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>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index cf9c69b9189cb831261a8d8ca0c27d96aacfb89f..8c3baa08b84ebac07e67a2b48e07cbbb401d7fa8 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -463,7 +463,7 @@ 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)
        STD_EXCEPTION_COMMON_IDLE(0xf00, performance_monitor, .performance_monitor_exception)
        STD_EXCEPTION_COMMON(0x1300, instruction_breakpoint, .instruction_breakpoint_exception)

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 82dcd4d8b4eb7138d6530b94abbba447fdd7b69a..9844662a8014eb58be86c1532deff4031b487ffc 100644 (file)
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -1036,6 +1036,16 @@ 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;