RFA: Overhaul arm-linux signal handling

[Daniel Jacobowitz <drow at false dot org>]

This patch rips out the previous ARM signal frame unwinding, and replaces it
with a more current method.  It removes a bunch of deprecated definitions.

It also fixes a bug in RT signals; the offsets were wrong.  Probably they
were right when added around 2000, but the kernel interface hasn't changed
in quite a while now, so I couldn't pinpoint exactly where they became
wrong.

And it adds support for the new r7-based, rather than swi based, syscall
convention for EABI.

Tested by hand on both ARM ABIs.  OK?

-- 
Daniel Jacobowitz
CodeSourcery, LLC

2005-11-16  Daniel Jacobowitz  <dan@codesourcery.com>

	* arm-linux-tdep.c (ARM_SET_R7_SIGRETURN, ARM_SET_R7_RT_SIGRETURN)
	(ARM_EABI_SYSCALL, arm_linux_sigtramp_cache, arm_linux_sigreturn_init)
	(arm_linux_rt_sigreturn_init, arm_linux_sigreturn_tramp_frame)
	(arm_linux_rt_sigreturn_tramp_frame)
	(arm_eabi_linux_sigreturn_tramp_frame)
	(arm_eabi_linux_rt_sigreturn_tramp_frame): New.
	(arm_linux_init_abi): Register the new signal unwinders.
	(arm_linux_in_sigtramp, arm_linux_sigcontext_register_address):
	Delete.
	* arm-tdep.c (SIGCONTEXT_REGISTER_ADDRESS_P)
	(SIGCONTEXT_REGISTER_ADDRESS, arm_make_sigtramp_cache)
	(arm_sigtramp_this_id, arm_sigtramp_prev_register)
	(arm_sigtramp_unwind, arm_sigtramp_unwind_sniffer): Delete.
	(arm_gdbarch_init): Don't register a signal unwinder.
	* config/arm/tm-linux.h (arm_linux_in_sigtramp)
	(arm_linux_sigcontext_register_address): Delete prototypes.
	(DEPRECATED_IN_SIGTRAMP, SIGCONTEXT_REGISTER_ADDRESS): Delete.
	* Makefile.in (arm-linux-tdep.o): Update.

Index: src/gdb/arm-linux-tdep.c
===================================================================
--- src.orig/gdb/arm-linux-tdep.c	2005-11-16 12:18:17.000000000 -0500
+++ src/gdb/arm-linux-tdep.c	2005-11-16 12:23:13.000000000 -0500
@@ -1,7 +1,7 @@
 /* GNU/Linux on ARM target support.
 
-   Copyright 1999, 2000, 2001, 2002, 2003, 2005 Free Software
-   Foundation, Inc.
+   Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2005
+   Free Software Foundation, Inc.
 
    This file is part of GDB.
 
@@ -31,10 +31,14 @@
 #include "doublest.h"
 #include "solib-svr4.h"
 #include "osabi.h"
+#include "trad-frame.h"
+#include "tramp-frame.h"
 
 #include "arm-tdep.h"
 #include "glibc-tdep.h"
 
+#include "gdb_string.h"
+
 /* Under ARM GNU/Linux the traditional way of performing a breakpoint
    is to execute a particular software interrupt, rather than use a
    particular undefined instruction to provoke a trap.  Upon exection
@@ -262,77 +266,98 @@ arm_linux_svr4_fetch_link_map_offsets (v
 #define ARM_LINUX_SIGRETURN_INSTR	0xef900077
 #define ARM_LINUX_RT_SIGRETURN_INSTR	0xef9000ad
 
-/* arm_linux_in_sigtramp determines if PC points at one of the
-   instructions which cause control to return to the Linux kernel upon
-   return from a signal handler.  FUNC_NAME is unused.  */
+/* For ARM EABI, recognize the pattern that glibc uses...  alternatively,
+   we could arrange to do this by function name, but they are not always
+   exported.  */
+#define ARM_SET_R7_SIGRETURN		0xe3a07077
+#define ARM_SET_R7_RT_SIGRETURN		0xe3a070ad
+#define ARM_EABI_SYSCALL		0xef000000
 
