diff options
| author | Ilya Leoshkevich <iii@linux.ibm.com> | 2019-11-15 13:37:22 +0100 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2019-11-15 22:25:00 +0100 |
| commit | b7b3fc8dd95bc02bd30680da258e09dda55270db (patch) | |
| tree | f495c80bad776b25b2734b3257f6906de6b9365d | |
| parent | bpf, testing: Add missing object file to TEST_FILES (diff) | |
| download | linux-b7b3fc8dd95bc02bd30680da258e09dda55270db.tar.xz linux-b7b3fc8dd95bc02bd30680da258e09dda55270db.zip | |
bpf: Support doubleword alignment in bpf_jit_binary_alloc
Currently passing alignment greater than 4 to bpf_jit_binary_alloc does
not work: in such cases it silently aligns only to 4 bytes.
On s390, in order to load a constant from memory in a large (>512k) BPF
program, one must use lgrl instruction, whose memory operand must be
aligned on an 8-byte boundary.
This patch makes it possible to request 8-byte alignment from
bpf_jit_binary_alloc, and also makes it issue a warning when an
unsupported alignment is requested.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191115123722.58462-1-iii@linux.ibm.com
| -rw-r--r-- | include/linux/filter.h | 6 | ||||
| -rw-r--r-- | kernel/bpf/core.c | 4 |
2 files changed, 8 insertions, 2 deletions
diff --git a/include/linux/filter.h b/include/linux/filter.h index 7a6f8f6f1da4..ad80e9c6111c 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -515,10 +515,12 @@ struct sock_fprog_kern { struct sock_filter *filter; }; +/* Some arches need doubleword alignment for their instructions and/or data */ +#define BPF_IMAGE_ALIGNMENT 8 + struct bpf_binary_header { u32 pages; - /* Some arches need word alignment for their instructions */ - u8 image[] __aligned(4); + u8 image[] __aligned(BPF_IMAGE_ALIGNMENT); }; struct bpf_prog { diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index c1fde0303280..99693f3c4e99 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -31,6 +31,7 @@ #include <linux/rcupdate.h> #include <linux/perf_event.h> #include <linux/extable.h> +#include <linux/log2.h> #include <asm/unaligned.h> /* Registers */ @@ -815,6 +816,9 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr, struct bpf_binary_header *hdr; u32 size, hole, start, pages; + WARN_ON_ONCE(!is_power_of_2(alignment) || + alignment > BPF_IMAGE_ALIGNMENT); + /* Most of BPF filters are really small, but if some of them * fill a page, allow at least 128 extra bytes to insert a * random section of illegal instructions. |