Re: BPF relocation 'perf test' entries failing was: Re: [GIT PULL 00/27] perf/core improvements and fixes

From: Sandipan Das
Date: Thu Jul 26 2018 - 13:38:24 EST

Hi Arnaldo,

I came across the same problem. Does the following patch fix it?
https://lkml.org/lkml/2018/7/26/669

- Sandipan

On Thursday 26 July 2018 06:45 PM, Arnaldo Carvalho de Melo wrote:
> Em Wed, Jul 25, 2018 at 02:59:34PM -0300, Arnaldo Carvalho de Melo escreveu:
>> Hi Ingo,
>>
>> Please consider pulling, I'm now investigating why these failed:
>>
>> 38: LLVM search and compile :
>> 38.1: Basic BPF llvm compile : Ok
>> 38.2: kbuild searching : Ok
>> 38.3: Compile source for BPF prologue generation : Ok
>> 38.4: Compile source for BPF relocation : FAILED!
>> 40: BPF filter :
>> 40.1: Basic BPF filtering : Ok
>> 40.2: BPF pinning : Ok
>> 40.3: BPF prologue generation : Ok
>> 40.4: BPF relocation checker : FAILED!
>>
>> I think these failures are not related to changes in this patch
>> kit. Details about the test environment, versions, etc.
>
> So, here are more details:
>
> The relevant bit seems to be:
>
> libbpf: Program 'func=sys_write' contains non-map related relo data pointing to section 65522
>
> So this seems to be something that was caught by the kernel verifier and
> now is being caught by libbpf, /me goes to read the tools/lib/bpf
> changelog...
>
> - Arnaldo
>
> BPF filter subtest 2: Ok
> 40.3: BPF prologue generation :
> --- start ---
> test child forked, pid 13336
> Kernel build dir is set to /lib/modules/4.18.0-rc6-00093-g9981b4fb8684/build
> set env: KBUILD_DIR=/lib/modules/4.18.0-rc6-00093-g9981b4fb8684/build
> unset env: KBUILD_OPTS
> include option is set to -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/7/include -I/home/acme/git/linux/arch/x86/include -I./arch/x86/include/generated -I/home/acme/git/linux/include -I./include -I/home/acme/git/linux/arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I/home/acme/git/linux/include/uapi -I./include/generated/uapi -include /home/acme/git/linux/include/linux/kconfig.h
> set env: NR_CPUS=4
> set env: LINUX_VERSION_CODE=0x41200
> set env: CLANG_EXEC=/usr/lib64/ccache/clang
> set env: CLANG_OPTIONS=-xc
> set env: KERNEL_INC_OPTIONS= -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/7/include -I/home/acme/git/linux/arch/x86/include -I./arch/x86/include/generated -I/home/acme/git/linux/include -I./include -I/home/acme/git/linux/arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I/home/acme/git/linux/include/uapi -I./include/generated/uapi -include /home/acme/git/linux/include/linux/kconfig.h
> set env: PERF_BPF_INC_OPTIONS=-I/home/acme/lib/include/perf/bpf
> set env: WORKING_DIR=/lib/modules/4.18.0-rc6-00093-g9981b4fb8684/build
> set env: CLANG_SOURCE=-
> llvm compiling command template: echo '/*
> * bpf-script-test-relocation.c
> * Test BPF loader checking relocation
> */
> #ifndef LINUX_VERSION_CODE
> # error Need LINUX_VERSION_CODE
> # error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
> #endif
> #define BPF_ANY 0
> #define BPF_MAP_TYPE_ARRAY 2
> #define BPF_FUNC_map_lookup_elem 1
> #define BPF_FUNC_map_update_elem 2
>
> static void *(*bpf_map_lookup_elem)(void *map, void *key) =
> (void *) BPF_FUNC_map_lookup_elem;
> static void *(*bpf_map_update_elem)(void *map, void *key, void *value, int flags) =
> (void *) BPF_FUNC_map_update_elem;
>
> struct bpf_map_def {
> unsigned int type;
> unsigned int key_size;
> unsigned int value_size;
> unsigned int max_entries;
> };
>
> #define SEC(NAME) __attribute__((section(NAME), used))
> struct bpf_map_def SEC("maps") my_table = {
> .type = BPF_MAP_TYPE_ARRAY,
> .key_size = sizeof(int),
> .value_size = sizeof(int),
> .max_entries = 1,
> };
>
> int this_is_a_global_val;
>
> SEC("func=sys_write")
> int bpf_func__sys_write(void *ctx)
> {
> int key = 0;
> int value = 0;
>
> /*
> * Incorrect relocation. Should not allow this program be
