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-rw-r--r--include/asm-generic/vmlinux.lds.h3
-rw-r--r--kernel/bpf/sysfs_btf.c32
-rw-r--r--tools/lib/bpf/btf.c89
-rw-r--r--tools/testing/selftests/bpf/prog_tests/btf_sysfs.c81
4 files changed, 186 insertions, 19 deletions
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 58a635a6d5bd..1750390735fa 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_PROPELLER_CLANG)
*/
#ifdef CONFIG_DEBUG_INFO_BTF
#define BTF \
+ . = ALIGN(PAGE_SIZE); \
.BTF : AT(ADDR(.BTF) - LOAD_OFFSET) { \
BOUNDED_SECTION_BY(.BTF, _BTF) \
} \
- . = ALIGN(4); \
+ . = 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 81d6cf90584a..941d0d2427e3 100644
--- a/kernel/bpf/sysfs_btf.c
+++ b/kernel/bpf/sysfs_btf.c
@@ -7,14 +7,46 @@
#include <linux/kobject.h>
#include <linux/init.h>
#include <linux/sysfs.h>
+#include <linux/mm.h>
+#include <linux/io.h>
+#include <linux/btf.h>
/* See scripts/link-vmlinux.sh, gen_btf() func for details */
extern char __start_BTF[];
extern char __stop_BTF[];
+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 = PAGE_ALIGN(attr->size) >> PAGE_SHIFT;
+ size_t vm_size = vma->vm_end - vma->vm_start;
+ phys_addr_t addr = virt_to_phys(__start_BTF);
+ unsigned long pfn = addr >> PAGE_SHIFT;
+
+ if (attr->private != __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_prot);
+}
+
static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init = {
.attr = { .name = "vmlinux", .mode = 0444, },
.read_new = sysfs_bin_attr_simple_read,
+ .mmap = btf_sysfs_vmlinux_mmap,
};
struct kobject *btf_kobj;
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 8d0d0b645a75..f1d495dc66bb 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -12,6 +12,7 @@
#include <sys/utsname.h>
#include <sys/param.h>
#include <sys/stat.h>
+#include <sys/mman.h>
#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/btf.h>
@@ -120,6 +121,9 @@ struct btf {
/* whether base_btf should be freed in btf_free for this instance */
bool owns_base;
+ /* whether raw_data is a (read-only) mmap */
+ bool raw_data_is_mmap;
+
/* BTF object FD, if loaded into kernel */
int fd;
@@ -951,6 +955,17 @@ static bool btf_is_modifiable(const struct btf *btf)
return (void *)btf->hdr != btf->raw_data;
}
+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 = false;
+ } else {
+ free(btf->raw_data);
+ }
+ btf->raw_data = 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));
}
-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 = base_btf->hdr->str_len;
}
- btf->raw_data = malloc(size);
- if (!btf->raw_data) {
- err = -ENOMEM;
- goto done;
+ if (is_mmap) {
+ btf->raw_data = (void *)data;
+ btf->raw_data_is_mmap = true;
+ } else {
+ btf->raw_data = malloc(size);
+ if (!btf->raw_data) {
+ err = -ENOMEM;
+ goto done;
+ }
+ memcpy(btf->raw_data, data, size);
}
- memcpy(btf->raw_data, data, size);
+
btf->raw_size = size;
btf->hdr = btf->raw_data;
@@ -1083,12 +1104,12 @@ done:
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));
}
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));
}
struct btf_elf_secs {
@@ -1209,7 +1230,7 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
if (secs.btf_base_data) {
dist_base_btf = btf_new(secs.btf_base_data->d_buf, secs.btf_base_data->d_size,
- NULL);
+ NULL, false);
if (IS_ERR(dist_base_btf)) {
err = PTR_ERR(dist_base_btf);
dist_base_btf = NULL;
@@ -1218,7 +1239,7 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
}
btf = 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 = PTR_ERR(btf);
