[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>

29 files changed, 553 insertions, 601 deletions

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index d890dfb..6dc577e 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -14,9 +14,11 @@ jobs:
           fetch-depth: 0
       - name: Install packages
         run: |
+          sudo dpkg --add-architecture i386
           sudo apt update
           sudo apt install -y -o Acquire::Retries=50 \
-                           mtools syslinux isolinux libc6-dev-i386 valgrind
+                           mtools syslinux isolinux \
+                           libc6-dev-i386 libc6-dbg:i386 valgrind
       - name: Build (BIOS)
         run: |
           make -j 4 -C src
diff --git a/src/Makefile.linux b/src/Makefile.linux
new file mode 100644
index 0000000..4a78379
--- /dev/null
+++ b/src/Makefile.linux
@@ -0,0 +1,39 @@
+# -*- makefile -*- : Force emacs to use Makefile mode
+
+# Prefix all iPXE symbols to avoid collisions with platform libraries
+#
+SYMBOL_PREFIX	= _ipxe__
+
+# Enable valgrind
+#
+CFLAGS		+= -UNVALGRIND
+
+# Use a two-stage link
+#
+LDFLAGS		+= -r -d
+
+# Source directories
+#
+SRCDIRS		+= drivers/linux
+SRCDIRS		+= interface/linux
+NON_AUTO_SRCS	+= interface/linux/linux_api.c
+
+# Media types
+#
+NON_AUTO_MEDIA = linux
+
+# Compiler flags for building host API wrapper
+#
+LINUX_CFLAGS	+= -Os -idirafter include -DSYMBOL_PREFIX=$(SYMBOL_PREFIX)
+
+# Host API wrapper
+#
+$(BIN)/linux_api.o : interface/linux/linux_api.c $(MAKEDEPS)
+	$(QM)$(ECHO) "  [BUILD] $@"
+	$(Q)$(CC) $(LINUX_CFLAGS) $(WORKAROUND_CFLAGS) -o $@ -c $<
+
+# Rule to generate final binary
+#
+$(BIN)/%.linux : $(BIN)/%.linux.tmp $(BIN)/linux_api.o
+	$(QM)$(ECHO) "  [FINISH] $@"
+	$(Q)$(CC) $(LINUX_CFLAGS) $(WORKAROUND_CFLAGS) -o $@ $^
diff --git a/src/arch/i386/Makefile.linux b/src/arch/i386/Makefile.linux
index 46328c8..fe4229e 100644
--- a/src/arch/i386/Makefile.linux
+++ b/src/arch/i386/Makefile.linux
@@ -1,6 +1,14 @@
+# -*- makefile -*- : Force emacs to use Makefile mode
+
+# Linker script
+#
 LDSCRIPT = arch/i386/scripts/linux.lds
 
-SRCDIRS += arch/i386/core/linux
+# Compiler flags for building host API wrapper
+#
+LINUX_CFLAGS	+= -m32
 
