lkml.org 
[lkml]   [2022]   [May]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v3] libbpf: Fix determine_ptr_size() guessing
Date
From: Douglas Raillard <douglas.raillard@arm.com>

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.

Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>
---
tools/lib/bpf/btf.c | 29 +++++++++++++++++++++--------
1 file changed, 21 insertions(+), 8 deletions(-)

CHANGELOG
v2:
* Added missing case for "long"
v3:
* Refactor a bit to use a table
* Provide the type names used by gcc and clang in commit msg

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 1383e26c5d1f..65c492a6807f 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -470,12 +470,25 @@ const struct btf_type *btf__type_by_id(const struct btf *btf, __u32 type_id)
return btf_type_by_id((struct btf *)btf, type_id);
}

+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",
+};
+
static int determine_ptr_size(const struct btf *btf)
{
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;

@@ -489,12 +502,12 @@ 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 (t->size != 4 && t->size != 8)
- continue;
- return t->size;
- }
+ if (t->size != 4 && t->size != 8)
+ continue;
+
+ for (j = 0; j < ARRAY_SIZE(long_aliases); j++)
+ if (!strcmp(name, long_aliases[j]))
+ return t->size;
}

return -1;
--
2.25.1
\
 
 \ /
  Last update: 2022-05-24 11:45    [W:0.656 / U:0.676 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site