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[2001:8b0:7a5a:26ff::600]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a099b17017sm1742342f8f.92.2025.05.02.03.20.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 May 2025 03:20:32 -0700 (PDT) From: Lorenz Bauer Date: Fri, 02 May 2025 11:20:05 +0100 Subject: [PATCH bpf-next v2 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: <20250502-vmlinux-mmap-v2-1-95c271434519@isovalent.com> References: <20250502-vmlinux-mmap-v2-0-95c271434519@isovalent.com> In-Reply-To: <20250502-vmlinux-mmap-v2-0-95c271434519@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 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. Signed-off-by: Lorenz Bauer --- include/asm-generic/vmlinux.lds.h | 3 ++- kernel/bpf/sysfs_btf.c | 36 ++++++++++++++++++++++++++++++++++-- 2 files changed, 36 insertions(+), 3 deletions(-) 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..f4b59b1c2e5b11ffffa80662ad3= 9334c730019ee 100644 --- a/kernel/bpf/sysfs_btf.c +++ b/kernel/bpf/sysfs_btf.c @@ -7,18 +7,50 @@ #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 +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) +{ + phys_addr_t start =3D virt_to_phys(__start_BTF); + size_t btf_size =3D __stop_BTF - __start_BTF; + size_t vm_size =3D vma->vm_end - vma->vm_start; + unsigned long pfn =3D start >> PAGE_SHIFT; + unsigned long pages =3D PAGE_ALIGN(btf_size) >> PAGE_SHIFT; + + if (kobj !=3D btf_kobj) + 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_vmlinux_mmap, }; =20 -struct kobject *btf_kobj; - static int __init btf_vmlinux_init(void) { bin_attr_btf_vmlinux.private =3D __start_BTF; --=20 2.49.0 From nobody Sun Feb 8 18:33:11 2026 Received: from mail-wm1-f41.google.com (mail-wm1-f41.google.com [209.85.128.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 904A523C4E9 for ; Fri, 2 May 2025 10:20:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.41 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746181238; cv=none; b=un8E2DfXMPiKZmicbjJYu5R67Z4TQHx218E9zCekQ6ZRE5D0uqHHsXcSO6YIiCyupz+MiLcxCGVAaiABUPq4SfM0N9359DkhG6kIe7hknwbmobvpLV1weLRoviCgAe+AU3EKes5Ba+1w9J13GYMuxNY9BxAacd3eqaYhetLXNW0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746181238; c=relaxed/simple; bh=ychg/Ta4S8UTx4Xf2MItnvBeDG7XnCP0C93pzW0Ay8Q=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; 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[2001:8b0:7a5a:26ff::600]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a099b17017sm1742342f8f.92.2025.05.02.03.20.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 May 2025 03:20:33 -0700 (PDT) From: Lorenz Bauer Date: Fri, 02 May 2025 11:20:06 +0100 Subject: [PATCH bpf-next v2 2/3] selftests: bpf: add a test for mmapable 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: <20250502-vmlinux-mmap-v2-2-95c271434519@isovalent.com> References: <20250502-vmlinux-mmap-v2-0-95c271434519@isovalent.com> In-Reply-To: <20250502-vmlinux-mmap-v2-0-95c271434519@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 X-Mailer: b4 0.14.2 Add a basic test for the ability to mmap /sys/kernel/btf/vmlinux. Since libbpf doesn't have an API to parse BTF from memory we do some basic sanity checks ourselves. Signed-off-by: Lorenz Bauer --- tools/testing/selftests/bpf/prog_tests/btf_sysfs.c | 82 ++++++++++++++++++= ++++ 1 file changed, 82 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/btf_sysfs.c