[v12,01/10] x86/boot: implement early command line parser in C
diff mbox

Message ID 1484876060-2236-2-git-send-email-daniel.kiper@oracle.com
State New, archived
Headers show

Commit Message

Daniel Kiper Jan. 20, 2017, 1:34 a.m. UTC
Current early command line parser implementation in assembler
is very difficult to change to relocatable stuff using segment
registers. This requires a lot of changes in very weird and
fragile code. So, reimplement this functionality in C. This
way code will be relocatable out of the box (without playing
with segment registers) and much easier to maintain.

Additionally, put all common cmdline.c and reloc.c definitions
into defs.h header. This way we do not duplicate needlessly
some stuff.

And finally remove unused xen/include/asm-x86/config.h
header from reloc.c dependencies.

Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>
---
v7 - suggestions/fixes:
   - add min() macro
     (suggested by Jan Beulich),
   - add padding to early_boot_opts_t
     in more standard way
     (suggested by Jan Beulich),
   - simplify defs.h dependencies
     (suggested by Jan Beulich).

v6 - suggestions/fixes:
   - put common cmdline.c and reloc.c
     definitions into defs.h header
     (suggested by Jan Beulich),
   - use xen/include/xen/stdbool.h
     and bool type from it instead
     of own defined bool_t
     (suggested by Jan Beulich),
   - define delim_chars as constant
     (suggested by Jan Beulich),
   - properly align trampoline.S:early_boot_opts struct
     (suggested by Jan Beulich),
   - fix overflow check in strtoui()
     (suggested by Jan Beulich),
   - remove unused xen/include/asm-x86/config.h
     header from reloc.c dependencies,
   - improve commit message.

v4 - suggestions/fixes:
   - move to stdcall calling convention
     (suggested by Jan Beulich),
   - define bool_t and use it properly
     (suggested by Jan Beulich),
   - put list of delimiter chars into
     static const char[]
     (suggested by Jan Beulich),
   - use strlen() instead of strlen_opt()
     (suggested by Jan Beulich),
   - change strtoi() to strtoui() and
     optimize it a bit
     (suggested by Jan Beulich),
   - define strchr() and use it in strtoui()
     (suggested by Jan Beulich),
   - optimize vga_parse()
     (suggested by Jan Beulich),
   - move !cmdline check from assembly to C
     (suggested by Jan Beulich),
   - remove my name from copyright (Oracle requirement)
     (suggested by Konrad Rzeszutek Wilk).

v3 - suggestions/fixes:
   - optimize some code
     (suggested by Jan Beulich),
   - put VESA data into early_boot_opts_t members
     (suggested by Jan Beulich),
   - rename some functions and variables
     (suggested by Jan Beulich),
   - move around video.h include in xen/arch/x86/boot/trampoline.S
     (suggested by Jan Beulich),
   - fix coding style
     (suggested by Jan Beulich),
   - fix build with older GCC
     (suggested by Konrad Rzeszutek Wilk),
   - remove redundant comments
     (suggested by Jan Beulich),
   - add some comments
   - improve commit message
     (suggested by Jan Beulich).
---
 .gitignore                     |    5 +-
 xen/arch/x86/Makefile          |    2 +-
 xen/arch/x86/boot/Makefile     |   11 +-
 xen/arch/x86/boot/build32.mk   |    2 +
 xen/arch/x86/boot/cmdline.S    |  367 ----------------------------------------
 xen/arch/x86/boot/cmdline.c    |  340 +++++++++++++++++++++++++++++++++++++
 xen/arch/x86/boot/defs.h       |   58 +++++++
 xen/arch/x86/boot/edd.S        |    3 -
 xen/arch/x86/boot/head.S       |    9 +
 xen/arch/x86/boot/reloc.c      |    9 +-
 xen/arch/x86/boot/trampoline.S |   15 ++
 xen/arch/x86/boot/video.S      |    7 -
 12 files changed, 438 insertions(+), 390 deletions(-)
 delete mode 100644 xen/arch/x86/boot/cmdline.S
 create mode 100644 xen/arch/x86/boot/cmdline.c
 create mode 100644 xen/arch/x86/boot/defs.h

Comments

Doug Goldstein Jan. 20, 2017, 4:37 p.m. UTC | #1
On 1/19/17 8:34 PM, Daniel Kiper wrote:
> diff --git a/xen/arch/x86/boot/Makefile b/xen/arch/x86/boot/Makefile
> index 5fdb5ae..6d20646 100644
> --- a/xen/arch/x86/boot/Makefile
> +++ b/xen/arch/x86/boot/Makefile
> @@ -1,8 +1,15 @@
>  obj-bin-y += head.o
>  
> -RELOC_DEPS = $(BASEDIR)/include/asm-x86/config.h $(BASEDIR)/include/xen/multiboot.h
> +DEFS_H_DEPS = defs.h $(BASEDIR)/include/xen/stdbool.h
>  
> -head.o: reloc.S
> +CMDLINE_DEPS = $(DEFS_H_DEPS) video.h
> +
> +RELOC_DEPS = $(DEFS_H_DEPS) $(BASEDIR)/include/xen/multiboot.h

