[PATCH] Add sparc64-linux sigtramp support

["David S. Miller" <davem at davemloft dot net>]

This patch gets signal backtraces working properly on sparc64/linux
targets.  The two non-straightforward parts of the implementation are:

1) proper stack bias adjusting of cache->base
2) registering the sniffer in the correct order

The issue in #2 is that we use the solaris2 sparc64 target support
as our base, then override and add things which are different for the
linux sparc64 target.

The solaris2 sparc64 osabi init which we call registers first the
solaris2 sigtramp sniffer, then the generic sparc64 frame sniffer,
via sparc64_init_abi().

Therefore we have to register the linux sparc64 sniffer before we
invoke sparc64_sol2_init_abi().

While doing this work I noticed that the signal trampoline symbols
names were wrong in the 32-bit sparc linux sigtramp support.  Those
are the i386 glibc symbol names, not the sparc ones :-)  So I corrected
those and also documented the "struct pt_regs" layout that we're
picking sigtramp registers from.

2005-04-20  David S. Miller  <davem@davemloft.net>

	* sparc-linux-tdep.c (sparc32_linux_sigtramp_p): Fix
	signal return stub symbol names, __restore and __restore_rt are
	the i386 symbol	names not the sparc ones.
	(sparc32_linux_sigtramp_frame_cache): Document the layout
	of the pt_regs structure we are fishing out of the
	signal frame.
	* sparc64-linux-tdep.c (LINUX64_RT_SIGTRAMP_INSN0,
	LINUX64_RT_SIGTRAMP_INSN1): New defines.
	(sparc64_linux_sigtramp_start, sparc64_linux_sigtramp_p,
	sparc64_linux_sigtramp_frame_cache,
	sparc64_linux_sigtramp_frame_this_id,
	sparc64_linux_sigtramp_frame_prev_register,
	sparc64_linux_sigtramp_frame_sniffer): New functions.
	(sparc64_linux_sigtramp_frame_unwind): New frame unwinder.
	(sparc64_linux_init_abi): Register sigtramp frame sniffer.
	* Makefile.in (sparc64-linux-tdep.o): Update dependencies.
	
--- Makefile.in	17 Apr 2005 22:20:19 -0000	1.716
+++ Makefile.in	21 Apr 2005 03:34:17 -0000
@@ -2565,8 +2565,10 @@ sparc64fbsd-tdep.o: sparc64fbsd-tdep.c $
 	$(sparc64_tdep_h) $(solib_svr4_h)
 sparc64-linux-nat.o: sparc64-linux-nat.c $(defs_h) $(sparc64_tdep_h) \
 	$(sparc_nat_h)
-sparc64-linux-tdep.o: sparc64-linux-tdep.c $(defs_h) $(gdbarch_h) $(osabi_h) \
-	$(solib_svr4_h) $(sparc64_tdep_h)
+sparc64-linux-tdep.o: sparc64-linux-tdep.c $(defs_h) $(frame_h) \
+	$(frame_unwind_h) $(gdbarch_h) $(osabi_h) $(solib_svr4_h) \
+	$(symtab_h) $(trad_frame_h) $(gdb_assert_h) $(gdb_string_h) \
+	$(sparc64_tdep_h)
 sparc64-nat.o: sparc64-nat.c $(defs_h) $(gdbarch_h) $(sparc64_tdep_h) \
 	$(sparc_nat_h)
 sparc64nbsd-nat.o: sparc64nbsd-nat.c $(defs_h) $(regcache_h) $(target_h) \
--- sparc-linux-tdep.c	31 Mar 2005 19:58:26 -0000	1.9
+++ sparc-linux-tdep.c	21 Apr 2005 03:34:17 -0000
@@ -144,16 +144,17 @@ sparc32_linux_sigtramp_p (struct frame_i
   find_pc_partial_function (pc, &name, NULL, NULL);
 
   /* If we have NAME, we can optimize the search.  The trampolines are
-     named __restore and __restore_rt.  However, they aren't dynamically
-     exported from the shared C library, so the trampoline may appear to
-     be part of the preceding function.  This should always be sigaction,
-     __sigaction, or __libc_sigaction (all aliases to the same function).  */
+     named __sigreturn_stub and __rt_sigreturn_stub.  However, they
+     aren't dynamically exported from the shared C library, so the
+     trampoline may appear to be part of the preceding function.  This
+     should always be sigaction, __sigaction, or __libc_sigaction (all
+     aliases to the same function).  */
   if (name == NULL || strstr (name, "sigaction") != NULL)
     return (sparc32_linux_sigtramp_start (next_frame) != 0
 	    || sparc32_linux_rt_sigtramp_start (next_frame) != 0);
 