b/tools/tes= ting/selftests/bpf/prog_tests/btf_sysfs.c new file mode 100644 index 0000000000000000000000000000000000000000..5c8095bedb0517930aabdecc17c= a7043f80f3692 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/btf_sysfs.c @@ -0,0 +1,82 @@ +// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause +/* Copyright (c) 2025 Isovalent */ + +#include +#include +#include +#include +#include +#include + +#define BTF_MAGIC 0xeB9F + +static const char *btf_path =3D "/sys/kernel/btf/vmlinux"; + +void test_btf_sysfs(void) +{ + struct stat st; + __u64 btf_size; + void *raw_data =3D NULL; + int fd =3D -1; + size_t trailing; + long page_size; + struct btf *btf =3D NULL; + + page_size =3D sysconf(_SC_PAGESIZE); + if (!ASSERT_GE(page_size, 0, "get_page_size")) + goto cleanup; + + if (!ASSERT_OK(stat(btf_path, &st), "stat_btf")) + goto cleanup; + + btf_size =3D st.st_size; + trailing =3D page_size - (btf_size % page_size) % page_size; + + fd =3D open(btf_path, O_RDONLY); + if (!ASSERT_GE(fd, 0, "open_btf")) + goto cleanup; + + raw_data =3D mmap(NULL, btf_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd= , 0); + if (!ASSERT_EQ(raw_data, MAP_FAILED, "mmap_btf_writable")) + goto cleanup; + + raw_data =3D mmap(NULL, btf_size, PROT_READ, MAP_SHARED, fd, 0); + if (!ASSERT_EQ(raw_data, MAP_FAILED, "mmap_btf_shared")) + goto cleanup; + + raw_data =3D mmap(NULL, btf_size + trailing + 1, PROT_READ, MAP_PRIVATE, = fd, 0); + if (!ASSERT_EQ(raw_data, MAP_FAILED, "mmap_btf_invalid_size")) + goto cleanup; + + raw_data =3D mmap(NULL, btf_size, PROT_READ, MAP_PRIVATE, fd, 0); + if (!ASSERT_NEQ(raw_data, MAP_FAILED, "mmap_btf")) + goto cleanup; + + if (!ASSERT_EQ(mprotect(raw_data, btf_size, PROT_READ | PROT_WRITE), -1, + "mprotect_writable")) + goto cleanup; + + if (!ASSERT_EQ(mprotect(raw_data, btf_size, PROT_READ | PROT_EXEC), -1, + "mprotect_executable")) + goto cleanup; 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[2001:8b0:7a5a:26ff::600]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a099b17017sm1742342f8f.92.2025.05.02.03.20.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 May 2025 03:20:34 -0700 (PDT) From: Lorenz Bauer Date: Fri, 02 May 2025 11:20:07 +0100 Subject: [PATCH bpf-next v2 3/3] libbpf: Use mmap to parse vmlinux BTF from sysfs 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: <20250502-vmlinux-mmap-v2-3-95c271434519@isovalent.com> References: <20250502-vmlinux-mmap-v2-0-95c271434519@isovalent.com> In-Reply-To: <20250502-vmlinux-mmap-v2-0-95c271434519@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 X-Mailer: b4 0.14.2 Teach libbpf to use mmap when parsing vmlinux BTF from /sys. We don't apply this to fall-back paths on the regular file system because there is no way to ensure that modifications underlying the MAP_PRIVATE mapping are not visible to the process. Signed-off-by: Lorenz Bauer --- tools/lib/bpf/btf.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++---= ---- 1 file changed, 71 insertions(+), 11 deletions(-) diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index b7513d4cce55b263310c341bc254df6364e829d9..7fec41a2dc617c9d388f9ab10d9= 850ef759c74d9 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -120,6 +121,9 @@ struct btf { /* whether base_btf should be freed in btf_free for this instance */ bool owns_base; =20 + /* whether raw_data is a (read-only) mmap */ + bool raw_data_is_mmap; + /* BTF object FD, if loaded into kernel */ int fd; =20 @@ -951,6 +955,17 @@ static bool btf_is_modifiable(const struct btf *btf) return (void *)btf->hdr !