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[2001:8b0:7a5a:26ff::600]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a099ae8117sm11328877f8f.56.2025.05.05.11.39.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 May 2025 11:39:40 -0700 (PDT) From: Lorenz Bauer Date: Mon, 05 May 2025 19:38:43 +0100 Subject: [PATCH bpf-next v3 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: <20250505-vmlinux-mmap-v3-1-5d53afa060e8@isovalent.com> References: <20250505-vmlinux-mmap-v3-0-5d53afa060e8@isovalent.com> In-Reply-To: <20250505-vmlinux-mmap-v3-0-5d53afa060e8@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 | 37 +++++++++++++++++++++++++++++++++++= ++ 2 files changed, 39 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..37278d7f38ae72f2d7efcfa859e= 86aaf12e39a25 100644 --- a/kernel/bpf/sysfs_btf.c +++ b/kernel/bpf/sysfs_btf.c @@ -7,14 +7,51 @@ #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; + unsigned long addr =3D (unsigned long)attr->private; + int i, err =3D 0; + + if (addr !=3D (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 =3D 0; i < pages && !err; i++, addr +=3D PAGE_SIZE) + err =3D 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 =3D { .attr =3D { .name =3D "vmlinux", .mode =3D 0444, }, .read_new =3D sysfs_bin_attr_simple_read, + .mmap =3D btf_sysfs_vmlinux_mmap, }; 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[2001:8b0:7a5a:26ff::600]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a099ae8117sm11328877f8f.56.2025.05.05.11.39.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 May 2025 11:39:41 -0700 (PDT) From: Lorenz Bauer Date: Mon, 05 May 2025 19:38:44 +0100 Subject: [PATCH bpf-next v3 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: <20250505-vmlinux-mmap-v3-2-5d53afa060e8@isovalent.com> References: <20250505-vmlinux-mmap-v3-0-5d53afa060e8@isovalent.com> In-Reply-To: <20250505-vmlinux-mmap-v3-0-5d53afa060e8@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 | 83 ++++++++++++++++++= ++++ 1 file changed, 83 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..3319cf758897d46cefa8ca25e16= acb162f4e9889 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/btf_sysfs.c @@ -0,0 +1,83 @@ +// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause +/* Copyright (c) 2025 Isovalent */ + +#include +#include +#include +#include +#include +#include + +static void test_btf_mmap_sysfs(const char *path, struct btf *base) +{ + struct stat st; + __u64 btf_size, end; + void *raw_data =3D NULL; + int fd =3D -1; + 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(path, &st), "stat_btf")) + goto cleanup; + + btf_size =3D st.st_size; + end =3D (btf_size + page_size - 1) / page_size * page_size; + + fd =3D open(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, end + 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, end, 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; + + /* Check padding is zeroed */ + for (int i =3D btf_size; 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Mon, 05 May 2025 11:39:42 -0700 (PDT) Received: from [192.168.1.240] (0.0.6.0.0.0.0.0.0.0.0.0.0.0.0.0.f.f.6.2.a.5.a.7.0.b.8.0.1.0.0.2.ip6.arpa. [2001:8b0:7a5a:26ff::600]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a099ae8117sm11328877f8f.56.2025.05.05.11.39.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 May 2025 11:39:42 -0700 (PDT) From: Lorenz Bauer Date: Mon, 05 May 2025 19:38:45 +0100 Subject: [PATCH bpf-next v3 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: <20250505-vmlinux-mmap-v3-3-5d53afa060e8@isovalent.com> References: <20250505-vmlinux-mmap-v3-0-5d53afa060e8@isovalent.com> In-Reply-To: <20250505-vmlinux-mmap-v3-0-5d53afa060e8@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 | 83 ++++++++++++++++++++++++++++++++++++++++++++++---= ---- 1 file changed, 72 insertions(+), 11 deletions(-) diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index b7513d4cce55b263310c341bc254df6364e829d9..3006c1ebb97ed899eb519b10927= 491d87ccdaca5 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)); @@ -1354,6 +1382,37 @@ struct btf *btf__parse_raw_split(const char *path, s= truct btf *base_btf) return libbpf_ptr(btf_parse_raw(path, base_btf)); } =20 +static struct btf *btf_parse_raw_mmap(const char *path, struct btf *base_b= tf) +{ + struct stat st; + void *data; + struct btf *btf; + int fd; + + fd =3D open(path, O_RDONLY); + if (fd < 0) + return libbpf_err_ptr(-errno); + + if (fstat(fd, &st) < 0) { + close(fd); + return libbpf_err_ptr(-errno); + } + + data =3D mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0); + close(fd); + + if (data =3D=3D MAP_FAILED) + return NULL; + + btf =3D btf_new_no_copy(data, st.st_size, base_btf); + if (!btf) + munmap(data, st.st_size); + else + btf->raw_data_is_mmap =3D true; + + return btf; +} + static struct btf *btf_parse(const char *path, struct btf *base_btf, struc= t btf_ext **btf_ext) { struct btf *btf; @@ -1659,8 +1718,7 @@ 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 +5348,10 @@ 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); + btf =3D btf_parse_raw_mmap(sysfs_btf_path, NULL); + if (IS_ERR_OR_NULL(btf)) + 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