[PATCH] Kernel fixes for Cygwin

[PATCH] Kernel fixes for Cygwin

[Christian Franke]

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This adds Cygwin support to kernel sources. It handles the issues 
introduced by PE->ELF conversion and adds support for HAVE_ASM_USCORE.

Christian

2007-07-20	Christian Franke  <franke@computer.org>

	* include/grub/dl.h: Remove .previous, gas supports this only
	for ELF format.

	* include/grub/symbol.h [__CYGWIN__] (#define FUNCTION/VARIABLE):
	Remove .type, gas supports this only for ELF format.

	* kern/dl.c (grub_dl_resolve_symbols): Add check for grub_mod_init
	and grub_mod_fini for symbols without a type. Handle HAVE_ASM_USCORE
	case for these symbols.
	(grub_dl_resolve_dependencies): Add check for trailing nullbytes
	in symbol table. This fixes an infinite loop if table is zero filled.

	* kern/i386/dl.c [__CYGWIN__] (fix_pc_rel_relocation): New function
	to fix bad PC relative relocation produced by objcopy.
	[__CYGWIN__] (grub_arch_dl_relocate_symbols): Add fix of PC relative relocation.
	(grub_arch_dl_relocate_symbols): Abort on unknown relocation type.



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diff --git a/include/grub/dl.h b/include/grub/dl.h
index b630c6f..3029f95 100644
--- a/include/grub/dl.h
+++ b/include/grub/dl.h
@@ -40,11 +40,12 @@ grub_##name##_fini (void) { grub_mod_fini (); } \
 static void \
 grub_mod_fini (void)
 
+/* Note: .previous not supported for non-ELF targets.  */
 #define GRUB_MOD_NAME(name)	\
-__asm__ (".section .modname,\"S\"\n.string \"" #name "\"\n.previous")
+__asm__ (".section .modname\n.string \"" #name "\"\n")
 
 #define GRUB_MOD_DEP(name)	\
-__asm__ (".section .moddeps,\"S\"\n.string \"" #name "\"\n.previous")
+__asm__ (".section .moddeps\n.string \"" #name "\"\n")
 
 struct grub_dl_segment
 {
diff --git a/include/grub/symbol.h b/include/grub/symbol.h
index aa0ea5a..72209d1 100644
--- a/include/grub/symbol.h
+++ b/include/grub/symbol.h
@@ -28,8 +28,14 @@
 # define EXT_C(sym)	sym
 #endif
 
+#ifndef __CYGWIN__
 #define FUNCTION(x)	.globl EXT_C(x) ; .type EXT_C(x), "function" ; EXT_C(x):
 #define VARIABLE(x)	.globl EXT_C(x) ; .type EXT_C(x), "object" ; EXT_C(x):
+#else
+/* .type not supported for non-ELF targets.  XXX: Check this in configure? */
+#define FUNCTION(x)	.globl EXT_C(x) ; EXT_C(x):
+#define VARIABLE(x)	.globl EXT_C(x) ; EXT_C(x):
+#endif
 
 /* Mark an exported symbol.  */
 #ifndef GRUB_SYMBOL_GENERATOR
diff --git a/kern/dl.c b/kern/dl.c
index c0d9f1d..7950c0d 100644
--- a/kern/dl.c
+++ b/kern/dl.c
@@ -53,6 +53,12 @@ typedef Elf64_Sym Elf_Sym;
 
 #endif
 
+#ifdef HAVE_ASM_USCORE
+# define SYM_USCORE "_"
+#else
+# define SYM_USCORE ""
+#endif
+
 \f
 
