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Message-Id: <20220218203906.317687-1-mauricio@kinvolk.io>
Date: Fri, 18 Feb 2022 15:39:06 -0500
From: Mauricio Vásquez <mauricio@...volk.io>
To: netdev@...r.kernel.org, bpf@...r.kernel.org
Cc: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Quentin Monnet <quentin@...valent.com>
Subject: [PATCH bpf-next] bpftool: Remove usage of reallocarray()
This commit fixes a compilation error on systems with glibc < 2.26 [0]:
```
In file included from main.h:14:0,
from gen.c:24:
linux/tools/include/tools/libc_compat.h:11:21: error: attempt to use poisoned "reallocarray"
static inline void *reallocarray(void *ptr, size_t nmemb, size_t size)
```
This happens because gen.c pulls <bpf/libbpf_internal.h>, and then
<tools/libc_compat.h> (through main.h). When
COMPAT_NEED_REALLOCARRAY is set, libc_compat.h defines reallocarray()
which libbpf_internal.h poisons with a GCC pragma.
This follows the same approach of libbpf in commit
029258d7b228 ("libbpf: Remove any use of reallocarray() in libbpf").
Reported-by: Quentin Monnet <quentin@...valent.com>
Signed-off-by: Mauricio Vásquez <mauricio@...volk.io>
[0]: https://lore.kernel.org/bpf/3bf2bd49-9f2d-a2df-5536-bc0dde70a83b@isovalent.com/
---
tools/bpf/bpftool/Makefile | 6 +-----
tools/bpf/bpftool/main.h | 34 ++++++++++++++++++++++++++++++-
tools/bpf/bpftool/prog.c | 6 +++---
tools/bpf/bpftool/xlated_dumper.c | 4 ++--
4 files changed, 39 insertions(+), 11 deletions(-)
diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index a137db96bd56..ba647aede0d6 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -93,7 +93,7 @@ INSTALL ?= install
RM ?= rm -f
FEATURE_USER = .bpftool
-FEATURE_TESTS = libbfd disassembler-four-args reallocarray zlib libcap \
+FEATURE_TESTS = libbfd disassembler-four-args zlib libcap \
clang-bpf-co-re
FEATURE_DISPLAY = libbfd disassembler-four-args zlib libcap \
clang-bpf-co-re
@@ -118,10 +118,6 @@ ifeq ($(feature-disassembler-four-args), 1)
CFLAGS += -DDISASM_FOUR_ARGS_SIGNATURE
endif
-ifeq ($(feature-reallocarray), 0)
-CFLAGS += -DCOMPAT_NEED_REALLOCARRAY
-endif
-
LIBS = $(LIBBPF) -lelf -lz
LIBS_BOOTSTRAP = $(LIBBPF_BOOTSTRAP) -lelf -lz
ifeq ($(feature-libcap), 1)
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index 0c3840596b5a..6a5775373640 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -8,10 +8,10 @@
#undef GCC_VERSION
#include <stdbool.h>
#include <stdio.h>
+#include <stdlib.h>
#include <linux/bpf.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
-#include <tools/libc_compat.h>
#include <bpf/hashmap.h>
#include <bpf/libbpf.h>
@@ -21,6 +21,9 @@
/* Make sure we do not use kernel-only integer typedefs */
#pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64
+/* prevent accidental re-addition of reallocarray() */
+#pragma GCC poison reallocarray
+
static inline __u64 ptr_to_u64(const void *ptr)
{
return (__u64)(unsigned long)ptr;
@@ -264,4 +267,33 @@ static inline bool hashmap__empty(struct hashmap *map)
return map ? hashmap__size(map) == 0 : true;
}
+#ifndef __has_builtin
+#define __has_builtin(x) 0
+#endif
+
+/*
+ * Re-implement glibc's reallocarray() for bpftool internal-only use.
+ * reallocarray(), unfortunately, is not available in all versions of glibc,
+ * so requires extra feature detection and using reallocarray() stub from
+ * <tools/libc_compat.h> and COMPAT_NEED_REALLOCARRAY. All this complicates
+ * build of bpftool unnecessarily and is just a maintenance burden. Instead,
+ * it's trivial to implement bpftool-specific internal version and use it
+ * throughout bpftool.
+ * Copied from tools/lib/bpf/libbpf_internal.h
+ */
+static inline void *bpftool_reallocarray(void *ptr, size_t nmemb, size_t size)
+{
+ size_t total;
+
+#if __has_builtin(__builtin_mul_overflow)
+ if (unlikely(__builtin_mul_overflow(nmemb, size, &total)))
+ return NULL;
+#else
+ if (size == 0 || nmemb > ULONG_MAX / size)
+ return NULL;
+ total = nmemb * size;
+#endif
+ return realloc(ptr, total);
+}
+
#endif
diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 92a6f679ef7d..860ad234166c 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -1558,9 +1558,9 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
if (fd < 0)
goto err_free_reuse_maps;
- new_map_replace = reallocarray(map_replace,
- old_map_fds + 1,
- sizeof(*map_replace));
+ new_map_replace = bpftool_reallocarray(map_replace,
+ old_map_fds + 1,
+ sizeof(*map_replace));
if (!new_map_replace) {
p_err("mem alloc failed");
goto err_free_reuse_maps;
diff --git a/tools/bpf/bpftool/xlated_dumper.c b/tools/bpf/bpftool/xlated_dumper.c
index f1f32e21d5cd..467bce9eee09 100644
--- a/tools/bpf/bpftool/xlated_dumper.c
+++ b/tools/bpf/bpftool/xlated_dumper.c
@@ -32,8 +32,8 @@ void kernel_syms_load(struct dump_data *dd)
return;
while (fgets(buff, sizeof(buff), fp)) {
- tmp = reallocarray(dd->sym_mapping, dd->sym_count + 1,
- sizeof(*dd->sym_mapping));
+ tmp = bpftool_reallocarray(dd->sym_mapping, dd->sym_count + 1,
+ sizeof(*dd->sym_mapping));
if (!tmp) {
out:
free(dd->sym_mapping);
--
2.25.1
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