-int
-arm_linux_in_sigtramp (CORE_ADDR pc, char *func_name)
+static void
+arm_linux_sigtramp_cache (struct frame_info *next_frame,
+			  struct trad_frame_cache *this_cache,
+			  CORE_ADDR func, int regs_offset)
 {
-  unsigned long inst;
+  CORE_ADDR sp = frame_unwind_register_unsigned (next_frame, ARM_SP_REGNUM);
+  CORE_ADDR base = sp + regs_offset;
+  int i;
 
-  inst = read_memory_integer (pc, 4);
+  for (i = 0; i < 16; i++)
+    trad_frame_set_reg_addr (this_cache, i, base + i * 4);
 
-  return (inst == ARM_LINUX_SIGRETURN_INSTR
-	  || inst == ARM_LINUX_RT_SIGRETURN_INSTR);
+  trad_frame_set_reg_addr (this_cache, ARM_PS_REGNUM, base + 16 * 4);
 
-}
+  /* The VFP or iWMMXt registers may be saved on the stack, but there's
+     no reliable way to restore them (yet).  */
 
-/* arm_linux_sigcontext_register_address returns the address in the
-   sigcontext of register REGNO given a stack pointer value SP and
-   program counter value PC.  The value 0 is returned if PC is not
-   pointing at one of the signal return instructions or if REGNO is
-   not saved in the sigcontext struct.  */
+  /* Save a frame ID.  */
+  trad_frame_set_id (this_cache, frame_id_build (sp, func));
+}
 
-CORE_ADDR
-arm_linux_sigcontext_register_address (CORE_ADDR sp, CORE_ADDR pc, int regno)
+static void
+arm_linux_sigreturn_init (const struct tramp_frame *self,
+			  struct frame_info *next_frame,
+			  struct trad_frame_cache *this_cache,
+			  CORE_ADDR func)
 {
-  unsigned long inst;
-  CORE_ADDR reg_addr = 0;
-
-  inst = read_memory_integer (pc, 4);
-
-  if (inst == ARM_LINUX_SIGRETURN_INSTR
-      || inst == ARM_LINUX_RT_SIGRETURN_INSTR)
-    {
-      CORE_ADDR sigcontext_addr;
-
-      /* The sigcontext structure is at different places for the two
-         signal return instructions.  For ARM_LINUX_SIGRETURN_INSTR,
-	 it starts at the SP value.  For ARM_LINUX_RT_SIGRETURN_INSTR,
-	 it is at SP+8.  For the latter instruction, it may also be
-	 the case that the address of this structure may be determined
-	 by reading the 4 bytes at SP, but I'm not convinced this is
-	 reliable.
-
-	 In any event, these magic constants (0 and 8) may be
-	 determined by examining struct sigframe and struct
-	 rt_sigframe in arch/arm/kernel/signal.c in the Linux kernel
-	 sources.  */
-
-      if (inst == ARM_LINUX_RT_SIGRETURN_INSTR)
-	sigcontext_addr = sp + 8;
-      else /* inst == ARM_LINUX_SIGRETURN_INSTR */
-        sigcontext_addr = sp + 0;
-
-      /* The layout of the sigcontext structure for ARM GNU/Linux is
-         in include/asm-arm/sigcontext.h in the Linux kernel sources.
-
-	 There are three 4-byte fields which precede the saved r0
-	 field.  (This accounts for the 12 in the code below.)  The
-	 sixteen registers (4 bytes per field) follow in order.  The
-	 PSR value follows the sixteen registers which accounts for
-	 the constant 19 below. */
-
-      if (0 <= regno && regno <= ARM_PC_REGNUM)
-	reg_addr = sigcontext_addr + 12 + (4 * regno);
-      else if (regno == ARM_PS_REGNUM)
-	reg_addr = sigcontext_addr + 19 * 4;
-    }
+  arm_linux_sigtramp_cache (next_frame, this_cache, func,
+			    0x0c /* Offset to registers.  */);
+}
 