 struct grub_dl_list
@@ -347,17 +353,31 @@ grub_dl_resolve_symbols (grub_dl_t mod, Elf_Ehdr *e)
       unsigned char type = ELF_ST_TYPE (sym->st_info);
       unsigned char bind = ELF_ST_BIND (sym->st_info);
       const char *name = str + sym->st_name;
-      
+      int check_mod_func = 0;
+
       switch (type)
 	{
 	case STT_NOTYPE:
-	  /* Resolve a global symbol.  */
-	  if (sym->st_name != 0 && sym->st_shndx == 0)
+	  if (sym->st_name != 0)
 	    {
-	      sym->st_value = (Elf_Addr) grub_dl_resolve_symbol (name);
-	      if (! sym->st_value)
-		return grub_error (GRUB_ERR_BAD_MODULE,
-				   "the symbol `%s' not found", name);
+	    if (sym->st_shndx == 0)
+	      {
+		/* Resolve a global symbol.  */
+		sym->st_value = (Elf_Addr) grub_dl_resolve_symbol (name);
+		if (! sym->st_value)
+		  return grub_error (GRUB_ERR_BAD_MODULE,
+				     "the symbol `%s' not found", name);
+	      }
+	    else
+	      { /* Static functions and global variables have no type
+		   if initial format was not ELF.  */
+		sym->st_value += (Elf_Addr) grub_dl_get_section_addr (mod,
+								      sym->st_shndx);
+		if (bind == STB_LOCAL)
+		  check_mod_func = 1;
+		else if (grub_dl_register_symbol (name, (void *) sym->st_value, mod))
+		  return grub_errno;
+	      }
 	    }
 	  else
 	    sym->st_value = 0;
@@ -374,14 +394,10 @@ grub_dl_resolve_symbols (grub_dl_t mod, Elf_Ehdr *e)
 	case STT_FUNC:
 	  sym->st_value += (Elf_Addr) grub_dl_get_section_addr (mod,
 								sym->st_shndx);
-	  if (bind != STB_LOCAL)
-	    if (grub_dl_register_symbol (name, (void *) sym->st_value, mod))
-	      return grub_errno;
-	  
-	  if (grub_strcmp (name, "grub_mod_init") == 0)
-	    mod->init = (void (*) (grub_dl_t)) sym->st_value;
-	  else if (grub_strcmp (name, "grub_mod_fini") == 0)
-	    mod->fini = (void (*) (void)) sym->st_value;
+	  if (bind == STB_LOCAL)
+	    check_mod_func = 1;
+	  else if (grub_dl_register_symbol (name, (void *) sym->st_value, mod))
+	    return grub_errno;
 	  break;
 
 	case STT_SECTION:
@@ -397,6 +413,13 @@ grub_dl_resolve_symbols (grub_dl_t mod, Elf_Ehdr *e)
 	  return grub_error (GRUB_ERR_BAD_MODULE,
 			     "unknown symbol type `%d'", (int) type);
 	}
+      if (check_mod_func)
+        {
+	  if (grub_strcmp (name, SYM_USCORE "grub_mod_init") == 0)
+	    mod->init = (void (*) (grub_dl_t)) sym->st_value;
+	  else if (grub_strcmp (name, SYM_USCORE "grub_mod_fini") == 0)
+	    mod->fini = (void (*) (void)) sym->st_value;
+        }
     }
 
   return GRUB_ERR_NONE;
@@ -454,7 +477,7 @@ grub_dl_resolve_dependencies (grub_dl_t mod, Elf_Ehdr *e)
 	const char *name = (char *) e + s->sh_offset;
 	const char *max = name + s->sh_size;
 
-	while (name < max)
+	while (name < max && *name) /* Segment may contain trailing 0.  */
 	  {
 	    grub_dl_t m;
 	    grub_dl_dep_t dep;
diff --git a/kern/i386/dl.c b/kern/i386/dl.c
index e9e43e5..94d1510 100644
--- a/kern/i386/dl.c
+++ b/kern/i386/dl.c
@@ -37,6 +37,28 @@ grub_arch_dl_check_header (void *ehdr)
   return GRUB_ERR_NONE;
 }
 
