Commit c599d4d6 authored by Peter Maydell's avatar Peter Maydell Committed by Riku Voipio
Browse files

linux-user: SIGSEGV from sigreturn need not be fatal 



If the sigreturn syscall fails to read memory then this causes a
SIGSEGV, but this is not necessarily a fatal signal -- the guest
process can catch it.

We don't implement this correctly because the behaviour of QEMU's
force_sig() function has drifted away from the kernel function of the
same name -- ours now does "always do a guest core dump and abort
execution", whereas the kernel version simply forces the guest to
take a signal, which may or may not eventually cause a core dump.

Rename our force_sig() to dump_core_and_abort(), and provide a
force_sig() which acts more like the kernel version as the sigreturn
implementations expect it to.  Since force_sig() now returns, we must
update all the callsites to return -TARGET_QEMU_ESIGRETURN so that
the main loop doesn't change the guest registers before the signal
handler is invoked.

Reviewed-by: default avatarRichard Henderson <rth@twiddle.net>
Signed-off-by: default avatarPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: default avatarRiku Voipio <riku.voipio@linaro.org>
parent 28298c91

linux-user/signal.c

+54 −27
Original line number Diff line number Diff line
@@ -512,6 +512,27 @@ void signal_init(void) 
    }

}



#if !defined(TARGET_OPENRISC) && !defined(TARGET_UNICORE32) && \

    !defined(TARGET_X86_64)

/* Force a synchronously taken signal. The kernel force_sig() function

 * also forces the signal to "not blocked, not ignored", but for QEMU

 * that work is done in process_pending_signals().

 */

static void force_sig(int sig)

{

    CPUState *cpu = thread_cpu;

    CPUArchState *env = cpu->env_ptr;

    target_siginfo_t info;



    info.si_signo = sig;

    info.si_errno = 0;

    info.si_code = TARGET_SI_KERNEL;

    info._sifields._kill._pid = 0;

    info._sifields._kill._uid = 0;

    queue_signal(env, info.si_signo, QEMU_SI_KILL, &info);

}

#endif



#if !(defined(TARGET_X86_64) || defined(TARGET_UNICORE32))



/* Force a SIGSEGV if we couldn't write to memory trying to set
@@ -526,7 +547,7 @@ static void force_sigsegv(int oldsig) 


    if (oldsig == SIGSEGV) {

        /* Make sure we don't try to deliver the signal again; this will

         * end up with handle_pending_signal() calling force_sig().

         * end up with handle_pending_signal() calling dump_core_and_abort().

         */

        sigact_table[oldsig - 1]._sa_handler = TARGET_SIG_DFL;

    }
@@ -540,7 +561,7 @@ static void force_sigsegv(int oldsig) 
#endif



/* abort execution with signal */

static void QEMU_NORETURN force_sig(int target_sig)

static void QEMU_NORETURN dump_core_and_abort(int target_sig)

{

    CPUState *cpu = thread_cpu;

    CPUArchState *env = cpu->env_ptr;
@@ -1181,7 +1202,7 @@ long do_sigreturn(CPUX86State *env) 
badframe:

    unlock_user_struct(frame, frame_addr, 0);

    force_sig(TARGET_SIGSEGV);

    return 0;

    return -TARGET_QEMU_ESIGRETURN;

}



long do_rt_sigreturn(CPUX86State *env)
@@ -1212,7 +1233,7 @@ long do_rt_sigreturn(CPUX86State *env) 
badframe:

    unlock_user_struct(frame, frame_addr, 0);

    force_sig(TARGET_SIGSEGV);

    return 0;

    return -TARGET_QEMU_ESIGRETURN;

}



#elif defined(TARGET_AARCH64)
@@ -1482,7 +1503,7 @@ long do_rt_sigreturn(CPUARMState *env) 
 badframe:

    unlock_user_struct(frame, frame_addr, 0);

    force_sig(TARGET_SIGSEGV);

    return 0;

    return -TARGET_QEMU_ESIGRETURN;