=3D btf->raw_data; } =20 +static void btf_free_raw_data(struct btf *btf) +{ + if (btf->raw_data_is_mmap) { + munmap(btf->raw_data, btf->raw_size); + btf->raw_data_is_mmap =3D false; + } else { + free(btf->raw_data); + } + btf->raw_data =3D NULL; +} + void btf__free(struct btf *btf) { if (IS_ERR_OR_NULL(btf)) @@ -970,7 +985,7 @@ void btf__free(struct btf *btf) free(btf->types_data); strset__free(btf->strs_set); } - free(btf->raw_data); + btf_free_raw_data(btf); free(btf->raw_data_swapped); free(btf->type_offs); if (btf->owns_base) @@ -1030,7 +1045,7 @@ struct btf *btf__new_empty_split(struct btf *base_btf) return libbpf_ptr(btf_new_empty(base_btf)); } =20 -static struct btf *btf_new(const void *data, __u32 size, struct btf *base_= btf) +static struct btf *btf_new_no_copy(void *data, __u32 size, struct btf *bas= e_btf) { struct btf *btf; int err; @@ -1050,12 +1065,7 @@ static struct btf *btf_new(const void *data, __u32 s= ize, struct btf *base_btf) btf->start_str_off =3D base_btf->hdr->str_len; } =20 - btf->raw_data =3D malloc(size); - if (!btf->raw_data) { - err =3D -ENOMEM; - goto done; - } - memcpy(btf->raw_data, data, size); + btf->raw_data =3D data; btf->raw_size =3D size; =20 btf->hdr =3D btf->raw_data; @@ -1081,6 +1091,24 @@ static struct btf *btf_new(const void *data, __u32 s= ize, struct btf *base_btf) return btf; } =20 +static struct btf *btf_new(const void *data, __u32 size, struct btf *base_= btf) +{ + struct btf *btf; + void *raw_data; + + raw_data =3D malloc(size); + if (!raw_data) + return ERR_PTR(-ENOMEM); + + memcpy(raw_data, data, size); + + btf =3D btf_new_no_copy(raw_data, size, base_btf); + if (IS_ERR(btf)) + free(raw_data); + + return btf; +} + struct btf *btf__new(const void *data, __u32 size) { return libbpf_ptr(btf_new(data, size, NULL)); @@ -1659,8 +1687,7 @@ struct btf *btf__load_from_kernel_by_id(__u32 id) static void btf_invalidate_raw_data(struct btf *btf) { if (btf->raw_data) { - free(btf->raw_data); - btf->raw_data =3D NULL; + btf_free_raw_data(btf); } if (btf->raw_data_swapped) { free(btf->raw_data_swapped); @@ -5290,7 +5317,40 @@ struct btf *btf__load_vmlinux_btf(void) pr_warn("kernel BTF is missing at '%s', was CONFIG_DEBUG_INFO_BTF enable= d?\n", sysfs_btf_path); } else { - btf =3D btf__parse(sysfs_btf_path, NULL); + struct stat st; + void *data =3D NULL; + int fd; + + fd =3D open(sysfs_btf_path, O_RDONLY); + if (fd < 0) { + err =3D -errno; + pr_warn("failed to open kernel BTF at '%s': %s\n", + sysfs_btf_path, errstr(err)); + return libbpf_err_ptr(err); + } + + if (fstat(fd, &st) < 0) { + err =3D -errno; + pr_warn("failed to stat kernel BTF at '%s': %s\n", + sysfs_btf_path, errstr(err)); + close(fd); + return libbpf_err_ptr(err); + } + + data =3D mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0); + close(fd); + + if (data !=3D MAP_FAILED) { + btf =3D libbpf_ptr(btf_new_no_copy(data, st.st_size, NULL)); + if (!btf) + munmap(data, st.st_size); + else + btf->raw_data_is_mmap =3D true; + } else { + pr_debug("reading kernel BTF via file-based fallback\n"); + btf =3D btf__parse(sysfs_btf_path, NULL); + } + if (!btf) { err =3D -errno; pr_warn("failed to read kernel BTF from '%s': %s\n", --=20 2.49.0