So when this was patch 8 this previously had:

+RELOC_DEPS = $(DEFS_H_DEPS) $(BASEDIR)/include/xen/multiboot.h \
+ 	     $(BASEDIR)/include/xen/multiboot2.h

Which its now moved to patch 1 so obviously can't include multiboot2.h
but then patch 2 in this series fails to add this and patch 5 fails to
add this.
Doug Goldstein Jan. 20, 2017, 4:41 p.m. UTC | #2
On 1/20/17 11:37 AM, Doug Goldstein wrote:
> On 1/19/17 8:34 PM, Daniel Kiper wrote:
>> diff --git a/xen/arch/x86/boot/Makefile b/xen/arch/x86/boot/Makefile
>> index 5fdb5ae..6d20646 100644
>> --- a/xen/arch/x86/boot/Makefile
>> +++ b/xen/arch/x86/boot/Makefile
>> @@ -1,8 +1,15 @@
>>  obj-bin-y += head.o
>>  
>> -RELOC_DEPS = $(BASEDIR)/include/asm-x86/config.h $(BASEDIR)/include/xen/multiboot.h
>> +DEFS_H_DEPS = defs.h $(BASEDIR)/include/xen/stdbool.h
>>  
>> -head.o: reloc.S
>> +CMDLINE_DEPS = $(DEFS_H_DEPS) video.h
>> +
>> +RELOC_DEPS = $(DEFS_H_DEPS) $(BASEDIR)/include/xen/multiboot.h
> 
> So when this was patch 8 this previously had:
> 
> +RELOC_DEPS = $(DEFS_H_DEPS) $(BASEDIR)/include/xen/multiboot.h \
> + 	     $(BASEDIR)/include/xen/multiboot2.h
> 
> Which its now moved to patch 1 so obviously can't include multiboot2.h
> but then patch 2 in this series fails to add this and patch 5 fails to
> add this.
> 

Ignore this. I missed it in patch 2 at first.

Patch
diff mbox

diff --git a/.gitignore b/.gitignore
index 7689596..f41c3d0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -252,9 +252,10 @@  xen/arch/arm/xen.lds
 xen/arch/x86/asm-offsets.s
 xen/arch/x86/boot/mkelf32
 xen/arch/x86/xen.lds
+xen/arch/x86/boot/cmdline.S
 xen/arch/x86/boot/reloc.S
-xen/arch/x86/boot/reloc.bin
-xen/arch/x86/boot/reloc.lnk
+xen/arch/x86/boot/*.bin
+xen/arch/x86/boot/*.lnk
 xen/arch/x86/efi.lds
 xen/arch/x86/efi/check.efi
 xen/arch/x86/efi/disabled
diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 7f6b5d7..007dced 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -220,5 +220,5 @@  clean::
 	rm -f asm-offsets.s *.lds boot/*.o boot/*~ boot/core boot/mkelf32
 	rm -f $(BASEDIR)/.xen-syms.[0-9]* boot/.*.d
 	rm -f $(BASEDIR)/.xen.efi.[0-9]* efi/*.o efi/.*.d efi/*.efi efi/disabled efi/mkreloc
-	rm -f boot/reloc.S boot/reloc.lnk boot/reloc.bin
+	rm -f boot/cmdline.S boot/reloc.S boot/*.lnk boot/*.bin
 	rm -f note.o
diff --git a/xen/arch/x86/boot/Makefile b/xen/arch/x86/boot/Makefile
index 5fdb5ae..6d20646 100644
--- a/xen/arch/x86/boot/Makefile
+++ b/xen/arch/x86/boot/Makefile
@@ -1,8 +1,15 @@ 
 obj-bin-y += head.o
 
-RELOC_DEPS = $(BASEDIR)/include/asm-x86/config.h $(BASEDIR)/include/xen/multiboot.h
+DEFS_H_DEPS = defs.h $(BASEDIR)/include/xen/stdbool.h
 
-head.o: reloc.S
+CMDLINE_DEPS = $(DEFS_H_DEPS) video.h
+
+RELOC_DEPS = $(DEFS_H_DEPS) $(BASEDIR)/include/xen/multiboot.h
+
+head.o: cmdline.S reloc.S
+
+cmdline.S: cmdline.c $(CMDLINE_DEPS)
+	$(MAKE) -f build32.mk $@ CMDLINE_DEPS="$(CMDLINE_DEPS)"
 
 reloc.S: reloc.c $(RELOC_DEPS)
 	$(MAKE) -f build32.mk $@ RELOC_DEPS="$(RELOC_DEPS)"
diff --git a/xen/arch/x86/boot/build32.mk b/xen/arch/x86/boot/build32.mk
index 272d942..f7e8ebe 100644
--- a/xen/arch/x86/boot/build32.mk
+++ b/xen/arch/x86/boot/build32.mk
@@ -32,6 +32,8 @@  CFLAGS := $(filter-out -flto,$(CFLAGS))
 %.o: %.c
 	$(CC) $(CFLAGS) -c -fpic $< -o $@
 
