Re: perf test LLVM & clang 6 failing

From: Daniel Borkmann
Date: Fri Nov 24 2017 - 10:17:04 EST

[ +Yonghong ]

On 11/24/2017 03:47 PM, Arnaldo Carvalho de Melo wrote:
> FYI, just noticed, recently updated clang to version 6, from its
> upstream git repo.

Do you recall what was your LLVM version prior to this where it was
working fine? (Wild guess from below would be the BPF inline asm
support that was added recently to LLVM (2865ab6996) vs asm() used
in headers included in the stdin header causing trouble due to arch
mixup?)

> root@jouet ~]# perf test -v LLVM
> 37: LLVM search and compile :
> 37.1: Basic BPF llvm compile :
> --- start ---
> test child forked, pid 5255
> Kernel build dir is set to /lib/modules/4.14.0+/build
> set env: KBUILD_DIR=/lib/modules/4.14.0+/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=0x40e00
> set env: CLANG_EXEC=/usr/local/bin/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: WORKING_DIR=/lib/modules/4.14.0+/build
> set env: CLANG_SOURCE=-
> llvm compiling command template: echo '/*
> * bpf-script-example.c
> * Test basic LLVM building
> */
> #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") flip_table = {
> .type = BPF_MAP_TYPE_ARRAY,
> .key_size = sizeof(int),
> .value_size = sizeof(int),
> .max_entries = 1,
> };
>
> SEC("func=SyS_epoll_wait")
> int bpf_func__SyS_epoll_wait(void *ctx)
> {
> int ind =0;
> int *flag = bpf_map_lookup_elem(&flip_table, &ind);
> int new_flag;
> if (!flag)
> return 0;
> /* flip flag and store back */
> new_flag = !*flag;
> bpf_map_update_elem(&flip_table, &ind, &new_flag, BPF_ANY);
> return new_flag;
> }
> 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 -Wno-unused-value -Wno-pointer-sign -working-directory $WORKING_DIR -c "$CLANG_SOURCE" -target bpf -O2 -o -
> test child finished with 0
> ---- end ----
> LLVM search and compile subtest 0: Ok
> 37.2: kbuild searching :
> --- start ---
> test child forked, pid 5728
> Kernel build dir is set to /lib/modules/4.14.0+/build
> set env: KBUILD_DIR=/lib/modules/4.14.0+/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=0x40e00
> set env: CLANG_EXEC=/usr/local/bin/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: WORKING_DIR=/lib/modules/4.14.0+/build
> set env: CLANG_SOURCE=-
> llvm compiling command template: echo '/*
> * bpf-script-test-kbuild.c
> * Test include from kernel header
> */
> #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 SEC(NAME) __attribute__((section(NAME), used))
>
> #include <uapi/linux/fs.h>
> #include <uapi/asm/ptrace.h>
>
> SEC("func=vfs_llseek")
> int bpf_func__vfs_llseek(void *ctx)
> {
> 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 -Wno-unused-value -Wno-pointer-sign -working-directory $WORKING_DIR -c "$CLANG_SOURCE" -target bpf -O2 -o -
> In file included from <stdin>:12:
> In file included from /home/acme/git/linux/arch/x86/include/uapi/asm/ptrace.h:5:
> In file included from /home/acme/git/linux/include/linux/compiler.h:237:
> In file included from /home/acme/git/linux/arch/x86/include/asm/barrier.h:5:
> In file included from /home/acme/git/linux/arch/x86/include/asm/alternative.h:10:
> /home/acme/git/linux/arch/x86/include/asm/asm.h:145:50: error: unknown register name 'esp' in asm
> register unsigned long current_stack_pointer asm(_ASM_SP);
> ^
> /home/acme/git/linux/arch/x86/include/asm/asm.h:44:18: note: expanded from macro '_ASM_SP'
> #define _ASM_SP __ASM_REG(sp)
> ^
> /home/acme/git/linux/arch/x86/include/asm/asm.h:27:32: note: expanded from macro '__ASM_REG'
> #define __ASM_REG(reg) __ASM_SEL_RAW(e##reg, r##reg)
> ^
> /home/acme/git/linux/arch/x86/include/asm/asm.h:18:29: note: expanded from macro '__ASM_SEL_RAW'
> # define __ASM_SEL_RAW(a,b) __ASM_FORM_RAW(a)
> ^
> /home/acme/git/linux/arch/x86/include/asm/asm.h:11:32: note: expanded from macro '__ASM_FORM_RAW'
> # define __ASM_FORM_RAW(x) #x
> ^
> <scratch space>:4:1: note: expanded from here
> "esp"
> ^
> 1 error generated.
> ERROR: unable to compile -
> Hint: Check error message shown above.
> Hint: You can also pre-compile it into .o using:
> clang -target bpf -O2 -c -
> with proper -I and -D options.
> Failed to compile test case: 'kbuild searching'
> test child finished with -1
> ---- end ----
> LLVM search and compile subtest 1: FAILED!
> 37.3: Compile source for BPF prologue generation :
> --- force skipped ---
> LLVM search and compile subtest 2: Skip
> 37.4: Compile source for BPF relocation :
> --- force skipped ---
> LLVM search and compile subtest 3: Skip
> [root@jouet ~]# clang -v
> clang version 6.0.0 (http://llvm.org/git/clang.git 56cc8f8880db2ebc433eeb6b6a707c101467a186) (http://llvm.org/git/llvm.git 3656d83960a4f3fedf6d8f19043abf52379f78c3)
> Target: x86_64-unknown-linux-gnu
> Thread model: posix
> InstalledDir: /usr/local/bin
> Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/7
> Selected GCC installation: /usr/lib/gcc/x86_64-redhat-linux/7
> Candidate multilib: .;@m64
> Candidate multilib: 32;@m32
> Selected multilib: .;@m64
> [root@jouet ~]#
>