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authorArd Biesheuvel <ardb@kernel.org>2024-04-15 18:20:45 +0200
committerDaniel Borkmann <daniel@iogearbox.net>2024-04-16 16:35:13 +0200
commitfc5eb4a84e4c063e75a6a6e92308e9533c0f19b5 (patch)
treea5e08b469477b03deed0c6a87e51ca925c53fc3c /kernel/bpf/sysfs_btf.c
parentselftests/bpf: Add read_trace_pipe_iter function (diff)
downloadlinux-fc5eb4a84e4c063e75a6a6e92308e9533c0f19b5.tar.xz
linux-fc5eb4a84e4c063e75a6a6e92308e9533c0f19b5.zip
btf: Avoid weak external references
If the BTF code is enabled in the build configuration, the start/stop BTF markers are guaranteed to exist. Only when CONFIG_DEBUG_INFO_BTF=n, the references in btf_parse_vmlinux() will remain unsatisfied, relying on the weak linkage of the external references to avoid breaking the build. Avoid GOT based relocations to these markers in the final executable by dropping the weak attribute and instead, make btf_parse_vmlinux() return ERR_PTR(-ENOENT) directly if CONFIG_DEBUG_INFO_BTF is not enabled to begin with. The compiler will drop any subsequent references to __start_BTF and __stop_BTF in that case, allowing the link to succeed. Note that Clang will notice that taking the address of __start_BTF can no longer yield NULL, so testing for that condition becomes unnecessary. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Jiri Olsa <jolsa@kernel.org> Link: https://lore.kernel.org/bpf/20240415162041.2491523-8-ardb+git@google.com
Diffstat (limited to 'kernel/bpf/sysfs_btf.c')
-rw-r--r--kernel/bpf/sysfs_btf.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c
index ef6911aee3bb..fedb54c94cdb 100644
--- a/kernel/bpf/sysfs_btf.c
+++ b/kernel/bpf/sysfs_btf.c
@@ -9,8 +9,8 @@
#include <linux/sysfs.h>
/* See scripts/link-vmlinux.sh, gen_btf() func for details */
-extern char __weak __start_BTF[];
-extern char __weak __stop_BTF[];
+extern char __start_BTF[];
+extern char __stop_BTF[];
static ssize_t
btf_vmlinux_read(struct file *file, struct kobject *kobj,
@@ -32,7 +32,7 @@ static int __init btf_vmlinux_init(void)
{
bin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF;
- if (!__start_BTF || bin_attr_btf_vmlinux.size == 0)
+ if (bin_attr_btf_vmlinux.size == 0)
return 0;
btf_kobj = kobject_create_and_add("btf", kernel_kobj);