tree-wide: introduce and use syscall number header

This allows us:
- to compile on kernels with outdated headers
- compile on older kernels but shipping on newer kernels

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

src/lxc/Makefile.am

@@ -43,6 +43,7 @@ noinst_HEADERS = api_extensions.h \
 		 storage/storage_utils.h \
 		 storage/zfs.h \
 		 string_utils.h \
+		 syscall_numbers.h \
 		 syscall_wrappers.h \
 		 terminal.h \
 		 ../tests/lxctest.h \
@@ -145,6 +146,7 @@ liblxc_la_SOURCES = af_unix.c af_unix.h \
 		    storage/zfs.c storage/zfs.h \
 		    string_utils.c string_utils.h \
 		    sync.c sync.h \
+		    syscall_numbers.h \
 		    syscall_wrappers.h \
 		    terminal.c \
 		    utils.c utils.h \
@@ -360,6 +362,7 @@ lxc_top_SOURCES = tools/lxc_top.c \
 lxc_unfreeze_SOURCES = tools/lxc_unfreeze.c \
 		       tools/arguments.c tools/arguments.h
 lxc_unshare_SOURCES = tools/lxc_unshare.c \
+		      syscall_numbers.h \
 		      tools/arguments.c tools/arguments.h
 lxc_wait_SOURCES = tools/lxc_wait.c \
 		   tools/arguments.c tools/arguments.h
@@ -381,6 +384,7 @@ init_lxc_SOURCES = cmd/lxc_init.c \
 		   memory_utils.h \
 		   parse.c parse.h \
 		   raw_syscalls.c raw_syscalls.h \
+		   syscall_numbers.h \
 		   string_utils.c string_utils.h
 
 init_lxc_LDFLAGS = -pthread
@@ -391,6 +395,7 @@ lxc_monitord_SOURCES = cmd/lxc_monitord.c \
 		       mainloop.c mainloop.h \
 		       monitor.c monitor.h \
 		       raw_syscalls.c raw_syscalls.h \
+		       syscall_numbers.h \
 		       utils.c utils.h
 lxc_user_nic_SOURCES = cmd/lxc_user_nic.c \
 		       ../include/netns_ifaddrs.c ../include/netns_ifaddrs.h \
@@ -399,6 +404,7 @@ lxc_user_nic_SOURCES = cmd/lxc_user_nic.c \
 		       network.c network.h \
 		       parse.c parse.h \
 		       raw_syscalls.c raw_syscalls.h \
+		       syscall_numbers.h \
 		       file_utils.c file_utils.h \
 		       string_utils.c string_utils.h \
 		       syscall_wrappers.h

src/lxc/cgroups/cgroup2_devices.h

@@ -17,50 +17,24 @@
 
 #include "conf.h"
 #include "config.h"
+#include "syscall_numbers.h"
 
 #ifdef HAVE_STRUCT_BPF_CGROUP_DEV_CTX
 #include <linux/bpf.h>
 #include <linux/filter.h>
 #endif
 
-#if !HAVE_BPF
-#if !(defined __NR_bpf && __NR_bpf > 0)
-#if defined __NR_bpf
-#undef __NR_bpf
-#endif
-#if defined __i386__
-#define __NR_bpf 357
-#elif defined __x86_64__
-#define __NR_bpf 321
-#elif defined __aarch64__
-#define __NR_bpf 280
-#elif defined __arm__
-#define __NR_bpf 386
-#elif defined __sparc__
-#define __NR_bpf 349
-#elif defined __s390__
-#define __NR_bpf 351
-#elif defined __tilegx__
-#define __NR_bpf 280
-#else
-#warning "__NR_bpf not defined for your architecture"
-#endif
-#endif
+#ifndef HAVE_BPF
 
 union bpf_attr;
 
 static inline int missing_bpf(int cmd, union bpf_attr *attr, size_t size)
 {
-#ifdef __NR_bpf
-	return (int)syscall(__NR_bpf, cmd, attr, size);
-#else
-	errno = ENOSYS;
-	return -1;
-#endif
+	return syscall(__NR_bpf, cmd, attr, size);
 }
 