+cmdline.o: cmdline.c $(CMDLINE_DEPS)
+
 reloc.o: reloc.c $(RELOC_DEPS)
 
 .PRECIOUS: %.bin %.lnk
diff --git a/xen/arch/x86/boot/cmdline.S b/xen/arch/x86/boot/cmdline.S
deleted file mode 100644
index 00687eb..0000000
--- a/xen/arch/x86/boot/cmdline.S
+++ /dev/null
@@ -1,367 +0,0 @@ 
-/******************************************************************************
- * cmdline.S
- *
- * Early command-line parsing.
- */
-
-        .code32
-
-#include "video.h"
-
-# NB. String pointer on stack is modified to point past parsed digits.
-.Latoi:
-        push    %ebx
-        push    %ecx
-        push    %edx
-        push    %esi
-        xor     %ebx,%ebx       /* %ebx = accumulator */
-        mov     $10,%ecx        /* %ecx = base (default base 10) */
-        mov     16+4(%esp),%esi /* %esi = pointer into ascii string. */
-        lodsb
-        cmpb    $'0',%al
-        jne     2f
-        mov     $8,%ecx         /* Prefix '0' => octal (base 8) */
-        lodsb
-        cmpb    $'x',%al
-        jne     2f
-        mov     $16,%ecx        /* Prefix '0x' => hex (base 16) */
-1:      lodsb
-2:      sub     $'0',%al
-        jb      4f
-        cmp     $9,%al
-        jbe     3f
-        sub     $'A'-'0'-10,%al
-        jb      4f
-        cmp     $15,%al
-        jbe     3f
-        sub     $'a'-'A',%al
-        jb      4f
-3:      cmp     %cl,%al
-        jae     4f
-        movzbl  %al,%eax
-        xchg    %eax,%ebx
-        mul     %ecx
-        xchg    %eax,%ebx
-        add     %eax,%ebx
-        jmp     1b
-4:      mov     %ebx,%eax
-        dec     %esi
-        mov     %esi,16+4(%esp)
-        pop     %esi
-        pop     %edx
-        pop     %ecx
-        pop     %ebx
-        ret
-
-.Lstrstr:
-        push    %ecx
-        push    %edx
-        push    %esi
-        push    %edi
-        xor     %eax,%eax
-        xor     %ecx,%ecx
-        not     %ecx
-        mov     16+4(%esp),%esi
-        mov     16+8(%esp),%edi
-        repne   scasb
-        not     %ecx
-        dec     %ecx
-        mov     %ecx,%edx
-1:      mov     16+8(%esp),%edi
-        mov     %esi,%eax
-        mov     %edx,%ecx
-        repe    cmpsb
-        je      2f
-        xchg    %eax,%esi
-        inc     %esi
-        cmpb    $0,-1(%eax)
-        jne     1b
-        xor     %eax,%eax
-2:      pop     %edi
-        pop     %esi
-        pop     %edx
-        pop     %ecx
-        ret
-
-.Lstr_prefix:
-        push    %esi
-        push    %edi
-        mov     8+4(%esp),%esi /* 1st arg is prefix string */
-        mov     8+8(%esp),%edi /* 2nd arg is main string */
-1:      lodsb
-        test    %al,%al
-        jz      2f
-        scasb
-        je      1b
-        sbb     %eax,%eax
-        or      $1,%al
-        jmp     3f
-2:      xor     %eax,%eax
-3:      pop     %edi
-        pop     %esi
-        ret
-
-.Lstrlen:
-        push    %ecx
-        push    %esi
-        push    %edi
-        xor     %eax,%eax
-        xor     %ecx,%ecx
-        not     %ecx
-        mov     12+4(%esp),%edi
-        repne   scasb
-        not     %ecx
-        dec     %ecx
-        mov     %ecx,%eax
-        pop     %edi
-        pop     %esi
-        pop     %ecx
-        ret
-
-.Lfind_option:
-        mov     4(%esp),%eax
-        dec     %eax
-        push    %ebx
-1:      pushl   4+8(%esp)
-        inc     %eax
-        push    %eax
-        call    .Lstrstr
-        add     $8,%esp
-        test    %eax,%eax
-        jz      3f
-        cmp     %eax,4+4(%esp)
-        je      2f
-        cmpb    $' ',-1(%eax)
-        jne     1b
-2:      mov     %eax,%ebx
-        pushl   4+8(%esp)
-        call    .Lstrlen
-        add     $4,%esp
-        xadd    %eax,%ebx
-        /* NUL check (as $'\0' == 0x30 in GAS) */
-        cmpb    $0,(%ebx)
-        je      3f
-        cmpb    $' ',(%ebx)
-        je      3f
-        cmpb    $'=',(%ebx)