+# Include generic Linux Makefile
+#
 MAKEDEPS += arch/x86/Makefile.linux
 include arch/x86/Makefile.linux
diff --git a/src/arch/i386/core/linux/linux_syscall.S b/src/arch/i386/core/linux/linux_syscall.S
deleted file mode 100644
index 38a3e74..0000000
--- a/src/arch/i386/core/linux/linux_syscall.S
+++ /dev/null
@@ -1,45 +0,0 @@
-
-	.section ".data"
-	.globl linux_errno
-
-linux_errno:	.int 0
-
-	.section ".text"
-	.code32
-	.globl linux_syscall
-	.type  linux_syscall, @function
-
-linux_syscall:
-	/* Save registers */
-	pushl	%ebx
-	pushl	%esi
-	pushl	%edi
-	pushl	%ebp
-
-	movl	20(%esp), %eax  // C arg1 -> syscall number
-	movl	24(%esp), %ebx  // C arg2 -> syscall arg1
-	movl	28(%esp), %ecx  // C arg3 -> syscall arg2
-	movl	32(%esp), %edx  // C arg4 -> syscall arg3
-	movl	36(%esp), %esi  // C arg5 -> syscall arg4
-	movl	40(%esp), %edi  // C arg6 -> syscall arg5
-	movl	44(%esp), %ebp  // C arg7 -> syscall arg6
-
-	int	$0x80
-
-	/* Restore registers */
-	popl	%ebp
-	popl	%edi
-	popl	%esi
-	popl	%ebx
-
-	cmpl	$-4095, %eax
-	jae	1f
-	ret
-
-1:
-	negl	%eax
-	movl	%eax, linux_errno
-	movl	$-1, %eax
-	ret
-
-	.size linux_syscall, . - linux_syscall
diff --git a/src/arch/i386/core/linux/linuxprefix.S b/src/arch/i386/core/linux/linuxprefix.S
deleted file mode 100644
index 398d3cb..0000000
--- a/src/arch/i386/core/linux/linuxprefix.S
+++ /dev/null
@@ -1,28 +0,0 @@
-#include <linux/unistd.h>
-
-	.section ".text"
-	.code32
-	.globl _linux_start
-	.type _linux_start, @function
-
-_linux_start:
-	xorl	%ebp, %ebp
-
-	popl	%esi       // save argc
-	movl	%esp, %edi // save argv
-
-	andl	$~15, %esp // 16-byte align the stack
-
-	pushl	%edi // argv -> C arg2
-	pushl	%esi // argc -> C arg1
-
-	call	save_args
-
-	/* Our main doesn't use any arguments */
-	call	main
-
-	movl	%eax, %ebx // rc -> syscall arg1
-	movl	$__NR_exit, %eax
-	int	$0x80
-
-	.size _linux_start, . - _linux_start
diff --git a/src/arch/i386/include/bits/linux_api.h b/src/arch/i386/include/bits/linux_api.h
deleted file mode 100644
index dc6e741..0000000
--- a/src/arch/i386/include/bits/linux_api.h
+++ /dev/null
@@ -1,6 +0,0 @@
-#ifndef _I386_LINUX_API_H
-#define _I386_LINUX_API_H
-
-#define __SYSCALL_mmap __NR_mmap2
-
-#endif /* _I386_LINUX_API_H */
diff --git a/src/arch/x86/Makefile.linux b/src/arch/x86/Makefile.linux
index 3740cc8..b600655 100644
--- a/src/arch/x86/Makefile.linux
+++ b/src/arch/x86/Makefile.linux
@@ -1,15 +1,10 @@
-MEDIA = linux
-
-# enable valgrind
-CFLAGS += -UNVALGRIND
-
-SYMBOL_PREFIX = _ipxe__
+# -*- makefile -*- : Force emacs to use Makefile mode
 
+# Include x86 Linux headers
+#
 INCDIRS += arch/x86/include/linux
-SRCDIRS += interface/linux
-SRCDIRS += drivers/linux
-SRCDIRS += arch/x86/core/linux
 