+#ifdef __CYGWIN__
+/* Fix PC relative relocation.  Objcopy does not adjust
+the addent when converting from pe-i386 to elf32-i386.  */
+static int
+fix_pc_rel_relocation (Elf32_Word *addr)
+{
+  /* To be safe, check instruction first.  */
+  const unsigned char * pc = (const unsigned char *)addr - 1;
+  if (!(*pc == 0xe8/*call*/ || *pc == 0xe9/*jmp*/))
+    return grub_error (GRUB_ERR_BAD_MODULE, "unknown pc-relative instruction %02x", *pc);
+  /* Check and adjust offset.  */
+  if (*addr != (Elf32_Word)-4)
+    {
+      if (*addr != 0)
+	return grub_error (GRUB_ERR_BAD_MODULE, "invalid pc-relative relocation base %lx",
+			   (long)(*addr));
+      *addr = (Elf32_Word)-4;
+    }
+  return GRUB_ERR_NONE;
+}
+#endif
+
 /* Relocate symbols.  */
 grub_err_t
 grub_arch_dl_relocate_symbols (grub_dl_t mod, void *ehdr)
@@ -99,9 +121,17 @@ grub_arch_dl_relocate_symbols (grub_dl_t mod, void *ehdr)
 		    break;
 
 		  case R_386_PC32:
+#ifdef __CYGWIN__
+		    if (fix_pc_rel_relocation (addr))
+		      return grub_errno;
+#endif
 		    *addr += (sym->st_value - (Elf32_Word) seg->addr
 			      - rel->r_offset);
 		    break;
+
+		  default:
+		    return grub_error (GRUB_ERR_BAD_MODULE, "unknown relocation type %x.",
+				       ELF32_R_TYPE (rel->r_info));
 		  }
 	      }
 	  }

Re: [PATCH] Kernel fixes for Cygwin

[Bean]

On Mon, Jul 21, 2008 at 4:51 AM, Christian Franke
<Christian.Franke@t-online.de> wrote:
> This adds Cygwin support to kernel sources. It handles the issues introduced
> by PE->ELF conversion and adds support for HAVE_ASM_USCORE.
>
> Christian
>
> 2007-07-20      Christian Franke  <franke@computer.org>
>
>        * include/grub/dl.h: Remove .previous, gas supports this only
>        for ELF format.
>
>        * include/grub/symbol.h [__CYGWIN__] (#define FUNCTION/VARIABLE):
>        Remove .type, gas supports this only for ELF format.
>
>        * kern/dl.c (grub_dl_resolve_symbols): Add check for grub_mod_init
>        and grub_mod_fini for symbols without a type. Handle HAVE_ASM_USCORE
>        case for these symbols.
>        (grub_dl_resolve_dependencies): Add check for trailing nullbytes
>        in symbol table. This fixes an infinite loop if table is zero filled.
>
>        * kern/i386/dl.c [__CYGWIN__] (fix_pc_rel_relocation): New function
>        to fix bad PC relative relocation produced by objcopy.
>        [__CYGWIN__] (grub_arch_dl_relocate_symbols): Add fix of PC relative
> relocation.
>        (grub_arch_dl_relocate_symbols): Abort on unknown relocation type.

Hi,

I'm not fond of fixing elf relocation bug in dl.c. First of all, this
is an objcopy bug, it may be changed in the future, also, it makes
modules compiled by cygwin not compatible with those compiled by elf
gcc.

Perhaps you can write a small tool, which fix various bugs after using
objcopy to generate the module file.

-- 
Bean

Re: [PATCH] Kernel fixes for Cygwin

[Bean]

