Inline assembly used by asm/sysreg.h is incompatible with latest llvm,
If bpf C program include "linux/ptrace.h" (which is common), compile will fail:
# perf --debug verbose record -e bpf-output/no-inherit,name=evt/ \
-e ./perf_bpf_test.c/map:channel.event=evt/ ls
[SNIP]
/lib/modules/5.17/build/./arch/x86/include/asm/arch_hweight.h:20:7: error: invalid output constraint '=a' in asm
: "="REG_OUT (res)
^
/lib/modules/5.17/build/./arch/x86/include/asm/arch_hweight.h:48:7: error: invalid output constraint '=a' in asm
: "="REG_OUT (res)
^
In file included from /root/projects/perf-bpf/perf_bpf_test.c:2:
In file included from /lib/modules/5.17/build/./include/linux/ptrace.h:6:
In file included from /lib/modules/5.17/build/./include/linux/sched.h:12:
In file included from /lib/modules/5.17/build/./arch/x86/include/asm/current.h:6:
In file included from /lib/modules/5.17/build/./arch/x86/include/asm/percpu.h:27:
In file included from /lib/modules/5.17/build/./include/linux/kernel.h:25:
In file included from /lib/modules/5.17/build/./include/linux/math.h:6:
/lib/modules/5.17.0/build/./arch/x86/include/asm/div64.h:85:28: error: invalid output constraint '=a' in asm
asm ("mulq %2; divq %3" : "=a" (q)
[SNIP]
# cat /root/projects/perf-bpf/perf_bpf_test.c
/************************ BEGIN **************************/
#include <uapi/linux/bpf.h>
#include <linux/ptrace.h>
#include <linux/types.h>
#define SEC(NAME) __attribute__((section(NAME), used))
struct bpf_map_def {
unsigned int type;
unsigned int key_size;
unsigned int value_size;
unsigned int max_entries;
};
static int (*perf_event_output)(void *, struct bpf_map_def *, int, void *,
unsigned long) = (void *)BPF_FUNC_perf_event_output;
struct bpf_map_def SEC("maps") channel = {
.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
.key_size = sizeof(int),
.value_size = sizeof(__u32),
.max_entries = __NR_CPUS__,
};
#define MIN_BYTES 1024
SEC("func=vfs_read")
int bpf_myprog(struct pt_regs *ctx)
{
long bytes = ctx->dx;
if (bytes >= MIN_BYTES) {
perf_event_output(ctx, &channel, BPF_F_CURRENT_CPU,
&bytes, sizeof(bytes));
}
return 0;
}
char _license[] SEC("license") = "GPL";
int _version SEC("version") = LINUX_VERSION_CODE;
/************************* END ***************************/
Compilation command is modified to be the same as that in samples/bpf/Makefile,
use clang | opt | llvm-dis | llc chain of commands to solve the problem.
see the comment in samples/bpf/Makefile.
Modifications:
1. Change "clang --target bpf" to chain of commands "clang | opt | llvm-dis | llc"
2. Delete "CLANG_EMIT_LLVM" and "LLVM_OPTIONS_PIPE" macros from the compilation
command because the two macros are not defined and the content is empty.
3. Add options llvm.llvm-opt-path, llvm.llvm-dis-path, and llvm.llc-path to
perf config for user-defined settings, which are similar to llvm.clang-path.
4. Add "-Wno-address-of-packed-member" to resolve the compilation warning of
"/lib/modules/5.17/build/./arch/x86/include/asm/processor.h:552:17: \
warning: taking address of packed member 'sp0' of class or structure \
'x86_hw_tss' may result in an unaligned pointer value [-Waddress-of-packed-member]
this_cpu_write(cpu_tss_rw.x86_tss.sp0, sp0);
^~~~~~~~~~~~~~~~~~~~~~
/lib/modules/5.17/build/./include/linux/percpu-defs.h:508:68: note: \
expanded from macro 'this_cpu_write' \
#define this_cpu_write(pcp, val) __pcpu_size_call(this_cpu_write_, pcp, val)",
which is similar to that of sample/bpf/Makefile.