goto done;
@@ -1335,7 +1356,7 @@ static struct btf *btf_parse_raw(const char *path, struct btf *base_btf)
}
/* finally parse BTF data */
- btf = btf_new(data, sz, base_btf);
+ btf = btf_new(data, sz, base_btf, false);
err_out:
free(data);
@@ -1354,6 +1375,37 @@ struct btf *btf__parse_raw_split(const char *path, struct btf *base_btf)
return libbpf_ptr(btf_parse_raw(path, base_btf));
}
+static struct btf *btf_parse_raw_mmap(const char *path, struct btf *base_btf)
+{
+ struct stat st;
+ void *data;
+ struct btf *btf;
+ int fd, err;
+
+ fd = open(path, O_RDONLY);
+ if (fd < 0)
+ return libbpf_err_ptr(-errno);
+
+ if (fstat(fd, &st) < 0) {
+ err = -errno;
+ close(fd);
+ return libbpf_err_ptr(err);
+ }
+
+ data = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+ err = -errno;
+ close(fd);
+
+ if (data == MAP_FAILED)
+ return libbpf_err_ptr(err);
+
+ btf = 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, struct btf_ext **btf_ext)
{
struct btf *btf;
@@ -1618,7 +1670,7 @@ struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf)
goto exit_free;
}
- btf = btf_new(ptr, btf_info.btf_size, base_btf);
+ btf = btf_new(ptr, btf_info.btf_size, base_btf, false);
exit_free:
free(ptr);
@@ -1658,10 +1710,8 @@ 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 = NULL;
- }
+ if (btf->raw_data)
+ btf_free_raw_data(btf);
if (btf->raw_data_swapped) {
free(btf->raw_data_swapped);
btf->raw_data_swapped = NULL;
@@ -5331,7 +5381,10 @@ struct btf *btf__load_vmlinux_btf(void)
pr_warn("kernel BTF is missing at '%s', was CONFIG_DEBUG_INFO_BTF enabled?\n",
sysfs_btf_path);
} else {
- btf = btf__parse(sysfs_btf_path, NULL);
+ btf = btf_parse_raw_mmap(sysfs_btf_path, NULL);
+ if (IS_ERR(btf))
+ btf = btf__parse(sysfs_btf_path, NULL);
+
if (!btf) {
err = -errno;
pr_warn("failed to read kernel BTF from '%s': %s\n",
diff --git a/tools/testing/selftests/bpf/prog_tests/btf_sysfs.c b/tools/testing/selftests/bpf/prog_tests/btf_sysfs.c
new file mode 100644
index 000000000000..3923e64c4c1d
--- /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 <test_progs.h>
+#include <bpf/btf.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+static void test_btf_mmap_sysfs(const char *path, struct btf *base)
+{
+ struct stat st;
+ __u64 btf_size, end;
+ void *raw_data = NULL;
+ int fd = -1;
+ long page_size;
+ struct btf *btf = NULL;
+
+ page_size = 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 = st.st_size;
+ end = (btf_size + page_size - 1) / page_size * page_size;
+
+ fd = open(path, O_RDONLY);
+ if (!ASSERT_GE(fd, 0, "open_btf"))
+ goto cleanup;
+
+ raw_data = 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 = mmap(NULL, btf_size, PROT_READ, MAP_SHARED, fd, 0);
+ if (!ASSERT_EQ(raw_data, MAP_FAILED, "mmap_btf_shared"))
+ goto cleanup;
+
+ raw_data = 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 = 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 = btf_size; i < end; i++) {
+ if (((__u8 *)raw_data)[i] != 0) {
+ PRINT_FAIL("tail of BTF is not zero at page offset %d\n", i);
+ goto cleanup;
+ }
+ }
+
+ btf = btf__new_split(raw_data, btf_size, base);
+ if (!ASSERT_OK_PTR(btf, "parse_btf"))
+ goto cleanup;
+
+cleanup:
+ btf__free(btf);
+ if (raw_data && raw_data != MAP_FAILED)
+ munmap(raw_data, btf_size);
+ if (fd >= 0)
+ close(fd);
+}
+
+void test_btf_sysfs(void)
+{
+ test_btf_mmap_sysfs("/sys/kernel/btf/vmlinux", NULL);
+}
generated by cgit v1.2.3 (git 2.46.0) at 2025-07-31 14:58:21 +0000