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bpf: Add BPF_F_ANY_ALIGNMENT.

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Often we want to write tests cases that check things like bad context
offset accesses.  And one way to do this is to use an odd offset on,
for example, a 32-bit load.

This unfortunately triggers the alignment checks first on platforms
that do not set CONFIG_EFFICIENT_UNALIGNED_ACCESS.  So the test
case see the alignment failure rather than what it was testing for.

It is often not completely possible to respect the original intention
of the test, or even test the same exact thing, while solving the
alignment issue.

Another option could have been to check the alignment after the
context and other validations are performed by the verifier, but
that is a non-trivial change to the verifier.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
David Miller 2018-11-30 21:08:14 -08:00 • committed by Alexei Starovoitov
parent 88945f4606
commit e9ee9efc0d
8 changed files with 45 additions and 9 deletions
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8
tools/lib/bpf/bpf.c
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@ -279,9 +279,9 @@ int bpf_load_program(enum bpf_prog_type type, const struct bpf_insn *insns,
}
int bpf_verify_program(enum bpf_prog_type type, const struct bpf_insn *insns,
size_t insns_cnt, int strict_alignment,
const char *license, __u32 kern_version,
char *log_buf, size_t log_buf_sz, int log_level)
size_t insns_cnt, __u32 prog_flags, const char *license,
__u32 kern_version, char *log_buf, size_t log_buf_sz,
int log_level)
{
union bpf_attr attr;
@ -295,7 +295,7 @@ int bpf_verify_program(enum bpf_prog_type type, const struct bpf_insn *insns,
attr.log_level = log_level;
log_buf[0] = 0;
attr.kern_version = kern_version;
attr.prog_flags = strict_alignment ? BPF_F_STRICT_ALIGNMENT : 0;
attr.prog_flags = prog_flags;
return sys_bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
}