diff mbox

[v6,10/15] x86/boot: implement early command line parser in C

Message ID 1473711511-11931-11-git-send-email-daniel.kiper@oracle.com (mailing list archive)
State New, archived
Headers show

Commit Message

Daniel Kiper Sept. 12, 2016, 8:18 p.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>
---
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    |  339 +++++++++++++++++++++++++++++++++++++
 xen/arch/x86/boot/defs.h       |   52 ++++++
 xen/arch/x86/boot/edd.S        |    3 -
 xen/arch/x86/boot/head.S       |    8 +
 xen/arch/x86/boot/reloc.c      |   13 +-
 xen/arch/x86/boot/trampoline.S |   14 ++
 xen/arch/x86/boot/video.S      |    7 -
 12 files changed, 429 insertions(+), 394 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

Jan Beulich Sept. 19, 2016, 12:47 p.m. UTC | #1
>>> On 12.09.16 at 22:18, <daniel.kiper@oracle.com> wrote:
> --- a/xen/arch/x86/boot/Makefile
> +++ b/xen/arch/x86/boot/Makefile
> @@ -1,9 +1,16 @@
>  obj-bin-y += head.o
>  
> -RELOC_DEPS = $(BASEDIR)/include/asm-x86/config.h $(BASEDIR)/include/xen/multiboot.h \
> +DEFS_H_DEPS = $(BASEDIR)/include/xen/stdbool.h
> +
> +CMDLINE_DEPS = defs.h $(DEFS_H_DEPS) video.h
> +
> +RELOC_DEPS = defs.h $(DEFS_H_DEPS) $(BASEDIR)/include/xen/multiboot.h \

I think it would be more natural for DEFS_H_DEPS to include defs.h,
as I can't see a valid use of one without the other; perhaps it would
then better be renamed.

> --- /dev/null
> +++ b/xen/arch/x86/boot/defs.h
> @@ -0,0 +1,52 @@
> +/*
> + * 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 max(x,y) ({ \
> +        const typeof(x) _x = (x);       \
> +        const typeof(y) _y = (y);       \
> +        (void) (&_x == &_y);            \
> +        _x > _y ? _x : _y; })

Please don't add max() without also adding min().

> --- a/xen/arch/x86/boot/trampoline.S
> +++ b/xen/arch/x86/boot/trampoline.S
> @@ -220,8 +220,22 @@ trampoline_boot_cpu_entry:
>          /* Jump to the common bootstrap entry point. */
>          jmp     trampoline_protmode_entry
>  
> +#include "video.h"
> +
> +        .align  2
> +        .byte   0

While this odd placement of the requested padding byte will fulfill
the immediate purpose, please do it the originally requested more
conventional way (putting it inside the structure and adding a
respective field to the C representation). For someone wanting to
add another field it'll then be far more obvious what to do without
re-introducing mis-alignment.

Jan
Daniel Kiper Sept. 19, 2016, 3:27 p.m. UTC | #2
On Mon, Sep 19, 2016 at 06:47:50AM -0600, Jan Beulich wrote:
> >>> On 12.09.16 at 22:18, <daniel.kiper@oracle.com> wrote:

[...]

> > --- a/xen/arch/x86/boot/trampoline.S
> > +++ b/xen/arch/x86/boot/trampoline.S
> > @@ -220,8 +220,22 @@ trampoline_boot_cpu_entry:
> >          /* Jump to the common bootstrap entry point. */
> >          jmp     trampoline_protmode_entry
> >
> > +#include "video.h"
> > +
> > +        .align  2
> > +        .byte   0
>
> While this odd placement of the requested padding byte will fulfill
> the immediate purpose, please do it the originally requested more
> conventional way (putting it inside the structure and adding a
> respective field to the C representation). For someone wanting to
> add another field it'll then be far more obvious what to do without
> re-introducing mis-alignment.

OK, however, I am still thinking how to automatically synchronize C and
assembly early_boot_opts struct definitions or generate one from another.
This way we can avoid __packed attribute and probably do not care about
member alignments at all. Do you have an idea how to do that?

