| Message ID | 1e96c3f-d45c-b128-907b-ca2fba5f6a2d@redhat.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | parisc: fix unaligned accesses in BPF | expand |
On 7/27/24 12:11, Mikulas Patocka wrote: > There were spurious unaligned access warnings when calling BPF code. > Sometimes, the warnings were triggered with any incoming packet, making > the machine hard to use. > > The reason for the warnings is this: on parisc64, pointers to functions > are not really pointers to functions, they are pointers to 16-byte > descriptor. The first 8 bytes of the descriptor is a pointer to the > function and the next 8 bytes of the descriptor is the content of the > "dp" register. This descriptor is generated in the function > bpf_jit_build_prologue. > > The problem is that the function bpf_int_jit_compile advertises 4-byte > alignment when calling bpf_jit_binary_alloc, bpf_jit_binary_alloc > randomizes the returned array and if the array happens to be not aligned > on 8-byte boundary, the descriptor generated in bpf_jit_build_prologue is > also not aligned and this triggers the unaligned access warning. > > Fix this by advertising 8-byte alignment on parisc64 when calling > bpf_jit_binary_alloc. > > Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> > Cc: stable@vger.kernel.org Nice catch! Applied. Thanks! Helge > > --- > arch/parisc/net/bpf_jit_core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > Index: linux-6.10/arch/parisc/net/bpf_jit_core.c > =================================================================== > --- linux-6.10.orig/arch/parisc/net/bpf_jit_core.c 2024-07-23 20:35:34.000000000 +0200 > +++ linux-6.10/arch/parisc/net/bpf_jit_core.c 2024-07-27 11:40:17.000000000 +0200 > @@ -114,7 +114,7 @@ struct bpf_prog *bpf_int_jit_compile(str > jit_data->header = > bpf_jit_binary_alloc(prog_size + extable_size, > &jit_data->image, > - sizeof(u32), > + sizeof(long), > bpf_fill_ill_insns); > if (!jit_data->header) { > prog = orig_prog; >
Index: linux-6.10/arch/parisc/net/bpf_jit_core.c =================================================================== --- linux-6.10.orig/arch/parisc/net/bpf_jit_core.c 2024-07-23 20:35:34.000000000 +0200 +++ linux-6.10/arch/parisc/net/bpf_jit_core.c 2024-07-27 11:40:17.000000000 +0200 @@ -114,7 +114,7 @@ struct bpf_prog *bpf_int_jit_compile(str jit_data->header = bpf_jit_binary_alloc(prog_size + extable_size, &jit_data->image, - sizeof(u32), + sizeof(long), bpf_fill_ill_insns); if (!jit_data->header) { prog = orig_prog;
There were spurious unaligned access warnings when calling BPF code. Sometimes, the warnings were triggered with any incoming packet, making the machine hard to use. The reason for the warnings is this: on parisc64, pointers to functions are not really pointers to functions, they are pointers to 16-byte descriptor. The first 8 bytes of the descriptor is a pointer to the function and the next 8 bytes of the descriptor is the content of the "dp" register. This descriptor is generated in the function bpf_jit_build_prologue. The problem is that the function bpf_int_jit_compile advertises 4-byte alignment when calling bpf_jit_binary_alloc, bpf_jit_binary_alloc randomizes the returned array and if the array happens to be not aligned on 8-byte boundary, the descriptor generated in bpf_jit_build_prologue is also not aligned and this triggers the unaligned access warning. Fix this by advertising 8-byte alignment on parisc64 when calling bpf_jit_binary_alloc. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org --- arch/parisc/net/bpf_jit_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)