Re: arm-wince-pe support resurrection

[Dmitry Semyonov <Dmitry dot Semyonov at oktet dot ru>]

Nick,

On Thu, 4 Dec 2003, Nick Clifton wrote:

>   With regards to this patch:
> -------------------------------------------------------------------------------
> 2003-11-18  Dmitry Semyonov  <Dmitry.Semyonov@oktet.ru>
>
> 	* bfd/peXXigen.c (_bfd_XXi_swap_scnhdr_out): Set flags for some special
> 	sections (.text, .rdata, .data, .bss) as described in
> 	"MS PE & COFF Specification".
>
> diff -rNc3p binutils-031114/bfd/peXXigen.c /home/sdv/cross/binutils-031114/bfd/peXXigen.c
> *** binutils-031114/bfd/peXXigen.c	Fri Nov 14 21:46:53 2003
> --- /home/sdv/cross/binutils-031114/bfd/peXXigen.c	Fri Nov 14 22:11:43 2003
> *************** _bfd_XXi_swap_scnhdr_out (abfd, in, out)
> *** 959,964 ****
> --- 959,993 ----
>
>     {
>       int flags = scnhdr_int->s_flags;

[...]

>       H_PUT_32 (abfd, flags, scnhdr_ext->s_flags);
>     }
> -------------------------------------------------------------------------------
>
> I am not sure that this is the right place to be doing this.

May be, but I'm not familiar enough with binutils to quickly find the
right place. I was hoping that somebody (you?) could point to the good
place for the fix.


> So you have an example of how, without this patch applied, the linker is
> producing section with incorrect flag bits set ?

Refer to the beginning of section 6 (Special sections) of MS PE COFF
specification.


Warnings produced by MS linker are:
a.obj : warning LNK4078: multiple '.text' sections found with different attributes (E0000020)
a.obj : warning LNK4078: multiple '.rdata' sections found with different attributes (C0000040)


I don't know whether different flags affect the final result, but I'm
feeling more comfortable without any warnings.


The source file file I'm compiling with arm-wince-pe is:
 --- begin ---
void show(const char *s);

static const char *str = "xxx";
static char arr[3] = { 1, 2 ,3 };

void
test(void)
{
    show(str);
}
 --- end ---


It was compiled with the command:
$ arm-wince-pe-gcc -c -fno-leading-underscore test.c


Section flags are:
$ arm-wince-pe-objdump -h test.o

test.o:     file format pe-arm-little

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         00000020  00000000  00000000  000000b4  2**2
                  CONTENTS, ALLOC, LOAD, RELOC, CODE
  1 .data         00000008  00000000  00000000  000000d4  2**2
                  CONTENTS, RELOC
  2 .bss          00000000  00000000  00000000  00000000  2**2
                  ALLOC
  3 .rdata        00000004  00000000  00000000  000000dc  2**2
                  CONTENTS, ALLOC, LOAD, DATA


Below is the file I'm compiling with WinCE compiler, and linking
with the mentioned above object:
 -- begin --
extern void test(void);

static wchar_t *b = L"Error\r\n";

void show(const char *s)
{
    if (s[0] != 'x' || s[1] != 'x' || s[2] != 'x')
        NKDbgPrintfW (b);
}

int main(void)
{
    b[0] = L'e';
    test();
    return 0;
}
 --- end ---


Below are some extras from MS's 'dumpbin /headers' command output
(dumpbin is - Microsoft (R) COFF/PE Dumper Version 6.24.3064):

GNU arm-wince-pe created object
-------------------------------

FILE HEADER VALUES
             1C0 machine (ARM)
               4 number of sections
               0 time date stamp Thu Jan 01 03:00:00 1970
              FE file pointer to symbol table
               F number of symbols
               0 size of optional header
            4D04 characteristics
                   Line numbers stripped
                   32 bit word machine
                   CD - run from swapfile
                   Net - run from swapfile
                   Uniprocessor Only

SECTION HEADER #1
   .text name
    [...]
E0000020 flags
         Code
         (no align specified)
         Execute Read Write

SECTION HEADER #2
   .data name
    [...]
C0000000 flags
         (no align specified)
         Read Write

SECTION HEADER #3
    .bss name
    [...]
C0000080 flags
         Uninitialized Data
         (no align specified)
         Read Write

SECTION HEADER #4
  .rdata name
    [...]
C0000040 flags
         Initialized Data
         (no align specified)
         Read Write



MS's compiler (clarm) created object
------------------------------------

FILE HEADER VALUES
             1C0 machine (ARM)
               6 number of sections
        3FCF98AF time date stamp Thu Dec 04 23:27:27 2003
             770 file pointer to symbol table
              2B number of symbols
               0 size of optional header
             100 characteristics
                   32 bit word machine
    [...]

SECTION HEADER #3
   .data name
    [...]
C0300040 flags
         Initialized Data
         4 byte align
         Read Write

SECTION HEADER #4
   .text name
    [...]
60300020 flags
         Code
         4 byte align
         Execute Read

SECTION HEADER #5
  .pdata name
    [...]
40300040 flags
         Initialized Data
         4 byte align
         Read Only



With my patch applied the warnings are gone away. Although there could
be still a source of possible problem -- alignment is not set inside the
section flags by bfd.


...Bye..Dmitry.