From: Alan Maguire <alan.maguire@oracle.com>
Date: Wed, 30 Mar 2022 16:26:38 +0100
Subject: libbpf: Add auto-attach for uprobes based on section name
Patch-mainline: v5.19-rc1
Git-commit: 39f8dc43b7a05ab0e352655a14a9d613c2308b92
References: jsc#PED-1377
Now that u[ret]probes can use name-based specification, it makes
sense to add support for auto-attach based on SEC() definition.
The format proposed is
SEC("u[ret]probe/binary:[raw_offset|[function_name[+offset]]")
For example, to trace malloc() in libc:
SEC("uprobe/libc.so.6:malloc")
...or to trace function foo2 in /usr/bin/foo:
SEC("uprobe//usr/bin/foo:foo2")
Auto-attach is done for all tasks (pid -1). prog can be an absolute
path or simply a program/library name; in the latter case, we use
PATH/LD_LIBRARY_PATH to resolve the full path, falling back to
standard locations (/usr/bin:/usr/sbin or /usr/lib64:/usr/lib) if
the file is not found via environment-variable specified locations.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1648654000-21758-4-git-send-email-alan.maguire@oracle.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
tools/lib/bpf/libbpf.c | 74 +++++++++++++++++-
tools/testing/selftests/bpf/progs/test_bpf_cookie.c | 4
tools/testing/selftests/bpf/progs/test_task_pt_regs.c | 2
tools/testing/selftests/bpf/progs/trigger_bench.c | 2
4 files changed, 76 insertions(+), 6 deletions(-)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -8630,6 +8630,7 @@ int bpf_program__set_log_buf(struct bpf_
}
static int attach_kprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link);
+static int attach_uprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_raw_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_trace(const struct bpf_program *prog, long cookie, struct bpf_link **link);
@@ -8642,9 +8643,9 @@ static const struct bpf_sec_def section_
SEC_DEF("sk_reuseport/migrate", SK_REUSEPORT, BPF_SK_REUSEPORT_SELECT_OR_MIGRATE, SEC_ATTACHABLE | SEC_SLOPPY_PFX),
SEC_DEF("sk_reuseport", SK_REUSEPORT, BPF_SK_REUSEPORT_SELECT, SEC_ATTACHABLE | SEC_SLOPPY_PFX),
SEC_DEF("kprobe/", KPROBE, 0, SEC_NONE, attach_kprobe),
- SEC_DEF("uprobe/", KPROBE, 0, SEC_NONE),
+ SEC_DEF("uprobe+", KPROBE, 0, SEC_NONE, attach_uprobe),
SEC_DEF("kretprobe/", KPROBE, 0, SEC_NONE, attach_kprobe),
- SEC_DEF("uretprobe/", KPROBE, 0, SEC_NONE),
+ SEC_DEF("uretprobe+", KPROBE, 0, SEC_NONE, attach_uprobe),
SEC_DEF("kprobe.multi/", KPROBE, BPF_TRACE_KPROBE_MULTI, SEC_NONE, attach_kprobe_multi),
SEC_DEF("kretprobe.multi/", KPROBE, BPF_TRACE_KPROBE_MULTI, SEC_NONE, attach_kprobe_multi),
SEC_DEF("tc", SCHED_CLS, 0, SEC_NONE),
@@ -10845,6 +10846,75 @@ err_out:
}
+/* Format of u[ret]probe section definition supporting auto-attach:
+ * u[ret]probe/binary:function[+offset]
+ *
+ * binary can be an absolute/relative path or a filename; the latter is resolved to a
+ * full binary path via bpf_program__attach_uprobe_opts.
+ *
+ * Specifying uprobe+ ensures we carry out strict matching; either "uprobe" must be
+ * specified (and auto-attach is not possible) or the above format is specified for
+ * auto-attach.
+ */
+static int attach_uprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link)
+{
+ DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, opts);
+ char *func, *probe_name, *func_end;
+ char *func_name, binary_path[512];
+ unsigned long long raw_offset;
+ size_t offset = 0;
+ int n;
+
+ *link = NULL;
+
+ opts.retprobe = str_has_pfx(prog->sec_name, "uretprobe");
+ if (opts.retprobe)
+ probe_name = prog->sec_name + sizeof("uretprobe") - 1;
+ else
+ probe_name = prog->sec_name + sizeof("uprobe") - 1;
+ if (probe_name[0] == '/')
+ probe_name++;
+
+ /* handle SEC("u[ret]probe") - format is valid, but auto-attach is impossible. */
+ if (strlen(probe_name) == 0)
+ return 0;
+
+ snprintf(binary_path, sizeof(binary_path), "%s", probe_name);
+ /* ':' should be prior to function+offset */
+ func_name = strrchr(binary_path, ':');
+ if (!func_name) {
+ pr_warn("section '%s' missing ':function[+offset]' specification\n",
+ prog->sec_name);
+ return -EINVAL;
+ }
+ func_name[0] = '\0';
+ func_name++;
+ n = sscanf(func_name, "%m[a-zA-Z0-9_.]+%li", &func, &offset);
+ if (n < 1) {
+ pr_warn("uprobe name '%s' is invalid\n", func_name);
+ return -EINVAL;
+ }
+ if (opts.retprobe && offset != 0) {
+ free(func);
+ pr_warn("uretprobes do not support offset specification\n");
+ return -EINVAL;
+ }
+
+ /* Is func a raw address? */
+ errno = 0;
+ raw_offset = strtoull(func, &func_end, 0);
+ if (!errno && !*func_end) {
+ free(func);
+ func = NULL;
+ offset = (size_t)raw_offset;
+ }
+ opts.func_name = func;
+
+ *link = bpf_program__attach_uprobe_opts(prog, -1, binary_path, offset, &opts);
+ free(func);
+ return libbpf_get_error(*link);
+}
+
struct bpf_link *bpf_program__attach_uprobe(const struct bpf_program *prog,
bool retprobe, pid_t pid,
const char *binary_path,
--- a/tools/testing/selftests/bpf/progs/test_bpf_cookie.c
+++ b/tools/testing/selftests/bpf/progs/test_bpf_cookie.c
@@ -37,14 +37,14 @@ int handle_kretprobe(struct pt_regs *ctx
return 0;
}
-SEC("uprobe/trigger_func")
+SEC("uprobe")
int handle_uprobe(struct pt_regs *ctx)
{
update(ctx, &uprobe_res);
return 0;
}
-SEC("uretprobe/trigger_func")
+SEC("uretprobe")
int handle_uretprobe(struct pt_regs *ctx)
{
update(ctx, &uretprobe_res);
--- a/tools/testing/selftests/bpf/progs/test_task_pt_regs.c
+++ b/tools/testing/selftests/bpf/progs/test_task_pt_regs.c
@@ -14,7 +14,7 @@ char current_regs[PT_REGS_SIZE] = {};
char ctx_regs[PT_REGS_SIZE] = {};
int uprobe_res = 0;
-SEC("uprobe/trigger_func")
+SEC("uprobe")
int handle_uprobe(struct pt_regs *ctx)
{
struct task_struct *current;
--- a/tools/testing/selftests/bpf/progs/trigger_bench.c
+++ b/tools/testing/selftests/bpf/progs/trigger_bench.c
@@ -54,7 +54,7 @@ int bench_trigger_fmodret(void *ctx)
return -22;
}
-SEC("uprobe/self/uprobe_target")
+SEC("uprobe")
int bench_trigger_uprobe(void *ctx)
{
__sync_add_and_fetch(&hits, 1);