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[PATCH] target/mips: Fix ll/sc after 7dd547e5ab6b31e7a0cfc182d3ad131dd55

From: James Clarke
Subject: [PATCH] target/mips: Fix ll/sc after 7dd547e5ab6b31e7a0cfc182d3ad131dd55a948f
Date: Sun, 2 Feb 2020 15:34:09 +0000

From: Alex Richardson <address@hidden>

After 7dd547e5ab6b31e7a0cfc182d3ad131dd55a948f the env->llval value is
loaded as an unsigned value (instead of sign-extended as before).
Therefore, the CMPXCHG in gen_st_cond() in translate.c fails if the sign
bit is set in the loaded value.
Fix this by sign-extending the llval value for the 32-bit case.

I discovered this issue because FreeBSD MIPS64 was looping forever in an
atomic helper function when trying to start /sbin/init.

Signed-off-by: Alex Richardson <address@hidden>
Fixes: 7dd547e5ab6b ("target/mips: Use cpu_*_mmuidx_ra instead of 
Buglink: https://bugs.launchpad.net/qemu/+bug/1861605
Cc: Aurelien Jarno <address@hidden>
Cc: Aleksandar Markovic <address@hidden>
Cc: Aleksandar Rikalo <address@hidden>
Cc: Richard Henderson <address@hidden>
Signed-off-by: James Clarke <address@hidden>
 target/mips/op_helper.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/target/mips/op_helper.c b/target/mips/op_helper.c
index 15d05a5fbc..467914d1ca 100644
--- a/target/mips/op_helper.c
+++ b/target/mips/op_helper.c
@@ -305,7 +305,7 @@ static inline hwaddr do_translate_address(CPUMIPSState *env,

-#define HELPER_LD_ATOMIC(name, insn, almask)                                  \
+#define HELPER_LD_ATOMIC(name, insn, almask, do_cast)                         \
 target_ulong helper_##name(CPUMIPSState *env, target_ulong arg, int mem_idx)  \
 {                                                                             \
     if (arg & almask) {                                                       \
@@ -316,12 +316,12 @@ target_ulong helper_##name(CPUMIPSState *env, 
target_ulong arg, int mem_idx)  \
     }                                                                         \
     env->CP0_LLAddr = do_translate_address(env, arg, 0, GETPC());             \
     env->lladdr = arg;                                                        \
-    env->llval = cpu_##insn##_mmuidx_ra(env, arg, mem_idx, GETPC());          \
+    env->llval = do_cast cpu_##insn##_mmuidx_ra(env, arg, mem_idx, GETPC());  \
     return env->llval;                                                        \
-HELPER_LD_ATOMIC(ll, ldl, 0x3)
+HELPER_LD_ATOMIC(ll, ldl, 0x3, (target_long)(int32_t))
 #ifdef TARGET_MIPS64
-HELPER_LD_ATOMIC(lld, ldq, 0x7)
+HELPER_LD_ATOMIC(lld, ldq, 0x7, (target_ulong))

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