-        jne     1b
-3:      pop     %ebx
-        ret
-
-cmdline_parse_early:
-        pusha
-
-        /* Bail if there is no command line to parse. */
-        mov     sym_phys(multiboot_ptr),%ebx
-        mov     MB_flags(%ebx),%eax
-        test    $4,%al
-        jz      .Lcmdline_exit
-        mov     MB_cmdline(%ebx),%eax
-        test    %eax,%eax
-        jz      .Lcmdline_exit
-
-        /* Check for 'no-real-mode' command-line option. */
-        pushl   $sym_phys(.Lno_rm_opt)
-        pushl   MB_cmdline(%ebx)
-        call    .Lfind_option
-        test    %eax,%eax
-        setnz   %al
-        or      %al,sym_phys(skip_realmode)
-
-        /* Check for 'tboot=' command-line option. */
-        movl    $sym_phys(.Ltboot_opt),4(%esp)
-        call    .Lfind_option
-        test    %eax,%eax
-        setnz   %al
-        or      %al,sym_phys(skip_realmode) /* tboot= implies no-real-mode */
-
-.Lparse_edd:
-        /* Check for 'edd=' command-line option. */
-        movl    $sym_phys(.Ledd_opt),4(%esp)
-        call    .Lfind_option
-        test    %eax,%eax
-        jz      .Lparse_edid
-        cmpb    $'=',3(%eax)
-        jne     .Lparse_edid
-        add     $4,%eax
-        movb    $2,sym_phys(opt_edd)  /* opt_edd=2: edd=off */
-        cmpw    $0x666f,(%eax)            /* 0x666f == "of" */
-        je      .Lparse_edid
-        decb    sym_phys(opt_edd)     /* opt_edd=1: edd=skipmbr */
-        cmpw    $0x6b73,(%eax)            /* 0x6b73 == "sk" */
-        je      .Lparse_edid
-        decb    sym_phys(opt_edd)     /* opt_edd=0: edd=on (default) */
-
-.Lparse_edid:
-        /* Check for 'edid=' command-line option. */
-        movl    $sym_phys(.Ledid_opt),4(%esp)
-        call    .Lfind_option
-        test    %eax,%eax
-        jz      .Lparse_vga
-        cmpb    $'=',4(%eax)
-        jne     .Lparse_vga
-        add     $5,%eax
-        mov     %eax,%ebx
-        push    %ebx
-        pushl   $sym_phys(.Ledid_force)
-        call    .Lstr_prefix
-        add     $8,%esp
-        movb    $2,sym_phys(opt_edid) /* opt_edid=2: edid=force */
-        test    %eax,%eax
-        jz      .Lparse_vga
-        push    %ebx
-        pushl   $sym_phys(.Ledid_no)
-        call    .Lstr_prefix
-        add     $8,%esp
-        decb    sym_phys(opt_edid)    /* opt_edid=1: edid=no */
-        test    %eax,%eax
-        jz      .Lparse_vga
-        decb    sym_phys(opt_edid)    /* opt_edid=0: default */
-
-.Lparse_vga:
-        /* Check for 'vga=' command-line option. */
-        movl    $sym_phys(.Lvga_opt),4(%esp)
-        call    .Lfind_option
-        add     $8,%esp
-        test    %eax,%eax
-        jz      .Lcmdline_exit
-        cmpb    $'=',3(%eax)
-        jne     .Lcmdline_exit
-        add     $4,%eax
-
-        /* Found the 'vga=' option. Default option is to display vga menu. */
-        movw    $ASK_VGA,sym_phys(boot_vid_mode)
-
-        /* Check for 'vga=text-80x<rows>. */
-        mov     %eax,%ebx
-        push    %ebx
-        pushl   $sym_phys(.Lvga_text80)
-        call    .Lstr_prefix
-        add     $8,%esp
-        test    %eax,%eax
-        jnz     .Lparse_vga_gfx
-
-        /* We have 'vga=text-80x<rows>'. */
-        add     $8,%ebx
-        push    %ebx
-        call    .Latoi
-        add     $4,%esp
-        mov     %ax,%bx
-        lea     sym_phys(.Lvga_text_modes),%esi
-1:      lodsw
-        test    %ax,%ax
-        jz      .Lcmdline_exit
-        cmp     %ax,%bx
-        lodsw
-        jne     1b
-        mov     %ax,sym_phys(boot_vid_mode)
-        jmp     .Lcmdline_exit
-
-.Lparse_vga_gfx:
-        /* Check for 'vga=gfx-<width>x<height>x<depth>'. */
-        push    %ebx
-        pushl   $sym_phys(.Lvga_gfx)
-        call    .Lstr_prefix
-        add     $8,%esp
-        test    %eax,%eax
-        jnz     .Lparse_vga_mode
-
-        /* We have 'vga=gfx-<width>x<height>x<depth>'. */
