path: root/target-mips/op_helper.c
diff options
authorMaciej W. Rozycki <macro@codesourcery.com>2014-11-18 03:59:07 +0000
committerLeon Alrae <leon.alrae@imgtec.com>2014-12-16 12:45:20 +0000
commit90f12d735d66ac1196d9a2bced039a432eefc03d (patch)
tree61461dcd9c906f39ac7b8e52fb2d56ddd364f26c /target-mips/op_helper.c
parent27e1fb13f21e132011673f0a39e17bcc97583633 (diff)
target-mips: Fix CP0.Config3.ISAOnExc write accesses
Fix CP0.Config3.ISAOnExc write accesses on microMIPS processors. This bit is mandatory for any processor that implements the microMIPS instruction set. This bit is r/w for processors that implement both the standard MIPS and the microMIPS instruction set. This bit is r/o and hardwired to 1 if only the microMIPS instruction set is implemented. There is no other bit ever writable in CP0.Config3 so defining a corresponding `CP0_Config3_rw_bitmask' member in `CPUMIPSState' is I think an overkill. Therefore make the ability to write the bit rely on the presence of ASE_MICROMIPS set in the instruction flags. The read-only case of the microMIPS instruction set being implemented only can be added when we add support for such a configuration. We do not currently have such support, we have no instruction flag that would control the presence of the standard MIPS instruction set nor any associated code in instruction decoding. This change is needed to boot a microMIPS Linux kernel successfully, otherwise it hangs early on as interrupts are enabled and then the exception handler invoked loops as its first instruction is interpreted in the wrong execution mode and triggers another exception right away. And then over and over again. We already check the current setting of the CP0.Config3.ISAOnExc in `set_hflags_for_handler' to set the ISA bit correctly on the exception handler entry so it is the ability to set it that is missing only. Signed-off-by: Maciej W. Rozycki <macro@codesourcery.com> Reviewed-by: Leon Alrae <leon.alrae@imgtec.com> Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>
Diffstat (limited to 'target-mips/op_helper.c')
1 files changed, 8 insertions, 0 deletions
diff --git a/target-mips/op_helper.c b/target-mips/op_helper.c
index 1ec2756373..1267ef297c 100644
--- a/target-mips/op_helper.c
+++ b/target-mips/op_helper.c
@@ -1503,6 +1503,14 @@ void helper_mtc0_config2(CPUMIPSState *env, target_ulong arg1)
env->CP0_Config2 = (env->CP0_Config2 & 0x8FFF0FFF);
+void helper_mtc0_config3(CPUMIPSState *env, target_ulong arg1)
+ if (env->insn_flags & ASE_MICROMIPS) {
+ env->CP0_Config3 = (env->CP0_Config3 & ~(1 << CP0C3_ISA_ON_EXC)) |
+ (arg1 & (1 << CP0C3_ISA_ON_EXC));
+ }
void helper_mtc0_config4(CPUMIPSState *env, target_ulong arg1)
env->CP0_Config4 = (env->CP0_Config4 & (~env->CP0_Config4_rw_bitmask)) |