linux-kernel - [PATCH v2] libbpf: Fix determine_ptr

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Date:   Mon, 23 May 2022 11:29:55 +0100
From:   Douglas RAILLARD <douglas.raillard@....com>
To:     bpf@...r.kernel.org
Cc:     beata.michalska@....com,
        Douglas Raillard <douglas.raillard@....com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: [PATCH v2] libbpf: Fix determine_ptr_size() guessing

From: Douglas Raillard <douglas.raillard@....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 name in debug info.

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@....com>
---
 tools/lib/bpf/btf.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

 CHANGELOG
	v2:
		* Added missing case for "long"

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 1383e26c5d1f..ab92b3bc2724 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -489,8 +489,19 @@ 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") == 0 ||
+			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
+		) {
 			if (t->size != 4 && t->size != 8)
 				continue;
 			return t->size;
-- 
2.25.1