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[2001:8b0:7a5a:26ff::600]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a35ca5a8cfsm16538095f8f.37.2025.05.20.06.01.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 May 2025 06:01:39 -0700 (PDT) From: Lorenz Bauer Date: Tue, 20 May 2025 14:01:17 +0100 Subject: [PATCH bpf-next v5 1/3] btf: allow mmap of vmlinux btf Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250520-vmlinux-mmap-v5-1-e8c941acc414@isovalent.com> References: <20250520-vmlinux-mmap-v5-0-e8c941acc414@isovalent.com> In-Reply-To: <20250520-vmlinux-mmap-v5-0-e8c941acc414@isovalent.com> To: Arnd Bergmann , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Mykola Lysenko , Shuah Khan Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, Lorenz Bauer , Alan Maguire X-Mailer: b4 0.14.2 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. remap_pfn_range is used instead of vm_insert_page due to aarch64 compatibility issues. Tested-by: Alan Maguire Signed-off-by: Lorenz Bauer Reviewed-by: Shakeel Butt --- include/asm-generic/vmlinux.lds.h | 3 ++- kernel/bpf/sysfs_btf.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 34 insertions(+), 1 deletion(-) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinu= x.lds.h index 58a635a6d5bdf0c53c267c2a3d21a5ed8678ce73..1750390735fac7637cc4d2fa05f= 96cb2a36aa448 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_PROPE= LLER_CLANG) */ #ifdef CONFIG_DEBUG_INFO_BTF #define BTF \ + . =3D ALIGN(PAGE_SIZE); \ .BTF : AT(ADDR(.BTF) - LOAD_OFFSET) { \ BOUNDED_SECTION_BY(.BTF, _BTF) \ } \ - . =3D ALIGN(4); \ + . =3D 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..941d0d2427e3a2d27e8f1cff7b6= 424d0d41817c1 100644 --- a/kernel/bpf/sysfs_btf.c +++ b/kernel/bpf/sysfs_btf.c @@ -7,14 +7,46 @@ #include #include #include +#include +#include +#include =20 /* See scripts/link-vmlinux.sh, gen_btf() func for details */ extern char __start_BTF[]; extern char __stop_BTF[]; =20 +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 =3D PAGE_ALIGN(attr->size) >> PAGE_SHIFT; + size_t vm_size =3D vma->vm_end - vma->vm_start; + phys_addr_t addr =3D virt_to_phys(__start_BTF); + unsigned long pfn =3D addr >> PAGE_SHIFT; + + if (attr->private !=3D __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 (pfn + pages < pfn) + return -EINVAL; + + if ((vm_size >> PAGE_SHIFT) > pages) + return -EINVAL; + + vm_flags_mod(vma, VM_DONTDUMP, VM_MAYEXEC | VM_MAYWRITE); + return remap_pfn_range(vma, vma->vm_start, pfn, vm_size, vma->vm_page_pro= t); +} + static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init =3D { .attr =3D { .name =3D "vmlinux", .mode =3D 0444, }, .read_new =3D sysfs_bin_attr_simple_read, + .mmap =3D btf_sysfs_vmlinux_mmap, }; =20 struct kobject *btf_kobj; --=20 2.49.0