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Re: [rfa:amd64] Fetch 32-bit thread area
Date: Sat, 28 Feb 2004 10:22:29 -0500
From: Andrew Cagney <cagney@gnu.org>
> Date: Thu, 26 Feb 2004 20:24:47 -0500
> From: Andrew Cagney <ac131313@redhat.com>
>
> Hello,
>
> This modifies the amd64 code so that, when 32-bit, it fetches the 32-bit
> thread area register (I think this has been posted before?).
>
> Why #if 0 ... #else ... #endif?
Tipo from testing.
Typo? You mean that you intended to remove the #if 0 block before
submitting the patch? Or what?
Yes, "tipo". As Stan Shebs where the word comes from.
> Anyway, I'm not really happy with the
>
> switch (TARGET_ARCHITECTURE->mach)
>
> construction. The other AMD64 native code uses an
>
> if (gdbarch_ptr_bit (current_gdbarch) == 32)
>
> to distinguish between 32-bit and 64-bit code. While this may not be
> completely correct (someone might come up with a native AMD64 ABI with
> 32-bit pointers), I'd rather not use multiple variations of the
> 32-bit/64-bit check in the code.
Is it ok with that change?
If you remove the #if 0 block and re-indent the #else block. Yes.
Done. Committed the attached.
Andrew
2004-02-28 Andrew Cagney <cagney@redhat.com>
* amd64-linux-nat.c (ps_get_thread_area): When architecture is
i386 use PTRACE_GET_THREAD_AREA. Suggested by Roland McGrath.
Index: amd64-linux-nat.c
===================================================================
RCS file: /cvs/src/src/gdb/amd64-linux-nat.c,v
retrieving revision 1.3
diff -u -r1.3 amd64-linux-nat.c
--- amd64-linux-nat.c 28 Feb 2004 18:54:31 -0000 1.3
+++ amd64-linux-nat.c 28 Feb 2004 19:28:56 -0000
@@ -350,31 +350,60 @@
}
+/* This function is called by libthread_db as part of its handling of
+ a request for a thread's local storage address. */
+
ps_err_e
ps_get_thread_area (const struct ps_prochandle *ph,
lwpid_t lwpid, int idx, void **base)
{
-/* This definition comes from prctl.h, but some kernels may not have it. */
+ if (gdbarch_ptr_bit (current_gdbarch) == 32)
+ {
+ /* The full structure is found in <asm-i386/ldt.h>. The second
+ integer is the LDT's base_address and that is used to locate
+ the thread's local storage. See i386-linux-nat.c more
+ info. */
+ unsigned int desc[4];
+
+ /* This code assumes that "int" is 32 bits and that
+ GET_THREAD_AREA returns no more than 4 int values. */
+ gdb_assert (sizeof (int) == 4);
+#ifndef PTRACE_GET_THREAD_AREA
+#define PTRACE_GET_THREAD_AREA 25
+#endif
+ if (ptrace (PTRACE_GET_THREAD_AREA,
+ lwpid, (void *) (long) idx, (unsigned long) &desc) < 0)
+ return PS_ERR;
+
+ /* Extend the value to 64 bits. Here it's assumed that a "long"
+ and a "void *" are the same. */
+ (*base) = (void *) (long) desc[1];
+ return PS_OK;
+ }
+ else
+ {
+ /* This definition comes from prctl.h, but some kernels may not
+ have it. */
#ifndef PTRACE_ARCH_PRCTL
#define PTRACE_ARCH_PRCTL 30
#endif
-
- /* FIXME: ezannoni-2003-07-09 see comment above about include file order.
- We could be getting bogus values for these two. */
- gdb_assert (FS < ELF_NGREG);
- gdb_assert (GS < ELF_NGREG);
- switch (idx)
- {
- case FS:
- if (ptrace (PTRACE_ARCH_PRCTL, lwpid, base, ARCH_GET_FS) == 0)
- return PS_OK;
- break;
- case GS:
- if (ptrace (PTRACE_ARCH_PRCTL, lwpid, base, ARCH_GET_GS) == 0)
- return PS_OK;
- break;
- default: /* Should not happen. */
- return PS_BADADDR;
+ /* FIXME: ezannoni-2003-07-09 see comment above about include
+ file order. We could be getting bogus values for these two. */
+ gdb_assert (FS < ELF_NGREG);
+ gdb_assert (GS < ELF_NGREG);
+ switch (idx)
+ {
+ case FS:
+ if (ptrace (PTRACE_ARCH_PRCTL, lwpid, base, ARCH_GET_FS) == 0)
+ return PS_OK;
+ break;
+ case GS:
+ if (ptrace (PTRACE_ARCH_PRCTL, lwpid, base, ARCH_GET_GS) == 0)
+ return PS_OK;
+ break;
+ default: /* Should not happen. */
+ return PS_BADADDR;
+ }
}
return PS_ERR; /* ptrace failed. */
}