On Mon, Jul 21, 2008 at 3:02 PM, Bean <bean123ch@gmail.com> wrote:
> On Mon, Jul 21, 2008 at 4:51 AM, Christian Franke
> <Christian.Franke@t-online.de> wrote:
>> This adds Cygwin support to kernel sources. It handles the issues introduced
>> by PE->ELF conversion and adds support for HAVE_ASM_USCORE.
>>
>> Christian
>>
>> 2007-07-20      Christian Franke  <franke@computer.org>
>>
>>        * include/grub/dl.h: Remove .previous, gas supports this only
>>        for ELF format.
>>
>>        * include/grub/symbol.h [__CYGWIN__] (#define FUNCTION/VARIABLE):
>>        Remove .type, gas supports this only for ELF format.
>>
>>        * kern/dl.c (grub_dl_resolve_symbols): Add check for grub_mod_init
>>        and grub_mod_fini for symbols without a type. Handle HAVE_ASM_USCORE
>>        case for these symbols.
>>        (grub_dl_resolve_dependencies): Add check for trailing nullbytes
>>        in symbol table. This fixes an infinite loop if table is zero filled.
>>
>>        * kern/i386/dl.c [__CYGWIN__] (fix_pc_rel_relocation): New function
>>        to fix bad PC relative relocation produced by objcopy.
>>        [__CYGWIN__] (grub_arch_dl_relocate_symbols): Add fix of PC relative
>> relocation.
>>        (grub_arch_dl_relocate_symbols): Abort on unknown relocation type.
>
> Hi,
>
> I'm not fond of fixing elf relocation bug in dl.c. First of all, this
> is an objcopy bug, it may be changed in the future, also, it makes
> modules compiled by cygwin not compatible with those compiled by elf
> gcc.
>
> Perhaps you can write a small tool, which fix various bugs after using
> objcopy to generate the module file.

Hi,

BTW, if you have time, you can consider writing a tool that convert pe
to elf directly, thus avoiding objcopy altogether. This shouldn't be
too difficult, you can take a look at util/i386/efi/grub-mkimage.c,
which does exactly the opposite, converting elf to pe32.


-- 
Bean

Re: [PATCH] Kernel fixes for Cygwin

[Christian Franke]

Bean wrote:
> On Mon, Jul 21, 2008 at 4:51 AM, Christian Franke
> <...> wrote:
> > This adds Cygwin support to kernel sources. It handles the issues
> > introduced by PE->ELF conversion and adds support for
> > HAVE_ASM_USCORE.
> > 
> > Christian
> > 
> > 2007-07-20      Christian Franke  <franke@computer.org>
> > 
> > * include/grub/dl.h: Remove .previous, gas supports this only for
> > ELF format.
> > 
> > * include/grub/symbol.h [__CYGWIN__] (#define FUNCTION/VARIABLE):
> > Remove .type, gas supports this only for ELF format.
> > 
> > * kern/dl.c (grub_dl_resolve_symbols): Add check for grub_mod_init
> > and grub_mod_fini for symbols without a type. Handle HAVE_ASM_USCORE
> > case for these symbols.
> > (grub_dl_resolve_dependencies): Add check for trailing nullbytes in
> > symbol table. This fixes an infinite loop if table is zero filled.
> > 
> > * kern/i386/dl.c [__CYGWIN__] (fix_pc_rel_relocation): New function
> > to fix bad PC relative relocation produced by objcopy.
> > [__CYGWIN__] (grub_arch_dl_relocate_symbols): Add fix of PC relative
> > relocation.
> > (grub_arch_dl_relocate_symbols): Abort on unknown relocation type.
> > 
> 
> Hi,
> 
> I'm not fond of fixing elf relocation bug in dl.c. ...
> 

Hi,

I agree that kern/i386/dl.c:fix_pc_rel_relocation() is an ugly hack and
shall be removed when a better solution is available.


> ... First of all, this
> is an objcopy bug, it may be changed in the future, ...
> 

My patch for objcopy was rejected upstream. According to binutils
mailing list, this is not an objcopy bug, but a BFD design limitation:
http://sourceware.org/ml/binutils/2007-10/msg00306.html

So I don't expect a fix before time_t wraps around ...


> ... also, it makes
> modules compiled by cygwin not compatible with those compiled by elf
> gcc.
> 

The fix_pc_rel_relocation() works also with correct ELF files, because
the (-4) fix is only applied if necessary.

Supporting Modules compiled with ELF gcc would also require to handle
the different syntax of C-Symbols (HAVE_ASM_USCORE or NOT).

Actually my first version of supported this by aliasing symbols
with/without underscore in kern/dl.c. It was tested with modules
compiled with Linux gcc loaded by kernel.img compiled with Cygwin gcc
and vice versa and all this *worked*.

But according to a comment from Robert, this is possibly useless or not
desired, see:
http://lists.gnu.org/archive/html/grub-devel/2007-11/msg00152.html

So I removed this (non?-)feature for now. Would be easy to re-add later.

