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2004-06-22  Andrew Cagney  <cagney@gnu.org>
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	* rs6000-tdep.c (struct rs6000_framedata): Add field "func_start".
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	(skip_prologue): Delete local variable "orig_pc", use
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	"func_start".  Add local variable "num_skip_linux_syscall_insn",
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	use to skip over first half of a GNU/Linux syscall and update
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	"func_start".
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Index: gdb-7.2.50.20110117/gdb/rs6000-tdep.c
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===================================================================
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--- gdb-7.2.50.20110117.orig/gdb/rs6000-tdep.c	2011-01-11 20:23:02.000000000 +0100
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+++ gdb-7.2.50.20110117/gdb/rs6000-tdep.c	2011-01-17 15:48:19.000000000 +0100
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@@ -126,6 +126,7 @@ static const char *powerpc_vector_abi_st
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 struct rs6000_framedata
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   {
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+    CORE_ADDR func_start;	/* True function start.  */
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     int offset;			/* total size of frame --- the distance
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 				   by which we decrement sp to allocate
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 				   the frame */
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@@ -1496,7 +1497,6 @@ static CORE_ADDR
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 skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc, CORE_ADDR lim_pc,
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 	       struct rs6000_framedata *fdata)
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 {
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-  CORE_ADDR orig_pc = pc;
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   CORE_ADDR last_prologue_pc = pc;
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   CORE_ADDR li_found_pc = 0;
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   gdb_byte buf[4];
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@@ -1514,12 +1514,14 @@ skip_prologue (struct gdbarch *gdbarch, 
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   int minimal_toc_loaded = 0;
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   int prev_insn_was_prologue_insn = 1;
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   int num_skip_non_prologue_insns = 0;
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+  int num_skip_ppc64_gnu_linux_syscall_insn = 0;
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   int r0_contains_arg = 0;
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   const struct bfd_arch_info *arch_info = gdbarch_bfd_arch_info (gdbarch);
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   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
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   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
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   memset (fdata, 0, sizeof (struct rs6000_framedata));
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+  fdata->func_start = pc;
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   fdata->saved_gpr = -1;
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   fdata->saved_fpr = -1;
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   fdata->saved_vr = -1;
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@@ -1553,6 +1555,55 @@ skip_prologue (struct gdbarch *gdbarch, 
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 	break;
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       op = extract_unsigned_integer (buf, 4, byte_order);
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+      /* A PPC64 GNU/Linux system call function is split into two
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+	 sub-functions: a non-threaded fast-path (__NAME_nocancel)
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+	 which does not use a frame; and a threaded slow-path
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+	 (Lpseudo_cancel) that does create a frame.  Ref:
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+	 nptl/sysdeps/unix/sysv/linux/powerpc/powerpc32/sysdep-cancel.h
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+
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+	 *INDENT-OFF*
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+	 NAME:
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+	 	SINGLE_THREAD_P
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+	 	bne- .Lpseudo_cancel
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+	 __NAME_nocancel:
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+	 	li r0,162
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+	 	sc
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+	 	bnslr+
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+	 	b 0x7fe014ef64 <.__syscall_error>
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+	 Lpseudo_cancel:
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+	 	stdu r1,-128(r1)
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+	 	...
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+	 *INDENT-ON*
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+
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+	 Unfortunatly, because the latter case uses a local label (not
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+	 in the symbol table) a PC in "Lpseudo_cancel" appears to be
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+	 in "__NAME_nocancel".  The following code recognizes this,
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+	 adjusting FUNC_START to point to where "Lpseudo_cancel"
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+	 should be, and parsing the prologue sequence as if
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+	 "Lpseudo_cancel" was the entry point.  */
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+
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+      if (((op & 0xffff0000) == 0x38000000 /* li r0,N */
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+	   && pc == fdata->func_start + 0
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+	   && num_skip_ppc64_gnu_linux_syscall_insn == 0)
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+	  || (op == 0x44000002 /* sc */
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+	      && pc == fdata->func_start + 4
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+	      && num_skip_ppc64_gnu_linux_syscall_insn == 1)
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+	  || (op == 0x4ca30020 /* bnslr+ */
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+	      && pc == fdata->func_start + 8
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+	      && num_skip_ppc64_gnu_linux_syscall_insn == 2))
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+	{
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+	  num_skip_ppc64_gnu_linux_syscall_insn++;
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+	  continue;
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+	}
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+      else if ((op & 0xfc000003) == 0x48000000 /* b __syscall_error */
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+	       && pc == fdata->func_start + 12
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+	       && num_skip_ppc64_gnu_linux_syscall_insn == 3)
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+	{
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+	  num_skip_ppc64_gnu_linux_syscall_insn = -1;
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+	  fdata->func_start = pc;
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+	  continue;
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+	}
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+
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       if ((op & 0xfc1fffff) == 0x7c0802a6)
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 	{			/* mflr Rx */
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 	  /* Since shared library / PIC code, which needs to get its
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@@ -1734,9 +1785,9 @@ skip_prologue (struct gdbarch *gdbarch, 
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 	     we have no line table information or the line info tells
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 	     us that the subroutine call is not part of the line
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 	     associated with the prologue.  */
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-	  if ((pc - orig_pc) > 8)
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+	  if ((pc - fdata->func_start) > 8)
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 	    {
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-	      struct symtab_and_line prologue_sal = find_pc_line (orig_pc, 0);
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+	      struct symtab_and_line prologue_sal = find_pc_line (fdata->func_start, 0);
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 	      struct symtab_and_line this_sal = find_pc_line (pc, 0);
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 	      if ((prologue_sal.line == 0)