diff mbox series

[PATCHv4,bpf-next,3/8] bpf: Add bpf_get_func_ip helper for tracing programs

Message ID 20210714094400.396467-4-jolsa@kernel.org
State New
Headers show
Series bpf, x86: Add bpf_get_func_ip helper | expand

Commit Message

Jiri Olsa July 14, 2021, 9:43 a.m. UTC 
Adding bpf_get_func_ip helper for BPF_PROG_TYPE_TRACING programs,
specifically for all trampoline attach types.

The trampoline's caller IP address is stored in (ctx - 8) address.
so there's no reason to actually call the helper, but rather fixup
the call instruction and return [ctx - 8] value directly (suggested
by Alexei).

[fixed has_get_func_ip wrong return type]
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 include/uapi/linux/bpf.h       |  7 ++++++
 kernel/bpf/verifier.c          | 43 ++++++++++++++++++++++++++++++++++
 kernel/trace/bpf_trace.c       | 15 ++++++++++++
 tools/include/uapi/linux/bpf.h |  7 ++++++
 4 files changed, 72 insertions(+)

Comments

Alexei Starovoitov July 16, 2021, 1:09 a.m. UTC | #1 
On Wed, Jul 14, 2021 at 2:44 AM Jiri Olsa <jolsa@redhat.com> wrote:
>

> Adding bpf_get_func_ip helper for BPF_PROG_TYPE_TRACING programs,

> specifically for all trampoline attach types.

>

> The trampoline's caller IP address is stored in (ctx - 8) address.

> so there's no reason to actually call the helper, but rather fixup

> the call instruction and return [ctx - 8] value directly (suggested

> by Alexei).

>

> [fixed has_get_func_ip wrong return type]

> Reported-by: kernel test robot <lkp@intel.com>

> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>


I removed these tags, since they don't correspond to any real commit in the git.
Otherwise all patches would have been full of such things when patch series
go through iterations. Also fixed a few typos here and there,
manually rebased and applied.
Thanks!
Jiri Olsa July 18, 2021, 7:30 p.m. UTC | #2 
On Thu, Jul 15, 2021 at 06:09:22PM -0700, Alexei Starovoitov wrote:
> On Wed, Jul 14, 2021 at 2:44 AM Jiri Olsa <jolsa@redhat.com> wrote:

> >

> > Adding bpf_get_func_ip helper for BPF_PROG_TYPE_TRACING programs,

> > specifically for all trampoline attach types.

> >

> > The trampoline's caller IP address is stored in (ctx - 8) address.

> > so there's no reason to actually call the helper, but rather fixup

> > the call instruction and return [ctx - 8] value directly (suggested

> > by Alexei).

> >

> > [fixed has_get_func_ip wrong return type]

> > Reported-by: kernel test robot <lkp@intel.com>

> > Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

> 

> I removed these tags, since they don't correspond to any real commit in the git.

> Otherwise all patches would have been full of such things when patch series

> go through iterations. Also fixed a few typos here and there,

> manually rebased and applied.

> Thanks!

> 


thanks,
jirka
diff mbox series

Patch

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index b46a383e8db7..31dd386b64ec 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4777,6 +4777,12 @@  union bpf_attr {
  * 		Execute close syscall for given FD.
  * 	Return
  * 		A syscall result.
+ *
+ * u64 bpf_get_func_ip(void *ctx)
+ * 	Description
+ * 		Get address of the traced function (for tracing programs).
+ * 	Return
+ * 		Address of the traced function.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -4948,6 +4954,7 @@  union bpf_attr {
 	FN(sys_bpf),			\
 	FN(btf_find_by_name_kind),	\
 	FN(sys_close),			\
+	FN(get_func_ip),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index be38bb930bf1..d27aa23fb572 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5955,6 +5955,27 @@  static int check_bpf_snprintf_call(struct bpf_verifier_env *env,
 	return err;
 }
 
