Re: [Linux-ia64] Newbie questions

Re: [Linux-ia64] Newbie questions

[Matthew Wilcox]

On Sat, Nov 09, 2002 at 12:21:40AM +0530, CH Gowri Kumar wrote:
> I wrote the above program and compiled it and found the appropriate codes
> for the instructions using objdump -d and wrote the following program
> 
> char sc[] ="\x0a"
>            "\x10"
>            "\x00"
>            "\x18\x00\x21\x00\x92\x00\x00\x42\xe0\x11\x00\x20\x84\x0a";
>        main()
>        {
>          void (*fp)(void);
>          fp = (void*)sc;
>          fp();
>       }
> 
> But this program on execution gives me the error:
> "Illegal instruction (core dumped)"
> (A similar program for IA-32 worked well.)

function pointers on ia64 are "fat" -- that is, they are not the address
of the function, they are the address of a function descriptor which
contains (iirc) the GP and the address of the function.  i believe glibc
pokes around with this kind of thing, so you may wish to look at the
ia64 assembly code in there to see how it does it.

-- 
Revolutions do not require corporate support.

[Linux-ia64] Newbie questions

[CH Gowri Kumar]

hello all,
I am a post-graduate student trying to write a JIT compiler for .NET CLR
on Linux,IA-64.

I have some queries related to IA-64 assembly programming

I plan to write the JIT this way:
I generate the native code directly (instead of assembly language and
then using assembler)for a particular method and jump to the address
of the starting memory location where I have generated the native code. I
have written a small program to check whether such a thing is feasible, 
which is as follows:

#include<unistd.h>
int main()
{
  __asm__("
      mov r32\x18
      mov r15\x1025
      break 0x100000"
  );
}

I wrote the above program and compiled it and found the appropriate codes
for the instructions using objdump -d and wrote the following program

char sc[] ="\x0a"
           "\x10"
           "\x00"
           "\x18\x00\x21\x00\x92\x00\x00\x42\xe0\x11\x00\x20\x84\x0a";
       main()
       {
         void (*fp)(void);
         fp = (void*)sc;
         fp();
      }

But this program on execution gives me the error:
"Illegal instruction (core dumped)"
(A similar program for IA-32 worked well.)

I couldn't figure out what could be the problem.
I also tried using "br instruction" approach instead of the function
pointer approach, but couldn't succeed.

Can anyone explain why it is failing or atleast give me pointers where to
look for?

Thanks in advance.
Gowri Kumar

Re: [Linux-ia64] Newbie questions

[Stephane Eranian]

On Fri, Nov 08, 2002 at 07:01:10PM +0000, Matthew Wilcox wrote:
> On Sat, Nov 09, 2002 at 12:21:40AM +0530, CH Gowri Kumar wrote:
> > I wrote the above program and compiled it and found the appropriate codes
> > for the instructions using objdump -d and wrote the following program
> > 
> > char sc[] ="\x0a"
> >            "\x10"
> >            "\x00"
> >            "\x18\x00\x21\x00\x92\x00\x00\x42\xe0\x11\x00\x20\x84\x0a";
> >        main()
> >        {
> >          void (*fp)(void);
> >          fp = (void*)sc;
> >          fp();
> >       }
> > 
> > But this program on execution gives me the error:
> > "Illegal instruction (core dumped)"
> > (A similar program for IA-32 worked well.)
> 
> function pointers on ia64 are "fat" -- that is, they are not the address
> of the function, they are the address of a function descriptor which
> contains (iirc) the GP and the address of the function.  i believe glibc
> pokes around with this kind of thing, so you may wish to look at the
> ia64 assembly code in there to see how it does it.
> 

to be more precise a function descriptors is:
	struct {
		unsigned long func_addr;
		unsigned long gp;
	};

You should also take a look at the calling convention documentation
at:
	http://developer.intel.com/design/itanium
-- 
-Stephane

Re: [Linux-ia64] Newbie questions

[David Mosberger]

>>>>> On Sat, 9 Nov 2002 00:21:40 +0530 (IST), CH Gowri Kumar <gkumar@csa.iisc.ernet.in> said:

  Gowri> char sc[] ="\x0a" "\x10" "\x00"
  Gowri> "\x18\x00\x21\x00\x92\x00\x00\x42\xe0\x11\x00\x20\x84\x0a";
  Gowri> main() { void (*fp)(void); fp = (void*)sc; fp(); }

  Gowri> But this program on execution gives me the error: "Illegal
  Gowri> instruction (core dumped)" (A similar program for IA-32
  Gowri> worked well.)

