tools: bpftool: resolve calls without using imm field

Currently, we resolve the callee's address for a JITed function
call by using the imm field of the call instruction as an offset
from __bpf_call_base. If bpf_jit_kallsyms is enabled, we further
use this address to get the callee's kernel symbol's name.

For some architectures, such as powerpc64, the imm field is not
large enough to hold this offset. So, instead of assigning this
offset to the imm field, the verifier now assigns the subprog
id. Also, a list of kernel symbol addresses for all the JITed
functions is provided in the program info. We now use the imm
field as an index for this list to lookup a callee's symbol's
address and resolve its name.

Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 24 insertions, 0 deletions

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 9bdfdf2d3fbe..e05ab58d39e2 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -420,7 +420,9 @@ static int do_show(int argc, char **argv)
 
 static int do_dump(int argc, char **argv)
 {
+	unsigned long *func_ksyms = NULL;
 	struct bpf_prog_info info = {};
+	unsigned int nr_func_ksyms;
 	struct dump_data dd = {};
 	__u32 len = sizeof(info);
 	unsigned int buf_size;
@@ -496,10 +498,22 @@ static int do_dump(int argc, char **argv)
 		return -1;
 	}
 
+	nr_func_ksyms = info.nr_jited_ksyms;
+	if (nr_func_ksyms) {
+		func_ksyms = malloc(nr_func_ksyms * sizeof(__u64));
+		if (!func_ksyms) {
+			p_err("mem alloc failed");
+			close(fd);
+			goto err_free;
+		}
+	}
+
 	memset(&info, 0, sizeof(info));
 
 	*member_ptr = ptr_to_u64(buf);
 	*member_len = buf_size;
+	info.jited_ksyms = ptr_to_u64(func_ksyms);
+	info.nr_jited_ksyms = nr_func_ksyms;
 
 	err = bpf_obj_get_info_by_fd(fd, &info, &len);
 	close(fd);
@@ -513,6 +527,11 @@ static int do_dump(int argc, char **argv)
 		goto err_free;
 	}
 
+	if (info.nr_jited_ksyms > nr_func_ksyms) {
+		p_err("too many addresses returned");
+		goto err_free;
+	}
+
 	if ((member_len == &info.jited_prog_len &&
 	     info.jited_prog_insns == 0) ||
 	    (member_len == &info.xlated_prog_len &&
@@ -558,6 +577,9 @@ static int do_dump(int argc, char **argv)
 			dump_xlated_cfg(buf, *member_len);
 	} else {
 		kernel_syms_load(&dd);
+		dd.nr_jited_ksyms = info.nr_jited_ksyms;
+		dd.jited_ksyms = (__u64 *) info.jited_ksyms;
+
 		if (json_output)
 			dump_xlated_json(&dd, buf, *member_len, opcodes);
 		else
@@ -566,10 +588,12 @@ static int do_dump(int argc, char **argv)
 	}
 
 	free(buf);
+	free(func_ksyms);
 	return 0;
 
 err_free:
 	free(buf);
+	free(func_ksyms);
 	return -1;
 }