Merge branch 'bpf-libbpf-read-sysfs-btf'
Andrii Nakryiko says: ==================== Now that kernel's BTF is exposed through sysfs at well-known location, attempt to load it first as a target BTF for the purpose of BPF CO-RE relocations. Patch #1 is a follow-up patch to rename /sys/kernel/btf/kernel into /sys/kernel/btf/vmlinux. Patch #2 adds ability to load raw BTF contents from sysfs and expands the list of locations libbpf attempts to load vmlinux BTF from. ==================== Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Daniel Borkmann
commit
72ef80b5ee
@ -6,7 +6,7 @@ Description:
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Contains BTF type information and related data for kernel and
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kernel modules.
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What: /sys/kernel/btf/kernel
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What: /sys/kernel/btf/vmlinux
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Date: Aug 2019
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KernelVersion: 5.5
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Contact: bpf@vger.kernel.org
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@ -9,30 +9,30 @@
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#include <linux/sysfs.h>
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/* See scripts/link-vmlinux.sh, gen_btf() func for details */
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extern char __weak _binary__btf_kernel_bin_start[];
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extern char __weak _binary__btf_kernel_bin_end[];
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extern char __weak _binary__btf_vmlinux_bin_start[];
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extern char __weak _binary__btf_vmlinux_bin_end[];
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static ssize_t
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btf_kernel_read(struct file *file, struct kobject *kobj,
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struct bin_attribute *bin_attr,
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char *buf, loff_t off, size_t len)
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btf_vmlinux_read(struct file *file, struct kobject *kobj,
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struct bin_attribute *bin_attr,
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char *buf, loff_t off, size_t len)
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{
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memcpy(buf, _binary__btf_kernel_bin_start + off, len);
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memcpy(buf, _binary__btf_vmlinux_bin_start + off, len);
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return len;
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}
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static struct bin_attribute bin_attr_btf_kernel __ro_after_init = {
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.attr = { .name = "kernel", .mode = 0444, },
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.read = btf_kernel_read,
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static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init = {
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.attr = { .name = "vmlinux", .mode = 0444, },
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.read = btf_vmlinux_read,
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};
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static struct kobject *btf_kobj;
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static int __init btf_kernel_init(void)
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static int __init btf_vmlinux_init(void)
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{
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int err;
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if (!_binary__btf_kernel_bin_start)
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if (!_binary__btf_vmlinux_bin_start)
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return 0;
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btf_kobj = kobject_create_and_add("btf", kernel_kobj);
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@ -42,10 +42,10 @@ static int __init btf_kernel_init(void)
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return err;
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}
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bin_attr_btf_kernel.size = _binary__btf_kernel_bin_end -
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_binary__btf_kernel_bin_start;
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bin_attr_btf_vmlinux.size = _binary__btf_vmlinux_bin_end -
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_binary__btf_vmlinux_bin_start;
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return sysfs_create_bin_file(btf_kobj, &bin_attr_btf_kernel);
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return sysfs_create_bin_file(btf_kobj, &bin_attr_btf_vmlinux);
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}
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subsys_initcall(btf_kernel_init);
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subsys_initcall(btf_vmlinux_init);
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@ -117,9 +117,9 @@ gen_btf()
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# dump .BTF section into raw binary file to link with final vmlinux
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bin_arch=$(${OBJDUMP} -f ${1} | grep architecture | \
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cut -d, -f1 | cut -d' ' -f2)
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${OBJCOPY} --dump-section .BTF=.btf.kernel.bin ${1} 2>/dev/null
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${OBJCOPY} --dump-section .BTF=.btf.vmlinux.bin ${1} 2>/dev/null
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${OBJCOPY} -I binary -O ${CONFIG_OUTPUT_FORMAT} -B ${bin_arch} \
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--rename-section .data=.BTF .btf.kernel.bin ${2}
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--rename-section .data=.BTF .btf.vmlinux.bin ${2}
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}
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# Create ${2} .o file with all symbols from the ${1} object file
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@ -227,10 +227,10 @@ ${MAKE} -f "${srctree}/scripts/Makefile.modpost" vmlinux.o
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info MODINFO modules.builtin.modinfo
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${OBJCOPY} -j .modinfo -O binary vmlinux.o modules.builtin.modinfo
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btf_kernel_bin_o=""
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btf_vmlinux_bin_o=""
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if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then
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if gen_btf .tmp_vmlinux.btf .btf.kernel.bin.o ; then
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btf_kernel_bin_o=.btf.kernel.bin.o
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if gen_btf .tmp_vmlinux.btf .btf.vmlinux.bin.o ; then
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btf_vmlinux_bin_o=.btf.vmlinux.bin.o
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fi
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fi
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@ -265,11 +265,11 @@ if [ -n "${CONFIG_KALLSYMS}" ]; then
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kallsyms_vmlinux=.tmp_vmlinux2
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# step 1
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vmlinux_link .tmp_vmlinux1 ${btf_kernel_bin_o}
