From: Sandipan Das <sandipan@linux.vnet.ibm.com>
Date: Thu, 24 May 2018 12:26:50 +0530
Subject: tools: bpftool: resolve calls without using imm field
Patch-mainline: v4.18-rc1
Git-commit: f84192ee00b7d8b3c38545d3a61d4191f80cc81a
References: bsc#1109837

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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 tools/bpf/bpftool/prog.c          |   24 ++++++++++++++++++++++++
 tools/bpf/bpftool/xlated_dumper.c |   10 +++++++++-
 tools/bpf/bpftool/xlated_dumper.h |    2 ++
 3 files changed, 35 insertions(+), 1 deletion(-)

--- 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;
 }
 
--- a/tools/bpf/bpftool/xlated_dumper.c
+++ b/tools/bpf/bpftool/xlated_dumper.c
@@ -174,7 +174,11 @@ static const char *print_call_pcrel(stru
 				    unsigned long address,
 				    const struct bpf_insn *insn)
 {
-	if (sym)
+	if (!dd->nr_jited_ksyms)
+		/* Do not show address for interpreted programs */
+		snprintf(dd->scratch_buff, sizeof(dd->scratch_buff),
+			"%+d", insn->off);
+	else if (sym)
 		snprintf(dd->scratch_buff, sizeof(dd->scratch_buff),
 			 "%+d#%s", insn->off, sym->name);
 	else
@@ -203,6 +207,10 @@ static const char *print_call(void *priv
 	unsigned long address = dd->address_call_base + insn->imm;
 	struct kernel_sym *sym;
 
+	if (insn->src_reg == BPF_PSEUDO_CALL &&
+	    (__u32) insn->imm < dd->nr_jited_ksyms)
+		address = dd->jited_ksyms[insn->imm];
+
 	sym = kernel_syms_search(dd, address);
 	if (insn->src_reg == BPF_PSEUDO_CALL)
 		return print_call_pcrel(dd, sym, address, insn);
--- a/tools/bpf/bpftool/xlated_dumper.h
+++ b/tools/bpf/bpftool/xlated_dumper.h
@@ -49,6 +49,8 @@ struct dump_data {
 	unsigned long address_call_base;
 	struct kernel_sym *sym_mapping;
 	__u32 sym_count;
+	__u64 *jited_ksyms;
+	__u32 nr_jited_ksyms;
 	char scratch_buff[SYM_MAX_NAME + 8];
 };