[PATCH] gdb/csky add unwinder for sigtramp frame when kernel 4.x and later

[Jiangshuai Li via Gdb-patches <gdb-patches@sourceware.org>]

When kernel veriosn >= V4.x, the characteristic values used to determine
whether it is a signal function call are:
	movi r7, 139
	trap 0

Registers are saved at (sp + CSKY_SIGINFO_OFFSET + CSKY_SIGINFO_SIZE
+ CSKY_UCONTEXT_SIGCONTEXT + CSKY_SIGCONTEXT_PT_REGS_TLS). The order is
described in csky_linux_rt_sigreturn_init_pt_regs.
---
 gdb/csky-linux-tdep.c | 47 +++++++++++++++++++++++++++++++++++++++++++
 gdb/csky-tdep.h       |  6 ++++++
 2 files changed, 53 insertions(+)

diff --git a/gdb/csky-linux-tdep.c b/gdb/csky-linux-tdep.c
index 106f629b8b0..89d3a60c43c 100644
--- a/gdb/csky-linux-tdep.c
+++ b/gdb/csky-linux-tdep.c
@@ -353,6 +353,51 @@ csky_linux_rt_sigreturn_tramp_frame = {
   csky_linux_rt_sigreturn_init
 };
 
+static void
+csky_linux_rt_sigreturn_init_pt_regs (const struct tramp_frame *self,
+				      struct frame_info *this_frame,
+				      struct trad_frame_cache *this_cache,
+				      CORE_ADDR func)
+{
+  int i;
+  CORE_ADDR sp = get_frame_register_unsigned (this_frame, CSKY_SP_REGNUM);
+
+  CORE_ADDR base = sp + CSKY_SIGINFO_OFFSET + CSKY_SIGINFO_SIZE
+		   + CSKY_UCONTEXT_SIGCONTEXT
+		   + CSKY_SIGCONTEXT_PT_REGS_TLS;
+
+  /* LR */
+  trad_frame_set_reg_addr (this_cache, CSKY_R15_REGNUM, base);
+
+  /* PC */
+  trad_frame_set_reg_addr (this_cache, CSKY_PC_REGNUM, base + 4);
+
+  /* PSR */
+  trad_frame_set_reg_addr (this_cache, CSKY_CR0_REGNUM, base + 8);
+
+  /* SP */
+  trad_frame_set_reg_addr (this_cache, CSKY_SP_REGNUM, base + 12);
+
+  /* Set addrs of R0 ~ R13.  */
+  for (i = 0; i < 14; i++)
+    trad_frame_set_reg_addr (this_cache, i, base + i * 4 + 20);
+
+  trad_frame_set_id (this_cache, frame_id_build (sp, func));
+}
+
+
+static struct tramp_frame
+csky_linux_rt_sigreturn_tramp_frame_kernel_4x = {
+  SIGTRAMP_FRAME,
+  4,
+  {
+    { CSKY_MOVI_R7_139, ULONGEST_MAX },
+    { CSKY_TRAP_0, ULONGEST_MAX },
+    { TRAMP_SENTINEL_INSN }
+  },
+  csky_linux_rt_sigreturn_init_pt_regs
+};
+
 /* Hook function for gdbarch_register_osabi.  */
 
 static void
@@ -378,6 +423,8 @@ csky_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 
   tramp_frame_prepend_unwinder (gdbarch,
 				&csky_linux_rt_sigreturn_tramp_frame);
+  tramp_frame_prepend_unwinder (gdbarch,
+				&csky_linux_rt_sigreturn_tramp_frame_kernel_4x);
 }
 
 void _initialize_csky_linux_tdep ();
diff --git a/gdb/csky-tdep.h b/gdb/csky-tdep.h
index 3ee50fc5931..f845b9ab744 100644
--- a/gdb/csky-tdep.h
+++ b/gdb/csky-tdep.h
@@ -379,4 +379,10 @@ enum csky_regnum
 #define CSKY_MOVI_R7_173 0x00adea07
 #define CSKY_TRAP_0 0x2020c000
 
+/* Sizeof (tls) */
+#define CSKY_SIGCONTEXT_PT_REGS_TLS  4
+
+/* Macro for kernel 4.x  */
+#define CSKY_MOVI_R7_139 0x008bea07
+
 #endif
-- 
2.25.1