Signed-off-by: Yang Jihong <yangjihong1@xxxxxxxxxx>
---
tools/perf/Documentation/perf-config.txt | 16 ++++++++++-
tools/perf/util/llvm-utils.c | 35 ++++++++++++++++++------
tools/perf/util/llvm-utils.h | 4 +++
3 files changed, 45 insertions(+), 10 deletions(-)
diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt
index 0420e71698ee..48f12bd6ca9a 100644
--- a/tools/perf/Documentation/perf-config.txt
+++ b/tools/perf/Documentation/perf-config.txt
@@ -655,6 +655,15 @@ llvm.*::
llvm.clang-path::
Path to clang. If omit, search it from $PATH.
+ llvm.llvm-opt-path::
+ Path to llvm opt. If omit, search it from $PATH.
+
+ llvm.llvm-dis-path::
+ Path to llvm-dis. If omit, search it from $PATH.
+
+ llvm.llc-path::
+ Path to llc. If omit, search it from $PATH.
+
llvm.clang-bpf-cmd-template::
Cmdline template. Below lines show its default value. Environment
variable is used to pass options.
@@ -662,8 +671,13 @@ llvm.*::
"-DLINUX_VERSION_CODE=$LINUX_VERSION_CODE " \
"$CLANG_OPTIONS $PERF_BPF_INC_OPTIONS $KERNEL_INC_OPTIONS " \
"-Wno-unused-value -Wno-pointer-sign " \
+ "-Wno-address-of-packed-member " \
"-working-directory $WORKING_DIR " \
- "-c \"$CLANG_SOURCE\" -target bpf $CLANG_EMIT_LLVM -O2 -o - $LLVM_OPTIONS_PIPE"
+ "-c \"$CLANG_SOURCE\" " \
+ "-O2 -emit-llvm -Xclang -disable-llvm-passes -o - | " \
+ "$LLVM_OPT_EXEC -O2 -mtriple=bpf-pc-linux | " \
+ "$LLVM_DIS_EXEC | " \
+ "$LLC_EXEC -march=bpf -filetype=obj -o -"
llvm.clang-opt::
Options passed to clang.
diff --git a/tools/perf/util/llvm-utils.c b/tools/perf/util/llvm-utils.c
index 96c8ef60f4f8..c939681dfafb 100644
--- a/tools/perf/util/llvm-utils.c
+++ b/tools/perf/util/llvm-utils.c
@@ -24,11 +24,18 @@
"-DLINUX_VERSION_CODE=$LINUX_VERSION_CODE " \
"$CLANG_OPTIONS $PERF_BPF_INC_OPTIONS $KERNEL_INC_OPTIONS " \
"-Wno-unused-value -Wno-pointer-sign " \
+ "-Wno-address-of-packed-member " \
"-working-directory $WORKING_DIR " \
- "-c \"$CLANG_SOURCE\" -target bpf $CLANG_EMIT_LLVM -O2 -o - $LLVM_OPTIONS_PIPE"
+ "-c \"$CLANG_SOURCE\" " \
+ "-O2 -emit-llvm -Xclang -disable-llvm-passes -o - | " \
+ "$LLVM_OPT_EXEC -O2 -mtriple=bpf-pc-linux | " \
+ "$LLVM_DIS_EXEC | " \
+ "$LLC_EXEC -march=bpf -filetype=obj -o -"
struct llvm_param llvm_param = {
.clang_path = "clang",
+ .llvm_opt_path = "opt",
+ .llvm_dis_path = "llvm-dis",
.llc_path = "llc",
.clang_bpf_cmd_template = CLANG_BPF_CMD_DEFAULT_TEMPLATE,
.clang_opt = NULL,
@@ -48,6 +55,12 @@ int perf_llvm_config(const char *var, const char *value)
if (!strcmp(var, "clang-path"))
llvm_param.clang_path = strdup(value);
+ else if (!strcmp(var, "llvm-opt-path"))
+ llvm_param.llvm_opt_path = strdup(value);
+ else if (!strcmp(var, "llvm-dis-path"))
+ llvm_param.llvm_dis_path = strdup(value);