Daniel
Jan Beulich Sept. 19, 2016, 4:03 p.m. UTC | #3
>>> On 19.09.16 at 17:27, <daniel.kiper@oracle.com> wrote:
> On Mon, Sep 19, 2016 at 06:47:50AM -0600, Jan Beulich wrote:
>> >>> On 12.09.16 at 22:18, <daniel.kiper@oracle.com> wrote:
> 
> [...]
> 
>> > --- a/xen/arch/x86/boot/trampoline.S
>> > +++ b/xen/arch/x86/boot/trampoline.S
>> > @@ -220,8 +220,22 @@ trampoline_boot_cpu_entry:
>> >          /* Jump to the common bootstrap entry point. */
>> >          jmp     trampoline_protmode_entry
>> >
>> > +#include "video.h"
>> > +
>> > +        .align  2
>> > +        .byte   0
>>
>> While this odd placement of the requested padding byte will fulfill
>> the immediate purpose, please do it the originally requested more
>> conventional way (putting it inside the structure and adding a
>> respective field to the C representation). For someone wanting to
>> add another field it'll then be far more obvious what to do without
>> re-introducing mis-alignment.
> 
> OK, however, I am still thinking how to automatically synchronize C and
> assembly early_boot_opts struct definitions or generate one from another.
> This way we can avoid __packed attribute and probably do not care about
> member alignments at all. Do you have an idea how to do that?

I would have ideas, but I think they're all not really suitable for this
little bit of data. If we had this problem in a more widespread manner,
then perhaps. But we're actually aiming at reducing the amount of
assembly language use.

Jan
Daniel Kiper Sept. 20, 2016, 9:49 a.m. UTC | #4
On Mon, Sep 19, 2016 at 10:03:08AM -0600, Jan Beulich wrote:
> >>> On 19.09.16 at 17:27, <daniel.kiper@oracle.com> wrote:
> > On Mon, Sep 19, 2016 at 06:47:50AM -0600, Jan Beulich wrote:
> >> >>> On 12.09.16 at 22:18, <daniel.kiper@oracle.com> wrote:
> >
> > [...]
> >
> >> > --- a/xen/arch/x86/boot/trampoline.S
> >> > +++ b/xen/arch/x86/boot/trampoline.S
> >> > @@ -220,8 +220,22 @@ trampoline_boot_cpu_entry:
> >> >          /* Jump to the common bootstrap entry point. */
> >> >          jmp     trampoline_protmode_entry
> >> >
> >> > +#include "video.h"
> >> > +
> >> > +        .align  2
> >> > +        .byte   0
> >>
> >> While this odd placement of the requested padding byte will fulfill
> >> the immediate purpose, please do it the originally requested more
> >> conventional way (putting it inside the structure and adding a
> >> respective field to the C representation). For someone wanting to
> >> add another field it'll then be far more obvious what to do without
> >> re-introducing mis-alignment.
> >
> > OK, however, I am still thinking how to automatically synchronize C and
> > assembly early_boot_opts struct definitions or generate one from another.
> > This way we can avoid __packed attribute and probably do not care about
> > member alignments at all. Do you have an idea how to do that?
>
> I would have ideas, but I think they're all not really suitable for this
> little bit of data. If we had this problem in a more widespread manner,
> then perhaps. But we're actually aiming at reducing the amount of
> assembly language use.

OK, I will leave it as is with some adjustments suggested by you earlier.
Out of curiosity, could you outline in a few words your idea?

Daniel
Jan Beulich Sept. 20, 2016, 10:05 a.m. UTC | #5
>>> On 20.09.16 at 11:49, <daniel.kiper@oracle.com> wrote:
> Out of curiosity, could you outline in a few words your idea?

Well, one approach would be something along the lines of
the public headers errno.h and cpufeatureset.h: Have a helper
header invoking some macro, where the macro arguments
specify both the C and assembly representation. Prior to
#include-ing the use sites would actually #define that macro,
suitably using / omitting the use of the various parameters.

Another would be to simply have a translation tool (at least
old Windows SDKs [or DDKs] had something like that, h2inc
I think).

And then there would of course be the pretty obvious
asm-offsets approach we're already using for other purposes.