Christian

Re: [PATCH] Kernel fixes for Cygwin

[Christian Franke]

Bean wrote:
> 
> Hi,
> 
> BTW, if you have time, you can consider writing a tool that convert pe
> to elf directly, thus avoiding objcopy altogether. This shouldn't be
> too difficult, you can take a look at util/i386/efi/grub-mkimage.c,
> which does exactly the opposite, converting elf to pe32.
> 
> 

Hi,

due to the complexity of PE, a stand-alone converter may likely be
larger than the ~680 LoC converter I already offered here. It was
rejected, see this thread:
http://lists.gnu.org/archive/html/grub-devel/2007-11/msg00174.html

It should be possible to build a smaller tool that only fixes the
relocation info in the generated ELF. But due to the C++ redesign of
smartmontools, my open source time is somewhat limited in the moment :-)

To provide Cygwin support for the next release, I would suggest to
accept the small hack in kern/i386/dl.c for now. It is already available
it and it works. It can be removed when a tool is available. Or accept
the converter mentioned above.

Christian

Re: [PATCH] Kernel fixes for Cygwin

[Bean]

On Mon, Jul 21, 2008 at 6:33 PM, Christian Franke
<Christian.Franke@t-online.de> wrote:
> Hi,
>
> due to the complexity of PE, a stand-alone converter may likely be
> larger than the ~680 LoC converter I already offered here. It was
> rejected, see this thread:
> http://lists.gnu.org/archive/html/grub-devel/2007-11/msg00174.html
>

Hi,

I can't find the source code for your converter, perhaps you can repost it ?

IMO, it's better to use our own tool, if it's not very complicated. I
learn this lesson when writing efi support for x86_64. The gnu-efi
toolchain can produce efi image, but it turns out to have some
limitation on relocation, and it's hard to fix. I end up modifying
grub-mkimage to support converting elf to pe32+. Relying on external
tool means we are at the mercy of them, it's annoying when they have
issue, as we can't expect upstream to fix it soon.

-- 
Bean

Re: [PATCH] Kernel fixes for Cygwin

[Javier Martín]

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El lun, 21-07-2008 a las 12:33 +0200, Christian Franke escribió:
> Bean wrote:
> > BTW, if you have time, you can consider writing a tool that convert pe
> > to elf directly, thus avoiding objcopy altogether. This shouldn't be
> > too difficult, you can take a look at util/i386/efi/grub-mkimage.c,
> > which does exactly the opposite, converting elf to pe32.
> 
> due to the complexity of PE, a stand-alone converter may likely be
> larger than the ~680 LoC converter I already offered here.
Why do we even consider a PE->ELF converter? I think the easier way to
go would have the people building GRUB in cygwin (not exactly newbies)
to have an i386-pc-elf "cross compiler" built first, then use that for
the bootloader programs and the normal gcc for tools. Even a "naked"
(i.e. libraryless) cross compiler would work, since the bootloader part
of GRUB is does not need libs (in C terminology, it's "freestanding").
That way, we are free from "objcopy bugs" or "BFD design limitations".

This scheme is kinda like what's done with x86_64-pc-linux, with the
difference that in that case we use the same gcc for both "host" and
"target" by adding -m32 to the latter, but it's essentially the same
concept.

Habbit

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Re: [PATCH] Kernel fixes for Cygwin

[Christian Franke]

Javier Martín wrote:
> El lun, 21-07-2008 a las 12:33 +0200, Christian Franke escribió:
> > Bean wrote:
> > > BTW, if you have time, you can consider writing a tool that
> > > convert pe to elf directly, thus avoiding objcopy altogether. This
> > > shouldn't be too difficult, you can take a look at
> > > util/i386/efi/grub-mkimage.c, which does exactly the opposite,
> > > converting elf to pe32.
> > > 
> > 
> > due to the complexity of PE, a stand-alone converter may likely be
> > larger than the ~680 LoC converter I already offered here.
> Why do we even consider a PE->ELF converter? I think the easier way to
> go would have the people building GRUB in cygwin (not exactly newbies)
> to have an i386-pc-elf "cross compiler" built first, then use that for
> the bootloader programs and the normal gcc for tools. Even a "naked"
> (i.e. libraryless) cross compiler would work, since the bootloader
> part of GRUB is does not need libs (in C terminology, it's
> "freestanding").
> That way, we are free from "objcopy bugs" or "BFD design limitations".
> 

