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make libbpf standalone-ready
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Break the c++ dependency in libbpf.c, and turn it into a separate lib
from cmake point of view.

Signed-off-by: Brenden Blanco <[email protected]>
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@drzaeus77
drzaeus77 committed May 31, 2017
1 parent cb7855b commit fa07345
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Showing 2 changed files with 105 additions and 26 deletions.
35 changes: 25 additions & 10 deletions src/cc/CMakeLists.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,8 +14,6 @@ include_directories(${CMAKE_CURRENT_SOURCE_DIR}/compat)
add_definitions(${LLVM_DEFINITIONS})
configure_file(libbcc.pc.in ${CMAKE_CURRENT_BINARY_DIR}/libbcc.pc @ONLY)

# prune unused llvm static library stuff when linking into the new .so
set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,--exclude-libs=ALL")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fPIC")

Expand All @@ -35,15 +33,20 @@ if (CMAKE_COMPILER_IS_GNUCC AND LIBCLANG_ISSTATIC)
endif()
endif()

add_library(bcc-shared SHARED bpf_common.cc bpf_module.cc libbpf.c perf_reader.c
table_storage.cc shared_table.cc bpffs_table.cc json_map_decl_visitor.cc
exported_files.cc bcc_elf.c bcc_perf_map.c bcc_proc.c bcc_syms.cc ns_guard.cc
usdt_args.cc usdt.cc common.cc BPF.cc BPFTable.cc)
add_library(bpf-static STATIC libbpf.c perf_reader.c)
set_target_properties(bpf-static PROPERTIES OUTPUT_NAME bpf)
add_library(bpf-shared SHARED libbpf.c perf_reader.c)
set_target_properties(bpf-shared PROPERTIES OUTPUT_NAME bpf)

add_library(bcc-shared SHARED bpf_common.cc bpf_module.cc table_storage.cc
shared_table.cc bpffs_table.cc json_map_decl_visitor.cc exported_files.cc
bcc_elf.c bcc_perf_map.c bcc_proc.c bcc_syms.cc ns_guard.cc usdt_args.cc
usdt.cc common.cc BPF.cc BPFTable.cc)
set_target_properties(bcc-shared PROPERTIES VERSION ${REVISION_LAST} SOVERSION 0)
set_target_properties(bcc-shared PROPERTIES OUTPUT_NAME bcc)

add_library(bcc-loader-static STATIC libbpf.c perf_reader.c bcc_elf.c
bcc_perf_map.c bcc_proc.c bcc_syms.cc ns_guard.cc)
add_library(bcc-loader-static STATIC bcc_elf.c bcc_perf_map.c bcc_proc.c
bcc_syms.cc ns_guard.cc)
add_library(bcc-static STATIC bpf_common.cc bpf_module.cc shared_table.cc
bpffs_table.cc json_map_decl_visitor.cc table_storage.cc exported_files.cc
usdt_args.cc usdt.cc common.cc BPF.cc BPFTable.cc)
Expand All @@ -67,9 +70,21 @@ set(clang_libs ${libclangFrontend} ${libclangSerialization} ${libclangDriver} ${
${libclangSema} ${libclangCodeGen} ${libclangAnalysis} ${libclangRewrite} ${libclangEdit}
${libclangAST} ${libclangLex} ${libclangBasic})

# prune unused llvm static library stuff when linking into the new .so
foreach(lib ${clang_libs})
get_filename_component(lib ${lib} NAME)
set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,--exclude-libs=${lib}")
endforeach(lib)
foreach(lib ${expanded_libs})
get_filename_component(lib ${lib} NAME)
set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,--exclude-libs=lib${lib}.a")
endforeach(lib)

# Link against LLVM libraries
target_link_libraries(bcc-shared b_frontend clang_frontend ${clang_libs} ${expanded_libs} ${LIBELF_LIBRARIES})
target_link_libraries(bcc-static b_frontend clang_frontend bcc-loader-static ${clang_libs} ${expanded_libs} ${LIBELF_LIBRARIES})
target_link_libraries(bcc-shared b_frontend clang_frontend bpf-static
${clang_libs} ${expanded_libs} ${LIBELF_LIBRARIES})
target_link_libraries(bcc-static b_frontend clang_frontend bcc-loader-static
bpf-static ${clang_libs} ${expanded_libs} ${LIBELF_LIBRARIES})

install(TARGETS bcc-shared LIBRARY COMPONENT libbcc
DESTINATION ${CMAKE_INSTALL_LIBDIR})
Expand Down
96 changes: 80 additions & 16 deletions src/cc/libbpf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@
#include <linux/bpf_common.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
Expand All @@ -38,7 +39,6 @@
#include <sys/stat.h>
#include <sys/types.h>

#include "bcc_syms.h"
#include "libbpf.h"
#include "perf_reader.h"

