[PATCH v6 2/2] bpftool: Align bpf_load_and_run_opts insns and data

From: Ian Rogers
Date: Sat Oct 07 2023 - 01:06:59 EST


A C string lacks alignment so use aligned arrays to avoid potential
alignment problems. Switch to using sizeof (less 1 for the \0
terminator) rather than a hardcode size constant.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
Acked-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
---
tools/bpf/bpftool/gen.c | 43 ++++++++++++++++++++++-------------------
1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index 882bf8e6e70e..ee3ce2b8000d 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -708,17 +708,22 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h

codegen("\
\n\
- skel->%1$s = skel_prep_map_data((void *)\"\\ \n\
- ", ident);
+ { \n\
+ static const char data[] __attribute__((__aligned__(8))) = \"\\\n\
+ ");
mmap_data = bpf_map__initial_value(map, &mmap_size);
print_hex(mmap_data, mmap_size);
codegen("\
\n\
- \", %1$zd, %2$zd); \n\
- if (!skel->%3$s) \n\
- goto cleanup; \n\
- skel->maps.%3$s.initial_value = (__u64) (long) skel->%3$s;\n\
- ", bpf_map_mmap_sz(map), mmap_size, ident);
+ \"; \n\
+ \n\
+ skel->%1$s = skel_prep_map_data((void *)data, %2$zd,\n\
+ sizeof(data) - 1);\n\
+ if (!skel->%1$s) \n\
+ goto cleanup; \n\
+ skel->maps.%1$s.initial_value = (__u64) (long) skel->%1$s;\n\
+ } \n\
+ ", ident, bpf_map_mmap_sz(map));
}
codegen("\
\n\
@@ -733,32 +738,30 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
{ \n\
struct bpf_load_and_run_opts opts = {}; \n\
int err; \n\
- \n\
- opts.ctx = (struct bpf_loader_ctx *)skel; \n\
- opts.data_sz = %2$d; \n\
- opts.data = (void *)\"\\ \n\
+ static const char opts_data[] __attribute__((__aligned__(8))) = \"\\\n\
",
- obj_name, opts.data_sz);
+ obj_name);
print_hex(opts.data, opts.data_sz);
codegen("\
\n\
\"; \n\
+ static const char opts_insn[] __attribute__((__aligned__(8))) = \"\\\n\
");
-
- codegen("\
- \n\
- opts.insns_sz = %d; \n\
- opts.insns = (void *)\"\\ \n\
- ",
- opts.insns_sz);
print_hex(opts.insns, opts.insns_sz);
codegen("\
\n\
\"; \n\
+ \n\
+ opts.ctx = (struct bpf_loader_ctx *)skel; \n\
+ opts.data_sz = sizeof(opts_data) - 1; \n\
+ opts.data = (void *)opts_data; \n\
+ opts.insns_sz = sizeof(opts_insn) - 1; \n\
+ opts.insns = (void *)opts_insn; \n\
+ \n\
err = bpf_load_and_run(&opts); \n\
if (err < 0) \n\
return err; \n\
- ", obj_name);
+ ");
bpf_object__for_each_map(map, obj) {
const char *mmap_flags;

--
2.42.0.609.gbb76f46606-goog