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 <l...@isovalent.com>
---
include/asm-generic/vmlinux.lds.h | 3 ++-
kernel/bpf/sysfs_btf.c | 37 +++++++++++++++++++++++++++++++++++++
2 files changed, 39 insertions(+), 1 deletion(-)
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..37278d7f38ae72f2d7efcfa859e86aaf12e39a25
100644
--- a/kernel/bpf/sysfs_btf.c
+++ b/kernel/bpf/sysfs_btf.c
@@ -7,14 +7,51 @@
#include <linux/kobject.h>
#include <linux/init.h>
#include <linux/sysfs.h>
+#include <linux/mm.h>
+#include <linux/io.h>
+#include <linux/btf.h>
/* See scripts/link-vmlinux.sh, gen_btf() func for details */
extern char __start_BTF[];
extern char __stop_BTF[];
+static int btf_sysfs_vmlinux_mmap(struct file *filp, struct kobject *kobj,
+ const struct bin_attribute *attr,
+ struct vm_area_struct *vma)
+{
+ unsigned long pages = PAGE_ALIGN(attr->size) >> PAGE_SHIFT;
+ size_t vm_size = vma->vm_end - vma->vm_start;
+ unsigned long addr = (unsigned long)attr->private;
+ int i, err = 0;
+
+ if (addr != (unsigned long)__start_BTF || !PAGE_ALIGNED(addr))
+ return -EINVAL;
+
+ if (vma->vm_pgoff)
+ return -EINVAL;
+
+ if (vma->vm_flags & (VM_WRITE | VM_EXEC | VM_MAYSHARE))
+ return -EACCES;
+
+ if (vm_size >> PAGE_SHIFT > pages)
+ return -EINVAL;
+
+ vm_flags_mod(vma, VM_DONTDUMP, VM_MAYEXEC | VM_MAYWRITE);
+
+ for (i = 0; i < pages && !err; i++, addr += PAGE_SIZE)
+ err = vm_insert_page(vma, vma->vm_start + i * PAGE_SIZE,
+ virt_to_page(addr));
+
+ if (err)
+ zap_vma_pages(vma);
+
+ return err;
+}
+
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_sysfs_vmlinux_mmap,
};
struct kobject *btf_kobj;
--
2.49.0
