struct bpf_insn *disasm_insn(struct bpf_insn *insn, char *buf, size_t buf_sz);
Disassembles instruction 'insn' to a text buffer 'buf'.
Removes insn->code hex prefix added by kernel disassembly routine.
Returns a pointer to the next instruction
(increments insn by either 1 or 2).
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240722233844.1406874-5-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Function verifier.c:convert_ctx_access() applies some rewrites to BPF
instructions that read or write BPF program context. This commit adds
machinery to allow test cases that inspect BPF program after these
rewrites are applied.
An example of a test case:
{
// Shorthand for field offset and size specification
N(CGROUP_SOCKOPT, struct bpf_sockopt, retval),
// Pattern generated for field read
.read = "$dst = *(u64 *)($ctx + bpf_sockopt_kern::current_task);"
"$dst = *(u64 *)($dst + task_struct::bpf_ctx);"
"$dst = *(u32 *)($dst + bpf_cg_run_ctx::retval);",
// Pattern generated for field write
.write = "*(u64 *)($ctx + bpf_sockopt_kern::tmp_reg) = r9;"
"r9 = *(u64 *)($ctx + bpf_sockopt_kern::current_task);"
"r9 = *(u64 *)(r9 + task_struct::bpf_ctx);"
"*(u32 *)(r9 + bpf_cg_run_ctx::retval) = $src;"
"r9 = *(u64 *)($ctx + bpf_sockopt_kern::tmp_reg);" ,
},
For each test case, up to three programs are created:
- One that uses BPF_LDX_MEM to read the context field.
- One that uses BPF_STX_MEM to write to the context field.
- One that uses BPF_ST_MEM to write to the context field.
The disassembly of each program is compared with the pattern specified
in the test case.
Kernel code for disassembly is reused (as is in the bpftool).
To keep Makefile changes to the minimum, symbolic links to
`kernel/bpf/disasm.c` and `kernel/bpf/disasm.h ` are added.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20230304011247.566040-4-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
