User space needs access to kernel BTF for many modern features of BPF. Right now each process needs to read the BTF blob either in pieces or as a whole. Allow mmaping the sysfs file so that processes can directly access the memory allocated for it in the kernel.
Signed-off-by: Lorenz Bauer lmb@isovalent.com --- include/asm-generic/vmlinux.lds.h | 3 ++- kernel/bpf/sysfs_btf.c | 25 +++++++++++++++++++++++-- 2 files changed, 25 insertions(+), 3 deletions(-)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 58a635a6d5bdf0c53c267c2a3d21a5ed8678ce73..1750390735fac7637cc4d2fa05f96cb2a36aa448 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -667,10 +667,11 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) */ #ifdef CONFIG_DEBUG_INFO_BTF #define BTF \ + . = ALIGN(PAGE_SIZE); \ .BTF : AT(ADDR(.BTF) - LOAD_OFFSET) { \ BOUNDED_SECTION_BY(.BTF, _BTF) \ } \ - . = ALIGN(4); \ + . = ALIGN(PAGE_SIZE); \ .BTF_ids : AT(ADDR(.BTF_ids) - LOAD_OFFSET) { \ *(.BTF_ids) \ } diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c index 81d6cf90584a7157929c50f62a5c6862e7a3d081..7651f37b82c78b8afd96078567a5b6612f5f4d97 100644 --- a/kernel/bpf/sysfs_btf.c +++ b/kernel/bpf/sysfs_btf.c @@ -7,18 +7,39 @@ #include <linux/kobject.h> #include <linux/init.h> #include <linux/sysfs.h> +#include <linux/mm.h> +#include <linux/io.h>
/* See scripts/link-vmlinux.sh, gen_btf() func for details */ extern char __start_BTF[]; extern char __stop_BTF[];
+struct kobject *btf_kobj; + +static int btf_vmlinux_mmap(struct file *filp, struct kobject *kobj, + const struct bin_attribute *attr, + struct vm_area_struct *vma) +{ + size_t btf_size = __stop_BTF - __start_BTF; + + if (kobj != btf_kobj) + return -EINVAL; + + if (vma->vm_flags & (VM_WRITE|VM_EXEC|VM_MAYSHARE)) + return -EACCES; + + vm_flags_clear(vma, VM_MAYEXEC); + vm_flags_clear(vma, VM_MAYWRITE); + + return vm_iomap_memory(vma, virt_to_phys(__start_BTF), btf_size); +} + static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init = { .attr = { .name = "vmlinux", .mode = 0444, }, .read_new = sysfs_bin_attr_simple_read, + .mmap = btf_vmlinux_mmap, };
-struct kobject *btf_kobj; - static int __init btf_vmlinux_init(void) { bin_attr_btf_vmlinux.private = __start_BTF;