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Date: Fri, 23 Feb 2024 15:57:28 -0800 Message-Id: <20240223235728.13981-4-alexei.starovoitov@gmail.com> X-Mailer: git-send-email 2.39.3 (Apple Git-145) In-Reply-To: <20240223235728.13981-1-alexei.starovoitov@gmail.com> References: <20240223235728.13981-1-alexei.starovoitov@gmail.com> MIME-Version: 1.0 From: Alexei Starovoitov vmap/vmalloc APIs are used to map a set of pages into contiguous kernel virtual space. get_vm_area() with appropriate flag is used to request an area of kernel address range. It'se used for vmalloc, vmap, ioremap, xen use cases. - vmalloc use case dominates the usage. Such vm areas have VM_ALLOC flag. - the areas created by vmap() function should be tagged with VM_MAP. - ioremap areas are tagged with VM_IOREMAP. - xen use cases are VM_XEN. BPF would like to extend the vmap API to implement a lazily-populated sparse, yet contiguous kernel virtual space. Introduce VM_SPARSE vm_area flag and vm_area_map_pages(area, start_addr, count, pages) API to map a set of pages within a given area. It has the same sanity checks as vmap() does. It also checks that get_vm_area() was created with VM_SPARSE flag which identifies such areas in /proc/vmallocinfo and returns zero pages on read through /proc/kcore. The next commits will introduce bpf_arena which is a sparsely populated shared memory region between bpf program and user space process. It will map privately-managed pages into a sparse vm area with the following steps: area = get_vm_area(area_size, VM_SPARSE); // at bpf prog verification time vm_area_map_pages(area, kaddr, 1, page); // on demand // it will return an error if kaddr is out of range vm_area_unmap_pages(area, kaddr, 1); free_vm_area(area); // after bpf prog is unloaded Signed-off-by: Alexei Starovoitov --- include/linux/vmalloc.h | 4 +++ mm/vmalloc.c | 55 +++++++++++++++++++++++++++++++++++++++-- 2 files changed, 57 insertions(+), 2 deletions(-) diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h index 223e51c243bc..416bc7b0b4db 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -29,6 +29,7 @@ struct iov_iter; /* in uio.h */ #define VM_MAP_PUT_PAGES 0x00000200 /* put pages and free array in vfree */ #define VM_ALLOW_HUGE_VMAP 0x00000400 /* Allow for huge pages on archs with HAVE_ARCH_HUGE_VMALLOC */ #define VM_XEN 0x00000800 /* xen use cases */ +#define VM_SPARSE 0x00001000 /* sparse vm_area. not all pages are present. */ #if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) && \ !defined(CONFIG_KASAN_VMALLOC) @@ -233,6 +234,9 @@ static inline bool is_vm_area_hugepages(const void *addr) } #ifdef CONFIG_MMU +int vm_area_map_pages(struct vm_struct *area, unsigned long addr, unsigned int count, + struct page **pages); +int vm_area_unmap_pages(struct vm_struct *area, unsigned long addr, unsigned int count); void vunmap_range(unsigned long addr, unsigned long end); static inline void set_vm_flush_reset_perms(void *addr) { diff --git a/mm/vmalloc.c b/mm/vmalloc.c index d769a65bddad..a05dfbbacb78 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -648,6 +648,54 @@ static int vmap_pages_range(unsigned long addr, unsigned long end, return err; } +/** + * vm_area_map_pages - map pages inside given vm_area + * @area: vm_area + * @addr: start address inside vm_area + * @count: number of pages + * @pages: pages to map (always PAGE_SIZE pages) + */ +int vm_area_map_pages(struct vm_struct *area, unsigned long addr, unsigned int count, + struct page **pages) +{ + unsigned long size = ((unsigned long)count) * PAGE_SIZE; + unsigned long end = addr + size; + + might_sleep(); + if (WARN_ON_ONCE(area->flags & VM_FLUSH_RESET_PERMS)) + return -EINVAL; + if (WARN_ON_ONCE(area->flags & VM_NO_GUARD)) + return -EINVAL; + if (WARN_ON_ONCE(!(area->flags & VM_SPARSE))) + return -EINVAL; + if (count > totalram_pages()) + return -E2BIG; + if (addr < (unsigned long)area->addr || (void *)end > area->addr + area->size) + return -ERANGE; + + return vmap_pages_range(addr, end, PAGE_KERNEL, pages, PAGE_SHIFT); +} + +/** + * vm_area_unmap_pages - unmap pages inside given vm_area + * @area: vm_area + * @addr: start address inside vm_area + * @count: number of pages to unmap + */ +int vm_area_unmap_pages(struct vm_struct *area, unsigned long addr, unsigned int count) +{ + unsigned long size = ((unsigned long)count) * PAGE_SIZE; + unsigned long end = addr + size; + + if (WARN_ON_ONCE(!(area->flags & VM_SPARSE))) + return -EINVAL; + if (addr < (unsigned long)area->addr || (void *)end > area->addr + area->size) + return -ERANGE; + + vunmap_range(addr, end); + return 0; +} + int is_vmalloc_or_module_addr(const void *x) { /* @@ -3822,9 +3870,9 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count) if (flags & VMAP_RAM) copied = vmap_ram_vread_iter(iter, addr, n, flags); - else if (!(vm && (vm->flags & (VM_IOREMAP | VM_XEN)))) + else if (!(vm && (vm->flags & (VM_IOREMAP | VM_XEN | VM_SPARSE)))) copied = aligned_vread_iter(iter, addr, n); - else /* IOREMAP|XEN area is treated as memory hole */ + else /* IOREMAP|XEN|SPARSE area is treated as memory hole */ copied = zero_iter(iter, n); addr += copied; @@ -4418,6 +4466,9 @@ static int s_show(struct seq_file *m, void *p) if (v->flags & VM_XEN) seq_puts(m, " xen"); + if (v->flags & VM_SPARSE) + seq_puts(m, " sparse"); + if (v->flags & VM_ALLOC) seq_puts(m, " vmalloc");