signal/m68k: Use force_sigsegv(SIGSEGV) in fpsp040_die

commit a3616a3c02722d1edb95acc7fceade242f6553ba upstream.

In the fpsp040 code when copyin or copyout fails call
force_sigsegv(SIGSEGV) instead of do_exit(SIGSEGV).

This solves a couple of problems.  Because do_exit embeds the ptrace
stop PTRACE_EVENT_EXIT a complete stack frame needs to be present for
that to work correctly.  There is always the information needed for a
ptrace stop where get_signal is called.  So exiting with a signal
solves the ptrace issue.

Further exiting with a signal ensures that all of the threads in a
process are killed not just the thread that malfunctioned.  Which
avoids confusing userspace.

To make force_sigsegv(SIGSEGV) work in fpsp040_die modify the code to
save all of the registers and jump to ret_from_exception (which
ultimately calls get_signal) after fpsp040_die returns.

v2: Updated the branches to use gas's pseudo ops that automatically
    calculate the best branch instruction to use for the purpose.

v1: https://lkml.kernel.org/r/87a6m8kgtx.fsf_-_@disp2133
Link: https://lkml.kernel.org/r/87tukghjfs.fsf_-_@disp2133
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/m68k/fpsp040/skeleton.S b/arch/m68k/fpsp040/skeleton.S
index 31a9c634c81ed2a0db75274b6360e6aa0d6e3ede..081922c72daaaa487326ffc33db98188cc2e0dd7 100644 (file)
--- a/arch/m68k/fpsp040/skeleton.S
+++ b/arch/m68k/fpsp040/skeleton.S
@@ -502,7 +502,8 @@ in_ea:
        .section .fixup,"ax"
        .even
 1:
-       jbra    fpsp040_die
+       jbsr    fpsp040_die
+       jbra    .Lnotkern
 
        .section __ex_table,"a"
        .align  4

diff --git a/arch/m68k/kernel/traps.c b/arch/m68k/kernel/traps.c
index 7d42c84649ac215c0a91606efc0fe23a8f7213c7..f6706ef6b195e142b0d23f517e69650763029b51 100644 (file)
--- a/arch/m68k/kernel/traps.c
+++ b/arch/m68k/kernel/traps.c
@@ -1152,7 +1152,7 @@ asmlinkage void set_esp0(unsigned long ssp)
  */
 asmlinkage void fpsp040_die(void)
 {
-       do_exit(SIGSEGV);
+       force_sigsegv(SIGSEGV);
 }
 
 #ifdef CONFIG_M68KFPU_EMU