-  return reg_addr;
+static void
+arm_linux_rt_sigreturn_init (const struct tramp_frame *self,
+			  struct frame_info *next_frame,
+			  struct trad_frame_cache *this_cache,
+			  CORE_ADDR func)
+{
+  arm_linux_sigtramp_cache (next_frame, this_cache, func,
+			    0x88 /* Offset to ucontext_t.  */
+			    + 0x14 /* Offset to sigcontext.  */
+			    + 0x0c /* Offset to registers.  */);
 }
 
+static struct tramp_frame arm_linux_sigreturn_tramp_frame = {
+  SIGTRAMP_FRAME,
+  4,
+  {
+    { ARM_LINUX_SIGRETURN_INSTR, -1 },
+    { TRAMP_SENTINEL_INSN }
+  },
+  arm_linux_sigreturn_init
+};
+
+static struct tramp_frame arm_linux_rt_sigreturn_tramp_frame = {
+  SIGTRAMP_FRAME,
+  4,
+  {
+    { ARM_LINUX_RT_SIGRETURN_INSTR, -1 },
+    { TRAMP_SENTINEL_INSN }
+  },
+  arm_linux_rt_sigreturn_init
+};
+
+static struct tramp_frame arm_eabi_linux_sigreturn_tramp_frame = {
+  SIGTRAMP_FRAME,
+  4,
+  {
+    { ARM_SET_R7_SIGRETURN, -1 },
+    { ARM_EABI_SYSCALL, -1 },
+    { TRAMP_SENTINEL_INSN }
+  },
+  arm_linux_sigreturn_init
+};
+
+static struct tramp_frame arm_eabi_linux_rt_sigreturn_tramp_frame = {
+  SIGTRAMP_FRAME,
+  4,
+  {
+    { ARM_SET_R7_RT_SIGRETURN, -1 },
+    { ARM_EABI_SYSCALL, -1 },
+    { TRAMP_SENTINEL_INSN }
+  },
+  arm_linux_rt_sigreturn_init
+};
+
 static void
 arm_linux_init_abi (struct gdbarch_info info,
 		    struct gdbarch *gdbarch)
@@ -378,6 +403,15 @@ arm_linux_init_abi (struct gdbarch_info 
   /* Enable TLS support.  */
   set_gdbarch_fetch_tls_load_module_address (gdbarch,
                                              svr4_fetch_objfile_link_map);
+
+  tramp_frame_prepend_unwinder (gdbarch,
+				&arm_linux_sigreturn_tramp_frame);
+  tramp_frame_prepend_unwinder (gdbarch,
+				&arm_linux_rt_sigreturn_tramp_frame);
+  tramp_frame_prepend_unwinder (gdbarch,
+				&arm_eabi_linux_sigreturn_tramp_frame);
+  tramp_frame_prepend_unwinder (gdbarch,
+				&arm_eabi_linux_rt_sigreturn_tramp_frame);
 }
 
 void
Index: src/gdb/arm-tdep.c
===================================================================
--- src.orig/gdb/arm-tdep.c	2005-11-16 12:18:17.000000000 -0500
+++ src/gdb/arm-tdep.c	2005-11-16 12:18:19.000000000 -0500
@@ -51,36 +51,6 @@
 
 static int arm_debug;
 
