mirror of
https://github.com/torvalds/linux
synced 2024-07-09 04:38:56 +00:00
fc5eb4a84e
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
46 lines
1.1 KiB
C
46 lines
1.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* Provide kernel BTF information for introspection and use by eBPF tools.
|
|
*/
|
|
#include <linux/kernel.h>
|
|
#include <linux/module.h>
|
|
#include <linux/kobject.h>
|
|
#include <linux/init.h>
|
|
#include <linux/sysfs.h>
|
|
|
|
/* See scripts/link-vmlinux.sh, gen_btf() func for details */
|
|
extern char __start_BTF[];
|
|
extern char __stop_BTF[];
|
|
|
|
static ssize_t
|
|
btf_vmlinux_read(struct file *file, struct kobject *kobj,
|
|
struct bin_attribute *bin_attr,
|
|
char *buf, loff_t off, size_t len)
|
|
{
|
|
memcpy(buf, __start_BTF + off, len);
|
|
return len;
|
|
}
|
|
|
|
static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init = {
|
|
.attr = { .name = "vmlinux", .mode = 0444, },
|
|
.read = btf_vmlinux_read,
|
|
};
|
|
|
|
struct kobject *btf_kobj;
|
|
|
|
static int __init btf_vmlinux_init(void)
|
|
{
|
|
bin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF;
|
|
|
|
if (bin_attr_btf_vmlinux.size == 0)
|
|
return 0;
|
|
|
|
btf_kobj = kobject_create_and_add("btf", kernel_kobj);
|
|
if (!btf_kobj)
|
|
return -ENOMEM;
|
|
|
|
return sysfs_create_bin_file(btf_kobj, &bin_attr_btf_vmlinux);
|
|
}
|
|
|
|
subsys_initcall(btf_vmlinux_init);
|