diff options
| author | Jiri Olsa <jolsa@redhat.com> | 2021-07-14 11:43:53 +0200 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2021-07-15 17:16:06 -0700 |
| commit | 7e6f3cd89f04a0a577002d5696288b482109d25c (patch) | |
| tree | dd610c2eeeeab77706fdbe55b881323d4b01dc9e /arch/x86/net | |
| parent | 7628317192f590123c615946c432465e817627a8 (diff) | |
bpf, x86: Store caller's ip in trampoline stack
Storing caller's ip in trampoline's stack. Trampoline programs
can reach the IP in (ctx - 8) address, so there's no change in
program's arguments interface.
The IP address is takes from [fp + 8], which is return address
from the initial 'call fentry' call to trampoline.
This IP address will be returned via bpf_get_func_ip helper
helper, which is added in following patches.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210714094400.396467-2-jolsa@kernel.org
Diffstat (limited to 'arch/x86/net')
| -rw-r--r-- | arch/x86/net/bpf_jit_comp.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index e835164189f1..c320b3ce7b58 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1951,6 +1951,9 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i if (flags & BPF_TRAMP_F_CALL_ORIG) stack_size += 8; /* room for return value of orig_call */ + if (flags & BPF_TRAMP_F_IP_ARG) + stack_size += 8; /* room for IP address argument */ + if (flags & BPF_TRAMP_F_SKIP_FRAME) /* skip patched call instruction and point orig_call to actual * body of the kernel function. @@ -1964,6 +1967,22 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i EMIT4(0x48, 0x83, 0xEC, stack_size); /* sub rsp, stack_size */ EMIT1(0x53); /* push rbx */ + if (flags & BPF_TRAMP_F_IP_ARG) { + /* Store IP address of the traced function: + * mov rax, QWORD PTR [rbp + 8] + * sub rax, X86_PATCH_SIZE + * mov QWORD PTR [rbp - stack_size], rax + */ + emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8); + EMIT4(0x48, 0x83, 0xe8, X86_PATCH_SIZE); + emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -stack_size); + + /* Continue with stack_size for regs storage, stack will + * be correctly restored with 'leave' instruction. + */ + stack_size -= 8; + } + save_regs(m, &prog, nr_args, stack_size); if (flags & BPF_TRAMP_F_CALL_ORIG) { |