}



long do_sigreturn(CPUARMState *env)
@@ -2004,8 +2025,8 @@ static long do_sigreturn_v1(CPUARMState *env) 
    return -TARGET_QEMU_ESIGRETURN;



badframe:

    force_sig(TARGET_SIGSEGV /* , current */);

    return 0;

    force_sig(TARGET_SIGSEGV);

    return -TARGET_QEMU_ESIGRETURN;

}



static abi_ulong *restore_sigframe_v2_vfp(CPUARMState *env, abi_ulong *regspace)
@@ -2131,8 +2152,8 @@ static long do_sigreturn_v2(CPUARMState *env) 


badframe:

    unlock_user_struct(frame, frame_addr, 0);

    force_sig(TARGET_SIGSEGV /* , current */);

    return 0;

    force_sig(TARGET_SIGSEGV);

    return -TARGET_QEMU_ESIGRETURN;

}



long do_sigreturn(CPUARMState *env)
@@ -2185,8 +2206,8 @@ static long do_rt_sigreturn_v1(CPUARMState *env) 


badframe:

    unlock_user_struct(frame, frame_addr, 0);

    force_sig(TARGET_SIGSEGV /* , current */);

    return 0;

    force_sig(TARGET_SIGSEGV);

    return -TARGET_QEMU_ESIGRETURN;

}



static long do_rt_sigreturn_v2(CPUARMState *env)
@@ -2218,8 +2239,8 @@ static long do_rt_sigreturn_v2(CPUARMState *env) 


badframe:

    unlock_user_struct(frame, frame_addr, 0);

    force_sig(TARGET_SIGSEGV /* , current */);

    return 0;

    force_sig(TARGET_SIGSEGV);

    return -TARGET_QEMU_ESIGRETURN;

}



long do_rt_sigreturn(CPUARMState *env)
@@ -2553,6 +2574,7 @@ long do_sigreturn(CPUSPARCState *env) 
segv_and_exit:

    unlock_user_struct(sf, sf_addr, 0);

    force_sig(TARGET_SIGSEGV);

    return -TARGET_QEMU_ESIGRETURN;

}



long do_rt_sigreturn(CPUSPARCState *env)
@@ -3110,8 +3132,8 @@ long do_sigreturn(CPUMIPSState *regs) 
    return -TARGET_QEMU_ESIGRETURN;



badframe:

    force_sig(TARGET_SIGSEGV/*, current*/);

    return 0;

    force_sig(TARGET_SIGSEGV);

    return -TARGET_QEMU_ESIGRETURN;

}

# endif /* O32 */
@@ -3207,8 +3229,8 @@ long do_rt_sigreturn(CPUMIPSState *env) 
    return -TARGET_QEMU_ESIGRETURN;



badframe:

    force_sig(TARGET_SIGSEGV/*, current*/);

    return 0;

    force_sig(TARGET_SIGSEGV);

    return -TARGET_QEMU_ESIGRETURN;

}



#elif defined(TARGET_SH4)
@@ -3474,7 +3496,7 @@ long do_sigreturn(CPUSH4State *regs) 
badframe:

    unlock_user_struct(frame, frame_addr, 0);

    force_sig(TARGET_SIGSEGV);

    return 0;

    return -TARGET_QEMU_ESIGRETURN;

}



long do_rt_sigreturn(CPUSH4State *regs)
@@ -3506,7 +3528,7 @@ long do_rt_sigreturn(CPUSH4State *regs) 
badframe:

    unlock_user_struct(frame, frame_addr, 0);

    force_sig(TARGET_SIGSEGV);

    return 0;

    return -TARGET_QEMU_ESIGRETURN;

}

#elif defined(TARGET_MICROBLAZE)
@@ -3725,6 +3747,7 @@ long do_sigreturn(CPUMBState *env) 
    return -TARGET_QEMU_ESIGRETURN;

badframe:

    force_sig(TARGET_SIGSEGV);

    return -TARGET_QEMU_ESIGRETURN;