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vmlinux_link .tmp_vmlinux1 ${btf_vmlinux_bin_o}
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kallsyms .tmp_vmlinux1 .tmp_kallsyms1.o
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# step 2
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vmlinux_link .tmp_vmlinux2 .tmp_kallsyms1.o ${btf_kernel_bin_o}
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vmlinux_link .tmp_vmlinux2 .tmp_kallsyms1.o ${btf_vmlinux_bin_o}
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kallsyms .tmp_vmlinux2 .tmp_kallsyms2.o
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# step 3
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@ -280,13 +280,13 @@ if [ -n "${CONFIG_KALLSYMS}" ]; then
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kallsymso=.tmp_kallsyms3.o
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kallsyms_vmlinux=.tmp_vmlinux3
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vmlinux_link .tmp_vmlinux3 .tmp_kallsyms2.o ${btf_kernel_bin_o}
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vmlinux_link .tmp_vmlinux3 .tmp_kallsyms2.o ${btf_vmlinux_bin_o}
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kallsyms .tmp_vmlinux3 .tmp_kallsyms3.o
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fi
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fi
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info LD vmlinux
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vmlinux_link vmlinux "${kallsymso}" "${btf_kernel_bin_o}"
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vmlinux_link vmlinux "${kallsymso}" "${btf_vmlinux_bin_o}"
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if [ -n "${CONFIG_BUILDTIME_EXTABLE_SORT}" ]; then
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info SORTEX vmlinux
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@ -2807,15 +2807,61 @@ static int bpf_core_reloc_insn(struct bpf_program *prog, int insn_off,
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return 0;
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}
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static struct btf *btf_load_raw(const char *path)
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{
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struct btf *btf;
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size_t read_cnt;
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struct stat st;
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void *data;
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FILE *f;
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if (stat(path, &st))
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return ERR_PTR(-errno);
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data = malloc(st.st_size);
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if (!data)
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return ERR_PTR(-ENOMEM);
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f = fopen(path, "rb");
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if (!f) {
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btf = ERR_PTR(-errno);
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goto cleanup;
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}
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read_cnt = fread(data, 1, st.st_size, f);
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fclose(f);
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if (read_cnt < st.st_size) {
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btf = ERR_PTR(-EBADF);
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goto cleanup;
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}
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btf = btf__new(data, read_cnt);
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cleanup:
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free(data);
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return btf;
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}
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/*
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* Probe few well-known locations for vmlinux kernel image and try to load BTF
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* data out of it to use for target BTF.
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*/
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static struct btf *bpf_core_find_kernel_btf(void)
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{
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const char *locations[] = {
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"/lib/modules/%1$s/vmlinux-%1$s",
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"/usr/lib/modules/%1$s/kernel/vmlinux",
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struct {
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const char *path_fmt;
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bool raw_btf;
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} locations[] = {
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/* try canonical vmlinux BTF through sysfs first */
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{ "/sys/kernel/btf/vmlinux", true /* raw BTF */ },
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/* fall back to trying to find vmlinux ELF on disk otherwise */
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{ "/boot/vmlinux-%1$s" },
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{ "/lib/modules/%1$s/vmlinux-%1$s" },
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{ "/lib/modules/%1$s/build/vmlinux" },
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{ "/usr/lib/modules/%1$s/kernel/vmlinux" },
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{ "/usr/lib/debug/boot/vmlinux-%1$s" },
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{ "/usr/lib/debug/boot/vmlinux-%1$s.debug" },
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{ "/usr/lib/debug/lib/modules/%1$s/vmlinux" },
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};
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char path[PATH_MAX + 1];
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struct utsname buf;
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@ -2825,14 +2871,18 @@ static struct btf *bpf_core_find_kernel_btf(void)
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uname(&buf);
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for (i = 0; i < ARRAY_SIZE(locations); i++) {
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snprintf(path, PATH_MAX, locations[i], buf.release);
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snprintf(path, PATH_MAX, locations[i].path_fmt, buf.release);
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if (access(path, R_OK))
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continue;
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btf = btf__parse_elf(path, NULL);
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pr_debug("kernel BTF load from '%s': %ld\n",
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path, PTR_ERR(btf));
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if (locations[i].raw_btf)
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btf = btf_load_raw(path);
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else
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btf = btf__parse_elf(path, NULL);
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pr_debug("loading kernel BTF '%s': %ld\n",
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path, IS_ERR(btf) ? PTR_ERR(btf) : 0);
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if (IS_ERR(btf))
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continue;
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