-/* Each OS has a different mechanism for accessing the various
-   registers stored in the sigcontext structure.
-
-   SIGCONTEXT_REGISTER_ADDRESS should be defined to the name (or
-   function pointer) which may be used to determine the addresses
-   of the various saved registers in the sigcontext structure.
-
-   For the ARM target, there are three parameters to this function. 
-   The first is the pc value of the frame under consideration, the
-   second the stack pointer of this frame, and the last is the
-   register number to fetch.  
-
-   If the tm.h file does not define this macro, then it's assumed that
-   no mechanism is needed and we define SIGCONTEXT_REGISTER_ADDRESS to
-   be 0. 
-   
-   When it comes time to multi-arching this code, see the identically
-   named machinery in ia64-tdep.c for an example of how it could be
-   done.  It should not be necessary to modify the code below where
-   this macro is used.  */
-
-#ifdef SIGCONTEXT_REGISTER_ADDRESS
-#ifndef SIGCONTEXT_REGISTER_ADDRESS_P
-#define SIGCONTEXT_REGISTER_ADDRESS_P() 1
-#endif
-#else
-#define SIGCONTEXT_REGISTER_ADDRESS(SP,PC,REG) 0
-#define SIGCONTEXT_REGISTER_ADDRESS_P() 0
-#endif
-
 /* Macros for setting and testing a bit in a minimal symbol that marks
    it as Thumb function.  The MSB of the minimal symbol's "info" field
    is used for this purpose.
@@ -1063,84 +1033,6 @@ struct frame_base arm_normal_base = {
   arm_normal_frame_base
 };
 
-static struct arm_prologue_cache *
-arm_make_sigtramp_cache (struct frame_info *next_frame)
-{
-  struct arm_prologue_cache *cache;
-  int reg;
-
-  cache = frame_obstack_zalloc (sizeof (struct arm_prologue_cache));
-
-  cache->prev_sp = frame_unwind_register_unsigned (next_frame, ARM_SP_REGNUM);
-
-  cache->saved_regs = trad_frame_alloc_saved_regs (next_frame);
-
-  for (reg = 0; reg < NUM_REGS; reg++)
-    cache->saved_regs[reg].addr
-      = SIGCONTEXT_REGISTER_ADDRESS (cache->prev_sp,
-				     frame_pc_unwind (next_frame), reg);
-
-  /* FIXME: What about thumb mode?  */
-  cache->framereg = ARM_SP_REGNUM;
-  cache->prev_sp
-    = read_memory_integer (cache->saved_regs[cache->framereg].addr,
-			   register_size (current_gdbarch, cache->framereg));
-
-  return cache;
-}
-
-static void
-arm_sigtramp_this_id (struct frame_info *next_frame,
-		      void **this_cache,
-		      struct frame_id *this_id)
-{
-  struct arm_prologue_cache *cache;
-
-  if (*this_cache == NULL)
-    *this_cache = arm_make_sigtramp_cache (next_frame);
-  cache = *this_cache;
-
-  /* FIXME drow/2003-07-07: This isn't right if we single-step within
-     the sigtramp frame; the PC should be the beginning of the trampoline.  */
-  *this_id = frame_id_build (cache->prev_sp, frame_pc_unwind (next_frame));
-}
-
-static void
-arm_sigtramp_prev_register (struct frame_info *next_frame,
-			    void **this_cache,
-			    int prev_regnum,
-			    int *optimized,
-			    enum lval_type *lvalp,
-			    CORE_ADDR *addrp,
-			    int *realnump,
-			    gdb_byte *valuep)
-{
-  struct arm_prologue_cache *cache;
-
-  if (*this_cache == NULL)
-    *this_cache = arm_make_sigtramp_cache (next_frame);
-  cache = *this_cache;
-
-  trad_frame_get_prev_register (next_frame, cache->saved_regs, prev_regnum,
-				optimized, lvalp, addrp, realnump, valuep);
-}
-
-struct frame_unwind arm_sigtramp_unwind = {
-  SIGTRAMP_FRAME,
-  arm_sigtramp_this_id,
-  arm_sigtramp_prev_register
-};
-
-static const struct frame_unwind *
-arm_sigtramp_unwind_sniffer (struct frame_info *next_frame)
-{
-  if (SIGCONTEXT_REGISTER_ADDRESS_P ()
-      && legacy_pc_in_sigtramp (frame_pc_unwind (next_frame), (char *) 0))
-    return &arm_sigtramp_unwind;
-
-  return NULL;
-}
-
 /* Assuming NEXT_FRAME->prev is a dummy, return the frame ID of that
    dummy frame.  The frame ID's base needs to match the TOS value
    saved by save_dummy_frame_tos() and returned from
@@ -2907,7 +2799,6 @@ arm_gdbarch_init (struct gdbarch_info in
 
