Currently, the pahole treats 'char' or 'signed char' type
as unsigned in BTF generation. The following is an example,
$ cat t.c
signed char a;
char b;
$ clang -O2 -g -c t.c
$ pahole -JV t.o
...
[1] INT signed char size=1 nr_bits=8 encoding=(none)
[2] INT char size=1 nr_bits=8 encoding=(none)
In the above encoding '(none)' implies unsigned type.
But if the same program is compiled with bpf target,
$ clang -target bpf -O2 -g -c t.c
$ bpftool btf dump file t.o
[1] INT 'signed char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED
[2] VAR 'a' type_id=1, linkage=global
[3] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED
[4] VAR 'b' type_id=3, linkage=global
[5] DATASEC '.bss' size=0 vlen=2
type_id=2 offset=0 size=1 (VAR 'a')
type_id=4 offset=0 size=1 (VAR 'b')
the 'char' and 'signed char' are encoded as SIGNED integers.
Encode 'char' and 'signed char' as SIGNED should be a right to
do and it will be consistent with bpf implementation.
With this patch,
$ pahole -JV t.o
...
[1] INT signed char size=1 nr_bits=8 encoding=SIGNED
[2] INT char size=1 nr_bits=8 encoding=SIGNED
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
dwarf_loader.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/dwarf_loader.c b/dwarf_loader.c
index d892bc3..c2ad2a0 100644
--- a/dwarf_loader.c
+++ b/dwarf_loader.c
@@ -560,7 +560,7 @@ static struct base_type *base_type__new(Dwarf_Die *die, struct cu *cu, struct co
bt->bit_size = attr_numeric(die, DW_AT_byte_size) * 8;
uint64_t encoding = attr_numeric(die, DW_AT_encoding);
bt->is_bool = encoding == DW_ATE_boolean;
- bt->is_signed = encoding == DW_ATE_signed;
+ bt->is_signed = (encoding == DW_ATE_signed) || (encoding == DW_ATE_signed_char);
bt->is_varargs = false;
bt->name_has_encoding = true;
bt->float_type = encoding_to_float_type(encoding);
--
2.30.2