-        /* skip 'gfx-' */
-        add     $4,%ebx
-        /* parse <width> */
-        push    %ebx
-        call    .Latoi
-        pop     %esi
-        mov     %ax,sym_phys(vesa_size)+0
-        /* skip 'x' */
-        lodsb
-        cmpb    $'x',%al
-        jne     .Lcmdline_exit
-        /* parse <height> */
-        push    %esi
-        call    .Latoi
-        pop     %esi
-        mov     %ax,sym_phys(vesa_size)+2
-        /* skip 'x' */
-        lodsb
-        cmpb    $'x',%al
-        jne     .Lcmdline_exit
-        /* parse <depth> */
-        push    %esi
-        call    .Latoi
-        pop     %esi
-        mov     %ax,sym_phys(vesa_size)+4
-        /* commit to vesa mode */
-        movw    $VIDEO_VESA_BY_SIZE,sym_phys(boot_vid_mode)
-        jmp     .Lcmdline_exit
-
-.Lparse_vga_mode:
-        /* Check for 'vga=mode-<mode>'. */
-        push    %ebx
-        pushl   $sym_phys(.Lvga_mode)
-        call    .Lstr_prefix
-        add     $8,%esp
-        test    %eax,%eax
-        jnz     .Lparse_vga_current
-
-        /* We have 'vga=mode-<mode>'. */
-        add     $5,%ebx
-        push    %ebx
-        call    .Latoi
-        add     $4,%esp
-        mov     %ax,sym_phys(boot_vid_mode)
-        jmp     .Lcmdline_exit
-
-.Lparse_vga_current:
-        /* Check for 'vga=current'. */
-        push    %ebx
-        pushl   $sym_phys(.Lvga_current)
-        call    .Lstr_prefix
-        add     $8,%esp
-        test    %eax,%eax
-        jnz     .Lcmdline_exit
-
-        /* We have 'vga=current'. */
-        movw    $VIDEO_CURRENT_MODE,sym_phys(boot_vid_mode)
-
-.Lcmdline_exit:
-        popa
-        ret
-
-        .pushsection .init.rodata, "a", @progbits
-
-.Lvga_text_modes: /* rows, mode_number */
-        .word   25,VIDEO_80x25
-        .word   50,VIDEO_80x50
-        .word   43,VIDEO_80x43
-        .word   28,VIDEO_80x28
-        .word   30,VIDEO_80x30
-        .word   34,VIDEO_80x34
-        .word   60,VIDEO_80x60
-        .word   0
-
-.Lvga_opt:
-        .asciz  "vga"
-.Lvga_text80:
-        .asciz  "text-80x"
-.Lvga_gfx:
-        .asciz  "gfx-"
-.Lvga_mode:
-        .asciz  "mode-"
-.Lvga_current:
-        .asciz  "current"
-.Lno_rm_opt:
-        .asciz  "no-real-mode"
-.Ltboot_opt:
-        .asciz  "tboot"
-.Ledid_opt:
-        .asciz  "edid"
-.Ledid_force:
-        .asciz  "force"
-.Ledid_no:
-        .asciz  "no"
-.Ledd_opt:
-        .asciz  "edd"
-
-        .popsection
diff --git a/xen/arch/x86/boot/cmdline.c b/xen/arch/x86/boot/cmdline.c
new file mode 100644
index 0000000..06aa064
--- /dev/null
+++ b/xen/arch/x86/boot/cmdline.c
@@ -0,0 +1,340 @@ 
+/*
+ * Copyright (c) 2015, 2016 Oracle and/or its affiliates. All rights reserved.
+ *
+ * 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
+ * (at your option) 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, see <http://www.gnu.org/licenses/>.
+ *
+ * strlen(), strncmp(), strchr(), strspn() and strcspn() were copied from
+ * Linux kernel source (linux/lib/string.c).
+ */
+
+/*
+ * This entry point is entered from xen/arch/x86/boot/head.S with:
+ *   - 0x4(%esp) = &cmdline,
+ *   - 0x8(%esp) = &early_boot_opts.
+ */
+asm (
+    "    .text                         \n"
+    "    .globl _start                 \n"
+    "_start:                           \n"
+    "    jmp  cmdline_parse_early      \n"
+    );
+
+#include "defs.h"
+#include "video.h"
+
+/* Keep in sync with trampoline.S:early_boot_opts label! */
+typedef struct __packed {
+    u8 skip_realmode;
+    u8 opt_edd;
+    u8 opt_edid;
+    u8 padding;
+    u16 boot_vid_mode;
+    u16 vesa_width;
+    u16 vesa_height;
+    u16 vesa_depth;
+} early_boot_opts_t;
+
+/*
+ * Space and TAB are obvious delimiters. However, I am
+ * adding "\n" and "\r" here too. Just in case when
+ * crazy bootloader/user puts them somewhere.
+ */
+static const char delim_chars_comma[] = ", \n\r\t";
+