-  return (strcmp ("__restore", name) == 0
-	  || strcmp ("__restore_rt", name) == 0);
+  return (strcmp ("__sigreturn_stub", name) == 0
+	  || strcmp ("__rt_sigreturn_stub", name) == 0);
 }
 
 static struct sparc_frame_cache *
@@ -192,6 +193,14 @@ sparc32_linux_sigtramp_frame_cache (stru
 
   cache->saved_regs = trad_frame_alloc_saved_regs (next_frame);
 
+  /* Layout of pt_regs on sparc is:
+     0x00: PSR
+     0x04: PC
+     0x08: NPC
+     0x0c: Y
+     0x10: 8 global registers
+     0x30: 8 output registers  */
+
   cache->saved_regs[SPARC32_PSR_REGNUM].addr = sigcontext_addr + 0;
   cache->saved_regs[SPARC32_PC_REGNUM].addr = sigcontext_addr + 4;
   cache->saved_regs[SPARC32_NPC_REGNUM].addr = sigcontext_addr + 8;
--- sparc64-linux-tdep.c	31 Mar 2005 19:58:26 -0000	1.4
+++ sparc64-linux-tdep.c	21 Apr 2005 03:34:17 -0000
@@ -20,17 +20,201 @@
    Boston, MA 02111-1307, USA.  */
 
 #include "defs.h"
+#include "frame.h"
+#include "frame-unwind.h"
 #include "gdbarch.h"
 #include "osabi.h"
 #include "solib-svr4.h"
+#include "symtab.h"
+#include "trad-frame.h"
+
+#include "gdb_assert.h"
+#include "gdb_string.h"
 
 #include "sparc64-tdep.h"
 
