arch/tile: work around a hardware issue with the return-address stack

In certain circumstances we need to do a bunch of jump-and-link
instructions to fill the hardware return-address stack with nonzero values.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/tile/kernel/traps.c b/arch/tile/kernel/traps.c
index 2bb6602a1ee7..32acfd9e23d0 100644
--- a/arch/tile/kernel/traps.c
+++ b/arch/tile/kernel/traps.c
@@ -289,7 +289,10 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
                 address = regs->pc;
                 break;
 #ifdef __tilegx__
-        case INT_ILL_TRANS:
+        case INT_ILL_TRANS: {
+                /* Avoid a hardware erratum with the return address stack. */
+                fill_ra_stack();
+
                 signo = SIGSEGV;
                 code = SEGV_MAPERR;
                 if (reason & SPR_ILL_TRANS_REASON__I_STREAM_VA_RMASK)
@@ -297,6 +300,7 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
                 else
                         address = 0;  /* FIXME: GX: single-step for address */
                 break;
+        }
 #endif
         default:
                 panic("Unexpected do_trap interrupt number %d", fault_num);