Bug 136700 – 64-bit PowerPC GDB can't fetch FPSCR

Bug 136700 - 64-bit PowerPC GDB can't fetch FPSCR

Summary:	64-bit PowerPC GDB can't fetch FPSCR

Status:	CLOSED DUPLICATE of bug 91727

Aliases:	None

Product:	Fedora
Classification:	Fedora
Component:	kernel (Show other bugs)
Sub Component:
Version:	rawhide
Hardware:	powerpc Linux

Priority	medium Severity medium
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Assigned To:	David Woodhouse
QA Contact:	Brian Brock
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Blocks:	116894
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Reported:	2004-10-21 15:41 EDT by Andrew Cagney
Modified:	2007-11-30 17:10 EST (History)
CC List:	1 user (show)

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Doc Type:	Bug Fix
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Last Closed:	2006-02-21 14:06:32 EST
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Description Andrew Cagney 2004-10-21 15:41:42 EDT

GDB can't fetch the PowerPC's FPSCR register: 

  (gdb) print $fpscr
  reading register fpscr (#70): Input/output error.
  (gdb)

as occures when GDB is doing an inferior function call.

Version-Release number of selected component (if applicable):

 2.6.9-rc4

strace shows:

  ptrace(PTRACE_PEEKUSER, 503, 0x288, 0xffffcdb0) = -1 EIO

and grubbing the headers:

  #define PT_FPR0 48
  define PT_FPSCR (PT_FPR0 + 32 + 1)
  (gdb) print/x (48 + 32 + 1) * 8
  $1 = 0x288

suggests that the value is correct.

Comment 1 David Woodhouse 2004-10-25 18:22:33 EDT

See bug #91727. 

The value of PT_FPSCR for 64-bit userspace is different to the value
for 32-bit. This is because a 'double' is worth two longs for 32-bit
code, and only one for 64-bit code.

I think the kernel is doing the right thing -- if there's a kernel bug
it's purely the evilness of the way the interface is done. If we're
going to start criticising the ptrace interface... :)

Closing NOTABUG. Feel free to argue if you feel strongly ;)

Comment 2 Andrew Cagney 2004-10-25 20:53:05 EDT


*** This bug has been marked as a duplicate of 91727 ***

Comment 3 Red Hat Bugzilla 2006-02-21 14:06:32 EST

Changed to 'CLOSED' state since 'RESOLVED' has been deprecated.

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