-$(BIN)/%.linux : $(BIN)/%.linux.tmp
-	$(QM)$(ECHO) "  [FINISH] $@"
-	$(Q)$(CP) $< $@
+# Include generic Linux Makefile
+#
+MAKEDEPS	+= Makefile.linux
+include Makefile.linux
diff --git a/src/arch/x86/core/linux/linux_api.c b/src/arch/x86/core/linux/linux_api.c
deleted file mode 100644
index 17b1f3f..0000000
--- a/src/arch/x86/core/linux/linux_api.c
+++ /dev/null
@@ -1,149 +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.
- */
-
-FILE_LICENCE ( GPL2_OR_LATER );
-
-/** @file
- *
- * Implementation of most of the linux API.
- */
-
-#include <linux_api.h>
-
-#include <stdarg.h>
-#include <asm/unistd.h>
-#include <string.h>
-
-int linux_open ( const char *pathname, int flags ) {
-	return linux_syscall ( __NR_open, pathname, flags );
-}
-
-int linux_close ( int fd ) {
-	return linux_syscall ( __NR_close, fd );
-}
-
-off_t linux_lseek ( int fd, off_t offset, int whence ) {
-	return linux_syscall ( __NR_lseek, fd, offset, whence );
-}
-
-__kernel_ssize_t linux_read ( int fd, void *buf, __kernel_size_t count ) {
-	return linux_syscall ( __NR_read, fd, buf, count );
-}
-
-__kernel_ssize_t linux_write ( int fd, const void *buf,
-			       __kernel_size_t count ) {
-	return linux_syscall  (  __NR_write, fd, buf, count );
-}
-
-int linux_fcntl ( int fd, int cmd, ... ) {
-	long arg;
-	va_list list;
-
-	va_start ( list, cmd );
-	arg = va_arg ( list, long );
-	va_end ( list );
-
-	return linux_syscall ( __NR_fcntl, fd, cmd, arg );
-}
-
-int linux_ioctl ( int fd, int request, ... ) {
-	void *arg;
-	va_list list;
-
-	va_start ( list, request );
-	arg = va_arg ( list, void * );
-	va_end ( list );
-
-	return linux_syscall ( __NR_ioctl, fd, request, arg );
-}
-
-int linux_poll ( struct pollfd *fds, nfds_t nfds, int timeout ) {
-	return linux_syscall ( __NR_poll, fds, nfds, timeout );
-}
-
-int linux_nanosleep ( const struct timespec *req, struct timespec *rem ) {
-	return linux_syscall ( __NR_nanosleep, req, rem );
-}
-
-int linux_usleep ( useconds_t usec ) {
-	struct timespec ts = {
-		.tv_sec = ( ( long ) ( usec / 1000000 ) ),
-		.tv_nsec = ( ( long ) ( usec % 1000000 ) * 1000UL ),
-	};
-
-	return linux_nanosleep ( &ts, NULL );
-}
-
-int linux_gettimeofday ( struct timeval *tv, struct timezone *tz ) {
-	return linux_syscall ( __NR_gettimeofday, tv, tz );
-}
-
-void * linux_mmap ( void *addr, __kernel_size_t length, int prot, int flags,
-		    int fd, __kernel_off_t offset ) {
-	return ( void * ) linux_syscall ( __SYSCALL_mmap, addr, length, prot,
-					  flags, fd, offset );
-}
-
-void * linux_mremap ( void *old_address, __kernel_size_t old_size,
-		      __kernel_size_t new_size, int flags ) {
-	return ( void * ) linux_syscall ( __NR_mremap, old_address, old_size,
-					  new_size, flags );
-}
-
-int linux_munmap ( void *addr, __kernel_size_t length ) {
-	return linux_syscall ( __NR_munmap, addr, length );
-}
-
-int linux_socket ( int domain, int type_, int protocol ) {
-#ifdef __NR_socket
-	return linux_syscall ( __NR_socket, domain, type_, protocol );
-#else
-#ifndef SOCKOP_socket
-# define SOCKOP_socket 1
-#endif
-	unsigned long sc_args[] = { domain, type_, protocol };
-	return linux_syscall ( __NR_socketcall, SOCKOP_socket, sc_args );
-#endif
-}
-
-int linux_bind ( int fd, const struct sockaddr *addr, socklen_t addrlen ) {
-#ifdef __NR_bind
-	return linux_syscall ( __NR_bind, fd, addr, addrlen );
-#else
-#ifndef SOCKOP_bind
-# define SOCKOP_bind 2
-#endif
-	unsigned long sc_args[] = { fd, (unsigned long)addr, addrlen };
-	return linux_syscall ( __NR_socketcall, SOCKOP_bind, sc_args );
-#endif
-}
-
-ssize_t linux_sendto ( int fd, const void *buf, size_t len, int flags,
-		       const struct sockaddr *daddr, socklen_t addrlen ) {
-#ifdef __NR_sendto
-	return linux_syscall ( __NR_sendto, fd, buf, len, flags,
-			       daddr, addrlen );
-#else
-#ifndef SOCKOP_sendto
-# define SOCKOP_sendto 11
-#endif
-	unsigned long sc_args[] = { fd, (unsigned long)buf, len,
-				    flags, (unsigned long)daddr, addrlen };
-	return linux_syscall ( __NR_socketcall, SOCKOP_sendto, sc_args );
-#endif
-}
diff --git a/src/arch/x86/core/linux/linux_strerror.c b/src/arch/x86/core/linux/linux_strerror.c
deleted file mode 100644
index 24c9b77..0000000
--- a/src/arch/x86/core/linux/linux_strerror.c
+++ /dev/null
@@ -1,169 +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.
- */
-
-FILE_LICENCE(GPL2_OR_LATER);
-
-/** @file
- *
- * linux_strerror implementation
- */
-
-#include <linux_api.h>
-#include <stdio.h>
-
-/** Error names from glibc */
-static const char *errors[] = {
