[PATCH][SH] Signal handler unwinding for SH-Linux

[Chung-Lin Tang <cltang@codesourcery.com>]

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Hi,

This patch adds support for unwinding across signal handlers for
SH/Linux. The implementation is quite straightforward, following the
overall pattern for recognizing signal frames using the 'tramp_frame'
facilities. Currently, only 32-bit SH support is implemented.

The test results show improvement on many sighandler related tests, with
no regressions. Some gdb.base/sigbpt.exp tests change from FAIL->KFAIL,
though I'm not completely sure what that indicates.

Thanks,
Chung-Lin

2012-04-29  Chung-Lin Tang  <cltang@codesourcery.com>

	* sh-linux-tdep.c: Include trad-frame.h and tramp-frame.h.
	(sh_linux_sigtramp_cache): New function.
	(sh_linux_sigreturn_init): New function.
	(sh_linux_rt_sigreturn_init): New function.
	(SH_MOVW,SH_TRAP,SH_OR_R0_R0): New symbols for instruction
	patterns.
	(SH_NR_SIGRETURN,SH_NR_RT_SIGRETURN): New symbols for sigreturn
	syscall codes.
	(sh_linux_sigreturn_tramp_frame): New tramp_frame definition.
	(sh_linux_rt_sigreturn_tramp_frame): Likewise.
	(sh_linux_init_abi): Add init calls to register new tramp_frame
	definitions under 32-bit SH, update comments.

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Index: gdb/sh-linux-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/sh-linux-tdep.c,v
retrieving revision 1.13
diff -u -p -r1.13 sh-linux-tdep.c
--- gdb/sh-linux-tdep.c	4 Jan 2012 08:17:10 -0000	1.13
+++ gdb/sh-linux-tdep.c	29 Apr 2012 07:45:43 -0000
@@ -23,6 +23,9 @@
 #include "solib-svr4.h"
 #include "symtab.h"
 
+#include "trad-frame.h"
+#include "tramp-frame.h"
+
 #include "glibc-tdep.h"
 #include "sh-tdep.h"
 #include "linux-tdep.h"
@@ -70,6 +73,110 @@ static const struct sh_corefile_regmap f
   {-1 /* Terminator.  */, 0}
 };
 