Yes, but this is not yet possible for the grub2 package in the Cygwin
distro, see:
http://lists.gnu.org/archive/html/grub-devel/2008-07/msg00263.html

Christian

Re: [PATCH] Kernel fixes for Cygwin

[Pavel Roskin]

On Mon, 2008-07-21 at 13:02 +0200, Javier Martín wrote:
> El lun, 21-07-2008 a las 12:33 +0200, Christian Franke escribió:
> > due to the complexity of PE, a stand-alone converter may likely be
> > larger than the ~680 LoC converter I already offered here.
> Why do we even consider a PE->ELF converter? I think the easier way to
> go would have the people building GRUB in cygwin (not exactly newbies)
> to have an i386-pc-elf "cross compiler" built first, then use that for
> the bootloader programs and the normal gcc for tools. Even a "naked"
> (i.e. libraryless) cross compiler would work, since the bootloader part
> of GRUB is does not need libs (in C terminology, it's "freestanding").
> That way, we are free from "objcopy bugs" or "BFD design limitations".

Well, if we want users to recompile their toolchain first, it's too much
to ask.

Maybe we could treat ELF header like a multiboot header?  That means
that we write the header fields in the assembly language, substitute the
necessary variables and ask objcopy to make a raw binary that would
actually be an ELF file?

We could actually do it for all platforms, so that we won't depend on
the object file format.

-- 
Regards,
Pavel Roskin

Re: [PATCH] Kernel fixes for Cygwin

[Javier Martín]

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El lun, 21-07-2008 a las 11:51 -0400, Pavel Roskin escribió:
> On Mon, 2008-07-21 at 13:02 +0200, Javier Martín wrote:
> > El lun, 21-07-2008 a las 12:33 +0200, Christian Franke escribió:
> > > due to the complexity of PE, a stand-alone converter may likely be
> > > larger than the ~680 LoC converter I already offered here.
> > Why do we even consider a PE->ELF converter? I think the easier way to
> > go would have the people building GRUB in cygwin (not exactly newbies)
> > to have an i386-pc-elf "cross compiler" built first, then use that for
> > the bootloader programs and the normal gcc for tools. Even a "naked"
> > (i.e. libraryless) cross compiler would work, since the bootloader part
> > of GRUB is does not need libs (in C terminology, it's "freestanding").
> > That way, we are free from "objcopy bugs" or "BFD design limitations".
> 
> Well, if we want users to recompile their toolchain first, it's too much
> to ask.
I think it is not, since people building GRUB in Cygwin are not exactly
newcomers to the land of compiling: this package requires that its files
and modules be in ELF format; your compiler does not do it, so you need
another compiler. End of the problem.

Of course, another way to go could be to allow the bootloader part of
GRUB to be built in PE format: it would "just" be a matter of writing
the PE counterparts to kern/elf.c and abstracting kern/dl.c "a
bit" (i.e. a lot of work). The downside to this, apart from the
unspecified work required, is that Windows-built i386-pc-pe modules are
no longer compatible with Linux-built i386-pc-elf. Not a showstopper,
but might require a sober thinking. As I have a lot of free time right
now, I'll try to think whether it's possible or not.

> Maybe we could treat ELF header like a multiboot header?  That means
> that we write the header fields in the assembly language, substitute the
> necessary variables and ask objcopy to make a raw binary that would
> actually be an ELF file?
As far as I understand the ELF format, this would be too complex to get
right: there's a lot of info in there.
> 
> We could actually do it for all platforms, so that we won't depend on
> the object file format.
> 

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Re: [PATCH] Kernel fixes for Cygwin

[Pavel Roskin]

On Mon, 2008-07-21 at 18:50 +0200, Javier Martín wrote:

> Of course, another way to go could be to allow the bootloader part of
> GRUB to be built in PE format: it would "just" be a matter of writing
> the PE counterparts to kern/elf.c and abstracting kern/dl.c "a
> bit" (i.e. a lot of work). The downside to this, apart from the
> unspecified work required, is that Windows-built i386-pc-pe modules are
> no longer compatible with Linux-built i386-pc-elf. Not a showstopper,
> but might require a sober thinking. As I have a lot of free time right
> now, I'll try to think whether it's possible or not.

