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 <[email protected]>
Reviewed-by: Alan Maguire <[email protected]>
---
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$d; \n\
- return (const void *)\"\\ \n\
- "
- , file_sz, obj_name);
+ static const char data[] __attribute__((__aligned__(8))) = \"\\\n\
+ ",
+ obj_name
+ );
/* embed contents of BPF object file */
print_hex(obj_data, file_sz);
@@ -1231,6 +1231,9 @@ static int do_skeleton(int argc, char **argv)
codegen("\
\n\
\"; \n\
+ \n\
+ *sz = sizeof(data) - 1; \n\
+ return (const void *)data; \n\
} \n\
\n\
#ifdef __cplusplus \n\
--
2.42.0.609.gbb76f46606-goog
A C string lacks alignment so use aligned arrays to avoid potential
alignment problems. Switch to using sizeof (less 1 for the \0
terminator) rather than a hardcode size constant.
Signed-off-by: Ian Rogers <[email protected]>
---
tools/bpf/bpftool/gen.c | 47 ++++++++++++++++++++++-------------------
1 file changed, 25 insertions(+), 22 deletions(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index b8ebcee9bc56..7a545dcabe38 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -408,8 +408,8 @@ static void codegen(const char *template, ...)
/* skip baseline indentation tabs */
for (n = skip_tabs; n > 0; n--, src++) {
if (*src != '\t') {
- p_err("not enough tabs at pos %td in template '%s'",
- src - template - 1, template);
+ p_err("not enough tabs at pos %td in template '%s'\n'%s'",
+ src - template - 1, template, src);
free(s);
exit(-1);
}
@@ -708,17 +708,22 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
codegen("\
\n\
- skel->%1$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
On 04/10/2023 23:23, Ian Rogers wrote:
> 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 <[email protected]>
> ---
> 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..7a545dcabe38 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);
Nit: This line is no longer aligned with the opening parenthesis.
Other than that:
Acked-by: Quentin Monnet <[email protected]>
On 04/10/2023 23:23, Ian Rogers 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 <[email protected]>
> Reviewed-by: Alan Maguire <[email protected]>
Acked-by: Quentin Monnet <[email protected]>
Thanks
On Thu, Oct 5, 2023 at 8:54 AM Quentin Monnet <[email protected]> wrote:
>
> On 04/10/2023 23:23, Ian Rogers wrote:
> > 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 <[email protected]>
> > ---
> > 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..7a545dcabe38 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);
>
> Nit: This line is no longer aligned with the opening parenthesis.
>
> Other than that:
>
> Acked-by: Quentin Monnet <[email protected]>
Thanks! Nit fixed in v5.
Ian