  Gowri> I couldn't figure out what could be the problem.  I also
  Gowri> tried using "br instruction" approach instead of the function
  Gowri> pointer approach, but couldn't succeed.

  Gowri> Can anyone explain why it is failing or atleast give me
  Gowri> pointers where to look for?

You'll want to read the software convention manual, especially that
portion talking about function descriptors.  The manual is normally
available at:

	http://www.intel.com/design/Itanium/arch_spec.htm

Unfortunately, the URL it points to
(http://www.intel.com/design/itanium/downloads/24535803s.htm) is
currently broken.  [Could someone from Intel look into getting this
fixed?]

But briefly, a function descriptor consists of (at least) two words:
the first one being the entry point (instruction address) and the
second one being the global pointer.  I attached a small test program
that demos "dynamic" code generation (note: instruction bundles must
be aligned to 16-byte boundary, which wasn't guaranteed in your test
program).

	--david

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <malloc.h>

#include <sys/mman.h>

#ifdef __ia64__
typedef struct _fp
{
  long addr;
  long gp;
} IA64_FUNCTION;

static void flush_cache (void *addr, unsigned long len)
{
  void *end = (char *) addr + len;

  while (addr < end)
    {
      asm volatile ("fc %0" :: "r"(addr));
      addr = (char *) addr + 32;
    }
  asm volatile (";;sync.i;;srlz.i;;");
}
#endif

void TestApp(void)
{
#ifdef __ia64__
  __asm__ __volatile__ ("nop.i 0");
  __asm__ __volatile__ ("nop.i 0");
  __asm__ __volatile__ ("nop.i 0");
  __asm__ __volatile__ ("nop.i 0");
#else
  __asm__ __volatile__ ("nop");
#endif
  return;
}

int main(int argc, char *argv[])
{
  void (*pSubroutine)(void);
  unsigned char *pBuffer1;
  long alignment;
#ifdef __ia64__
  IA64_FUNCTION *fp;
  IA64_FUNCTION newfp;
#endif

  printf("Test ***\n");

  malloc(0x10000);

  // Allocate and align buffer on 16 byte boundary
  pBuffer1 = (unsigned char *)malloc(0x1000);
  alignment = ((unsigned long)pBuffer1 % 16);
  pBuffer1 = pBuffer1 + 16 - alignment;

#ifdef __ia64__
  fp = (IA64_FUNCTION *)TestApp;
  printf("pSub Addr = 0x%lX GP = 0x%lX\n", fp->addr, fp->gp);
  memcpy(pBuffer1, (unsigned char *)fp->addr, 256);
  flush_cache(pBuffer1, 0x1000);

  newfp.gp = fp->gp;
  newfp.addr = (long)pBuffer1;
  printf("pSub Addr = 0x%lX GP = 0x%lX\n", newfp.addr, newfp.gp);
  pSubroutine = (void (*)(void))&newfp;

  mprotect((void *) ((long) pBuffer1 & ~(getpagesize () - 1)),
	   getpagesize(), PROT_READ | PROT_WRITE | PROT_EXEC);
#else
  printf("pSub Addr = 0x%lX\n", pBuffer1);
  memcpy(pBuffer1, &TestApp, 32);
  pSubroutine = (void (*)(void)) pBuffer1;
#endif

  (*pSubroutine)();

  printf ("done!\n");
  return(0);
}

RE: [Linux-ia64] Newbie questions

[Saxena, Sunil]

The Software conventions document is at
http://developer.intel.com/design/itanium/downloads/245358.htm 

All documents can now be found at
http://developer.intel.com/design/itanium/arch_spec.htm 

Thanks
Sunil
-----Original Message-----
From: David Mosberger [mailto:davidm@napali.hpl.hp.com] 
Sent: Friday, November 08, 2002 11:09 AM
To: CH Gowri Kumar
Cc: 'linux-ia64@linuxia64.org '
Subject: Re: [Linux-ia64] Newbie questions

>>>>> On Sat, 9 Nov 2002 00:21:40 +0530 (IST), CH Gowri Kumar
<gkumar@csa.iisc.ernet.in> said:

  Gowri> char sc[] ="\x0a" "\x10" "\x00"
  Gowri> "\x18\x00\x21\x00\x92\x00\x00\x42\xe0\x11\x00\x20\x84\x0a";
  Gowri> main() { void (*fp)(void); fp = (void*)sc; fp(); }

  Gowri> But this program on execution gives me the error: "Illegal
  Gowri> instruction (core dumped)" (A similar program for IA-32
  Gowri> worked well.)

