mbox series

[bpf-next,0/2] Allow mmap of /sys/kernel/btf/vmlinux

Message ID 20250501-vmlinux-mmap-v1-0-aa2724572598@isovalent.com
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Series Allow mmap of /sys/kernel/btf/vmlinux | expand

Message

Lorenz Bauer May 1, 2025, 2:28 p.m. UTC 
I'd like to cut down the memory usage of parsing vmlinux BTF in ebpf-go.
With some upcoming changes the library is sitting at 5MiB for a parse.
Most of that memory is simply copying the BTF blob into user space.
By allowing vmlinux BTF to be mmapped read-only into user space I can
cut memory usage by about 75%.

Signed-off-by: Lorenz Bauer <lmb@isovalent.com>
---
Lorenz Bauer (2):
      btf: allow mmap of vmlinux btf
      selftests: bpf: add a test for mmapable vmlinux BTF

 include/asm-generic/vmlinux.lds.h                  |  3 +-
 kernel/bpf/sysfs_btf.c                             | 25 ++++++-
 tools/testing/selftests/bpf/prog_tests/btf_sysfs.c | 79 ++++++++++++++++++++++
 3 files changed, 104 insertions(+), 3 deletions(-)
---
base-commit: 38d976c32d85ef12dcd2b8a231196f7049548477
change-id: 20250501-vmlinux-mmap-2ec5563c3ef1

Best regards,

Comments

Lorenz Bauer May 2, 2025, 10:19 a.m. UTC | #1 
On Thu, May 1, 2025 at 9:26 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
> > +
> > +       return vm_iomap_memory(vma, virt_to_phys(__start_BTF), btf_size);
>
> and this one should probably be vm_insert_pages().
> Since it's not an IO area.

FYI I went with open coding with remap_pfn_range since that allows me
to avoid struct page.

Lorenz