Expand Down Expand Up @@ -70,9 +70,9 @@

static int probe_perf_reader_page_cnt = 8;

static __u64 ptr_to_u64(void *ptr)
static uint64_t ptr_to_u64(void *ptr)
{
return (__u64) (unsigned long) ptr;
return (uint64_t) (unsigned long) ptr;
}

int bpf_create_map(enum bpf_map_type map_type, int key_size, int value_size, int max_entries, int map_flags)
Expand Down Expand Up @@ -182,7 +182,7 @@ int bpf_get_next_key(int fd, void *key, void *next_key)
return syscall(__NR_bpf, BPF_MAP_GET_NEXT_KEY, &attr, sizeof(attr));
}

void bpf_print_hints(char *log)
static void bpf_print_hints(char *log)
{
if (log == NULL)
return;
Expand Down Expand Up @@ -441,6 +441,67 @@ void * bpf_attach_kprobe(int progfd, enum bpf_probe_attach_type attach_type, con

}

static int enter_mount_ns(int pid) {
struct stat self_stat, target_stat;
int self_fd = -1, target_fd = -1;
char buf[64];

if (pid < 0)
return -1;

if ((size_t)snprintf(buf, sizeof(buf), "/proc/%d/ns/mnt", pid) >= sizeof(buf))
return -1;

self_fd = open("/proc/self/ns/mnt", O_RDONLY);
if (self_fd < 0) {
perror("open(/proc/self/ns/mnt)");
return -1;
}

target_fd = open(buf, O_RDONLY);
if (target_fd < 0) {
perror("open(/proc/<pid>/ns/mnt)");
goto error;
}

if (fstat(self_fd, &self_stat)) {
perror("fstat(self_fd)");
goto error;
}

if (fstat(target_fd, &target_stat)) {
perror("fstat(target_fd)");
goto error;
}

// both target and current ns are same, avoid setns and close all fds
if (self_stat.st_ino == target_stat.st_ino)
goto error;

if (setns(target_fd, CLONE_NEWNS)) {
perror("setns(target)");
goto error;
}

close(target_fd);
return self_fd;

error:
if (self_fd >= 0)
close(self_fd);
if (target_fd >= 0)
close(target_fd);
return -1;
}

static void exit_mount_ns(int fd) {
if (fd < 0)
return;

if (setns(fd, CLONE_NEWNS))
perror("setns");
}

void * bpf_attach_uprobe(int progfd, enum bpf_probe_attach_type attach_type, const char *ev_name,
const char *binary_path, uint64_t offset,
pid_t pid, int cpu, int group_fd,
Expand All @@ -451,8 +512,8 @@ void * bpf_attach_uprobe(int progfd, enum bpf_probe_attach_type attach_type, con
char new_name[128];
struct perf_reader *reader = NULL;
static char *event_type = "uprobe";
int ns_fd = -1;
int n;
void* mount_ns_guard = NULL;

snprintf(new_name, sizeof(new_name), "%s_bcc_%d", ev_name, getpid());
reader = perf_reader_new(cb, NULL, NULL, cb_cookie, probe_perf_reader_page_cnt);
Expand All @@ -473,15 +534,16 @@ void * bpf_attach_uprobe(int progfd, enum bpf_probe_attach_type attach_type, con
goto error;
}

mount_ns_guard = bcc_enter_mount_ns(pid);
ns_fd = enter_mount_ns(pid);
if (write(kfd, buf, strlen(buf)) < 0) {
if (errno == EINVAL)
fprintf(stderr, "check dmesg output for possible cause\n");
close(kfd);
goto error;
}
close(kfd);
bcc_exit_mount_ns(&mount_ns_guard);
exit_mount_ns(ns_fd);
ns_fd = -1;

snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/events/%ss/%s", event_type, new_name);
if (bpf_attach_tracing_event(progfd, buf, reader, pid, cpu, group_fd) < 0)
Expand All @@ -490,7 +552,7 @@ void * bpf_attach_uprobe(int progfd, enum bpf_probe_attach_type attach_type, con
return reader;

error:
bcc_exit_mount_ns(&mount_ns_guard);
exit_mount_ns(ns_fd);
perf_reader_free(reader);
return NULL;
}
Expand Down Expand Up @@ -604,7 +666,7 @@ void * bpf_open_perf_buffer(perf_reader_raw_cb raw_cb,
return NULL;
}

int invalid_perf_config(uint32_t type, uint64_t config) {
static int invalid_perf_config(uint32_t type, uint64_t config) {
switch (type) {
case PERF_TYPE_HARDWARE:
return config >= PERF_COUNT_HW_MAX;
Expand Down Expand Up @@ -827,19 +889,21 @@ int bpf_close_perf_event_fd(int fd) {

int bpf_obj_pin(int fd, const char *pathname)
{
union bpf_attr attr = {
.pathname = ptr_to_u64((void *)pathname),
.bpf_fd = fd,
};
union bpf_attr attr;

memset(&attr, 0, sizeof(attr));
attr.pathname = ptr_to_u64((void *)pathname);
attr.bpf_fd = fd;

return syscall(__NR_bpf, BPF_OBJ_PIN, &attr, sizeof(attr));
}

int bpf_obj_get(const char *pathname)
{
union bpf_attr attr = {
.pathname = ptr_to_u64((void *)pathname),
};
union bpf_attr attr;

memset(&attr, 0, sizeof(attr));
attr.pathname = ptr_to_u64((void *)pathname);

return syscall(__NR_bpf, BPF_OBJ_GET, &attr, sizeof(attr));
}

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