Commit 23671f4d authored by Ian Rogers's avatar Ian Rogers Committed by Andrii Nakryiko
Browse files

bpftool: Align output skeleton ELF code 



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: a6cc6b34 ("bpftool: Provide a helper method for accessing skeleton's embedded ELF data")
Signed-off-by: default avatarIan Rogers <irogers@google.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Reviewed-by: default avatarAlan Maguire <alan.maguire@oracle.com>
Acked-by: default avatarQuentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20231007044439.25171-1-irogers@google.com
parent 0d7ae068

tools/bpf/bpftool/gen.c

+9 −6
Original line number Diff line number Diff line
@@ -1209,7 +1209,7 @@ static int do_skeleton(int argc, char **argv) 
	codegen("\

		\n\

									    \n\

			s->data = %2$s__elf_bytes(&s->data_sz);		    \n\

			s->data = %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\