+/* SH signal handler frame support.  */
+
+static void
+sh_linux_sigtramp_cache (struct frame_info *this_frame,
+			 struct trad_frame_cache *this_cache,
+			 CORE_ADDR func, int regs_offset)
+{
+  int i;
+  struct gdbarch *gdbarch = get_frame_arch (this_frame);
+  CORE_ADDR base = get_frame_register_unsigned (this_frame,
+						gdbarch_sp_regnum (gdbarch));
+  CORE_ADDR regs = base + regs_offset;
+
+  for (i = 0; i < 18; i++)
+    trad_frame_set_reg_addr (this_cache, i, regs + i * 4);
+
+  trad_frame_set_reg_addr (this_cache, SR_REGNUM, regs + 18 * 4);
+  trad_frame_set_reg_addr (this_cache, GBR_REGNUM, regs + 19 * 4);
+  trad_frame_set_reg_addr (this_cache, MACH_REGNUM, regs + 20 * 4);
+  trad_frame_set_reg_addr (this_cache, MACL_REGNUM, regs + 21 * 4);
+
+  /* Restore FP state if we have an FPU.  */
+  if (gdbarch_fp0_regnum (gdbarch) != -1)
+    {
+      CORE_ADDR fpregs = regs + 22 * 4;
+      for (i = FR0_REGNUM; i <= FP_LAST_REGNUM; i++)
+	trad_frame_set_reg_addr (this_cache, i, fpregs + i * 4);
+      trad_frame_set_reg_addr (this_cache, FPSCR_REGNUM, fpregs + 32 * 4);
+      trad_frame_set_reg_addr (this_cache, FPUL_REGNUM, fpregs + 33 * 4);
+    }
+
+  /* Save a frame ID.  */
+  trad_frame_set_id (this_cache, frame_id_build (base, func));
+}
+
+static void
+sh_linux_sigreturn_init (const struct tramp_frame *self,
+			 struct frame_info *this_frame,
+			 struct trad_frame_cache *this_cache,
+			 CORE_ADDR func)
+{
+  /* SH 32-bit sigframe: sigcontext at start of sigframe,
+     registers start after a single 'oldmask' word.  */
+  sh_linux_sigtramp_cache (this_frame, this_cache, func, 4);
+}
+
+static void
+sh_linux_rt_sigreturn_init (const struct tramp_frame *self,
+			    struct frame_info *this_frame,
+			    struct trad_frame_cache *this_cache,
+			    CORE_ADDR func)
+{
+  /* SH 32-bit rt_sigframe: starts with a siginfo (128 bytes), then
+     we can find sigcontext embedded within a ucontext (offset 20 bytes).
+     Then registers start after a single 'oldmask' word.  */
+  sh_linux_sigtramp_cache (this_frame, this_cache, func,
+			   128 /* sizeof (struct siginfo)  */
+			   + 20 /* offsetof (struct ucontext, uc_mcontext) */
+			   + 4 /* oldmask word at start of sigcontext */);
+}
+
+/* Instruction patterns.  */
+#define SH_MOVW     0x9305
+#define SH_TRAP     0xc300
+#define SH_OR_R0_R0 0x200b       
+
+/* SH sigreturn syscall numbers.  */
+#define SH_NR_SIGRETURN 0x0077
+#define SH_NR_RT_SIGRETURN 0x00ad
+
+static struct tramp_frame sh_linux_sigreturn_tramp_frame = {
+  SIGTRAMP_FRAME,
+  2,
+  {
+    { SH_MOVW, 0xffff },
+    { SH_TRAP, 0xff00 }, /* #imm argument part filtered out.  */
+    { SH_OR_R0_R0, 0xffff },
+    { SH_OR_R0_R0, 0xffff },
+    { SH_OR_R0_R0, 0xffff },
+    { SH_OR_R0_R0, 0xffff },
+    { SH_OR_R0_R0, 0xffff },
+    { SH_NR_SIGRETURN, 0xffff },
+    { TRAMP_SENTINEL_INSN }
+  },
+  sh_linux_sigreturn_init
+};
+
+static struct tramp_frame sh_linux_rt_sigreturn_tramp_frame = {
+  SIGTRAMP_FRAME,
+  2,
+  {
+    { SH_MOVW, 0xffff },
+    { SH_TRAP, 0xff00 }, /* #imm argument part filtered out.  */
+    { SH_OR_R0_R0, 0xffff },
+    { SH_OR_R0_R0, 0xffff },
+    { SH_OR_R0_R0, 0xffff },
+    { SH_OR_R0_R0, 0xffff },
+    { SH_OR_R0_R0, 0xffff },
+    { SH_NR_RT_SIGRETURN, 0xffff },
+    { TRAMP_SENTINEL_INSN }
+  },
+  sh_linux_rt_sigreturn_init
+};
+
 static void
 sh_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 {
@@ -84,13 +191,17 @@ sh_linux_init_abi (struct gdbarch_info i
   set_gdbarch_fetch_tls_load_module_address (gdbarch,
                                              svr4_fetch_objfile_link_map);
 
-  /* Core files are supported for 32-bit SH only, at present.  */
+  /* Core files and signal handler frame unwinding are supported for
+     32-bit SH only, at present.  */
   if (info.bfd_arch_info->mach != bfd_mach_sh5)
     {
       struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 
       tdep->core_gregmap = (struct sh_corefile_regmap *)gregs_table;
       tdep->core_fpregmap = (struct sh_corefile_regmap *)fpregs_table;
+
+      tramp_frame_prepend_unwinder (gdbarch, &sh_linux_sigreturn_tramp_frame);
+      tramp_frame_prepend_unwinder (gdbarch, &sh_linux_rt_sigreturn_tramp_frame);
     }
 }