-	"Success",
-	"Operation not permitted",
-	"No such file or directory",
-	"No such process",
-	"Interrupted system call",
-	"Input/output error",
-	"No such device or address",
-	"Argument list too long",
-	"Exec format error",
-	"Bad file descriptor",
-	"No child processes",
-	"Resource temporarily unavailable",
-	"Cannot allocate memory",
-	"Permission denied",
-	"Bad address",
-	"Block device required",
-	"Device or resource busy",
-	"File exists",
-	"Invalid cross-device link",
-	"No such device",
-	"Not a directory",
-	"Is a directory",
-	"Invalid argument",
-	"Too many open files in system",
-	"Too many open files",
-	"Inappropriate ioctl for device",
-	"Text file busy",
-	"File too large",
-	"No space left on device",
-	"Illegal seek",
-	"Read-only file system",
-	"Too many links",
-	"Broken pipe",
-	"Numerical argument out of domain",
-	"Numerical result out of range",
-	"Resource deadlock avoided",
-	"File name too long",
-	"No locks available",
-	"Function not implemented",
-	"Directory not empty",
-	"Too many levels of symbolic links",
-	"",
-	"No message of desired type",
-	"Identifier removed",
-	"Channel number out of range",
-	"Level 2 not synchronized",
-	"Level 3 halted",
-	"Level 3 reset",
-	"Link number out of range",
-	"Protocol driver not attached",
-	"No CSI structure available",
-	"Level 2 halted",
-	"Invalid exchange",
-	"Invalid request descriptor",
-	"Exchange full",
-	"No anode",
-	"Invalid request code",
-	"Invalid slot",
-	"",
-	"Bad font file format",
-	"Device not a stream",
-	"No data available",
-	"Timer expired",
-	"Out of streams resources",
-	"Machine is not on the network",
-	"Package not installed",
-	"Object is remote",
-	"Link has been severed",
-	"Advertise error",
-	"Srmount error",
-	"Communication error on send",
-	"Protocol error",
-	"Multihop attempted",
-	"RFS specific error",
-	"Bad message",
-	"Value too large for defined data type",
-	"Name not unique on network",
-	"File descriptor in bad state",
-	"Remote address changed",
-	"Can not access a needed shared library",
-	"Accessing a corrupted shared library",
-	".lib section in a.out corrupted",
-	"Attempting to link in too many shared libraries",
-	"Cannot exec a shared library directly",
-	"Invalid or incomplete multibyte or wide character",
-	"Interrupted system call should be restarted",
-	"Streams pipe error",
-	"Too many users",
-	"Socket operation on non-socket",
-	"Destination address required",
-	"Message too long",
-	"Protocol wrong type for socket",
-	"Protocol not available",
-	"Protocol not supported",
-	"Socket type not supported",
-	"Operation not supported",
-	"Protocol family not supported",
-	"Address family not supported by protocol",
-	"Address already in use",
-	"Cannot assign requested address",
-	"Network is down",
-	"Network is unreachable",
-	"Network dropped connection on reset",
-	"Software caused connection abort",
-	"Connection reset by peer",
-	"No buffer space available",
-	"Transport endpoint is already connected",
-	"Transport endpoint is not connected",
-	"Cannot send after transport endpoint shutdown",
-	"Too many references: cannot splice",
-	"Connection timed out",
-	"Connection refused",
-	"Host is down",
-	"No route to host",
-	"Operation already in progress",
-	"Operation now in progress",
-	"Stale NFS file handle",
-	"Structure needs cleaning",
-	"Not a XENIX named type file",
-	"No XENIX semaphores available",
-	"Is a named type file",
-	"Remote I/O error",
-	"Disk quota exceeded",
-	"No medium found",
-	"Wrong medium type",
-};
-
-const char *linux_strerror(int errnum)
-{
-	static char errbuf[64];
-	static int errors_size = sizeof(errors) / sizeof(*errors);
-	
-	if (errnum >= errors_size || errnum < 0) {
-		snprintf(errbuf, sizeof(errbuf), "Error %#08x", errnum);
-		return errbuf;
-	} else {
-		return errors[errnum];
-	}
-}
diff --git a/src/arch/x86/include/bits/linux_api_platform.h b/src/arch/x86/include/bits/linux_api_platform.h
deleted file mode 100644
index 4a9ced5..0000000
--- a/src/arch/x86/include/bits/linux_api_platform.h
+++ /dev/null
@@ -1,6 +0,0 @@
-#ifndef _LINUX_API_PLATFORM_H
-#define _LINUX_API_PLATFORM_H
-
-extern int linux_errno;
-
-#endif /* _LINUX_API_PLATFORM_H */
diff --git a/src/arch/x86_64/Makefile.linux b/src/arch/x86_64/Makefile.linux
index 154f9d4..c41ee49 100644
--- a/src/arch/x86_64/Makefile.linux
+++ b/src/arch/x86_64/Makefile.linux
@@ -1,6 +1,10 @@
-LDSCRIPT = arch/x86_64/scripts/linux.lds
+# -*- makefile -*- : Force emacs to use Makefile mode
 
