powerpc: Fix emulation of illegal instructions on PowerNV platform

commit bf593907f7236e95698a76b7c7a2bbf8b1165327 upstream.

Normally, the kernel emulates a few instructions that are unimplemented
on some processors (e.g. the old dcba instruction), or privileged (e.g.
mfpvr).  The emulation of unimplemented instructions is currently not
working on the PowerNV platform.  The reason is that on these machines,
unimplemented and illegal instructions cause a hypervisor emulation
assist interrupt, rather than a program interrupt as on older CPUs.
Our vector for the emulation assist interrupt just calls
program_check_exception() directly, without setting the bit in SRR1
that indicates an illegal instruction interrupt.  This fixes it by
making the emulation assist interrupt set that bit before calling
program_check_interrupt().  With this, old programs that use no-longer
implemented instructions such as dcba now work again.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 3bbe7edf639f2e079cf0687d6c82ee950952145a..644378ef0aac7678b0fb53b07fc4d65a42ca4538 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -707,7 +707,7 @@ machine_check_common:
        STD_EXCEPTION_COMMON(0xb00, trap_0b, .unknown_exception)
        STD_EXCEPTION_COMMON(0xd00, single_step, .single_step_exception)
        STD_EXCEPTION_COMMON(0xe00, trap_0e, .unknown_exception)
-       STD_EXCEPTION_COMMON(0xe40, emulation_assist, .program_check_exception)
+       STD_EXCEPTION_COMMON(0xe40, emulation_assist, .emulation_assist_interrupt)
        STD_EXCEPTION_COMMON(0xe60, hmi_exception, .unknown_exception)
 #ifdef CONFIG_PPC_DOORBELL
        STD_EXCEPTION_COMMON_ASYNC(0xe80, h_doorbell, .doorbell_exception)

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 29857c6b6afa066a4e565b5495ef44d1d042ff94..bf33ace123acf3d2ae36cd0901c8d8b5166d5607 100644 (file)
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -1142,6 +1142,16 @@ void __kprobes program_check_exception(struct pt_regs *regs)
                _exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
 }
 
+/*
+ * This occurs when running in hypervisor mode on POWER6 or later
+ * and an illegal instruction is encountered.
+ */
+void __kprobes emulation_assist_interrupt(struct pt_regs *regs)
+{
+       regs->msr |= REASON_ILLEGAL;
+       program_check_exception(regs);
+}
+
 void alignment_exception(struct pt_regs *regs)
 {
        int sig, code, fixed = 0;