* [PATCH v3 2/2] bpftool: Align bpf_load_and_run_opts insns and data
2023-10-04 20:43 [PATCH v3 1/2] bpftool: Align output skeleton ELF code Ian Rogers
@ 2023-10-04 20:43 ` Ian Rogers
2023-10-04 21:56 ` [PATCH v3 1/2] bpftool: Align output skeleton ELF code Andrii Nakryiko
1 sibling, 0 replies; 4+ messages in thread
From: Ian Rogers @ 2023-10-04 20:43 UTC (permalink / raw)
To: Quentin Monnet, Alexei Starovoitov, Daniel Borkmann,
Andrii Nakryiko, Martin KaFai Lau, Song Liu, Yonghong Song,
John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa,
bpf, linux-kernel
Cc: Ian Rogers
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@google.com>
---
tools/bpf/bpftool/gen.c | 47 ++++++++++++++++++++++-------------------
1 file changed, 25 insertions(+), 22 deletions(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index b8ebcee9bc56..8c36c96cd692 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -408,8 +408,8 @@ static void codegen(const char *template, ...)
/* skip baseline indentation tabs */
for (n = skip_tabs; n > 0; n--, src++) {
if (*src != '\t') {
- p_err("not enough tabs at pos %td in template '%s'",
- src - template - 1, template);
+ p_err("not enough tabs at pos %td in template '%s'\n'%s'",
+ src - template - 1, template, src);
free(s);
exit(-1);
}
@@ -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
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH v3 1/2] bpftool: Align output skeleton ELF code
2023-10-04 20:43 [PATCH v3 1/2] bpftool: Align output skeleton ELF code Ian Rogers
2023-10-04 20:43 ` [PATCH v3 2/2] bpftool: Align bpf_load_and_run_opts insns and data Ian Rogers
@ 2023-10-04 21:56 ` Andrii Nakryiko
2023-10-04 22:21 ` Ian Rogers
1 sibling, 1 reply; 4+ messages in thread
From: Andrii Nakryiko @ 2023-10-04 21:56 UTC (permalink / raw)
To: Ian Rogers
Cc: Quentin Monnet, Alexei Starovoitov, Daniel Borkmann,
Andrii Nakryiko, Martin KaFai Lau, Song Liu, Yonghong Song,
John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa,
bpf, linux-kernel, Alan Maguire
On Wed, Oct 4, 2023 at 1:43 PM Ian Rogers <irogers@google.com> wrote:
>
> libbpf accesses the ELF data requiring at least 8 byte alignment,
> however, the data is generated into a C string that doesn't guarantee
> alignment. Fix this by assigning to an aligned char array. Use sizeof
> on the array, less one for the \0 terminator, rather than generating a
> constant.
>
> Fixes: a6cc6b34b93e ("bpftool: Provide a helper method for accessing skeleton's embedded ELF data")
> Signed-off-by: Ian Rogers <irogers@google.com>
> Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
> ---
> tools/bpf/bpftool/gen.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
CI is not happy still, see [0]
[0] https://github.com/kernel-patches/bpf/actions/runs/6411371996/job/17406696212
> diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
> index 2883660d6b67..b8ebcee9bc56 100644
> --- a/tools/bpf/bpftool/gen.c
> +++ b/tools/bpf/bpftool/gen.c
> @@ -1209,7 +1209,7 @@ static int do_skeleton(int argc, char **argv)
> codegen("\
> \n\
> \n\
> - s->data = (void *)%2$s__elf_bytes(&s->data_sz); \n\
> + s->data = (void *)%1$s__elf_bytes(&s->data_sz); \n\
> \n\
> obj->skeleton = s; \n\
> return 0; \n\
> @@ -1218,12 +1218,12 @@ static int do_skeleton(int argc, char **argv)
> return err; \n\
> } \n\
> \n\
> - static inline const void *%2$s__elf_bytes(size_t *sz) \n\
> + static inline const void *%1$s__elf_bytes(size_t *sz) \n\
> { \n\
> - *sz = %1$d; \n\
> - return (const void *)\"\\ \n\
> - "
> - , file_sz, obj_name);
> + static const char data[] __attribute__((__aligned__(8))) = \"\\\n\
> + ",
> + obj_name
> + );
>
> /* embed contents of BPF object file */
> print_hex(obj_data, file_sz);
> @@ -1231,6 +1231,9 @@ static int do_skeleton(int argc, char **argv)
> codegen("\
> \n\
> \"; \n\
> + \n\
> + *sz = sizeof(data) - 1; \n\
> + return (const void *)data; \n\
> } \n\
> \n\
> #ifdef __cplusplus \n\
> --
> 2.42.0.609.gbb76f46606-goog
>
^ permalink raw reply [flat|nested] 4+ messages in thread