-SRCDIRS += arch/x86_64/core/linux
+# Linker script
+#
+LDSCRIPT = arch/x86_64/scripts/linux.lds
 
+# Include generic Linux Makefile
+#
 MAKEDEPS += arch/x86/Makefile.linux
 include arch/x86/Makefile.linux
diff --git a/src/arch/x86_64/core/linux/linux_syscall.S b/src/arch/x86_64/core/linux/linux_syscall.S
deleted file mode 100644
index d2805f9..0000000
--- a/src/arch/x86_64/core/linux/linux_syscall.S
+++ /dev/null
@@ -1,33 +0,0 @@
-
-	.section ".data"
-	.globl linux_errno
-
-linux_errno:	.int 0
-
-	.section ".text"
-	.code64
-	.globl linux_syscall
-	.type  linux_syscall, @function
-
-linux_syscall:
-	movq	%rdi, %rax    // C arg1 -> syscall number
-	movq	%rsi, %rdi    // C arg2 -> syscall arg1
-	movq	%rdx, %rsi    // C arg3 -> syscall arg2
-	movq	%rcx, %rdx    // C arg4 -> syscall arg3
-	movq	%r8, %r10     // C arg5 -> syscall arg4
-	movq	%r9, %r8      // C arg6 -> syscall arg5
-	movq	8(%rsp), %r9  // C arg7 -> syscall arg6
-
-	syscall
-
-	cmpq	$-4095, %rax
-	jae	1f
-	ret
-
-1:
-	negq	%rax
-	movl	%eax, linux_errno
-	movq	$-1, %rax
-	ret
-
-	.size linux_syscall, . - linux_syscall
diff --git a/src/arch/x86_64/core/linux/linuxprefix.S b/src/arch/x86_64/core/linux/linuxprefix.S
deleted file mode 100644
index ec8a9de..0000000
--- a/src/arch/x86_64/core/linux/linuxprefix.S
+++ /dev/null
@@ -1,25 +0,0 @@
-#include <linux/unistd.h>
-
-	.section ".text"
-	.code64
-	.globl _linux_start
-	.type _linux_start, @function
-
-_linux_start:
-	xorq	%rbp, %rbp
-
-	popq	%rdi       // argc -> C arg1
-	movq	%rsp, %rsi // argv -> C arg2
-
-	andq	$~15, %rsp // 16-byte align the stack
-
-	call	save_args
-
-	/* Our main doesn't use any arguments */
-	call	main
-
-	movq	%rax, %rdi // rc -> syscall arg1
-	movq	$__NR_exit, %rax
-	syscall
-
-	.size _linux_start, . - _linux_start
diff --git a/src/arch/x86_64/include/bits/linux_api.h b/src/arch/x86_64/include/bits/linux_api.h
deleted file mode 100644
index 589fb58..0000000
--- a/src/arch/x86_64/include/bits/linux_api.h
+++ /dev/null
@@ -1,6 +0,0 @@
-#ifndef _X86_64_LINUX_API_H
-#define _X86_64_LINUX_API_H
-
-#define __SYSCALL_mmap __NR_mmap
-
-#endif /* _X86_64_LINUX_API_H */
diff --git a/src/drivers/linux/af_packet.c b/src/drivers/linux/af_packet.c
index 65aafc5..9fa6ef2 100644
--- a/src/drivers/linux/af_packet.c
+++ b/src/drivers/linux/af_packet.c
@@ -19,7 +19,7 @@
 #include <errno.h>
 #include <string.h>
 #include <stdio.h>
-#include <linux_api.h>
+#include <ipxe/linux_api.h>
 #include <ipxe/list.h>
 #include <ipxe/linux.h>
 #include <ipxe/malloc.h>
diff --git a/src/drivers/linux/tap.c b/src/drivers/linux/tap.c
index db3b795..ff1e08b 100644
--- a/src/drivers/linux/tap.c
+++ b/src/drivers/linux/tap.c
@@ -19,7 +19,7 @@
 #include <errno.h>
 #include <string.h>
 #include <stdio.h>
-#include <linux_api.h>
+#include <ipxe/linux_api.h>
 #include <ipxe/list.h>
 #include <ipxe/linux.h>
 #include <ipxe/malloc.h>
diff --git a/src/hci/linux_args.c b/src/hci/linux_args.c
index 5f903e3..12020bd 100644
--- a/src/hci/linux_args.c
+++ b/src/hci/linux_args.c
@@ -18,7 +18,6 @@
 
 FILE_LICENCE(GPL2_OR_LATER);
 
-#include <hci/linux_args.h>
 #include <getopt.h>
 #include <string.h>
 #include <stdio.h>
@@ -27,21 +26,8 @@ FILE_LICENCE(GPL2_OR_LATER);
 #include <ipxe/malloc.h>
 #include <ipxe/init.h>
 
