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libbpf: Fix determine_ptr_size() guessing

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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: Douglas Raillard <douglas.raillard@arm.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220524094447.332186-1-douglas.raillard@arm.com
This commit is contained in:
Douglas Raillard
2022-05-24 10:44:47 +01:00
committed by Andrii Nakryiko
parent 37218f49fa
commit a5d75daa8c
1 changed files with 20 additions and 6 deletions
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26
src/btf.c
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@@ -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 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 struct btf_type *t;
const char *name; const char *name;
int i, n; int i, j, n;
if (btf->base_btf && btf->base_btf->ptr_sz > 0) if (btf->base_btf && btf->base_btf->ptr_sz > 0)
return btf->base_btf->ptr_sz; return btf->base_btf->ptr_sz;
@@ -485,15 +498,16 @@ static int determine_ptr_size(const struct btf *btf)
if (!btf_is_int(t)) if (!btf_is_int(t))
continue; continue;
if (t->size != 4 && t->size != 8)
continue;
name = btf__name_by_offset(btf, t->name_off); name = btf__name_by_offset(btf, t->name_off);
if (!name) if (!name)
continue; continue;
if (strcmp(name, "long int") == 0 || for (j = 0; j < ARRAY_SIZE(long_aliases); j++) {
strcmp(name, "long unsigned int") == 0) { if (strcmp(name, long_aliases[j]) == 0)
if (t->size != 4 && t->size != 8) return t->size;
continue;
return t->size;
} }
} }