[linux] Use host glibc system call wrappers

When building as a Linux userspace application, iPXE currently
implements its own system calls to the host kernel rather than relying
on the host's C library.  The output binary is statically linked and
has no external dependencies.

This matches the general philosophy of other platforms on which iPXE
runs, since there are no external libraries available on either BIOS
or UEFI bare metal.  However, it would be useful for the Linux
userspace application to be able to link against host libraries such
as libslirp.

Modify the build process to perform a two-stage link: first picking
out the requested objects in the usual way from blib.a but with
relocations left present, then linking again with a helper object to
create a standard hosted application.  The helper object provides the
standard main() entry point and wrappers for the Linux system calls
required by the iPXE Linux drivers and interface code.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

3 files changed, 86 insertions, 112 deletions

diff --git a/src/include/hci/linux_args.h b/src/include/hci/linux_args.h
deleted file mode 100644
index ae1ed05..0000000
--- a/src/include/hci/linux_args.h
+++ /dev/null
@@ -1,31 +0,0 @@
-/*
- * Copyright (C) 2010 Piotr Jaroszyński <p.jaroszynski@gmail.com>
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or any later version.
- *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- */
-
-#ifndef _HCI_LINUX_ARGS_H
-#define _HCI_LINUX_ARGS_H
-
-FILE_LICENCE(GPL2_OR_LATER);
-
-/**
- * Save argc and argv for later access.
- *
- * To be called by linuxprefix
- */
-extern __asmcall void save_args(int argc, char **argv);
-
-#endif /* _HCI_LINUX_ARGS_H */
diff --git a/src/include/ipxe/linux_api.h b/src/include/ipxe/linux_api.h
new file mode 100644
index 0000000..ea247a6
--- /dev/null
+++ b/src/include/ipxe/linux_api.h
@@ -0,0 +1,86 @@
+#ifndef _IPXE_LINUX_API_H
+#define _IPXE_LINUX_API_H
+
+/*
+ * Copyright (C) 2010 Piotr Jaroszyński <p.jaroszynski@gmail.com>.
+ * Copyright (C) 2021 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/** @file
+ *
+ * Linux host API
+ *
+ * This file is included from both the iPXE build environment and the
+ * host build environment.
+ *
+ */
+
+#if __STDC_HOSTED__
+#define __asmcall
+#define FILE_LICENCE(x)
+#endif
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+
+#if ! __STDC_HOSTED__
+#define __KERNEL_STRICT_NAMES
+#include <linux/time.h>
+#include <linux/mman.h>
+#include <linux/fcntl.h>
+#include <linux/ioctl.h>
+#include <linux/poll.h>
+#include <linux/fs.h>
+#define MAP_FAILED ( ( void * ) -1 )
+#endif
+
+struct sockaddr;
+
+extern int linux_errno;
+extern int linux_argc;
+extern char **linux_argv;
+
+extern int __asmcall linux_open ( const char *pathname, int flags, ... );
+extern int __asmcall linux_close ( int fd );
+extern off_t __asmcall linux_lseek ( int fd, off_t offset, int whence );
+extern ssize_t __asmcall linux_read ( int fd, void *buf, size_t count );
+extern ssize_t __asmcall linux_write ( int fd, const void *buf, size_t count );
+extern int __asmcall linux_fcntl ( int fd, int cmd, ... );
+extern int __asmcall linux_ioctl ( int fd, unsigned long request, ... );
+extern int __asmcall linux_poll ( struct pollfd *fds, unsigned int nfds,
+				  int timeout );
+extern int __asmcall linux_nanosleep ( const struct timespec *req,
+				       struct timespec *rem );
+extern int __asmcall linux_usleep ( unsigned int usec );
