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

[deliverable/binutils-gdb.git] / gdb / sparc-linux-tdep.c

diff --git a/gdb/sparc-linux-tdep.c b/gdb/sparc-linux-tdep.c
index ef7f37002127ea3ee71633c185f984c9d4757d68..446f05e46494e5b76a76a12e8f5c2e4c2087d9f8 100644 (file)
--- 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));
 }
 \f
+/* 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;
+}
+\f
 
 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);
 }