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

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Thu, Jul 26, 2018 at 11:04:08PM +0530, Sandipan Das escreveu:
> Hi Arnaldo,
> 
> I came across the same problem. Does the following patch fix it?
> https://lkml.org/lkml/2018/7/26/669

Oh my, that one was subtle... Checking...

- Arnaldo
 
> - 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 ~]#
> > 
> >