+static int check_get_func_ip(struct bpf_verifier_env *env)
+{
+	enum bpf_attach_type eatype = env->prog->expected_attach_type;
+	enum bpf_prog_type type = resolve_prog_type(env->prog);
+	int func_id = BPF_FUNC_get_func_ip;
+
+	if (type == BPF_PROG_TYPE_TRACING) {
+		if (eatype != BPF_TRACE_FENTRY && eatype != BPF_TRACE_FEXIT &&
+		    eatype != BPF_MODIFY_RETURN) {
+			verbose(env, "func %s#%d supported only for fentry/fexit/fmod_ret programs\n",
+				func_id_name(func_id), func_id);
+			return -ENOTSUPP;
+		}
+		return 0;
+	}
+
+	verbose(env, "func %s#%d not supported for program type %d\n",
+		func_id_name(func_id), func_id, type);
+	return -ENOTSUPP;
+}
+
 static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			     int *insn_idx_p)
 {
@@ -6225,6 +6246,12 @@  static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 	if (func_id == BPF_FUNC_get_stackid || func_id == BPF_FUNC_get_stack)
 		env->prog->call_get_stack = true;
 
+	if (func_id == BPF_FUNC_get_func_ip) {
+		if (check_get_func_ip(env))
+			return -ENOTSUPP;
+		env->prog->call_get_func_ip = true;
+	}
+
 	if (changes_data)
 		clear_all_pkt_pointers(env);
 	return 0;
@@ -12369,6 +12396,7 @@  static int do_misc_fixups(struct bpf_verifier_env *env)
 {
 	struct bpf_prog *prog = env->prog;
 	bool expect_blinding = bpf_jit_blinding_enabled(prog);
+	enum bpf_prog_type prog_type = resolve_prog_type(prog);
 	struct bpf_insn *insn = prog->insnsi;
 	const struct bpf_func_proto *fn;
 	const int insn_cnt = prog->len;
@@ -12702,6 +12730,21 @@  static int do_misc_fixups(struct bpf_verifier_env *env)
 			continue;
 		}
 
+		/* Implement bpf_get_func_ip inline. */
+		if (prog_type == BPF_PROG_TYPE_TRACING &&
+		    insn->imm == BPF_FUNC_get_func_ip) {
+			/* Load IP address from ctx - 8 */
+			insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8);
+
+			new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, 1);
+			if (!new_prog)
+				return -ENOMEM;
+
+			env->prog = prog = new_prog;
+			insn      = new_prog->insnsi + i + delta;
+			continue;
+		}
+
 patch_call_imm:
 		fn = env->ops->get_func_proto(insn->imm, env->prog);
 		/* all functions that have prototype and verifier allowed
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 64bd2d84367f..022cbe42ac57 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -948,6 +948,19 @@  const struct bpf_func_proto bpf_snprintf_btf_proto = {
 	.arg5_type	= ARG_ANYTHING,
 };
 
+BPF_CALL_1(bpf_get_func_ip_tracing, void *, ctx)
+{
+	/* This helper call is inlined by verifier. */
+	return ((u64 *)ctx)[-1];
+}
+
+static const struct bpf_func_proto bpf_get_func_ip_proto_tracing = {
+	.func		= bpf_get_func_ip_tracing,
+	.gpl_only	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+};
+
 const struct bpf_func_proto *
 bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -1058,6 +1071,8 @@  bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_for_each_map_elem_proto;
 	case BPF_FUNC_snprintf:
 		return &bpf_snprintf_proto;
+	case BPF_FUNC_get_func_ip:
+		return &bpf_get_func_ip_proto_tracing;
 	default:
 		return NULL;
 	}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index bf9252c7381e..83e87ffdbb6e 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4780,6 +4780,12 @@  union bpf_attr {
  * 		Execute close syscall for given FD.
  * 	Return
  * 		A syscall result.
+ *
+ * u64 bpf_get_func_ip(void *ctx)
+ * 	Description
+ * 		Get address of the traced function (for tracing programs).
+ * 	Return
+ * 		Address of the traced function.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -4951,6 +4957,7 @@  union bpf_attr {
 	FN(sys_bpf),			\
 	FN(btf_find_by_name_kind),	\
 	FN(sys_close),			\
+	FN(get_func_ip),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper