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[24.46.218.209]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6f6e39f588asm25725556d6.49.2025.05.10.05.35.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 10 May 2025 05:35:11 -0700 (PDT) From: Lorenz Bauer Date: Sat, 10 May 2025 08:34:54 -0400 Subject: [PATCH bpf-next v4 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: <20250510-vmlinux-mmap-v4-1-69e424b2a672@isovalent.com> References: <20250510-vmlinux-mmap-v4-0-69e424b2a672@isovalent.com> In-Reply-To: <20250510-vmlinux-mmap-v4-0-69e424b2a672@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. remap_pfn_range is used instead of vm_insert_page due to aarch64 compatibility issues. Signed-off-by: Lorenz Bauer Tested-by: Alan Maguire --- 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, }; 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[24.46.218.209]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6f6e39f588asm25725556d6.49.2025.05.10.05.35.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 10 May 2025 05:35:13 -0700 (PDT) From: Lorenz Bauer Date: Sat, 10 May 2025 08:34:55 -0400 Subject: [PATCH bpf-next v4 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: <20250510-vmlinux-mmap-v4-2-69e424b2a672@isovalent.com> References: <20250510-vmlinux-mmap-v4-0-69e424b2a672@isovalent.com> In-Reply-To: <20250510-vmlinux-mmap-v4-0-69e424b2a672@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. Ensure that the data is valid BTF and that it is padded with zero. Signed-off-by: Lorenz Bauer Tested-by: Alan Maguire --- tools/testing/selftests/bpf/prog_tests/btf_sysfs.c | 81 ++++++++++++++++++= ++++ 1 file changed, 81 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..3923e64c4c1d0f1dfeef2a39c7b= bab7c9a19f0ca --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/btf_sysfs.c @@ -0,0 +1,81 @@ +// 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_OK_PTR(raw_data, "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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[24.46.218.209]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6f6e39f588asm25725556d6.49.2025.05.10.05.35.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 10 May 2025 05:35:14 -0700 (PDT) From: Lorenz Bauer Date: Sat, 10 May 2025 08:34:56 -0400 Subject: [PATCH bpf-next v4 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: <20250510-vmlinux-mmap-v4-3-69e424b2a672@isovalent.com> References: <20250510-vmlinux-mmap-v4-0-69e424b2a672@isovalent.com> In-Reply-To: <20250510-vmlinux-mmap-v4-0-69e424b2a672@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 Acked-by: Andrii Nakryiko Tested-by: Alan Maguire --- tools/lib/bpf/btf.c | 85 +++++++++++++++++++++++++++++++++++++++++++------= ---- 1 file changed, 69 insertions(+), 16 deletions(-) diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index f18d7e6a453cd9e5c384487659df04f7efafdf5a..42815a29c0a52a1a7eed2c6b22b= 9b1754ae01c9a 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(const void *data, __u32 size, struct btf *base_= btf, bool is_mmap) { struct btf *btf; int err; @@ -1050,12 +1065,18 @@ static struct btf *btf_new(const void *data, __u32 = size, 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; + if (is_mmap) { + btf->raw_data =3D (void *)data; + btf->raw_data_is_mmap =3D true; + } else { + btf->raw_data =3D malloc(size); + if (!btf->raw_data) { + err =3D -ENOMEM; + goto done; + } + memcpy(btf->raw_data, data, size); } - memcpy(btf->raw_data, data, size); + btf->raw_size =3D size; =20 btf->hdr =3D btf->raw_data; @@ -1083,12 +1104,12 @@ static struct btf *btf_new(const void *data, __u32 = size, struct btf *base_btf) =20 struct btf *btf__new(const void *data, __u32 size) { - return libbpf_ptr(btf_new(data, size, NULL)); + return libbpf_ptr(btf_new(data, size, NULL, false)); } =20 struct btf *btf__new_split(const void *data, __u32 size, struct btf *base_= btf) { - return libbpf_ptr(btf_new(data, size, base_btf)); + return libbpf_ptr(btf_new(data, size, base_btf, false)); } =20 struct btf_elf_secs { @@ -1209,7 +1230,7 @@ static struct btf *btf_parse_elf(const char *path, st= ruct btf *base_btf, =20 if (secs.btf_base_data) { dist_base_btf =3D btf_new(secs.btf_base_data->d_buf, secs.btf_base_data-= >d_size, - NULL); + NULL, false); if (IS_ERR(dist_base_btf)) { err =3D PTR_ERR(dist_base_btf); dist_base_btf =3D NULL; @@ -1218,7 +1239,7 @@ static struct btf *btf_parse_elf(const char *path, st= ruct btf *base_btf, } =20 btf =3D btf_new(secs.btf_data->d_buf, secs.btf_data->d_size, - dist_base_btf ?: base_btf); + dist_base_btf ?: base_btf, false); if (IS_ERR(btf)) { err =3D PTR_ERR(btf); goto done; @@ -1335,7 +1356,7 @@ static struct btf *btf_parse_raw(const char *path, st= ruct btf *base_btf) } =20 /* finally parse BTF data */ - btf =3D btf_new(data, sz, base_btf); + btf =3D btf_new(data, sz, base_btf, false); =20 err_out: free(data); @@ -1354,6 +1375,36 @@ 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, err; + + fd =3D open(path, O_RDONLY); + if (fd < 0) + return libbpf_err_ptr(-errno); + + if (fstat(fd, &st) < 0) { + err =3D -errno; + 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=3D MAP_FAILED) + return NULL; + + btf =3D btf_new(data, st.st_size, base_btf, true); + if (IS_ERR(btf)) + munmap(data, st.st_size); + + return btf; +} + static struct btf *btf_parse(const char *path, struct btf *base_btf, struc= t btf_ext **btf_ext) { struct btf *btf; @@ -1618,7 +1669,7 @@ struct btf *btf_get_from_fd(int btf_fd, struct btf *b= ase_btf) goto exit_free; } =20 - btf =3D btf_new(ptr, btf_info.btf_size, base_btf); + btf =3D btf_new(ptr, btf_info.btf_size, base_btf, false); =20 exit_free: free(ptr); @@ -1659,8 +1710,7 @@ 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); @@ -5331,7 +5381,10 @@ 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