From 6839e235e4afd003bae61efdf12af225be66d589 Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich Date: Fri, 15 Nov 2019 13:37:22 +0100 Subject: [PATCH] BACKPORT: 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. Change-Id: Iee3d04012d22d54adb739c627fc7b9c31262dbc7 Signed-off-by: Ilya Leoshkevich Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20191115123722.58462-1-iii@linux.ibm.com --- include/linux/filter.h | 6 ++++-- 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 a7000864bb4d..4413655c0f33 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -535,13 +535,15 @@ struct sock_fprog_kern { #define BPF_BINARY_HEADER_MAGIC 0x05de0e82 +/* Some arches need doubleword alignment for their instructions and/or data */ +#define BPF_IMAGE_ALIGNMENT 8 + struct bpf_binary_header { #ifdef CONFIG_CFI_CLANG u32 magic; #endif 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 e29da1e92d79..f59ca4404237 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -31,6 +31,7 @@ #include #include #include +#include #include #include @@ -834,6 +835,9 @@ 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.