+extern int __asmcall linux_gettimeofday ( struct timeval *tv,
+					  struct timezone *tz );
+extern void * __asmcall linux_mmap ( void *addr, size_t length, int prot,
+				     int flags, int fd, off_t offset );
+extern void * __asmcall linux_mremap ( void *old_address, size_t old_size,
+				       size_t new_size, int flags, ... );
+extern int __asmcall linux_munmap ( void *addr, size_t length );
+extern int __asmcall linux_socket ( int domain, int type, int protocol );
+extern int __asmcall linux_bind ( int sockfd, const struct sockaddr *addr,
+				  size_t addrlen );
+extern ssize_t __asmcall linux_sendto ( int sockfd, const void *buf,
+					size_t len, int flags,
+					const struct sockaddr *dest_addr,
+					size_t addrlen );
+extern const char * __asmcall linux_strerror ( int linux_errno );
+
+#endif /* _IPXE_LINUX_API_H */
diff --git a/src/include/linux_api.h b/src/include/linux_api.h
deleted file mode 100644
index fe9fa91..0000000
--- a/src/include/linux_api.h
+++ /dev/null
@@ -1,81 +0,0 @@
-/*
- * Copyright (C) 2010 Piotr Jaroszyński <p.jaroszynski@gmail.com>
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or any later version.
- *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- */
-
-#ifndef _LINUX_API_H
-#define _LINUX_API_H
-
-/** * @file
- *
- * Linux API prototypes.
- * Most of the functions map directly to linux syscalls and are the equivalent
- * of POSIX functions with the linux_ prefix removed.
- */
-
-FILE_LICENCE(GPL2_OR_LATER);
-
-#include <bits/linux_api.h>
-#include <bits/linux_api_platform.h>
-
-#include <stdint.h>
-
-#define __KERNEL_STRICT_NAMES
-#include <linux/types.h>
-#include <linux/posix_types.h>
-typedef __kernel_pid_t pid_t;
-typedef __kernel_suseconds_t suseconds_t;
-typedef __kernel_loff_t loff_t;
-#include <linux/time.h>
-#include <linux/mman.h>
-#include <linux/fcntl.h>
-#include <linux/ioctl.h>
-#include <linux/poll.h>
-typedef unsigned long nfds_t;
-typedef uint32_t useconds_t;
-typedef uint32_t socklen_t;
-struct sockaddr;
-#define MAP_FAILED ( ( void * ) -1 )
-#define SEEK_SET 0
-
-extern long linux_syscall ( int number, ... );
-
-extern int linux_open ( const char *pathname, int flags );
-extern int linux_close ( int fd );
-extern off_t linux_lseek ( int fd, off_t offset, int whence );
-extern __kernel_ssize_t linux_read ( int fd, void *buf, __kernel_size_t count );
-extern __kernel_ssize_t linux_write ( int fd, const void *buf,
-				      __kernel_size_t count );
-extern int linux_fcntl ( int fd, int cmd, ... );
-extern int linux_ioctl ( int fd, int request, ... );
-extern int linux_poll ( struct pollfd *fds, nfds_t nfds, int timeout );
-extern int linux_nanosleep ( const struct timespec *req, struct timespec *rem );
-extern int linux_usleep ( useconds_t usec );
-extern int linux_gettimeofday ( struct timeval *tv, struct timezone *tz );
-extern void * linux_mmap ( void *addr, __kernel_size_t length, int prot,
-			   int flags, int fd, off_t offset );
-extern void * linux_mremap ( void *old_address, __kernel_size_t old_size,
-			     __kernel_size_t new_size, int flags );
-extern int linux_munmap ( void *addr, __kernel_size_t length );
-extern int linux_socket ( int domain, int type_, int protocol );
-extern int linux_bind ( int fd, const struct sockaddr *addr,
-			socklen_t addrlen );
-extern ssize_t linux_sendto ( int fd, const void *buf, size_t len, int flags,
-			      const struct sockaddr *daddr, socklen_t addrlen );
-
-extern const char * linux_strerror ( int errnum );
-
-#endif /* _LINUX_API_H */