commit f2205de0080d999c9b67872c9db471c31b53e378

Author: Hui Zhu <teawater@gmail.com>

Date:   Tue May 20 13:19:06 2014 +0800

    Fix issue #15778: GDB Aarch64 signal frame unwinder issue

    The root cause of this issue is unwinder of "#3  <signal handler called>"

    doesn't supply right values of registers.

    When GDB want to get the previous frame of "#3  <signal handler called>",

    it will call cache init function of unwinder "aarch64_linux_sigframe_init".

    The address or the value of the registers is get from this function.

    So the bug is inside thie function.

    I check the asm code of "#3  <signal handler called>":

    (gdb) frame 3

    (gdb) p $pc

    $1 = (void (*)()) 0x7f931fa4d0

    (gdb) disassemble $pc, +10

    Dump of assembler code from 0x7f931fa4d0 to 0x7f931fa4da:

    => 0x0000007f931fa4d0:	mov	x8, #0x8b                  	// #139

       0x0000007f931fa4d4:	svc	#0x0

       0x0000007f931fa4d8:	nop

    This is the syscall sys_rt_sigreturn, Linux kernel function "restore_sigframe"

    will set the frame:

    	for (i = 0; i < 31; i++)

    		__get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],

    				 err);

    	__get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);

    	__get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);

    The struct of uc_mcontext is:

    struct sigcontext {

    	__u64 fault_address;

    	/* AArch64 registers */

    	__u64 regs[31];

    	__u64 sp;

    	__u64 pc;

    	__u64 pstate;

    	/* 4K reserved for FP/SIMD state and future expansion */

    	__u8 __reserved[4096] __attribute__((__aligned__(16)));

    };

    But in GDB function "aarch64_linux_sigframe_init", the code the get address

    of registers is:

      for (i = 0; i < 31; i++)

        {

          trad_frame_set_reg_addr (this_cache,

    			       AARCH64_X0_REGNUM + i,

    			       sigcontext_addr + AARCH64_SIGCONTEXT_XO_OFFSET

    			       + i * AARCH64_SIGCONTEXT_REG_SIZE);

        }

      trad_frame_set_reg_addr (this_cache, AARCH64_FP_REGNUM, fp);

      trad_frame_set_reg_addr (this_cache, AARCH64_LR_REGNUM, fp + 8);

      trad_frame_set_reg_addr (this_cache, AARCH64_PC_REGNUM, fp + 8);

    The code that get pc and sp is not right, so I change the code according

    to Linux kernel code:

      trad_frame_set_reg_addr (this_cache, AARCH64_SP_REGNUM,

    			   sigcontext_addr + AARCH64_SIGCONTEXT_XO_OFFSET

    			     + 31 * AARCH64_SIGCONTEXT_REG_SIZE);

      trad_frame_set_reg_addr (this_cache, AARCH64_PC_REGNUM,

    			   sigcontext_addr + AARCH64_SIGCONTEXT_XO_OFFSET

    			     + 32 * AARCH64_SIGCONTEXT_REG_SIZE);

    The issue was fixed by this change, and I did the regression test.  It

    also fixed a lot of other XFAIL and FAIL.

    2014-05-20  Hui Zhu  <hui@codesourcery.com>

    	    Yao Qi  <yao@codesourcery.com>

    	PR backtrace/16558

    	* aarch64-linux-tdep.c (aarch64_linux_sigframe_init): Update comments

    	and change address of sp and pc.

Index: gdb-7.6.1/gdb/aarch64-linux-tdep.c

===================================================================

--- gdb-7.6.1.orig/gdb/aarch64-linux-tdep.c

+++ gdb-7.6.1/gdb/aarch64-linux-tdep.c

@@ -47,28 +47,30 @@

 /* Signal frame handling.

-      +----------+  ^

-      | saved lr |  |

-   +->| saved fp |--+

-   |  |          |

-   |  |          |

-   |  +----------+

-   |  | saved lr |

-   +--| saved fp |

-   ^  |          |

-   |  |          |

-   |  +----------+

-   ^  |          |

-   |  | signal   |

-   |  |          |

-   |  | saved lr |-->interrupted_function_pc

-   +--| saved fp |

-   |  +----------+

-   |  | saved lr |--> default_restorer (movz x8, NR_sys_rt_sigreturn; svc 0)

-   +--| saved fp |<- FP

-      |          |

-      |          |<- SP

-      +----------+

+      +------------+  ^

+      | saved lr   |  |

+   +->| saved fp   |--+

+   |  |            |

+   |  |            |

+   |  +------------+

+   |  | saved lr   |

+   +--| saved fp   |

+   ^  |            |

+   |  |            |

+   |  +------------+

+   ^  |            |

+   |  | signal     |

+   |  |            |        SIGTRAMP_FRAME (struct rt_sigframe)

+   |  | saved regs |

+   +--| saved sp   |--> interrupted_sp

+   |  | saved pc   |--> interrupted_pc

+   |  |            |

+   |  +------------+

+   |  | saved lr   |--> default_restorer (movz x8, NR_sys_rt_sigreturn; svc 0)

+   +--| saved fp   |<- FP

+      |            |         NORMAL_FRAME

+      |            |<- SP

+      +------------+

   On signal delivery, the kernel will create a signal handler stack

   frame and setup the return address in LR to point at restorer stub.

