, va->va_end - va->va_start); > > + set_memory_ro(va->va_start, (va->va_end - va->va_start) >> PAGE_SHIFT); > > + set_memory_x(va->va_start, (va->va_end - va->va_start) >> PAGE_SHIFT); > > + > > + /* add to all_text_vm */ > > + va->vm->next = all_text_vm; > > + all_text_vm = va->vm; > > + > > + /* add to free_text_area_root */ > > + spin_lock(&free_text_area_lock); > > + merge_or_add_vmap_area_augment(va, &free_text_area_root, &free_text_area_list); > > + spin_unlock(&free_text_area_lock); > > +} > > + > > +/** > > + * vmalloc_exec - allocate virtually contiguous RO+X memory > > + * @size: allocation size > > + * > > + * This is used to allocate dynamic kernel text, such as module text, BPF > > + * programs, etc. User need to use text_poke to update the memory allocated > > + * by vmalloc_exec. > > + * > > + * Return: pointer to the allocated memory or %NULL on error > > + */ > > +void *vmalloc_exec(unsigned long size, unsigned long align) > > +{ > > + struct vmap_area *va, *tmp; > > + unsigned long addr; > > + enum fit_type type; > > + int ret; > > + > > + va = kmem_cache_alloc_node(vmap_area_cachep, GFP_KERNEL, NUMA_NO_NODE); > > + if (unlikely(!va)) > > + return NULL; > > + > > +again: > > + preload_this_cpu_lock(&free_text_area_lock, GFP_KERNEL, NUMA_NO_NODE); > > + tmp = find_vmap_lowest_match(&free_text_area_root, size, align, 1, false); > > + > > + if (!tmp) { > > + unsigned long alloc_size; > > + void *ptr; > > + > > + spin_unlock(&free_text_area_lock); > > + > > + /* > > + * Not enough continuous space in free_text_area_root, try > > + * allocate more memory. The memory is first added to > > + * vmap_area_root, and then moved to free_text_area_root. > > + */ > > + alloc_size = roundup(size, PMD_SIZE * num_online_nodes()); > > + ptr = __vmalloc_node_range(alloc_size, PMD_SIZE, VMALLOC_EXEC_START, > > + VMALLOC_EXEC_END, GFP_KERNEL, PAGE_KERNEL, > > + VM_ALLOW_HUGE_VMAP | VM_NO_GUARD, > > + NUMA_NO_NODE, __builtin_return_address(0)); > > + if (unlikely(!ptr)) > > + goto err_out; > > + > > + move_vmap_to_free_text_tree(ptr); > > + goto again; > > > It is yet another allocator built on top of vmalloc. So there are 4 then. > Could you please avoid of doing it? I do not find it as something that is > reasonable. Could you please elaborate why this is not reasonable? Or, what would be a more reasonable alternative? Thanks, Song