+#define delim_chars	(delim_chars_comma + 1)
+
+static size_t strlen(const char *s)
+{
+    const char *sc;
+
+    for ( sc = s; *sc != '\0'; ++sc )
+        /* nothing */;
+    return sc - s;
+}
+
+static int strncmp(const char *cs, const char *ct, size_t count)
+{
+    unsigned char c1, c2;
+
+    while ( count )
+    {
+        c1 = *cs++;
+        c2 = *ct++;
+        if ( c1 != c2 )
+            return c1 < c2 ? -1 : 1;
+        if ( !c1 )
+            break;
+        count--;
+    }
+    return 0;
+}
+
+static char *strchr(const char *s, int c)
+{
+    for ( ; *s != (char)c; ++s )
+        if ( *s == '\0' )
+            return NULL;
+    return (char *)s;
+}
+
+static size_t strspn(const char *s, const char *accept)
+{
+    const char *p;
+    const char *a;
+    size_t count = 0;
+
+    for ( p = s; *p != '\0'; ++p )
+    {
+        for ( a = accept; *a != '\0'; ++a )
+        {
+            if ( *p == *a )
+                break;
+        }
+        if ( *a == '\0' )
+            return count;
+        ++count;
+    }
+    return count;
+}
+
+static size_t strcspn(const char *s, const char *reject)
+{
+    const char *p;
+    const char *r;
+    size_t count = 0;
+
+    for ( p = s; *p != '\0'; ++p )
+    {
+        for ( r = reject; *r != '\0'; ++r )
+        {
+            if ( *p == *r )
+                return count;
+        }
+        ++count;
+    }
+    return count;
+}
+
+static unsigned int strtoui(const char *s, const char *stop, const char **next)
+{
+    char base = 10, l;
+    unsigned long long res = 0;
+
+    if ( *s == '0' )
+      base = (tolower(*++s) == 'x') ? (++s, 16) : 8;
+
+    for ( ; *s != '\0'; ++s )
+    {
+        if ( stop && strchr(stop, *s) )
+            goto out;
+
+        if ( *s < '0' || (*s > '7' && base == 8) )
+        {
+            res = UINT_MAX;
+            goto out;
+        }
+
+        l = tolower(*s);
+
+        if ( *s > '9' && (base != 16 || l < 'a' || l > 'f') )
+        {
+            res = UINT_MAX;
+            goto out;
+        }
+
+        res *= base;
+        res += (l >= 'a') ? (l - 'a' + 10) : (*s - '0');
+
+        if ( res >= UINT_MAX )
+        {
+            res = UINT_MAX;
+            goto out;
+        }
+    }
+
+ out:
+    if ( next )
+      *next = s;
+
+    return res;
+}
+
+static int strmaxcmp(const char *cs, const char *ct, const char *_delim_chars)
+{
+    return strncmp(cs, ct, max(strcspn(cs, _delim_chars), strlen(ct)));
+}
+
+static int strsubcmp(const char *cs, const char *ct)
+{
+    return strncmp(cs, ct, strlen(ct));
+}
+
+static const char *find_opt(const char *cmdline, const char *opt, bool arg)
+{
+    size_t lc, lo;
+
+    lo = strlen(opt);
+
+    for ( ; ; )
+    {
+        cmdline += strspn(cmdline, delim_chars);
+
+        if ( *cmdline == '\0' )
+            return NULL;
+
+        if ( !strmaxcmp(cmdline, "--", delim_chars) )
+            return NULL;
+
+        lc = strcspn(cmdline, delim_chars);
+
+        if ( !strncmp(cmdline, opt, arg ? lo : max(lc, lo)) )
+            return cmdline + lo;
+
+        cmdline += lc;
+    }
+}
+
+static bool skip_realmode(const char *cmdline)
+{
+    return find_opt(cmdline, "no-real-mode", false) || find_opt(cmdline, "tboot=", true);
+}
+
+static u8 edd_parse(const char *cmdline)
+{
+    const char *c;
+
+    c = find_opt(cmdline, "edd=", true);
+
+    if ( !c )
+        return 0;
+
+    if ( !strmaxcmp(c, "off", delim_chars) )
+        return 2;
+
+    return !strmaxcmp(c, "skipmbr", delim_chars);
+}
+
+static u8 edid_parse(const char *cmdline)
+{
+    const char *c;
+
+    c = find_opt(cmdline, "edid=", true);
+
+    if ( !c )
+        return 0;
+
+    if ( !strmaxcmp(c, "force", delim_chars) )
+        return 2;
+
+    return !strmaxcmp(c, "no", delim_chars);
+}
+
+static u16 rows2vmode(unsigned int rows)
+{
+    switch ( rows )
+    {
+    case 25:
+        return VIDEO_80x25;