+/* The instruction sequence for RT signals is
+       mov __NR_rt_sigreturn, %g1	! hex: 0x82102065
+       ta  0x6d				! hex: 0x91d0206d
+
+   The effect is to call the system call rt_sigreturn.
+   Note that 64-bit binaries only use this RT signal return method.  */
+
+#define LINUX64_RT_SIGTRAMP_INSN0	0x82102065
+#define LINUX64_RT_SIGTRAMP_INSN1	0x91d0206d
+
+/* If PC is in a sigtramp routine consisting of the instructions
+   LINUX64_RT_SIGTRAMP_INSN0 and LINUX64_RT_SIGTRAMP_INSN1, return
+   the address of the start of the routine.  Otherwise, return 0.  */
+
+static CORE_ADDR
+sparc64_linux_sigtramp_start (struct frame_info *next_frame)
+{
+  CORE_ADDR pc = frame_pc_unwind (next_frame);
+  ULONGEST word0, word1;
+  unsigned char buf[8];		/* Two instructions.  */
+
+  /* We only recognize a signal trampoline if PC is at the start of
+     one of the instructions.  We optimize for finding the PC at the
+     start of the instruction sequence, as will be the case when the
+     trampoline is not the first frame on the stack.  We assume that
+     in the case where the PC is not at the start of the instruction
+     sequence, there will be a few trailing readable bytes on the
+     stack.  */
+
+  if (!safe_frame_unwind_memory (next_frame, pc, buf, sizeof buf))
+    return 0;
+
+  word0 = extract_unsigned_integer (buf, 4);
+  if (word0 != LINUX64_RT_SIGTRAMP_INSN0)
+    {
+      if (word0 != LINUX64_RT_SIGTRAMP_INSN1)
+	return 0;
+
+      pc -= 4;
+      if (!safe_frame_unwind_memory (next_frame, pc, buf, sizeof buf))
+	return 0;
+
+      word0 = extract_unsigned_integer (buf, 4);
+    }
+
+  word1 = extract_unsigned_integer (buf + 4, 4);
+  if (word0 != LINUX64_RT_SIGTRAMP_INSN0
+      || word1 != LINUX64_RT_SIGTRAMP_INSN1)
+    return 0;
+
+  return pc;
+}
+
+static int
+sparc64_linux_sigtramp_p (struct frame_info *next_frame)
+{
+  CORE_ADDR pc = frame_pc_unwind (next_frame);
+  char *name;
+
+  find_pc_partial_function (pc, &name, NULL, NULL);
+
+  /* If we have NAME, we can optimize the search.  The trampolines is
+     named __rt_sigreturn_stub.  However, is isn't dynamically exported
+     from the shared C library, so the trampoline may appear to be part
+     of the preceding function.  This should always be sigaction,
+     __sigaction, or __libc_sigaction (all aliases to the same function).  */
+  if (name == NULL || strstr (name, "sigaction") != NULL)
+    return (sparc64_linux_sigtramp_start (next_frame) != 0);
+
+  return (strcmp ("__rt_sigreturn_stub", name) == 0);
+}
+
+static struct sparc_frame_cache *
+sparc64_linux_sigtramp_frame_cache (struct frame_info *next_frame,
+				    void **this_cache)
+{
+  struct sparc_frame_cache *cache;
+  CORE_ADDR sigcontext_addr, addr;
+  int regnum;
+
+  if (*this_cache)
+    return *this_cache;
+
+  cache = sparc_frame_cache (next_frame, this_cache);
+  gdb_assert (cache == *this_cache);
+
+  regnum = SPARC_SP_REGNUM;
+  cache->base = frame_unwind_register_unsigned (next_frame, regnum);
+  if (cache->base & 1)
+    cache->base += BIAS;
+
+  regnum = SPARC_O1_REGNUM;
+  sigcontext_addr = frame_unwind_register_unsigned (next_frame, regnum);
+
+  /* If this is a RT signal trampoline, adjust SIGCONTEXT_ADDR
+     accordingly.  */
+  addr = sparc64_linux_sigtramp_start (next_frame);
+  if (addr)
+    sigcontext_addr += 128;
+  else
+    addr = frame_func_unwind (next_frame);
+
+  cache->pc = addr;
+
+  cache->saved_regs = trad_frame_alloc_saved_regs (next_frame);
+
+  /* Layout of pt_regs on sparc64 is:
+     0x00: 8 global registers
+     0x40: 8 output registers
+     0x80: TSTATE
+     0x88: TPC
+     0x90: TNPC
+     0x98: Y
+     0x9c: FPRS  */
+
+  /* Since %g0 is always zero, keep the identity encoding.  */
+  for (addr = sigcontext_addr + 8, regnum = SPARC_G1_REGNUM;
+       regnum <= SPARC_O7_REGNUM; regnum++, addr += 8)
+    cache->saved_regs[regnum].addr = addr;
+
+  cache->saved_regs[SPARC64_STATE_REGNUM].addr = addr + 0;
+  cache->saved_regs[SPARC64_PC_REGNUM].addr = addr + 8;
+  cache->saved_regs[SPARC64_NPC_REGNUM].addr = addr + 16;
+  cache->saved_regs[SPARC64_Y_REGNUM].addr = addr + 24;
+  cache->saved_regs[SPARC64_FPRS_REGNUM].addr = addr + 28;
+
+  for (regnum = SPARC_L0_REGNUM, addr = cache->base;
+       regnum <= SPARC_I7_REGNUM; regnum++, addr += 8)
+    cache->saved_regs[regnum].addr = addr;
+
+  return cache;
+}
+
+static void
+sparc64_linux_sigtramp_frame_this_id (struct frame_info *next_frame,
+				      void **this_cache,
+				      struct frame_id *this_id)
+{
+  struct sparc_frame_cache *cache =
+    sparc64_linux_sigtramp_frame_cache (next_frame, this_cache);
+
+  (*this_id) = frame_id_build (cache->base, cache->pc);
+}
+
+static void
+sparc64_linux_sigtramp_frame_prev_register (struct frame_info *next_frame,
+					    void **this_cache,
+					    int regnum, int *optimizedp,
+					    enum lval_type *lvalp,
+					    CORE_ADDR *addrp,
+					    int *realnump, void *valuep)
+{
+  struct sparc_frame_cache *cache =
+    sparc64_linux_sigtramp_frame_cache (next_frame, this_cache);
+
+  trad_frame_get_prev_register (next_frame, cache->saved_regs, regnum,
+				optimizedp, lvalp, addrp, realnump, valuep);
+}
+
+static const struct frame_unwind sparc64_linux_sigtramp_frame_unwind =
+{
+  SIGTRAMP_FRAME,
+  sparc64_linux_sigtramp_frame_this_id,
+  sparc64_linux_sigtramp_frame_prev_register
+};
+
+static const struct frame_unwind *
+sparc64_linux_sigtramp_frame_sniffer (struct frame_info *next_frame)
+{
+  if (sparc64_linux_sigtramp_p (next_frame))
+    return &sparc64_linux_sigtramp_frame_unwind;
+
+  return NULL;
+}
+
 static void
 sparc64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 {
   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 
+  frame_unwind_append_sniffer (gdbarch, sparc64_linux_sigtramp_frame_sniffer);
+
   /* GNU/Linux is very similar to Solaris ...  */
   sparc64_sol2_init_abi (info, gdbarch);