   /* Add some default predicates.  */
   frame_unwind_append_sniffer (gdbarch, arm_stub_unwind_sniffer);
-  frame_unwind_append_sniffer (gdbarch, arm_sigtramp_unwind_sniffer);
   frame_unwind_append_sniffer (gdbarch, dwarf2_frame_sniffer);
   frame_unwind_append_sniffer (gdbarch, arm_prologue_unwind_sniffer);
 
Index: src/gdb/config/arm/tm-linux.h
===================================================================
--- src.orig/gdb/config/arm/tm-linux.h	2005-11-16 12:18:17.000000000 -0500
+++ src/gdb/config/arm/tm-linux.h	2005-11-16 12:18:19.000000000 -0500
@@ -1,5 +1,6 @@
 /* Target definitions for GNU/Linux on ARM, for GDB.
-   Copyright 1999, 2000 Free Software Foundation, Inc.
+   Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2005
+   Free Software Foundation, Inc.
 
    This file is part of GDB.
 
@@ -43,26 +44,4 @@ extern CORE_ADDR in_svr4_dynsym_resolve_
 #define IN_SOLIB_DYNSYM_RESOLVE_CODE  in_svr4_dynsym_resolve_code */
 #endif
 
-/* When the ARM Linux kernel invokes a signal handler, the return
-   address points at a special instruction which'll trap back into
-   the kernel.  These definitions are used to identify this bit of
-   code as a signal trampoline in order to support backtracing
-   through calls to signal handlers. */
-
-int arm_linux_in_sigtramp (CORE_ADDR pc, char *name);
-#define DEPRECATED_IN_SIGTRAMP(pc, name) arm_linux_in_sigtramp (pc, name)
-
-/* Each OS has different mechanisms for accessing the various
-   registers stored in the sigcontext structure.  These definitions
-   provide a mechanism by which the generic code in arm-tdep.c can
-   find the addresses at which various registers are saved at in the
-   sigcontext structure.  If SIGCONTEXT_REGISTER_ADDRESS is not
-   defined, arm-tdep.c will define it to be 0.  (See ia64-tdep.c and
-   ia64-linux-tdep.c to see what a similar mechanism looks like when
-   multi-arched.) */
-
-extern CORE_ADDR arm_linux_sigcontext_register_address (CORE_ADDR, CORE_ADDR,
-                                                        int);
-#define SIGCONTEXT_REGISTER_ADDRESS arm_linux_sigcontext_register_address
-
 #endif /* TM_ARMLINUX_H */
Index: src/gdb/Makefile.in
===================================================================
--- src.orig/gdb/Makefile.in	2005-11-16 12:18:19.000000000 -0500
+++ src/gdb/Makefile.in	2005-11-16 12:20:03.000000000 -0500
@@ -1739,7 +1739,7 @@ arm-linux-nat.o: arm-linux-nat.c $(defs_
 arm-linux-tdep.o: arm-linux-tdep.c $(defs_h) $(target_h) $(value_h) \
 	$(gdbtypes_h) $(floatformat_h) $(gdbcore_h) $(frame_h) $(regcache_h) \
 	$(doublest_h) $(solib_svr4_h) $(osabi_h) $(arm_tdep_h) \
-	$(glibc_tdep_h)
+	$(glibc_tdep_h) $(trad_frame_h) $(tramp_frame_h) $(gdb_string_h)
 armnbsd-nat.o: armnbsd-nat.c $(defs_h) $(gdbcore_h) $(inferior_h) \
 	$(regcache_h) $(target_h) $(gdb_string_h) $(arm_tdep_h) $(inf_ptrace_h)
 armnbsd-tdep.o: armnbsd-tdep.c $(defs_h) $(osabi_h) $(gdb_string_h) \