[PATCH 10/19] bpf: Allow to store caller's ip as argument
From: Jiri Olsa <jolsa@kernel.org>
Date: 2021-06-05 11:11:19
Also in:
bpf
Subsystem:
bpf jit for x86 64-bit, bpf [core], bpf [general] (safe dynamic programs and tools), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
When we will have multiple functions attached to trampoline we need to propagate the function's address to the bpf program. Adding new BPF_TRAMP_F_IP_ARG flag to arch_prepare_bpf_trampoline function that will store origin caller's address before function's arguments. Signed-off-by: Jiri Olsa <jolsa@kernel.org> --- arch/x86/net/bpf_jit_comp.c | 18 ++++++++++++++---- include/linux/bpf.h | 5 +++++ 2 files changed, 19 insertions(+), 4 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index b77e6bd78354..d2425c18272a 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c@@ -1951,7 +1951,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i void *orig_call) { int ret, i, cnt = 0, nr_args = m->nr_args; - int stack_size = nr_args * 8; + int stack_size = nr_args * 8, ip_arg = 0; struct bpf_tramp_progs *fentry = &tprogs[BPF_TRAMP_FENTRY]; struct bpf_tramp_progs *fexit = &tprogs[BPF_TRAMP_FEXIT]; struct bpf_tramp_progs *fmod_ret = &tprogs[BPF_TRAMP_MODIFY_RETURN];
@@ -1975,6 +1975,9 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i */ orig_call += X86_PATCH_SIZE; + if (flags & BPF_TRAMP_F_IP_ARG) + stack_size += 8; + prog = image; EMIT1(0x55); /* push rbp */
@@ -1982,7 +1985,14 @@ 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 */ - save_regs(m, &prog, nr_args, stack_size); + if (flags & BPF_TRAMP_F_IP_ARG) { + emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8); + EMIT4(0x48, 0x83, 0xe8, X86_PATCH_SIZE); /* sub $X86_PATCH_SIZE,%rax*/ + emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -stack_size); + ip_arg = 8; + } + + save_regs(m, &prog, nr_args, stack_size - ip_arg); if (flags & BPF_TRAMP_F_CALL_ORIG) { /* arg1: mov rdi, im */
@@ -2011,7 +2021,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i } if (flags & BPF_TRAMP_F_CALL_ORIG) { - restore_regs(m, &prog, nr_args, stack_size); + restore_regs(m, &prog, nr_args, stack_size - ip_arg); if (flags & BPF_TRAMP_F_ORIG_STACK) { emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8);
@@ -2052,7 +2062,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i } if (flags & BPF_TRAMP_F_RESTORE_REGS) - restore_regs(m, &prog, nr_args, stack_size); + restore_regs(m, &prog, nr_args, stack_size - ip_arg); /* This needs to be done regardless. If there were fmod_ret programs, * the return value is only updated on the stack and still needs to be
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 16fc600503fb..6cbf3c81c650 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h@@ -559,6 +559,11 @@ struct btf_func_model { */ #define BPF_TRAMP_F_ORIG_STACK BIT(3) +/* First argument is IP address of the caller. Makes sense for fentry/fexit + * programs only. + */ +#define BPF_TRAMP_F_IP_ARG BIT(4) + /* Each call __bpf_prog_enter + call bpf_func + call __bpf_prog_exit is ~50 * bytes on x86. Pick a number to fit into BPF_IMAGE_SIZE / 2 */
--
2.31.1