+
+    case 28:
+        return VIDEO_80x28;
+
+    case 30:
+        return VIDEO_80x30;
+
+    case 34:
+        return VIDEO_80x34;
+
+    case 43:
+        return VIDEO_80x43;
+
+    case 50:
+        return VIDEO_80x50;
+
+    case 60:
+        return VIDEO_80x60;
+
+    default:
+        return ASK_VGA;
+    }
+}
+
+static void vga_parse(const char *cmdline, early_boot_opts_t *ebo)
+{
+    const char *c;
+    unsigned int tmp, vesa_depth, vesa_height, vesa_width;
+
+    c = find_opt(cmdline, "vga=", true);
+
+    if ( !c )
+        return;
+
+    ebo->boot_vid_mode = ASK_VGA;
+
+    if ( !strmaxcmp(c, "current", delim_chars_comma) )
+        ebo->boot_vid_mode = VIDEO_CURRENT_MODE;
+    else if ( !strsubcmp(c, "text-80x") )
+    {
+        c += strlen("text-80x");
+        ebo->boot_vid_mode = rows2vmode(strtoui(c, delim_chars_comma, NULL));
+    }
+    else if ( !strsubcmp(c, "gfx-") )
+    {
+        vesa_width = strtoui(c + strlen("gfx-"), "x", &c);
+
+        if ( vesa_width > U16_MAX )
+            return;
+
+        /*
+         * Increment c outside of strtoui() because otherwise some
+         * compiler may complain with following message:
+         * warning: operation on 'c' may be undefined.
+         */
+        ++c;
+        vesa_height = strtoui(c, "x", &c);
+
+        if ( vesa_height > U16_MAX )
+            return;
+
+        vesa_depth = strtoui(++c, delim_chars_comma, NULL);
+
+        if ( vesa_depth > U16_MAX )
+            return;
+
+        ebo->vesa_width = vesa_width;
+        ebo->vesa_height = vesa_height;
+        ebo->vesa_depth = vesa_depth;
+        ebo->boot_vid_mode = VIDEO_VESA_BY_SIZE;
+    }
+    else if ( !strsubcmp(c, "mode-") )
+    {
+        tmp = strtoui(c + strlen("mode-"), delim_chars_comma, NULL);
+
+        if ( tmp > U16_MAX )
+            return;
+
+        ebo->boot_vid_mode = tmp;
+    }
+}
+
+void __stdcall cmdline_parse_early(const char *cmdline, early_boot_opts_t *ebo)
+{
+    if ( !cmdline )
+        return;
+
+    ebo->skip_realmode = skip_realmode(cmdline);
+    ebo->opt_edd = edd_parse(cmdline);
+    ebo->opt_edid = edid_parse(cmdline);
+    vga_parse(cmdline, ebo);
+}
diff --git a/xen/arch/x86/boot/defs.h b/xen/arch/x86/boot/defs.h
new file mode 100644
index 0000000..6abdc15
--- /dev/null
+++ b/xen/arch/x86/boot/defs.h
@@ -0,0 +1,58 @@ 
+/*
+ * Copyright (c) 2016 Oracle and/or its affiliates. All rights reserved.
+ *
+ * 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
+ * (at your option) 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, see <http://www.gnu.org/licenses/>.
+ *
+ * max() was copied from xen/xen/include/xen/kernel.h.
+ */
+
+#ifndef __BOOT_DEFS_H__
+#define __BOOT_DEFS_H__
+
+#include "../../../include/xen/stdbool.h"
+
+#define __packed	__attribute__((__packed__))
+#define __stdcall	__attribute__((__stdcall__))
+
+#define NULL		((void *)0)
+
+#define ALIGN_UP(arg, align) \
+                (((arg) + (align) - 1) & ~((typeof(arg))(align) - 1))
+
+#define min(x,y) ({ \
+        const typeof(x) _x = (x);       \
+        const typeof(y) _y = (y);       \
+        (void) (&_x == &_y);            \
+        _x < _y ? _x : _y; })
+
+#define max(x,y) ({ \
+        const typeof(x) _x = (x);       \
+        const typeof(y) _y = (y);       \
+        (void) (&_x == &_y);            \
+        _x > _y ? _x : _y; })
+
+#define _p(val)		((void *)(unsigned long)(val))
+
+#define tolower(c)	((c) | 0x20)
+
+typedef unsigned char u8;
+typedef unsigned short u16;
+typedef unsigned int u32;
+typedef unsigned long long u64;
+typedef unsigned int size_t;
+
+#define U16_MAX		((u16)(~0U))
+#define UINT_MAX	(~0U)
+
+#endif /* __BOOT_DEFS_H__ */
diff --git a/xen/arch/x86/boot/edd.S b/xen/arch/x86/boot/edd.S
index 5c80da6..73371f9 100644
--- a/xen/arch/x86/boot/edd.S
+++ b/xen/arch/x86/boot/edd.S
@@ -142,9 +142,6 @@  edd_next:
 edd_done:
         ret
 