}



long do_rt_sigreturn(CPUMBState *env)
@@ -3892,6 +3915,7 @@ long do_sigreturn(CPUCRISState *env) 
    return -TARGET_QEMU_ESIGRETURN;

badframe:

    force_sig(TARGET_SIGSEGV);

    return -TARGET_QEMU_ESIGRETURN;

}



long do_rt_sigreturn(CPUCRISState *env)
@@ -4383,7 +4407,7 @@ long do_sigreturn(CPUS390XState *env) 


badframe:

    force_sig(TARGET_SIGSEGV);

    return 0;

    return -TARGET_QEMU_ESIGRETURN;

}



long do_rt_sigreturn(CPUS390XState *env)
@@ -4414,7 +4438,7 @@ long do_rt_sigreturn(CPUS390XState *env) 
badframe:

    unlock_user_struct(frame, frame_addr, 0);

    force_sig(TARGET_SIGSEGV);

    return 0;

    return -TARGET_QEMU_ESIGRETURN;

}



#elif defined(TARGET_PPC)
@@ -4973,7 +4997,7 @@ sigsegv: 
    unlock_user_struct(sr, sr_addr, 1);

    unlock_user_struct(sc, sc_addr, 1);

    force_sig(TARGET_SIGSEGV);

    return 0;

    return -TARGET_QEMU_ESIGRETURN;

}



/* See arch/powerpc/kernel/signal_32.c.  */
@@ -5028,7 +5052,7 @@ long do_rt_sigreturn(CPUPPCState *env) 
sigsegv:

    unlock_user_struct(rt_sf, rt_sf_addr, 1);

    force_sig(TARGET_SIGSEGV);

    return 0;

    return -TARGET_QEMU_ESIGRETURN;

}



#elif defined(TARGET_M68K)
@@ -5358,7 +5382,7 @@ long do_sigreturn(CPUM68KState *env) 


badframe:

    force_sig(TARGET_SIGSEGV);

    return 0;

    return -TARGET_QEMU_ESIGRETURN;

}



long do_rt_sigreturn(CPUM68KState *env)
@@ -5391,7 +5415,7 @@ long do_rt_sigreturn(CPUM68KState *env) 
badframe:

    unlock_user_struct(frame, frame_addr, 0);

    force_sig(TARGET_SIGSEGV);

    return 0;

    return -TARGET_QEMU_ESIGRETURN;

}



#elif defined(TARGET_ALPHA)
@@ -5620,6 +5644,7 @@ long do_sigreturn(CPUAlphaState *env) 


badframe:

    force_sig(TARGET_SIGSEGV);

    return -TARGET_QEMU_ESIGRETURN;

}



long do_rt_sigreturn(CPUAlphaState *env)
@@ -5649,6 +5674,7 @@ long do_rt_sigreturn(CPUAlphaState *env) 
badframe:

    unlock_user_struct(frame, frame_addr, 0);

    force_sig(TARGET_SIGSEGV);

    return -TARGET_QEMU_ESIGRETURN;

}



#elif defined(TARGET_TILEGX)
@@ -5813,6 +5839,7 @@ long do_rt_sigreturn(CPUTLGState *env) 
 badframe:

    unlock_user_struct(frame, frame_addr, 0);

    force_sig(TARGET_SIGSEGV);

    return -TARGET_QEMU_ESIGRETURN;

}



#else
@@ -5879,12 +5906,12 @@ static void handle_pending_signal(CPUArchState *cpu_env, int sig, 
                   sig != TARGET_SIGURG &&

                   sig != TARGET_SIGWINCH &&

                   sig != TARGET_SIGCONT) {

            force_sig(sig);

            dump_core_and_abort(sig);

        }

    } else if (handler == TARGET_SIG_IGN) {

        /* ignore sig */

    } else if (handler == TARGET_SIG_ERR) {

        force_sig(sig);

        dump_core_and_abort(sig);

    } else {

        /* compute the blocked signals during the handler execution */

        sigset_t *blocked_set;