[Qemu-devel] [Bug 1757363] Re: infinite loop due to improper deal with "eret" on mips32

[Philippe Mathieu-Daudé]

What model/cpu is your router?

Which MIPS guest CPU are you using? Are you sure it matches the CPU of
your router?

Is your tplink firmware publicly available? (to reproduce your problem).

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https://bugs.launchpad.net/bugs/1757363

Title:
  infinite loop due to improper deal with "eret" on mips32

Status in QEMU:
  New

Bug description:
  1.qemu 2.9.1 release on the official web build with tcg
  2.cmd: qemu-system-mips -kernel kernelfile
  3. host: ubuntu 16.04.1 with linux kernel 4.6.2 x86_64
     guest: mips bigendian 32bit (tplink firmware)

  
  detail:

  static inline void exception_return(CPUMIPSState *env)
  {
      debug_pre_eret(env);
      if (env->CP0_Status & (1 << CP0St_ERL)) {
          set_pc(env, env->CP0_ErrorEPC);
          env->CP0_Status &= ~(1 << CP0St_ERL);
      } else {
          set_pc(env, env->CP0_EPC);
          env->CP0_Status &= ~(1 << CP0St_EXL);====================> ISSUE????
      }
      compute_hflags(env);
      debug_post_eret(env);
  }

  void helper_eret(CPUMIPSState *env)
  {
      exception_return(env);
      env->lladdr = 1;
  }

  
  In the Issue Line, there is no check CP0_Status whether int is disabled 
(should not enter int routine),
  that result in the cpu can not jump out the int routine.

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