add: Definition of GetMemoryMode syscall

Update SetMemoryMode docs with new findings

Author: uyjulian

ee/kernel/Makefile

@@ -195,7 +195,7 @@ KERNEL_OBJS = ResetEE.o SetGsCrt.o $(EXEC_SYSCALLS) \
 	SetPgifHandler.o SetVSyncFlag.o SetSyscall.o SifDmaStat.o iSifDmaStat.o \
 	SifSetDma.o iSifSetDma.o SifSetDChain.o iSifSetDChain.o SifSetReg.o \
 	SifGetReg.o $(EXECOSD_SYSCALL) Deci2Call.o PSMode.o MachineType.o GetMemorySize.o _GetGsDxDyOffset.o \
-	_InitTLB.o SetMemoryMode.o \
+	_InitTLB.o SetMemoryMode.o GetMemoryMode.o \
 	SifWriteBackDCache.o _SyncDCache.o _InvalidDCache.o __errno.o errno.o \
 	strncpy.o strlen.o memcpy.o memset.o __syscall.o GPfuncs.o _print.o
 

ee/kernel/include/kernel.h

@@ -531,9 +531,12 @@ extern void _GetGsDxDyOffset(int mode, int *dx, int *dy, int *dw, int *dh);
 
 // Internal function for reinitializing the TLB, only present in later kernels. Please use InitTLB() instead to initialize the TLB with all kernels.
 extern int _InitTLB(void);
-/* (PSX only) Sets the memory size. 0 = 64MB mode, 1 = 32MB mode. The mode is only binding when either _InitTLB() or the PSX ExecPS2() syscall is called.
+/* (DESR kernels only) Sets the memory size. mode != 1 -> 64MB mode, mode == 1 -> 32MB mode.
+   The mode is only binding when either _InitTLB() or the PSX ExecPS2() syscall is called.
    The stack pointer must remain in range of usable memory, or a TLB exception will occur. */
 extern int SetMemoryMode(int mode); // Arbitrarily named.
+/* (DESR kernels only) Get the value set by SetMemoryMode. */
+extern int GetMemoryMode(void); // Arbitrarily named.
 
 extern void _SyncDCache(void *start, void *end);
 extern void _InvalidDCache(void *start, void *end);

ee/kernel/include/syscallnr.h

@@ -156,6 +156,7 @@
 #define __NR__InitTLB                 0x82
 #define __NR_FindAddress              0x83
 #define __NR_SetMemoryMode            0x85
+#define __NR_GetMemoryMode            0x86
 #define __NR_ExecPSX                  0x87
 
 #endif /* __SYSCALLNR_H__ */

ee/kernel/src/kernel.S

@@ -665,6 +665,10 @@ SYSCALL(_InitTLB)
 SYSCALL(SetMemoryMode)
 #endif
 
+#ifdef F_GetMemoryMode
+SYSCALL(GetMemoryMode)
+#endif
+
 #ifdef F_GPfuncs
 	.text
 	.align	2