-/** Saved argc */
-static int saved_argc = 0;
-/** Saved argv */
-static char ** saved_argv;
-
-/**
- * Save argc and argv for later access.
- *
- * To be called by linuxprefix
- */
-__asmcall void save_args(int argc, char **argv)
-{
-	saved_argc = argc;
-	saved_argv = argv;
-}
+int linux_argc;
+char **linux_argv;
 
 /** Supported command-line options */
 static struct option options[] = {
@@ -138,7 +124,7 @@ void linux_args_parse()
 	while (1) {
 		int option_index = 0;
 
-		c = getopt_long(saved_argc, saved_argv, "", options, &option_index);
+		c = getopt_long(linux_argc, linux_argv, "", options, &option_index);
 		if (c == -1)
 			break;
 
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 */
diff --git a/src/interface/linux/linux_api.c b/src/interface/linux/linux_api.c
new file mode 100644
index 0000000..4ab3c66
--- /dev/null
+++ b/src/interface/linux/linux_api.c
@@ -0,0 +1,373 @@
+/*
+ * 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 Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#define _GNU_SOURCE
+#include <stdint.h>
+#include <stdarg.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <time.h>
+#include <poll.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/socket.h>
+#include <sys/time.h>
+#include <ipxe/linux_api.h>
+
+/** @file
+ *
+ * Linux host API
+ *
+ */
+
+/** Construct prefixed symbol name */
+#define _C1( x, y ) x ## y
+#define _C2( x, y ) _C1 ( x, y )
+
+/** Construct prefixed symbol name for iPXE symbols */
+#define IPXE_SYM( symbol ) _C2 ( SYMBOL_PREFIX, symbol )
+
+/** Provide a prefixed symbol alias visible to iPXE code */
+#define PROVIDE_IPXE_SYM( symbol )					\
+	extern typeof ( symbol ) IPXE_SYM ( symbol )			\
+		__attribute__ (( alias ( #symbol) ))
+
+/** Most recent system call error */
+int linux_errno __attribute__ (( nocommon ));
+
+/******************************************************************************
+ *
+ * Host entry point
+ *
+ ******************************************************************************
+ */
+
+extern int IPXE_SYM ( _linux_start ) ( int argc, char **argv );
+
+/**
+ * Main entry point
+ *
+ * @v argc		Argument count
+ * @v argv		Argument list
+ * @ret rc		Exit status
+ */
+int main ( int argc, char **argv ) {
+
+	return IPXE_SYM ( _linux_start ) ( argc, argv );
+}
+
+/******************************************************************************
+ *
+ * System call wrappers
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Wrap open()
+ *
+ */
+int __asmcall linux_open ( const char *pathname, int flags, ... ) {
+	va_list args;
+	mode_t mode;
+	int ret;
+
+	va_start ( args, flags );
+	mode = va_arg ( args, mode_t );
+	va_end ( args );
+	ret = open ( pathname, flags, mode );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap close()
+ *
+ */
+int __asmcall linux_close ( int fd ) {
+	int ret;
+
+	ret = close ( fd );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap lseek()
+ *
+ */
+off_t __asmcall linux_lseek ( int fd, off_t offset, int whence ) {
+	off_t ret;
+
+	ret = lseek ( fd, offset, whence );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap read()
+ *
+ */
+ssize_t __asmcall linux_read ( int fd, void *buf, size_t count ) {
+	ssize_t ret;
+
+	ret = read ( fd, buf, count );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap write()
+ *
+ */
+ssize_t __asmcall linux_write ( int fd, const void *buf, size_t count ) {
+	ssize_t ret;
+
+	ret = write ( fd, buf, count );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap fcntl()
+ *
+ */
+int __asmcall linux_fcntl ( int fd, int cmd, ... ) {
+	va_list args;
+	long arg;
+	int ret;
+
+	va_start ( args, cmd );
+	arg = va_arg ( args, long );
+	va_end ( args );
+	ret = fcntl ( fd, cmd, arg );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap ioctl()
+ *
+ */
+int __asmcall linux_ioctl ( int fd, unsigned long request, ... ) {
+	va_list args;
+	void *arg;
+	int ret;
+
+	va_start ( args, request );
+	arg = va_arg ( args, void * );
+	va_end ( args );