+ else if (!strcmp(var, "llc-path"))
+ llvm_param.llc_path = strdup(value);
else if (!strcmp(var, "clang-bpf-cmd-template"))
llvm_param.clang_bpf_cmd_template = strdup(value);
else if (!strcmp(var, "clang-opt"))
@@ -456,6 +469,7 @@ int llvm__compile_bpf(const char *path, void **p_obj_buf,
char linux_version_code_str[64];
const char *clang_opt = llvm_param.clang_opt;
char clang_path[PATH_MAX], llc_path[PATH_MAX], abspath[PATH_MAX], nr_cpus_avail_str[64];
+ char llvm_opt_path[PATH_MAX], llvm_dis_path[PATH_MAX];
char serr[STRERR_BUFSIZE];
char *kbuild_dir = NULL, *kbuild_include_opts = NULL,
*perf_bpf_include_opts = NULL;
@@ -475,9 +489,10 @@ int llvm__compile_bpf(const char *path, void **p_obj_buf,
if (!template)
template = CLANG_BPF_CMD_DEFAULT_TEMPLATE;
- err = search_program_and_warn(llvm_param.clang_path,
- "clang", clang_path);
- if (err)
+ if (search_program_and_warn(llvm_param.clang_path, "clang", clang_path) ||
+ search_program_and_warn(llvm_param.llvm_opt_path, "opt", llvm_opt_path) ||
+ search_program_and_warn(llvm_param.llvm_dis_path, "llvm-dis", llvm_dis_path) ||
+ search_program_and_warn(llvm_param.llc_path, "llc", llc_path))
return -ENOENT;
/*
@@ -495,21 +510,23 @@ int llvm__compile_bpf(const char *path, void **p_obj_buf,
snprintf(linux_version_code_str, sizeof(linux_version_code_str),
"0x%x", kernel_version);
- if (asprintf(&perf_bpf_include_opts, "-I%s/bpf", perf_include_dir) < 0)
+ if (asprintf(&perf_bpf_include_opts, "-I%s/bpf", perf_include_dir) < 0) {
+ err = -ENOMEM;
goto errout;
+ }
+
force_set_env("NR_CPUS", nr_cpus_avail_str);
force_set_env("LINUX_VERSION_CODE", linux_version_code_str);
force_set_env("CLANG_EXEC", clang_path);
+ force_set_env("LLVM_OPT_EXEC", llvm_opt_path);
+ force_set_env("LLVM_DIS_EXEC", llvm_dis_path);
+ force_set_env("LLC_EXEC", llc_path);
force_set_env("CLANG_OPTIONS", clang_opt);
force_set_env("KERNEL_INC_OPTIONS", kbuild_include_opts);
force_set_env("PERF_BPF_INC_OPTIONS", perf_bpf_include_opts);
force_set_env("WORKING_DIR", kbuild_dir ? : ".");
if (opts) {
- err = search_program_and_warn(llvm_param.llc_path, "llc", llc_path);
- if (err)
- goto errout;
-
err = -ENOMEM;
if (asprintf(&pipe_template, "%s -emit-llvm | %s -march=bpf %s -filetype=obj -o -",
template, llc_path, opts) < 0) {
diff --git a/tools/perf/util/llvm-utils.h b/tools/perf/util/llvm-utils.h
index 7878a0e3fa98..e276d10f85b4 100644
--- a/tools/perf/util/llvm-utils.h
+++ b/tools/perf/util/llvm-utils.h
@@ -11,6 +11,10 @@
struct llvm_param {
/* Path of clang executable */
const char *clang_path;
+ /* Path of llvm opt executable */
+ const char *llvm_opt_path;
+ /* Path of llvm-dis executable */
+ const char *llvm_dis_path;
/* Path of llc executable */
const char *llc_path;
/*
--
2.30.GIT