  Gowri> I couldn't figure out what could be the problem.  I also
  Gowri> tried using "br instruction" approach instead of the function
  Gowri> pointer approach, but couldn't succeed.

  Gowri> Can anyone explain why it is failing or atleast give me
  Gowri> pointers where to look for?

You'll want to read the software convention manual, especially that
portion talking about function descriptors.  The manual is normally
available at:

	http://www.intel.com/design/Itanium/arch_spec.htm

Unfortunately, the URL it points to
(http://www.intel.com/design/itanium/downloads/24535803s.htm) is
currently broken.  [Could someone from Intel look into getting this
fixed?]

But briefly, a function descriptor consists of (at least) two words:
the first one being the entry point (instruction address) and the
second one being the global pointer.  I attached a small test program
that demos "dynamic" code generation (note: instruction bundles must
be aligned to 16-byte boundary, which wasn't guaranteed in your test
program).

	--david

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <malloc.h>

#include <sys/mman.h>

#ifdef __ia64__
typedef struct _fp
{
  long addr;
  long gp;
} IA64_FUNCTION;

static void flush_cache (void *addr, unsigned long len)
{
  void *end = (char *) addr + len;

  while (addr < end)
    {
      asm volatile ("fc %0" :: "r"(addr));
      addr = (char *) addr + 32;
    }
  asm volatile (";;sync.i;;srlz.i;;");
}
#endif

void TestApp(void)
{
#ifdef __ia64__
  __asm__ __volatile__ ("nop.i 0");
  __asm__ __volatile__ ("nop.i 0");
  __asm__ __volatile__ ("nop.i 0");
  __asm__ __volatile__ ("nop.i 0");
#else
  __asm__ __volatile__ ("nop");
#endif
  return;
}

int main(int argc, char *argv[])
{
  void (*pSubroutine)(void);
  unsigned char *pBuffer1;
  long alignment;
#ifdef __ia64__
  IA64_FUNCTION *fp;
  IA64_FUNCTION newfp;
#endif

  printf("Test ***\n");

  malloc(0x10000);

  // Allocate and align buffer on 16 byte boundary
  pBuffer1 = (unsigned char *)malloc(0x1000);
  alignment = ((unsigned long)pBuffer1 % 16);
  pBuffer1 = pBuffer1 + 16 - alignment;

#ifdef __ia64__
  fp = (IA64_FUNCTION *)TestApp;
  printf("pSub Addr = 0x%lX GP = 0x%lX\n", fp->addr, fp->gp);
  memcpy(pBuffer1, (unsigned char *)fp->addr, 256);
  flush_cache(pBuffer1, 0x1000);

  newfp.gp = fp->gp;
  newfp.addr = (long)pBuffer1;
  printf("pSub Addr = 0x%lX GP = 0x%lX\n", newfp.addr, newfp.gp);
  pSubroutine = (void (*)(void))&newfp;

  mprotect((void *) ((long) pBuffer1 & ~(getpagesize () - 1)),
	   getpagesize(), PROT_READ | PROT_WRITE | PROT_EXEC);
#else
  printf("pSub Addr = 0x%lX\n", pBuffer1);
  memcpy(pBuffer1, &TestApp, 32);
  pSubroutine = (void (*)(void)) pBuffer1;
#endif

  (*pSubroutine)();

  printf ("done!\n");
  return(0);
}

_______________________________________________
Linux-IA64 mailing list
Linux-IA64@linuxia64.org
http://lists.linuxia64.org/lists/listinfo/linux-ia64

RE: [Linux-ia64] Newbie questions

[David Mosberger]

>>>>> On Sun, 10 Nov 2002 18:56:12 -0800, "Saxena, Sunil" <sunil.saxena@intel.com> said:

  Sunil> The Software conventions document is at
  Sunil> http://developer.intel.com/design/itanium/downloads/245358.htm

Ah, yes, this works!

  Sunil> All documents can now be found at
  Sunil> http://developer.intel.com/design/itanium/arch_spec.htm

Should this be: http://developer.intel.com/design/itanium/family/ ?
The former results in a "this page has moved page" (it does redirect
eventually, but it's slower).

In any case, thanks for providing the URL for the conventions manual.

	--david