+	ret = ioctl ( fd, request, arg );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap poll()
+ *
+ */
+int __asmcall linux_poll ( struct pollfd *fds, unsigned int nfds,
+			   int timeout ) {
+	int ret;
+
+	ret = poll ( fds, nfds, timeout );
+	if ( ret == -1 )
+		linux_errno = errno;
+}
+
+/**
+ * Wrap nanosleep()
+ *
+ */
+int __asmcall linux_nanosleep ( const struct timespec *req,
+				struct timespec *rem ) {
+	int ret;
+
+	ret = nanosleep ( req, rem );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap usleep()
+ *
+ */
+int __asmcall linux_usleep ( unsigned int usec ) {
+	int ret;
+
+	ret = usleep ( usec );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap gettimeofday()
+ *
+ */
+int __asmcall linux_gettimeofday ( struct timeval *tv, struct timezone *tz ) {
+	int ret;
+
+	ret = gettimeofday ( tv, tz );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap mmap()
+ *
+*/
+void * __asmcall linux_mmap ( void *addr, size_t length, int prot, int flags,
+			      int fd, off_t offset ) {
+	void *ret;
+
+	ret = mmap ( addr, length, prot, flags, fd, offset );
+	if ( ret == MAP_FAILED )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap mremap()
+ *
+ */
+void * __asmcall linux_mremap ( void *old_address, size_t old_size,
+				size_t new_size, int flags, ... ) {
+	va_list args;
+	void *new_address;
+	void *ret;
+
+	va_start ( args, flags );
+	new_address = va_arg ( args, void * );
+	va_end ( args );
+	ret = mremap ( old_address, old_size, new_size, flags, new_address );
+	if ( ret == MAP_FAILED )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap munmap()
+ *
+ */
+int __asmcall linux_munmap ( void *addr, size_t length ) {
+	int ret;
+
+	ret = munmap ( addr, length );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap socket()
+ *
+ */
+int __asmcall linux_socket ( int domain, int type, int protocol ) {
+	int ret;
+
+	ret = socket ( domain, type, protocol );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap bind()
+ *
+ */
+int __asmcall linux_bind ( int sockfd, const struct sockaddr *addr,
+			   size_t addrlen ) {
+	int ret;
+
+	ret = bind ( sockfd, addr, addrlen );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/**
+ * Wrap sendto()
+ *
+ */
+ssize_t __asmcall linux_sendto ( int sockfd, const void *buf, size_t len,
+				 int flags, const struct sockaddr *dest_addr,
+				 size_t addrlen ) {
+	ssize_t ret;
+
+	ret = sendto ( sockfd, buf, len, flags, dest_addr, addrlen );
+	if ( ret == -1 )
+		linux_errno = errno;
+	return ret;
+}
+
+/******************************************************************************
+ *
+ * C library wrappers
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Wrap strerror()
+ *
+ */
+const char * __asmcall linux_strerror ( int linux_errno ) {
+
+	return strerror ( linux_errno );
+}
+
+/******************************************************************************
+ *
+ * Symbol aliases
+ *
+ ******************************************************************************
+ */
+
+PROVIDE_IPXE_SYM ( linux_errno );
+PROVIDE_IPXE_SYM ( linux_open );
+PROVIDE_IPXE_SYM ( linux_close );
+PROVIDE_IPXE_SYM ( linux_lseek );
+PROVIDE_IPXE_SYM ( linux_read );
+PROVIDE_IPXE_SYM ( linux_write );
+PROVIDE_IPXE_SYM ( linux_fcntl );
+PROVIDE_IPXE_SYM ( linux_ioctl );
+PROVIDE_IPXE_SYM ( linux_poll );
+PROVIDE_IPXE_SYM ( linux_nanosleep );
+PROVIDE_IPXE_SYM ( linux_usleep );
+PROVIDE_IPXE_SYM ( linux_gettimeofday );
+PROVIDE_IPXE_SYM ( linux_mmap );
+PROVIDE_IPXE_SYM ( linux_mremap );
+PROVIDE_IPXE_SYM ( linux_munmap );
+PROVIDE_IPXE_SYM ( linux_socket );
+PROVIDE_IPXE_SYM ( linux_bind );
+PROVIDE_IPXE_SYM ( linux_sendto );
+PROVIDE_IPXE_SYM ( linux_strerror );
diff --git a/src/interface/linux/linux_console.c b/src/interface/linux/linux_console.c
index 5294fca..d5415b6 100644
--- a/src/interface/linux/linux_console.c
+++ b/src/interface/linux/linux_console.c
@@ -28,7 +28,7 @@ FILE_LICENCE(GPL2_OR_LATER);
 
 #include <ipxe/init.h>
 #include <ipxe/keys.h>
-#include <linux_api.h>
+#include <ipxe/linux_api.h>
 
