* [PATCH v5 1/2] bpftool: Align output skeleton ELF code
@ 2023-10-05 22:03 Ian Rogers
2023-10-05 22:03 ` [PATCH v5 2/2] bpftool: Align bpf_load_and_run_opts insns and data Ian Rogers
2023-10-06 20:20 ` [PATCH v5 1/2] bpftool: Align output skeleton ELF code Andrii Nakryiko
0 siblings, 2 replies; 4+ messages in thread
From: Ian Rogers @ 2023-10-05 22:03 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, Alan Maguire
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>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
---
tools/bpf/bpftool/gen.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
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$d; \n\
- return (const void *)\"\\ \n\
- "
- , file_sz, obj_name);
+ static const char data[] __attribute__((__aligned__(8))) = \"\\\n\
+ ",
+ obj_name
+ );
/* embed contents of BPF object file */
print_hex(obj_data, file_sz);
@@ -1231,6 +1231,9 @@ static int do_skeleton(int argc, char **argv)
codegen("\
\n\
\"; \n\
+ \n\
+ *sz = sizeof(data) - 1; \n\
+ return (const void *)data; \n\
} \n\
\n\
#ifdef __cplusplus \n\
--
2.42.0.609.gbb76f46606-goog
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v5 2/2] bpftool: Align bpf_load_and_run_opts insns and data
2023-10-05 22:03 [PATCH v5 1/2] bpftool: Align output skeleton ELF code Ian Rogers
@ 2023-10-05 22:03 ` Ian Rogers
2023-10-06 20:20 ` [PATCH v5 1/2] bpftool: Align output skeleton ELF code Andrii Nakryiko
1 sibling, 0 replies; 4+ messages in thread
From: Ian Rogers @ 2023-10-05 22:03 UTC (permalink / raw)
To: Quentin Monnet, Alexei Starovoitov, Daniel Borkmann,
Andrii Nakryiko, Martin KaFai Lau, Song Liu, Yonghong Song,
John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa,
bpf, linux-kernel
Cc: Ian Rogers
A C string lacks alignment so use aligned arrays to avoid potential
alignment problems. Switch to using sizeof (less 1 for the \0
terminator) rather than a hardcode size constant.
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Quentin Monnet <quentin@isovalent.com>
---
tools/bpf/bpftool/gen.c | 43 ++++++++++++++++++++++-------------------
1 file changed, 23 insertions(+), 20 deletions(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index b8ebcee9bc56..bcd26946d10e 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -708,17 +708,22 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
codegen("\
\n\
- skel->%1$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
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v5 1/2] bpftool: Align output skeleton ELF code
2023-10-05 22:03 [PATCH v5 1/2] bpftool: Align output skeleton ELF code Ian Rogers
2023-10-05 22:03 ` [PATCH v5 2/2] bpftool: Align bpf_load_and_run_opts insns and data Ian Rogers
@ 2023-10-06 20:20 ` Andrii Nakryiko
2023-10-06 20:22 ` Ian Rogers
1 sibling, 1 reply; 4+ messages in thread
From: Andrii Nakryiko @ 2023-10-06 20:20 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 Thu, Oct 5, 2023 at 3:03 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>
> Acked-by: Quentin Monnet <quentin@isovalent.com>
> Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
> ---
> tools/bpf/bpftool/gen.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
> 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$s__elf_bytes(&s->data_sz); \n\
Seems like you based this on top of bpf tree, can you please rebase
onto bpf-next, it has a small change here and I can't apply it cleanly
anymore. Other than that it looks good. Thanks!
> \n\
> obj->skeleton = s; \n\
> return 0; \n\
> @@ -1218,12 +1218,12 @@ static int do_skeleton(int argc, char **argv)
> return err; \n\
> } \n\
> \n\
> - static inline const void *%2$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
* Re: [PATCH v5 1/2] bpftool: Align output skeleton ELF code
2023-10-06 20:20 ` [PATCH v5 1/2] bpftool: Align output skeleton ELF code Andrii Nakryiko
@ 2023-10-06 20:22 ` Ian Rogers
0 siblings, 0 replies; 4+ messages in thread
From: Ian Rogers @ 2023-10-06 20:22 UTC (permalink / raw)
To: Andrii Nakryiko
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 Fri, Oct 6, 2023 at 1:20 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Thu, Oct 5, 2023 at 3:03 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>
> > Acked-by: Quentin Monnet <quentin@isovalent.com>
> > Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
> > ---
> > tools/bpf/bpftool/gen.c | 15 +++++++++------
> > 1 file changed, 9 insertions(+), 6 deletions(-)
> >
> > 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\
>
> Seems like you based this on top of bpf tree, can you please rebase
> onto bpf-next, it has a small change here and I can't apply it cleanly
> anymore. Other than that it looks good. Thanks!
Sure thing, sorry for so many V-s, we'll get there in the end.
Thanks,
Ian
> > \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
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2023-10-05 22:03 [PATCH v5 1/2] bpftool: Align output skeleton ELF code Ian Rogers
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