Re: [Xen-devel] [PATCH v5 06/16] x86/boot/reloc: create generic alloc and copy functions

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Tue, Aug 30, 2016 at 09:12:45AM -0600, Jan Beulich wrote:
> >>> On 30.08.16 at 16:32, <daniel.kiper@xxxxxxxxxx> wrote:
> > On Thu, Aug 25, 2016 at 05:34:31AM -0600, Jan Beulich wrote:
> >> >>> On 20.08.16 at 00:43, <daniel.kiper@xxxxxxxxxx> wrote:
> >> > Create generic alloc and copy functions. We need
> >> > separate tools for memory allocation and copy to
> >> > provide multiboot2 protocol support.
> >> >
> >> > Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
> >>
> >> The amount of casting in this patch alone looks very reasonable now.
> >> Before ack-ing this and respective subsequent patches I'd like to see
> >> the final result though. To facilitate that I have to re-raise a previously
> >> asked question: Do you have a tree somewhere which one could use
> >> to look at the final result?
> >
> > Sadly no.
>
> Alternatively, could you simply send the final resulting source file?

Please look below...

Daniel

/*
 * reloc.c
 *
 * 32-bit flat memory-map routines for relocating Multiboot structures
 * and modules. This is most easily done early with paging disabled.
 *
 * Copyright (c) 2009, Citrix Systems, Inc.
 *
 * Authors:
 *    Keir Fraser <keir@xxxxxxx>
 */

/*
 * This entry point is entered from xen/arch/x86/boot/head.S with:
 *   - 0x4(%esp) = MULTIBOOT_INFORMATION_ADDRESS,
 *   - 0x8(%esp) = BOOT_TRAMPOLINE_ADDRESS.
 */
asm (
    "    .text                         \n"
    "    .globl _start                 \n"
    "_start:                           \n"
    "    jmp  reloc                    \n"
    );

typedef unsigned int u32;
#include "../../../include/xen/multiboot.h"

#define __stdcall       __attribute__((__stdcall__))

#define ALIGN_UP(arg, align) \
                (((arg) + (align) - 1) & ~((typeof(arg))(align) - 1))

static u32 alloc;

static u32 alloc_mem(u32 bytes)
{
    return alloc -= ALIGN_UP(bytes, 16);
}

static u32 copy_mem(u32 src, u32 bytes)
{
    u32 dst, dst_ret;

    dst = alloc_mem(bytes);
    dst_ret = dst;

    while ( bytes-- )
        *(char *)dst++ = *(char *)src++;

    return dst_ret;
}

static u32 copy_string(u32 src)
{
    u32 p;

    if ( src == 0 )
        return 0;

    for ( p = src; *(char *)p != '\0'; p++ )
        continue;

    return copy_mem(src, p - src + 1);
}

multiboot_info_t __stdcall *reloc(u32 mbi_old, u32 trampoline)
{
    multiboot_info_t *mbi;
    int i;

    alloc = trampoline;

    mbi = (multiboot_info_t *)copy_mem(mbi_old, sizeof(*mbi));

    if ( mbi->flags & MBI_CMDLINE )
        mbi->cmdline = copy_string(mbi->cmdline);

    if ( mbi->flags & MBI_MODULES )
    {
        module_t *mods;

        mbi->mods_addr = copy_mem(mbi->mods_addr, mbi->mods_count * 
sizeof(module_t));

        mods = (module_t *)mbi->mods_addr;

        for ( i = 0; i < mbi->mods_count; i++ )
        {
            if ( mods[i].string )
                mods[i].string = copy_string(mods[i].string);
        }
    }

    if ( mbi->flags & MBI_MEMMAP )
        mbi->mmap_addr = copy_mem(mbi->mmap_addr, mbi->mmap_length);

    if ( mbi->flags & MBI_LOADERNAME )
        mbi->boot_loader_name = copy_string(mbi->boot_loader_name);

    /* Mask features we don't understand or don't relocate. */
    mbi->flags &= (MBI_MEMLIMITS |
                   MBI_CMDLINE |
                   MBI_MODULES |
                   MBI_MEMMAP |
                   MBI_LOADERNAME);

    return mbi;
}

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