 #define bpf missing_bpf
-#endif
+#endif /* HAVE_BPF */
 
 struct bpf_program {
 	int device_list_type;
@@ -70,7 +44,7 @@ struct bpf_program {
 	size_t n_instructions;
 #ifdef HAVE_STRUCT_BPF_CGROUP_DEV_CTX
 	struct bpf_insn *instructions;
-#endif
+#endif /* HAVE_STRUCT_BPF_CGROUP_DEV_CTX */
 
 	char *attached_path;
 	int attached_type;
@@ -97,7 +71,7 @@ static inline void __auto_bpf_program_free__(struct bpf_program **prog)
 	}
 }
 int bpf_list_add_device(struct lxc_conf *conf, struct device_item *device);
-#else
+#else /* !HAVE_STRUCT_BPF_CGROUP_DEV_CTX */
 static inline struct bpf_program *bpf_program_new(uint32_t prog_type)
 {
 	errno = ENOSYS;
@@ -160,7 +134,7 @@ static inline int bpf_list_add_device(struct lxc_conf *conf,
 	errno = ENOSYS;
 	return -1;
 }
-#endif
+#endif /* !HAVE_STRUCT_BPF_CGROUP_DEV_CTX */
 
 #define __do_bpf_program_free \
 	__attribute__((__cleanup__(__auto_bpf_program_free__)))

src/lxc/lxccontainer.c

@@ -81,19 +81,6 @@
 #include "include/strlcpy.h"
 #endif
 
-/* Define faccessat() if missing from the C library */
-#ifndef HAVE_FACCESSAT
-static int faccessat(int __fd, const char *__file, int __type, int __flag)
-{
-#ifdef __NR_faccessat
-	return syscall(__NR_faccessat, __fd, __file, __type, __flag);
-#else
-	errno = ENOSYS;
-	return -1;
-#endif
-}
-#endif
-
 lxc_log_define(lxccontainer, lxc);
 
 static bool do_lxcapi_destroy(struct lxc_container *c);

src/lxc/raw_syscalls.c

@@ -15,16 +15,12 @@
 #include "config.h"
 #include "macro.h"
 #include "raw_syscalls.h"
+#include "syscall_numbers.h"
 
 int lxc_raw_execveat(int dirfd, const char *pathname, char *const argv[],
 		     char *const envp[], int flags)
 {
-#ifdef __NR_execveat
-	syscall(__NR_execveat, dirfd, pathname, argv, envp, flags);
-#else
-	errno = ENOSYS;
-#endif
-	return -1;
+	return syscall(__NR_execveat, dirfd, pathname, argv, envp, flags);
 }
 
 /*
@@ -123,11 +119,6 @@ pid_t lxc_raw_clone_cb(int (*fn)(void *), void *args, unsigned long flags,
 	return pid;
 }
 
-/* For all the architectures we care about it's the same syscall number. */
-#ifndef __NR_pidfd_send_signal
-#define __NR_pidfd_send_signal 424
-#endif
-
 int lxc_raw_pidfd_send_signal(int pidfd, int sig, siginfo_t *info,
 			      unsigned int flags)
 {

src/lxc/raw_syscalls.h

@@ -81,7 +81,7 @@ static inline pid_t lxc_raw_getpid(void)
 
 static inline pid_t lxc_raw_gettid(void)
 {
-#ifdef __NR_gettid
+#if __NR_gettid > 0
 	return syscall(__NR_gettid);
 #else
 	return lxc_raw_getpid();

src/lxc/seccomp.c

@@ -38,12 +38,7 @@ lxc_log_define(seccomp, lxc);
 static inline int __seccomp(unsigned int operation, unsigned int flags,
 			  void *args)
 {
-#ifdef __NR_seccomp
 	return syscall(__NR_seccomp, operation, flags, args);
-#else
-	errno = ENOSYS;
-	return -1;
-#endif
 }
 #endif