From: Daniel Kiper <daniel.kiper@oracle.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Juergen Gross <JGross@suse.com>,
stefano.stabellini@eu.citrix.com, andrew.cooper3@citrix.com,
cardoe@cardoe.com, pgnet.dev@gmail.com, ning.sun@intel.com,
david.vrabel@citrix.com, xen-devel@lists.xenproject.org,
qiaowei.ren@intel.com, richard.l.maliszewski@intel.com,
gang.wei@intel.com, fu.wei@linaro.org
Subject: Re: [PATCH v3 16/16] x86: add multiboot2 protocol support for relocatable images
Date: Wed, 1 Jun 2016 21:16:35 +0200 [thread overview]
Message-ID: <20160601191635.GH5490@olila.local.net-space.pl> (raw)
In-Reply-To: <574F10EF02000078000F076F@prv-mh.provo.novell.com>
On Wed, Jun 01, 2016 at 08:44:31AM -0600, Jan Beulich wrote:
> >>> On 01.06.16 at 15:35, <daniel.kiper@oracle.com> wrote:
> > On Wed, May 25, 2016 at 05:03:20AM -0600, Jan Beulich wrote:
> >> >>> On 15.04.16 at 14:33, <daniel.kiper@oracle.com> wrote:
> >> > --- a/xen/arch/x86/boot/head.S
> >> > +++ b/xen/arch/x86/boot/head.S
> >> > @@ -79,6 +79,13 @@ multiboot2_header_start:
> >> > /* Align modules at page boundry. */
> >> > mb2ht_init MB2_HT(MODULE_ALIGN), MB2_HT(REQUIRED)
> >> >
> >> > + /* Load address preference. */
> >> > + mb2ht_init MB2_HT(RELOCATABLE), MB2_HT(OPTIONAL), \
> >> > + sym_offset(start), /* Min load address. */ \
> >> > + 0xffffffff, /* Max load address (4 GiB - 1). */ \
> >>
> >> Hardly - that would allow us to be loaded at 4G - 2M, no matter
> >> how large the image. Or else the comment is misleading.
> >
> > This is the highest address at which memory region allocated for image
> > may end.
>
> You saying "end" then means the comment is misleading.
>
> >> > @@ -178,30 +185,39 @@ efi_multiboot2_proto:
> >> > and $~(MULTIBOOT2_TAG_ALIGN-1),%rcx
> >> >
> >> > 0:
> >> > + /* Get Xen image load base address from Multiboot2 information. */
> >> > + cmpl $MULTIBOOT2_TAG_TYPE_LOAD_BASE_ADDR,MB2_tag_type(%rcx)
> >> > + jne 1f
> >> > +
> >> > + mov MB2_load_base_addr(%rcx),%r15d
> >> > + sub $XEN_IMG_OFFSET,%r15
> >> > + jmp 4f
> >>
> >> Why do we need to read this from the table? Can't we easily calculate
> >> this ourselves?
> >
> > Potentially yes but why do not use data from boot loader?
>
> Because it's (a) likely easier to just calculate and (b) we should
In 64-bit mode yes but 32-bit mode requires additional call and pop.
Is it OK for you?
> perhaps trust ourselves more than an external entity?
:-)))
> >> > +1:
> >> > /* Get EFI SystemTable address from Multiboot2 information. */
> >> > cmpl $MULTIBOOT2_TAG_TYPE_EFI64,MB2_tag_type(%rcx)
> >> > - jne 1f
> >> > + jne 2f
> >> >
> >> > mov MB2_efi64_st(%rcx),%rsi
> >> >
> >> > /* Do not clear BSS twice and do not go into real mode. */
> >> > movb $1,skip_realmode(%rip)
> >> > - jmp 3f
> >> > + jmp 4f
> >> >
> >> > -1:
> >> > +2:
> >> > /* Get EFI ImageHandle address from Multiboot2 information. */
> >> > cmpl $MULTIBOOT2_TAG_TYPE_EFI64_IH,MB2_tag_type(%rcx)
> >> > - jne 2f
> >> > + jne 3f
> >> >
> >> > mov MB2_efi64_ih(%rcx),%rdi
> >> > - jmp 3f
> >> > + jmp 4f
> >> >
> >> > -2:
> >> > +3:
> >> > /* Is it the end of Multiboot2 information? */
> >> > cmpl $MULTIBOOT2_TAG_TYPE_END,MB2_tag_type(%rcx)
> >> > je run_bs
> >> >
> >> > -3:
> >> > +4:
> >> > /* Go to next Multiboot2 information tag. */
> >> > add MB2_tag_size(%rcx),%ecx
> >> > add $(MULTIBOOT2_TAG_ALIGN-1),%rcx
> >>
> >> See why numeric labels are bad in situations like this? The (much)
> >> earlier patch should use .L labels here, and the patch here then
> >> should simply follow suit.
> >
> > Then we should change legacy multiboot (v1) code too. Just to be in line
> > new stuff here. Does it pays? And I am not sure that patching convenience
> > overweight convenience of numeric labels here.
>
> Well, it's always this same discussion: Bad examples shouldn't be
> used as excuse to add further bad examples. If you feel like also
> changing the mb1 code - go for it. But if you don't, I'm fine with
> just new code avoiding old mistakes.
Make sense. However, do you suggest that I should avoid numeric labels at all?
Probably they are useful in some situations.
