[Bug backtrace/16558] GDB Aarch64 signal frame unwinder issue

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https://sourceware.org/bugzilla/show_bug.cgi?id=16558

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https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=f2205de0080d999c9b67872c9db471c31b53e378

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.

-----------------------------------------------------------------------

Summary of changes:
 gdb/ChangeLog            |    7 +++++
 gdb/aarch64-linux-tdep.c |   63 ++++++++++++++++++++++++---------------------
 2 files changed, 41 insertions(+), 29 deletions(-)

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