Commit 610cd93b authored by Douglas Raillard's avatar Douglas Raillard Committed by Andrii Nakryiko
Browse files

libbpf: Fix determine_ptr_size() guessing 



One strategy employed by libbpf to guess the pointer size is by finding
the size of "unsigned long" type. This is achieved by looking for a type
of with the expected name and checking its size.

Unfortunately, the C syntax is friendlier to humans than to computers
as there is some variety in how such a type can be named. Specifically,
gcc and clang do not use the same names for integer types in debug info:

    - clang uses "unsigned long"
    - gcc uses "long unsigned int"

Lookup all the names for such a type so that libbpf can hope to find the
information it wants.

Signed-off-by: default avatarDouglas Raillard <douglas.raillard@arm.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220524094447.332186-1-douglas.raillard@arm.com
parent 4c46091e

tools/lib/bpf/btf.c

+20 −6
Original line number Diff line number Diff line
@@ -472,9 +472,22 @@ const struct btf_type *btf__type_by_id(const struct btf *btf, __u32 type_id) 


static int determine_ptr_size(const struct btf *btf)

{

	static const char * const long_aliases[] = {

		"long",

		"long int",

		"int long",

		"unsigned long",

		"long unsigned",

		"unsigned long int",

		"unsigned int long",

		"long unsigned int",

		"long int unsigned",

		"int unsigned long",

		"int long unsigned",

	};

	const struct btf_type *t;

	const char *name;

	int i, n;

	int i, j, n;



	if (btf->base_btf && btf->base_btf->ptr_sz > 0)

		return btf->base_btf->ptr_sz;
@@ -485,14 +498,15 @@ static int determine_ptr_size(const struct btf *btf) 
		if (!btf_is_int(t))

			continue;



		if (t->size != 4 && t->size != 8)

			continue;



		name = btf__name_by_offset(btf, t->name_off);

		if (!name)

			continue;



		if (strcmp(name, "long int") == 0 ||

		    strcmp(name, "long unsigned int") == 0) {

			if (t->size != 4 && t->size != 8)

				continue;

		for (j = 0; j < ARRAY_SIZE(long_aliases); j++) {

			if (strcmp(name, long_aliases[j]) == 0)

				return t->size;

		}

	}