Jan
Daniel Kiper Sept. 20, 2016, 11:31 a.m. UTC | #6
On Tue, Sep 20, 2016 at 04:05:12AM -0600, Jan Beulich wrote:
> >>> On 20.09.16 at 11:49, <daniel.kiper@oracle.com> wrote:
> > Out of curiosity, could you outline in a few words your idea?
>
> Well, one approach would be something along the lines of
> the public headers errno.h and cpufeatureset.h: Have a helper
> header invoking some macro, where the macro arguments
> specify both the C and assembly representation. Prior to
> #include-ing the use sites would actually #define that macro,
> suitably using / omitting the use of the various parameters.
>
> Another would be to simply have a translation tool (at least
> old Windows SDKs [or DDKs] had something like that, h2inc
> I think).

Yep, I remember that there was such thing here and there.

> And then there would of course be the pretty obvious
> asm-offsets approach we're already using for other purposes.

I was thinking about that, however, I was not sure how to define
struct members in asm. Right now it seems to me that we could
use .skip/.space.

Thanks for explanation.

Daniel
diff mbox

Patch

diff --git a/.gitignore b/.gitignore
index cc64fc9..9aa47a1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -247,9 +247,10 @@  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 2766bff..d8fe0f1 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -224,6 +224,6 @@  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/*.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
 	$(MAKE) -f $(BASEDIR)/Rules.mk -C test clean
diff --git a/xen/arch/x86/boot/Makefile b/xen/arch/x86/boot/Makefile
index 06893d8..4a1bc45 100644
--- a/xen/arch/x86/boot/Makefile
+++ b/xen/arch/x86/boot/Makefile
@@ -1,9 +1,16 @@ 
 obj-bin-y += head.o
 
-RELOC_DEPS = $(BASEDIR)/include/asm-x86/config.h $(BASEDIR)/include/xen/multiboot.h \
+DEFS_H_DEPS = $(BASEDIR)/include/xen/stdbool.h
+
+CMDLINE_DEPS = defs.h $(DEFS_H_DEPS) video.h
+
+RELOC_DEPS = defs.h $(DEFS_H_DEPS) $(BASEDIR)/include/xen/multiboot.h \
 	     $(BASEDIR)/include/xen/multiboot2.h
 
-head.o: reloc.S
+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 39e6453..3d01698 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..291651b
--- /dev/null
+++ b/xen/arch/x86/boot/cmdline.c
@@ -0,0 +1,339 @@ 
+/*
+ * 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;
+    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..1b347c5
--- /dev/null
+++ b/xen/arch/x86/boot/defs.h
@@ -0,0 +1,52 @@ 
+/*
+ * 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 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 00fa47d..12bbd8e 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -506,6 +506,13 @@  trampoline_setup:
         cmpb    $0,sym_phys(skip_realmode)
         jnz     1f
 
+        /* 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:
@@ -524,6 +531,7 @@  trampoline_setup:
         /* 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 e421b07..cb8464d 100644
--- a/xen/arch/x86/boot/reloc.c
+++ b/xen/arch/x86/boot/reloc.c
@@ -25,21 +25,10 @@  asm (
     "    jmp  reloc                    \n"
     );
 
-typedef unsigned int u32;
-typedef unsigned long long u64;
-
+#include "defs.h"
 #include "../../../include/xen/multiboot.h"
 #include "../../../include/xen/multiboot2.h"
 
-#define NULL		((void *)0)
-
-#define __stdcall	__attribute__((__stdcall__))
-
-#define ALIGN_UP(arg, align) \
-                (((arg) + (align) - 1) & ~((typeof(arg))(align) - 1))
-
-#define _p(val)		((void *)(unsigned long)(val))
-
 #define get_mb2_data(tag, type, member)   (((multiboot2_tag_##type##_t *)(tag))->member)
 #define get_mb2_string(tag, type, member) ((u32)get_mb2_data(tag, type, member))
 
diff --git a/xen/arch/x86/boot/trampoline.S b/xen/arch/x86/boot/trampoline.S
index b013614..9f04b2c 100644
--- a/xen/arch/x86/boot/trampoline.S
+++ b/xen/arch/x86/boot/trampoline.S
@@ -220,8 +220,22 @@  trampoline_boot_cpu_entry:
         /* Jump to the common bootstrap entry point. */
         jmp     trampoline_protmode_entry
 
+#include "video.h"
+
+        .align  2
+        .byte   0
+/* 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). */
+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    */