[Qemu-devel] [PATCH] target-arm: Correct "preferred return address" for cpreg access exceptions

[Peter Maydell <peter.maydell@linaro.org>]

The architecture defines that when taking an exception trying to
access a coprocessor register, the "preferred return address" for
the exception is the address of the instruction that caused the
exception. Correct an off-by-4 error which meant we were returning
the address after the instruction for traps which happened because
of a failure of a runtime access-check function on an AArch32
register. (Traps caused by translate-time checkable permissions
failures had the correct address, as did traps on AArch64 registers.)

This fixes https://bugs.launchpad.net/qemu/+bug/1463338

Reported-by: Robert Buhren <robert@robertbuhren.de>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target-arm/translate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target-arm/translate.c b/target-arm/translate.c
index 39692d7..239322d 100644
--- a/target-arm/translate.c
+++ b/target-arm/translate.c
@@ -7175,7 +7175,7 @@ static int disas_coproc_insn(DisasContext *s, uint32_t insn)
                 break;
             }
 
-            gen_set_pc_im(s, s->pc);
+            gen_set_pc_im(s, s->pc - 4);
             tmpptr = tcg_const_ptr(ri);
             tcg_syn = tcg_const_i32(syndrome);
             gen_helper_access_check_cp_reg(cpu_env, tmpptr, tcg_syn);
-- 
1.9.1