 #include <linux/termios.h>
 #include <asm/errno.h>
diff --git a/src/interface/linux/linux_entropy.c b/src/interface/linux/linux_entropy.c
index 0f8e45d..257e993 100644
--- a/src/interface/linux/linux_entropy.c
+++ b/src/interface/linux/linux_entropy.c
@@ -31,7 +31,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
 #include <stdint.h>
 #include <errno.h>
-#include <linux_api.h>
+#include <ipxe/linux_api.h>
 #include <ipxe/entropy.h>
 
 /** Entropy source filename */
diff --git a/src/interface/linux/linux_nap.c b/src/interface/linux/linux_nap.c
index f1d3cd9..3e77bc7 100644
--- a/src/interface/linux/linux_nap.c
+++ b/src/interface/linux/linux_nap.c
@@ -21,7 +21,7 @@ FILE_LICENCE(GPL2_OR_LATER);
 
 #include <ipxe/nap.h>
 
-#include <linux_api.h>
+#include <ipxe/linux_api.h>
 
 /** @file
  *
diff --git a/src/interface/linux/linux_pci.c b/src/interface/linux/linux_pci.c
index 0c140cb..99c629c 100644
--- a/src/interface/linux/linux_pci.c
+++ b/src/interface/linux/linux_pci.c
@@ -26,7 +26,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #include <stdio.h>
 #include <errno.h>
 #include <byteswap.h>
-#include <linux_api.h>
+#include <ipxe/linux_api.h>
 #include <ipxe/linux.h>
 #include <ipxe/pci.h>
 
diff --git a/src/interface/linux/linux_smbios.c b/src/interface/linux/linux_smbios.c
index 6e5174d..494a60b 100644
--- a/src/interface/linux/linux_smbios.c
+++ b/src/interface/linux/linux_smbios.c
@@ -20,7 +20,7 @@
 FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <errno.h>
-#include <linux_api.h>
+#include <ipxe/linux_api.h>
 #include <ipxe/linux.h>
 #include <ipxe/smbios.h>
 
diff --git a/src/interface/linux/linux_time.c b/src/interface/linux/linux_time.c
index 9e99fe9..9d410f8 100644
--- a/src/interface/linux/linux_time.c
+++ b/src/interface/linux/linux_time.c
@@ -32,7 +32,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #include <stdint.h>
 #include <stddef.h>
 #include <errno.h>
-#include <linux_api.h>
+#include <ipxe/linux_api.h>
 #include <ipxe/time.h>
 
 /**
diff --git a/src/interface/linux/linux_timer.c b/src/interface/linux/linux_timer.c
index 9c5e96f..418fd04 100644
--- a/src/interface/linux/linux_timer.c
+++ b/src/interface/linux/linux_timer.c
@@ -21,7 +21,7 @@ FILE_LICENCE(GPL2_OR_LATER);
 #include <stddef.h>
 #include <ipxe/timer.h>
 
-#include <linux_api.h>
+#include <ipxe/linux_api.h>
 
 /** @file
  *
diff --git a/src/interface/linux/linux_umalloc.c b/src/interface/linux/linux_umalloc.c
index aa0052c..a7250fa 100644
--- a/src/interface/linux/linux_umalloc.c
+++ b/src/interface/linux/linux_umalloc.c
@@ -29,7 +29,7 @@ FILE_LICENCE(GPL2_OR_LATER);
 #include <assert.h>
 #include <ipxe/umalloc.h>
 
-#include <linux_api.h>
+#include <ipxe/linux_api.h>
 
 /** Special address returned for empty allocations */
 #define NOWHERE ((void *)-1)
diff --git a/src/include/hci/linux_args.h b/src/interface/linux/linuxprefix.c
index ae1ed05..f382362 100644
--- a/src/include/hci/linux_args.h
+++ b/src/interface/linux/linuxprefix.c
@@ -1,5 +1,5 @@
 /*
- * 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
@@ -13,19 +13,26 @@
  *
  * 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.
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
  */
 
-#ifndef _HCI_LINUX_ARGS_H
-#define _HCI_LINUX_ARGS_H
-
-FILE_LICENCE(GPL2_OR_LATER);
+#include <stdlib.h>
+#include <ipxe/linux_api.h>
 
 /**
- * Save argc and argv for later access.
+ * Linux entry point
  *
- * To be called by linuxprefix
+ * @v argc		Argument count
+ * @v argv		Argument list
+ * @ret rc		Return status code
  */
-extern __asmcall void save_args(int argc, char **argv);
+int __asmcall _linux_start ( int argc, char **argv ) {
+
+	/* Store command-line arguments */
+	linux_argc = argc;
+	linux_argv = argv;
 
-#endif /* _HCI_LINUX_ARGS_H */
+	/* Run iPXE */
+	return main();
+}