From 33a154a96e71a34a1bcca9f40da343dbbf7b38b4 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Thu, 1 Oct 2026 14:52:55 +0000 Subject: selftests/bpf: Test packet range of pointers sharing an id Add tests where two packet pointers share an id and tightening one pointer's umax from its var_off would put it less than their constant distance from the other's umax: with an index & 0x38 capped at 50, the base pointer keeps umax 50, so the pointer 8 bytes further on must keep umax 58, even though its known bits allow at most 56. These refused a valid program or accepted an out-of-bounds access before the fix: - check the advanced copy, load through the base: valid, was refused; - check the base, load the byte at base + 1 through a copy advanced by 8: was accepted; - check base + 4, load 4 bytes at base + 2 through base + 8: reads two bytes past the checked range, was accepted; - the same as the second with data_meta pointers checked against data: was accepted. These pass with and without the fix and cover nearby paths: - subtract an unknown scalar from a checked pointer and load below it (the range is kept across a new id); - reach a load through two paths whose checks cover 8 and 7 bytes after the loaded pointer; the second path must not be pruned by the first; - spill a copy of a pointer, check the pointer, fill the copy and load one byte past the checked range: the load is refused, and the copy has the range of the check. Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20261001145255.855630-2-alexei.starovoitov@gmail.com Signed-off-by: Kumar Kartikeya Dwivedi --- Documentation/driver-api/io-mapping.rst | 91 +++++++++++++++++++++++++++++++++ 1 file changed, 91 insertions(+) create mode 100644 Documentation/driver-api/io-mapping.rst (limited to 'Documentation/driver-api/io-mapping.rst') diff --git a/Documentation/driver-api/io-mapping.rst b/Documentation/driver-api/io-mapping.rst new file mode 100644 index 000000000..7274204b0 --- /dev/null +++ b/Documentation/driver-api/io-mapping.rst @@ -0,0 +1,91 @@ +======================== +The io_mapping functions +======================== + +API +=== + +The io_mapping functions in linux/io-mapping.h provide an abstraction for +efficiently mapping small regions of an I/O device to the CPU. The initial +usage is to support the large graphics aperture on 32-bit processors where +ioremap_wc cannot be used to statically map the entire aperture to the CPU +as it would consume too much of the kernel address space. + +A mapping object is created during driver initialization using:: + + struct io_mapping *io_mapping_create_wc(unsigned long base, + unsigned long size) + +'base' is the bus address of the region to be made +mappable, while 'size' indicates how large a mapping region to +enable. Both are in bytes. + +This _wc variant provides a mapping which may only be used with +io_mapping_map_atomic_wc(), io_mapping_map_local_wc() or +io_mapping_map_wc(). + +With this mapping object, individual pages can be mapped either temporarily +or long term, depending on the requirements. Of course, temporary maps are +more efficient. They come in two flavours:: + + void *io_mapping_map_local_wc(struct io_mapping *mapping, + unsigned long offset) + + void *io_mapping_map_atomic_wc(struct io_mapping *mapping, + unsigned long offset) + +'offset' is the offset within the defined mapping region. Accessing +addresses beyond the region specified in the creation function yields +undefined results. Using an offset which is not page aligned yields an +undefined result. The return value points to a single page in CPU address +space. + +This _wc variant returns a write-combining map to the page and may only be +used with mappings created by io_mapping_create_wc() + +Temporary mappings are only valid in the context of the caller. The mapping +is not guaranteed to be globally visible. + +io_mapping_map_local_wc() has a side effect on X86 32bit as it disables +migration to make the mapping code work. No caller can rely on this side +effect. + +io_mapping_map_atomic_wc() has the side effect of disabling preemption and +pagefaults. Don't use in new code. Use io_mapping_map_local_wc() instead. + +Nested mappings need to be undone in reverse order because the mapping +code uses a stack for keeping track of them:: + + addr1 = io_mapping_map_local_wc(map1, offset1); + addr2 = io_mapping_map_local_wc(map2, offset2); + ... + io_mapping_unmap_local(addr2); + io_mapping_unmap_local(addr1); + +The mappings are released with:: + + void io_mapping_unmap_local(void *vaddr) + void io_mapping_unmap_atomic(void *vaddr) + +'vaddr' must be the value returned by the last io_mapping_map_local_wc() or +io_mapping_map_atomic_wc() call. This unmaps the specified mapping and +undoes the side effects of the mapping functions. + +If you need to sleep while holding a mapping, you can use the regular +variant, although this may be significantly slower:: + + void *io_mapping_map_wc(struct io_mapping *mapping, + unsigned long offset) + +This works like io_mapping_map_atomic/local_wc() except it has no side +effects and the pointer is globally visible. + +The mappings are released with:: + + void io_mapping_unmap(void *vaddr) + +Use for pages mapped with io_mapping_map_wc(). + +At driver close time, the io_mapping object must be freed:: + + void io_mapping_free(struct io_mapping *mapping) -- cgit v1.3.1