[Qemu-devel] [PULL 2/3] ppc: Fix the bad exception NIP value and the range check in LSWX

[David Gibson <david@gibson.dropbear.id.au>]

From: Thomas Huth <thuth@redhat.com>

The range checks in the LSWX instruction are completely insufficient:
They do not take the wrap-around case into account, and the check
"reg < rx" should be "reg <= rx" instead. Fix it by using the new
lsw_reg_in_range() helper function that is already used for LSWI, too.

Then there is a second problem: In case the INVAL exception is generated,
the NIP value is wrong, it currently points to the instruction before
the LSWX instruction. This is because gen_lswx() already decreases the
NIP value by 4 (to be prepared for page fault exceptions), and
powerpc_excp() later decreases it again by 4 while handling the program
exception. So to get this right, we've got to undo the "- 4" from
gen_lswx() here before calling helper_raise_exception_err().

Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 target-ppc/mem_helper.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/target-ppc/mem_helper.c b/target-ppc/mem_helper.c
index 581d9fa..6d584c9 100644
--- a/target-ppc/mem_helper.c
+++ b/target-ppc/mem_helper.c
@@ -102,8 +102,9 @@ void helper_lswx(CPUPPCState *env, target_ulong addr, uint32_t reg,
 {
     if (likely(xer_bc != 0)) {
         int num_used_regs = (xer_bc + 3) / 4;
-        if (unlikely((ra != 0 && reg < ra && (reg + num_used_regs) > ra) ||
-                     (reg < rb && (reg + num_used_regs) > rb))) {
+        if (unlikely((ra != 0 && lsw_reg_in_range(reg, num_used_regs, ra)) ||
+                     lsw_reg_in_range(reg, num_used_regs, rb))) {
+            env->nip += 4;     /* Compensate the "nip - 4" from gen_lswx() */
             helper_raise_exception_err(env, POWERPC_EXCP_PROGRAM,
                                        POWERPC_EXCP_INVAL |
                                        POWERPC_EXCP_INVAL_LSWX);
-- 
2.5.5