* sparc-linux-tdep.c (sparc32_linux_step_trap): New.

	(sparc32_linux_init_abi): Hook it into tdep->step_trap.
	* sparc64-linux-tdep.c (sparc64_linux_step_trap): New.
	(sparc64_linux_init_abi): Hook it into tdep->step_trap.
	* Makefile.in: Update dependencies.

4 files changed, 92 insertions, 2 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index f3f2d68..e81143a 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,11 @@
+2006-04-08  David S. Miller  <davem@sunset.davemloft.net>
+
+	* sparc-linux-tdep.c (sparc32_linux_step_trap): New.
+	(sparc32_linux_init_abi): Hook it into tdep->step_trap.
+	* sparc64-linux-tdep.c (sparc64_linux_step_trap): New.
+	(sparc64_linux_init_abi): Hook it into tdep->step_trap.
+	* Makefile.in: Update dependencies.
+
 2006-04-07  David S. Miller  <davem@sunset.davemloft.net>
 
 	* linux-nat.c (linux_nat_thread_alive): Handle targets that
diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 00b8f46..bdc5da5 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -2616,8 +2616,9 @@ sparc64-linux-nat.o: sparc64-linux-nat.c $(defs_h) $(regcache_h) \
 	$(gregset_h) $(sparc64_tdep_h) $(sparc_tdep_h) \
 	$(sparc_nat_h) $(inferior_h) $(target_h) $(linux_nat_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) $(tramp_frame_h) $(sparc64_tdep_h)
+	$(frame_unwind_h) $(regcache_h) $(gdbarch_h) $(gdbcore_h) \
+	$(osabi_h) $(solib_svr4_h) $(symtab_h) $(trad_frame_h) \
+	$(tramp_frame_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) \
diff --git a/gdb/sparc-linux-tdep.c b/gdb/sparc-linux-tdep.c
index ef7f370..446f05e 100644
--- a/gdb/sparc-linux-tdep.c
+++ b/gdb/sparc-linux-tdep.c
@@ -126,6 +126,49 @@ sparc32_linux_sigframe_init (const struct tramp_frame *self,
   trad_frame_set_id (this_cache, frame_id_build (base, func));
 }
 
+/* Return the address of a system call's alternative return
+   address.  */
+
+static CORE_ADDR
+sparc32_linux_step_trap (unsigned long insn)
+{
+  if (insn == 0x91d02010)
+    {
+      ULONGEST sc_num;
+
+      regcache_cooked_read_unsigned (current_regcache,
+				     SPARC_G1_REGNUM, &sc_num);
+
+      /* __NR_rt_sigreturn is 101 and __NR_sigreturn is 216  */
+      if (sc_num == 101 || sc_num == 216)
+	{
+	  ULONGEST sp, pc_offset;
+
+	  regcache_cooked_read_unsigned (current_regcache,
+					 SPARC_SP_REGNUM, &sp);
+
+	  /* The kernel puts the sigreturn registers on the stack,
+	     and this is where the signal unwinding state is take from
+	     when returning from a signal.
+
+	     For __NR_sigreturn, this register area sits 96 bytes from
+	     the base of the stack.  The saved PC sits 4 bytes into the
+	     sigreturn register save area.
+
+	     For __NR_rt_sigreturn a siginfo_t, which is 128 bytes, sits
+	     right before the sigreturn register save area.  */
+
+	  pc_offset = 96 + 4;
+	  if (sc_num == 101)
+	    pc_offset += 128;
+
+	  return read_memory_unsigned_integer (sp + pc_offset, 4);
+	}
+    }
+
+  return 0;
+}
+
 
 static void
 sparc32_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
@@ -152,6 +195,9 @@ sparc32_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   set_gdbarch_fetch_tls_load_module_address (gdbarch,
                                              svr4_fetch_objfile_link_map);
 
+  /* Make sure we can single-step over signal return system calls.  */
+  tdep->step_trap = sparc32_linux_step_trap;
+
   /* Hook in the DWARF CFI frame unwinder.  */
   frame_unwind_append_sniffer (gdbarch, dwarf2_frame_sniffer);
 }
diff --git a/gdb/sparc64-linux-tdep.c b/gdb/sparc64-linux-tdep.c
index ce1c6cb..8e0498e 100644
--- a/gdb/sparc64-linux-tdep.c
+++ b/gdb/sparc64-linux-tdep.c
@@ -22,7 +22,9 @@
 #include "defs.h"
 #include "frame.h"
 #include "frame-unwind.h"
+#include "regcache.h"
 #include "gdbarch.h"
+#include "gdbcore.h"
 #include "osabi.h"
 #include "solib-svr4.h"
 #include "symtab.h"
@@ -98,6 +100,36 @@ sparc64_linux_sigframe_init (const struct tramp_frame *self,
   trad_frame_set_id (this_cache, frame_id_build (base, func));
 }
 
+/* Return the address of a system call's alternative return
+   address.  */
+
+static CORE_ADDR
+sparc64_linux_step_trap (unsigned long insn)
+{
+  if (insn == 0x91d0206d)
+    {
+      ULONGEST sp;
+
+      regcache_cooked_read_unsigned (current_regcache,
+				     SPARC_SP_REGNUM, &sp);
+      if (sp & 1)
+	sp += BIAS;
+
+      /* The kernel puts the sigreturn registers on the stack,
+	 and this is where the signal unwinding state is take from
+	 when returning from a signal.
+
+	 A siginfo_t sits 192 bytes from the base of the stack.  This
+	 siginfo_t is 128 bytes, and is followed by the sigreturn
+	 register save area.  The saved PC sits at a 136 byte offset
+	 into there.  */
+
+      return read_memory_unsigned_integer (sp + 192 + 128 + 136, 8);
+    }
+
+  return 0;
+}
+
 
 static void
 sparc64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
@@ -120,6 +152,9 @@ sparc64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   /* Enable TLS support.  */
   set_gdbarch_fetch_tls_load_module_address (gdbarch,
                                              svr4_fetch_objfile_link_map);
+
+  /* Make sure we can single-step over signal return system calls.  */
+  tdep->step_trap = sparc64_linux_step_trap;
 }