Daniel
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next prev parent reply other threads:[~2016-06-01 19:17 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-15 12:33 [PATCH v3 00/16] x86: multiboot2 protocol support Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 01/16] x86/boot: do not create unwind tables Daniel Kiper
2016-04-15 15:45 ` Andrew Cooper
2016-04-15 12:33 ` [PATCH v3 02/16] x86: zero BSS using stosl instead of stosb Daniel Kiper
2016-04-15 13:57 ` Konrad Rzeszutek Wilk
2016-04-15 15:48 ` Andrew Cooper
2016-04-15 12:33 ` [PATCH v3 03/16] x86/boot: call reloc() using cdecl calling convention Daniel Kiper
2016-04-15 15:56 ` Andrew Cooper
2016-06-17 8:41 ` Daniel Kiper
2016-06-17 9:30 ` Jan Beulich
2016-05-24 8:42 ` Jan Beulich
2016-04-15 12:33 ` [PATCH v3 04/16] x86/boot/reloc: create generic alloc and copy functions Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 05/16] x86/boot: use %ecx instead of %eax Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 06/16] x86/boot/reloc: Rename some variables and rearrange code a bit Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 07/16] x86/boot: create *.lnk files with linker script Daniel Kiper
2016-04-15 14:04 ` Konrad Rzeszutek Wilk
2016-05-24 9:05 ` Jan Beulich
2016-05-24 12:28 ` Daniel Kiper
2016-05-24 12:52 ` Jan Beulich
2016-06-17 9:06 ` Daniel Kiper
2016-06-17 10:04 ` Jan Beulich
2016-06-17 10:34 ` Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 08/16] x86: add multiboot2 protocol support Daniel Kiper
2016-05-24 15:46 ` Jan Beulich
2016-05-25 16:34 ` Daniel Kiper
2016-05-26 10:28 ` Andrew Cooper
2016-05-27 8:08 ` Jan Beulich
2016-05-27 8:13 ` Andrew Cooper
2016-05-27 8:24 ` Jan Beulich
2016-05-27 8:11 ` Jan Beulich
2016-04-15 12:33 ` [PATCH v3 09/16] efi: explicitly define efi struct in xen/arch/x86/efi/stub.c Daniel Kiper
2016-05-25 7:03 ` Jan Beulich
2016-05-25 16:45 ` Daniel Kiper
2016-05-27 8:16 ` Jan Beulich
2016-06-01 15:07 ` Daniel Kiper
2016-07-05 18:33 ` Daniel Kiper
2016-07-06 6:55 ` Jan Beulich
2016-07-06 10:27 ` Daniel Kiper
2016-07-06 12:00 ` Jan Beulich
2016-07-06 12:55 ` Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 10/16] efi: create efi_enabled() Daniel Kiper
2016-05-25 7:20 ` Jan Beulich
2016-05-25 17:15 ` Daniel Kiper
2016-05-26 10:31 ` Andrew Cooper
2016-05-27 8:22 ` Jan Beulich
2016-06-01 15:23 ` Daniel Kiper
2016-06-01 15:41 ` Jan Beulich
2016-06-01 19:28 ` Daniel Kiper
2016-06-02 8:06 ` Jan Beulich
2016-04-15 12:33 ` [PATCH v3 11/16] efi: build xen.gz with EFI code Daniel Kiper
2016-05-25 7:53 ` Jan Beulich
2016-05-25 19:07 ` Daniel Kiper
2016-05-27 8:31 ` Jan Beulich
2016-06-01 15:48 ` Daniel Kiper
2016-06-01 15:58 ` Jan Beulich
2016-06-01 19:39 ` Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 12/16 - RFC] x86/efi: create new early memory allocator Daniel Kiper
2016-05-25 8:39 ` Jan Beulich
2016-05-25 19:48 ` Daniel Kiper
2016-05-27 8:37 ` Jan Beulich
2016-06-01 15:58 ` Daniel Kiper
2016-06-01 16:02 ` Jan Beulich
2016-06-01 19:53 ` Daniel Kiper
2016-06-02 8:11 ` Jan Beulich
2016-06-02 10:43 ` Daniel Kiper
2016-06-02 11:10 ` Jan Beulich
2016-06-01 16:01 ` Daniel Kiper
2016-07-05 18:26 ` Daniel Kiper
2016-07-06 7:22 ` Jan Beulich
2016-07-06 11:15 ` Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 13/16 - RFC] x86: add multiboot2 protocol support for EFI platforms Daniel Kiper
2016-05-25 9:32 ` Jan Beulich
2016-05-25 10:29 ` Jan Beulich
2016-05-25 21:02 ` Daniel Kiper
2016-05-27 9:02 ` Jan Beulich
2016-06-01 19:03 ` Daniel Kiper
2016-06-02 8:34 ` Jan Beulich
2016-06-02 16:12 ` Daniel Kiper
2016-06-03 9:26 ` Jan Beulich
2016-06-03 17:06 ` Konrad Rzeszutek Wilk
2016-04-15 12:33 ` [PATCH v3 14/16] x86/boot: implement early command line parser in C Daniel Kiper
2016-05-25 10:33 ` Jan Beulich
2016-05-25 21:36 ` Daniel Kiper
2016-05-27 9:33 ` Jan Beulich
2016-06-02 8:15 ` Daniel Kiper
2016-06-02 8:39 ` Jan Beulich
2016-04-15 12:33 ` [PATCH v3 15/16 - RFC] x86: make Xen early boot code relocatable Daniel Kiper
2016-05-25 10:48 ` Jan Beulich
2016-04-15 12:33 ` [PATCH v3 16/16] x86: add multiboot2 protocol support for relocatable images Daniel Kiper
2016-05-25 11:03 ` Jan Beulich
2016-06-01 13:35 ` Daniel Kiper
2016-06-01 14:44 ` Jan Beulich
2016-06-01 19:16 ` Daniel Kiper [this message]
2016-06-02 8:41 ` Jan Beulich
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