[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>

1 files changed, 86 insertions, 0 deletions

diff --git a/src/include/ipxe/linux_api.h b/src/include/ipxe/linux_api.h
new file mode 100644
index 000000000..ea247a613
--- /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 */