Hi Yonghong,
On 5/20/22 20:19, Yonghong Song wrote:
On 5/20/22 8:38 AM, Douglas RAILLARD wrote:
From: Douglas Raillard <douglas.raillard@xxxxxxx>
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 name in debug info.
Yes, this is indeed the case.
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@xxxxxxx>
LGTM with some comments and needed change below.
Acked-by: Yonghong Song <yhs@xxxxxx>
---
tools/lib/bpf/btf.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 1383e26c5d1f..ce05e4b1febd 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -489,8 +489,18 @@ static int determine_ptr_size(const struct btf *btf)
if (!name)
continue;
- if (strcmp(name, "long int") == 0 ||
- strcmp(name, "long unsigned int") == 0) {
+ if (
+ strcmp(name, "long int") == 0 ||
+ strcmp(name, "int long") == 0 ||
+ strcmp(name, "unsigned long") == 0 ||
+ strcmp(name, "long unsigned") == 0 ||
+ strcmp(name, "unsigned long int") == 0 ||
+ strcmp(name, "unsigned int long") == 0 ||
+ strcmp(name, "long unsigned int") == 0 ||
+ strcmp(name, "long int unsigned") == 0 ||
+ strcmp(name, "int unsigned long") == 0 ||
+ strcmp(name, "int long unsigned") == 0
Please add "long" as well. For "long t" declaration, clang generates
the following dwarf:
Good catch, I missed this one thanks.
0x00000029: DW_TAG_base_type
DW_AT_name ("long")
DW_AT_encoding (DW_ATE_signed)
DW_AT_byte_size (0x08)
If the type name can be sorted with words, we only need
to compare the following 4 instead of 11
"long"
"int long"
"long unsigned"
"int long unsigned"
But I don't know whether we have an existing function
to do word sorting or not.
I could not find anything and was thinking it's probably more hassle than it's worth but if
we really want that I could add it somewhere.
+ ) {
if (t->size != 4 && t->size != 8)
continue;
return t->size;
Thanks,
Douglas
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