@@ -117,6 +119,8 @@

   d28015a8        movz    x8, #0xad

   d4000001        svc     #0x0

+  This is a system call sys_rt_sigreturn.

+

   We detect signal frames by snooping the return code for the restorer

   instruction sequence.

@@ -140,7 +144,6 @@ aarch64_linux_sigframe_init (const struc

 {

   struct gdbarch *gdbarch = get_frame_arch (this_frame);

   CORE_ADDR sp = get_frame_register_unsigned (this_frame, AARCH64_SP_REGNUM);

-  CORE_ADDR fp = get_frame_register_unsigned (this_frame, AARCH64_FP_REGNUM);

   CORE_ADDR sigcontext_addr =

     sp

     + AARCH64_RT_SIGFRAME_UCONTEXT_OFFSET

@@ -154,12 +157,14 @@ aarch64_linux_sigframe_init (const struc

 			       sigcontext_addr + AARCH64_SIGCONTEXT_XO_OFFSET

 			       + i * AARCH64_SIGCONTEXT_REG_SIZE);

     }

+  trad_frame_set_reg_addr (this_cache, AARCH64_SP_REGNUM,

+			   sigcontext_addr + AARCH64_SIGCONTEXT_XO_OFFSET

+			     + 31 * AARCH64_SIGCONTEXT_REG_SIZE);

+  trad_frame_set_reg_addr (this_cache, AARCH64_PC_REGNUM,

+			   sigcontext_addr + AARCH64_SIGCONTEXT_XO_OFFSET

+			     + 32 * AARCH64_SIGCONTEXT_REG_SIZE);

-  trad_frame_set_reg_addr (this_cache, AARCH64_FP_REGNUM, fp);

-  trad_frame_set_reg_addr (this_cache, AARCH64_LR_REGNUM, fp + 8);

-  trad_frame_set_reg_addr (this_cache, AARCH64_PC_REGNUM, fp + 8);

-

-  trad_frame_set_id (this_cache, frame_id_build (fp, func));

+  trad_frame_set_id (this_cache, frame_id_build (sp, func));

 }

 static const struct tramp_frame aarch64_linux_rt_sigframe =

Index: gdb-7.6.1/gdb/testsuite/gdb.arch/aarch64-rhbz1086894-bt-signal-handler.exp

===================================================================

--- /dev/null

+++ gdb-7.6.1/gdb/testsuite/gdb.arch/aarch64-rhbz1086894-bt-signal-handler.exp

@@ -0,0 +1,35 @@

+# Copyright (C) 2014 Free Software Foundation, Inc.

+#

+# This program is free software; you can redistribute it and/or modify

+# it under the terms of the GNU General Public License as published by

+# the Free Software Foundation; either version 3 of the License, or

+# (at your option) any later version.

+#

+# This program is distributed in the hope that it will be useful,

+# but WITHOUT ANY WARRANTY; without even the implied warranty of

+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+# GNU General Public License for more details.

+#

+# You should have received a copy of the GNU General Public License

+# along with this program.  If not, see <http://www.gnu.org/licenses/>.

+

+# Internal testing for RHEL-7.1.

+

+standard_testfile

+

+if { ![istarget "aarch64*"] } {

+        verbose "Skipping $testfile"

+        return

+}

+

+if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] } {

+        return -1

+}

+

+if ![runto_main] {

+        return -1

+}

+

+gdb_test "continue" "Continuing.\r\n\r\nProgram received signal SIGSEGV.*" "run until SIGSEGV"

+

+gdb_test "backtrace" "#$decimal\\s+$hex in pause .*from.*" "backtrace on signal handler"

Index: gdb-7.6.1/gdb/testsuite/gdb.arch/aarch64-rhbz1086894-bt-signal-handler.c

===================================================================

--- /dev/null

+++ gdb-7.6.1/gdb/testsuite/gdb.arch/aarch64-rhbz1086894-bt-signal-handler.c

@@ -0,0 +1,40 @@

+/* Copyright 2014 Free Software Foundation, Inc.

+

+   This file is part of GDB.

+

+   This program is free software; you can redistribute it and/or modify

+   it under the terms of the GNU General Public License as published by

+   the Free Software Foundation; either version 3 of the License, or

+   (at your option) any later version.

+

+   This program is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+   GNU General Public License for more details.

+

+   You should have received a copy of the GNU General Public License

+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

+

+/* Internal test for RHEL-7.1.  */

+

+#include <sys/types.h>

+#include <signal.h>

+#include <unistd.h>

+#include <assert.h>

+

+static void

+handle_alrm(int signo)

+{

+  kill (getpid (), SIGSEGV);

+  assert (0);

+}

+

+int

+main (int argc, char *argv[])

+{

+  signal (SIGALRM, handle_alrm);

+  alarm (1);

+  pause ();

+  assert (0);

+  return 0;

+}