I think it's important to have a consistent format for modules.

> > Maybe we could treat ELF header like a multiboot header?  That means
> > that we write the header fields in the assembly language, substitute the
> > necessary variables and ask objcopy to make a raw binary that would
> > actually be an ELF file?
> As far as I understand the ELF format, this would be too complex to get
> right: there's a lot of info in there.

If ELF is too complex to write manually, we can use another format
everywhere.  It could be something GRUB specific.  But I think we should
try to use ELF, as it's widespread and extensible.

-- 
Regards,
Pavel Roskin

Re: [PATCH] Kernel fixes for Cygwin

[Javier Martín]

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El lun, 21-07-2008 a las 13:03 -0400, Pavel Roskin escribió:
> On Mon, 2008-07-21 at 18:50 +0200, Javier Martín wrote:
> 
> > Of course, another way to go could be to allow the bootloader part of
> > GRUB to be built in PE format: it would "just" be a matter of writing
> > the PE counterparts to kern/elf.c and abstracting kern/dl.c "a
> > bit" (i.e. a lot of work). The downside to this, apart from the
> > unspecified work required, is that Windows-built i386-pc-pe modules are
> > no longer compatible with Linux-built i386-pc-elf. Not a showstopper,
> > but might require a sober thinking. As I have a lot of free time right
> > now, I'll try to think whether it's possible or not.
> 
> I think it's important to have a consistent format for modules.
I thought that two hours ago, but now I find no advantage other than the
sharing of modules between similar computers.

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Re: [PATCH] Kernel fixes for Cygwin

[Pavel Roskin]

On Mon, 2008-07-21 at 19:23 +0200, Javier Martín wrote:
> El lun, 21-07-2008 a las 13:03 -0400, Pavel Roskin escribió:

> > I think it's important to have a consistent format for modules.
> I thought that two hours ago, but now I find no advantage other than the
> sharing of modules between similar computers.

Sharing modules is unsafe.

My concern is sharing the code.  If we use different formats, there are
more place for bugs to hide or to appear.  There is more work to test
changes that can affect module loading.

-- 
Regards,
Pavel Roskin

Re: [PATCH] Kernel fixes for Cygwin

[Christian Franke]

Bean wrote:
> On Mon, Jul 21, 2008 at 6:33 PM, Christian Franke
> <Christian.Franke@t-online.de> wrote:
>   
>> Hi,
>>
>> due to the complexity of PE, a stand-alone converter may likely be
>> larger than the ~680 LoC converter I already offered here. It was
>> rejected, see this thread:
>> http://lists.gnu.org/archive/html/grub-devel/2007-11/msg00174.html
>>
>>     
>
> Hi,
>
> I can't find the source code for your converter, perhaps you can repost it ?
>
>   

I did not post it in the original thread from 2007-11.

It is actually a reduced version of objcopy with
- stuff not necessary for object format conversion removed,
- some functions from shared modules added to make it self-contained,
- the fix for the pc-relative relocation added to

It was intended as starting point to get rid of the hack in kern/i386/dl.c.

The hard work is still done by BFD.


> IMO, it's better to use our own tool, if it's not very complicated. I
> learn this lesson when writing efi support for x86_64. The gnu-efi
> toolchain can produce efi image, but it turns out to have some
> limitation on relocation, and it's hard to fix. I end up modifying
> grub-mkimage to support converting elf to pe32+. Relying on external
> tool means we are at the mercy of them, it's annoying when they have
> issue, as we can't expect upstream to fix it soon.
>
>   

Yes, an own tool is probably best in the long term.

But such a tool will be likely not available for GRUB 1.97 tarball release.

Christian