> * loaded into kernel.
> */
> bpf_map_update_elem(&this_is_a_global_val, &key, &value, 0);
> return 0;
> }
> char _license[] SEC("license") = "GPL";
> int _version SEC("version") = LINUX_VERSION_CODE;
> ' | $CLANG_EXEC -D__KERNEL__ -D__NR_CPUS__=$NR_CPUS -DLINUX_VERSION_CODE=$LINUX_VERSION_CODE $CLANG_OPTIONS $KERNEL_INC_OPTIONS $PERF_BPF_INC_OPTIONS -Wno-unused-value -Wno-pointer-sign -working-directory $WORKING_DIR -c "$CLANG_SOURCE" -target bpf -O2 -o -
> llvm compiling command : echo '/*
> * bpf-script-test-relocation.c
> * Test BPF loader checking relocation
> */
> #ifndef LINUX_VERSION_CODE
> # error Need LINUX_VERSION_CODE
> # error Example: for 4.2 kernel, put 'clang-opt=-DLINUX_VERSION_CODE=0x40200 into llvm section of ~/.perfconfig'
> #endif
> #define BPF_ANY 0
> #define BPF_MAP_TYPE_ARRAY 2
> #define BPF_FUNC_map_lookup_elem 1
> #define BPF_FUNC_map_update_elem 2
>
> static void *(*bpf_map_lookup_elem)(void *map, void *key) =
> (void *) BPF_FUNC_map_lookup_elem;
> static void *(*bpf_map_update_elem)(void *map, void *key, void *value, int flags) =
> (void *) BPF_FUNC_map_update_elem;
>
> struct bpf_map_def {
> unsigned int type;
> unsigned int key_size;
> unsigned int value_size;
> unsigned int max_entries;
> };
>
> #define SEC(NAME) __attribute__((section(NAME), used))
> struct bpf_map_def SEC(maps) my_table = {
> .type = BPF_MAP_TYPE_ARRAY,
> .key_size = sizeof(int),
> .value_size = sizeof(int),
> .max_entries = 1,
> };
>
> int this_is_a_global_val;
>
> SEC(func=sys_write)
> int bpf_func__sys_write(void *ctx)
> {
> int key = 0;
> int value = 0;
>
> /*
> * Incorrect relocation. Should not allow this program be
> * loaded into kernel.
> */
> bpf_map_update_elem(&this_is_a_global_val, &key, &value, 0);
> return 0;
> }
> char _license[] SEC(license) = GPL;
> int _version SEC(version) = LINUX_VERSION_CODE;
> ' | /usr/lib64/ccache/clang -D__KERNEL__ -D__NR_CPUS__=4 -DLINUX_VERSION_CODE=0x41200 -xc -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/7/include -I/home/acme/git/linux/arch/x86/include -I./arch/x86/include/generated -I/home/acme/git/linux/include -I./include -I/home/acme/git/linux/arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I/home/acme/git/linux/include/uapi -I./include/generated/uapi -include /home/acme/git/linux/include/linux/kconfig.h -I/home/acme/lib/include/perf/bpf -Wno-unused-value -Wno-pointer-sign -working-directory /lib/modules/4.18.0-rc6-00093-g9981b4fb8684/build -c - -target bpf -O2 -o -
> libbpf: loading object '[bpf_relocation_test]' from buffer
> libbpf: section(1) .strtab, size 115, link 0, flags 0, type=3
> libbpf: skip section(1) .strtab
> libbpf: section(2) .text, size 0, link 0, flags 6, type=1
> libbpf: skip section(2) .text
> libbpf: section(3) func=sys_write, size 104, link 0, flags 6, type=1
> libbpf: found program func=sys_write
> libbpf: section(4) .relfunc=sys_write, size 16, link 8, flags 0, type=9
> libbpf: section(5) maps, size 16, link 0, flags 3, type=1
> libbpf: section(6) license, size 4, link 0, flags 3, type=1
> libbpf: license of [bpf_relocation_test] is GPL
> libbpf: section(7) version, size 4, link 0, flags 3, type=1
> libbpf: kernel version of [bpf_relocation_test] is 41200
> libbpf: section(8) .symtab, size 144, link 1, flags 0, type=2
> libbpf: maps in [bpf_relocation_test]: 1 maps in 16 bytes
> libbpf: map 0 is "my_table"
> libbpf: collecting relocating info for: 'func=sys_write'
> libbpf: relo for 5 value 4 name 21
> libbpf: Program 'func=sys_write' contains non-map related relo data pointing to section 65522
> bpf: failed to load buffer
> Compile BPF program failed.
> test child finished with 0
> ---- end ----
> BPF filter subtest 3: Ok
> 40.4: BPF relocation checker :
> --- start ---
> test child forked, pid 13746
> test child finished with -1
> ---- end ----
> BPF filter subtest 4: FAILED!
> [root@seventh ~]#
>
>