From 7fd785685e2243bb639b31557e258d11464c3489 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Tue, 13 Aug 2019 11:54:42 -0700 Subject: [PATCH 1/2] btf: rename /sys/kernel/btf/kernel into /sys/kernel/btf/vmlinux Expose kernel's BTF under the name vmlinux to be more uniform with using kernel module names as file names in the future. Fixes: 341dfcf8d78e ("btf: expose BTF info through sysfs") Suggested-by: Daniel Borkmann Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann --- Documentation/ABI/testing/sysfs-kernel-btf | 2 +- kernel/bpf/sysfs_btf.c | 30 +++++++++++----------- scripts/link-vmlinux.sh | 18 ++++++------- 3 files changed, 25 insertions(+), 25 deletions(-) diff --git a/Documentation/ABI/testing/sysfs-kernel-btf b/Documentation/ABI/testing/sysfs-kernel-btf index 5390f8001f96..2c9744b2cd59 100644 --- a/Documentation/ABI/testing/sysfs-kernel-btf +++ b/Documentation/ABI/testing/sysfs-kernel-btf @@ -6,7 +6,7 @@ Description: Contains BTF type information and related data for kernel and kernel modules. -What: /sys/kernel/btf/kernel +What: /sys/kernel/btf/vmlinux Date: Aug 2019 KernelVersion: 5.5 Contact: bpf@vger.kernel.org diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c index 092e63b9758b..4659349fc795 100644 --- a/kernel/bpf/sysfs_btf.c +++ b/kernel/bpf/sysfs_btf.c @@ -9,30 +9,30 @@ #include /* See scripts/link-vmlinux.sh, gen_btf() func for details */ -extern char __weak _binary__btf_kernel_bin_start[]; -extern char __weak _binary__btf_kernel_bin_end[]; +extern char __weak _binary__btf_vmlinux_bin_start[]; +extern char __weak _binary__btf_vmlinux_bin_end[]; static ssize_t -btf_kernel_read(struct file *file, struct kobject *kobj, - struct bin_attribute *bin_attr, - char *buf, loff_t off, size_t len) +btf_vmlinux_read(struct file *file, struct kobject *kobj, + struct bin_attribute *bin_attr, + char *buf, loff_t off, size_t len) { - memcpy(buf, _binary__btf_kernel_bin_start + off, len); + memcpy(buf, _binary__btf_vmlinux_bin_start + off, len); return len; } -static struct bin_attribute bin_attr_btf_kernel __ro_after_init = { - .attr = { .name = "kernel", .mode = 0444, }, - .read = btf_kernel_read, +static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init = { + .attr = { .name = "vmlinux", .mode = 0444, }, + .read = btf_vmlinux_read, }; static struct kobject *btf_kobj; -static int __init btf_kernel_init(void) +static int __init btf_vmlinux_init(void) { int err; - if (!_binary__btf_kernel_bin_start) + if (!_binary__btf_vmlinux_bin_start) return 0; btf_kobj = kobject_create_and_add("btf", kernel_kobj); @@ -42,10 +42,10 @@ static int __init btf_kernel_init(void) return err; } - bin_attr_btf_kernel.size = _binary__btf_kernel_bin_end - - _binary__btf_kernel_bin_start; + bin_attr_btf_vmlinux.size = _binary__btf_vmlinux_bin_end - + _binary__btf_vmlinux_bin_start; - return sysfs_create_bin_file(btf_kobj, &bin_attr_btf_kernel); + return sysfs_create_bin_file(btf_kobj, &bin_attr_btf_vmlinux); } -subsys_initcall(btf_kernel_init); +subsys_initcall(btf_vmlinux_init); diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index cb93832c6ad7..f7933c606f27 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -117,9 +117,9 @@ gen_btf() # dump .BTF section into raw binary file to link with final vmlinux bin_arch=$(${OBJDUMP} -f ${1} | grep architecture | \ cut -d, -f1 | cut -d' ' -f2) - ${OBJCOPY} --dump-section .BTF=.btf.kernel.bin ${1} 2>/dev/null + ${OBJCOPY} --dump-section .BTF=.btf.vmlinux.bin ${1} 2>/dev/null ${OBJCOPY} -I binary -O ${CONFIG_OUTPUT_FORMAT} -B ${bin_arch} \ - --rename-section .data=.BTF .btf.kernel.bin ${2} + --rename-section .data=.BTF .btf.vmlinux.bin ${2} } # Create ${2} .o file with all symbols from the ${1} object file @@ -227,10 +227,10 @@ ${MAKE} -f "${srctree}/scripts/Makefile.modpost" vmlinux.o info MODINFO modules.builtin.modinfo ${OBJCOPY} -j .modinfo -O binary vmlinux.o modules.builtin.modinfo -btf_kernel_bin_o="" +btf_vmlinux_bin_o="" if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then - if gen_btf .tmp_vmlinux.btf .btf.kernel.bin.o ; then - btf_kernel_bin_o=.btf.kernel.bin.o + if gen_btf .tmp_vmlinux.btf .btf.vmlinux.bin.o ; then + btf_vmlinux_bin_o=.btf.vmlinux.bin.o fi fi @@ -265,11 +265,11 @@ if [ -n "${CONFIG_KALLSYMS}" ]; then kallsyms_vmlinux=.tmp_vmlinux2 # step 1 - vmlinux_link .tmp_vmlinux1 ${btf_kernel_bin_o} + vmlinux_link .tmp_vmlinux1 ${btf_vmlinux_bin_o} kallsyms .tmp_vmlinux1 .tmp_kallsyms1.o # step 2 - vmlinux_link .tmp_vmlinux2 .tmp_kallsyms1.o ${btf_kernel_bin_o} + vmlinux_link .tmp_vmlinux2 .tmp_kallsyms1.o ${btf_vmlinux_bin_o} kallsyms .tmp_vmlinux2 .tmp_kallsyms2.o # step 3 @@ -280,13 +280,13 @@ if [ -n "${CONFIG_KALLSYMS}" ]; then kallsymso=.tmp_kallsyms3.o kallsyms_vmlinux=.tmp_vmlinux3 - vmlinux_link .tmp_vmlinux3 .tmp_kallsyms2.o ${btf_kernel_bin_o} + vmlinux_link .tmp_vmlinux3 .tmp_kallsyms2.o ${btf_vmlinux_bin_o} kallsyms .tmp_vmlinux3 .tmp_kallsyms3.o fi fi info LD vmlinux -vmlinux_link vmlinux "${kallsymso}" "${btf_kernel_bin_o}" +vmlinux_link vmlinux "${kallsymso}" "${btf_vmlinux_bin_o}" if [ -n "${CONFIG_BUILDTIME_EXTABLE_SORT}" ]; then info SORTEX vmlinux From a1916a153c254cd0ad13b23bed262ed56922cc7a Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Tue, 13 Aug 2019 11:54:43 -0700 Subject: [PATCH 2/2] libbpf: attempt to load kernel BTF from sysfs first Add support for loading kernel BTF from sysfs (/sys/kernel/btf/vmlinux) as a target BTF. Also extend the list of on disk search paths for vmlinux ELF image with entries that perf is searching for. Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann --- tools/lib/bpf/libbpf.c | 64 +++++++++++++++++++++++++++++++++++++----- 1 file changed, 57 insertions(+), 7 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 3abf2dd1b3b5..8462dab02812 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -2807,15 +2807,61 @@ static int bpf_core_reloc_insn(struct bpf_program *prog, int insn_off, return 0; } +static struct btf *btf_load_raw(const char *path) +{ + struct btf *btf; + size_t read_cnt; + struct stat st; + void *data; + FILE *f; + + if (stat(path, &st)) + return ERR_PTR(-errno); + + data = malloc(st.st_size); + if (!data) + return ERR_PTR(-ENOMEM); + + f = fopen(path, "rb"); + if (!f) { + btf = ERR_PTR(-errno); + goto cleanup; + } + + read_cnt = fread(data, 1, st.st_size, f); + fclose(f); + if (read_cnt < st.st_size) { + btf = ERR_PTR(-EBADF); + goto cleanup; + } + + btf = btf__new(data, read_cnt); + +cleanup: + free(data); + return btf; +} + /* * Probe few well-known locations for vmlinux kernel image and try to load BTF * data out of it to use for target BTF. */ static struct btf *bpf_core_find_kernel_btf(void) { - const char *locations[] = { - "/lib/modules/%1$s/vmlinux-%1$s", - "/usr/lib/modules/%1$s/kernel/vmlinux", + struct { + const char *path_fmt; + bool raw_btf; + } locations[] = { + /* try canonical vmlinux BTF through sysfs first */ + { "/sys/kernel/btf/vmlinux", true /* raw BTF */ }, + /* fall back to trying to find vmlinux ELF on disk otherwise */ + { "/boot/vmlinux-%1$s" }, + { "/lib/modules/%1$s/vmlinux-%1$s" }, + { "/lib/modules/%1$s/build/vmlinux" }, + { "/usr/lib/modules/%1$s/kernel/vmlinux" }, + { "/usr/lib/debug/boot/vmlinux-%1$s" }, + { "/usr/lib/debug/boot/vmlinux-%1$s.debug" }, + { "/usr/lib/debug/lib/modules/%1$s/vmlinux" }, }; char path[PATH_MAX + 1]; struct utsname buf; @@ -2825,14 +2871,18 @@ static struct btf *bpf_core_find_kernel_btf(void) uname(&buf); for (i = 0; i < ARRAY_SIZE(locations); i++) { - snprintf(path, PATH_MAX, locations[i], buf.release); + snprintf(path, PATH_MAX, locations[i].path_fmt, buf.release); if (access(path, R_OK)) continue; - btf = btf__parse_elf(path, NULL); - pr_debug("kernel BTF load from '%s': %ld\n", - path, PTR_ERR(btf)); + if (locations[i].raw_btf) + btf = btf_load_raw(path); + else + btf = btf__parse_elf(path, NULL); + + pr_debug("loading kernel BTF '%s': %ld\n", + path, IS_ERR(btf) ? PTR_ERR(btf) : 0); if (IS_ERR(btf)) continue;