-opt_edd:
-        .byte   0                               # edd=on/off/skipmbr
-
 GLOBAL(boot_edd_info_nr)
         .byte   0
 GLOBAL(boot_mbr_signature_nr)
diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
index 6f2c668..126e2e2 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -183,8 +183,16 @@  __start:
         cmp     $sym_phys(__trampoline_seg_stop),%edi
         jb      1b
 
+        /* Bail if there is no command line to parse. */
+        mov     sym_phys(multiboot_ptr),%ebx
+        testl   $MBI_CMDLINE,MB_flags(%ebx)
+        jz      1f
+
+        pushl   $sym_phys(early_boot_opts)
+        pushl   MB_cmdline(%ebx)
         call    cmdline_parse_early
 
+1:
         /* Switch to low-memory stack.  */
         mov     sym_phys(trampoline_phys),%edi
         lea     0x10000(%edi),%esp
@@ -200,6 +208,7 @@  __start:
         /* Jump into the relocated trampoline. */
         lret
 
+cmdline_parse_early:
 #include "cmdline.S"
 
 reloc:
diff --git a/xen/arch/x86/boot/reloc.c b/xen/arch/x86/boot/reloc.c
index ea8cb37..91405e9 100644
--- a/xen/arch/x86/boot/reloc.c
+++ b/xen/arch/x86/boot/reloc.c
@@ -22,16 +22,9 @@  asm (
     "    jmp  reloc                    \n"
     );
 
-typedef unsigned int u32;
+#include "defs.h"
 #include "../../../include/xen/multiboot.h"
 
-#define __stdcall	__attribute__((__stdcall__))
-
-#define ALIGN_UP(arg, align) \
-                (((arg) + (align) - 1) & ~((typeof(arg))(align) - 1))
-
-#define _p(val)		((void *)(unsigned long)(val))
-
 static u32 alloc;
 
 static u32 alloc_mem(u32 bytes)
diff --git a/xen/arch/x86/boot/trampoline.S b/xen/arch/x86/boot/trampoline.S
index b013614..2715d17 100644
--- a/xen/arch/x86/boot/trampoline.S
+++ b/xen/arch/x86/boot/trampoline.S
@@ -220,8 +220,23 @@  trampoline_boot_cpu_entry:
         /* Jump to the common bootstrap entry point. */
         jmp     trampoline_protmode_entry
 
+#include "video.h"
+
+        .align  2
+/* Keep in sync with cmdline.c:early_boot_opts_t type! */
+early_boot_opts:
 skip_realmode:
         .byte   0
+opt_edd:
+        .byte   0                               /* edd=on/off/skipmbr */
+opt_edid:
+        .byte   0                               /* EDID parsing option (force/no/default). */
+/* Padding. */
+        .byte   0
+GLOBAL(boot_vid_mode)
+        .word   VIDEO_80x25                     /* If we don't run at all, assume basic video mode 3 at 80x25. */
+vesa_size:
+        .word   0,0,0                           /* width x depth x height */
 
 GLOBAL(kbd_shift_flags)
         .byte   0
diff --git a/xen/arch/x86/boot/video.S b/xen/arch/x86/boot/video.S
index 2aafbeb..335a51c 100644
--- a/xen/arch/x86/boot/video.S
+++ b/xen/arch/x86/boot/video.S
@@ -945,7 +945,6 @@  store_edid:
 #endif
         ret
 
-opt_edid:       .byte   0       # EDID parsing option (force/no/default)
 mt_end:         .word   0       # End of video mode table if built
 edit_buf:       .space  6       # Line editor buffer
 card_name:      .word   0       # Pointer to adapter name
@@ -991,12 +990,6 @@  name_bann:      .asciz  "Video adapter: "
 
 force_size:     .word   0       # Use this size instead of the one in BIOS vars
 
-vesa_size:      .word   0,0,0   # width x depth x height
-
-/* If we don't run at all, assume basic video mode 3 at 80x25. */
-        .align  2
-GLOBAL(boot_vid_mode)
-        .word   VIDEO_80x25
 GLOBAL(boot_vid_info)
         .byte   0, 0    /* orig_x, orig_y */
         .byte   3       /* text mode 3    */