elf-loader: embed second loader stub built without IOP reset

ee/elf-loader/Makefile

@@ -6,7 +6,7 @@
 # Licenced under Academic Free License version 2.0
 # Review ps2sdk README & LICENSE files for further details.
 
-EE_OBJS = elf.o loader.o
+EE_OBJS = elf.o loader.o loader_noreset.o
 
 include $(PS2SDKSRC)/Defs.make
 include $(PS2SDKSRC)/ee/Rules.lib.make
@@ -19,16 +19,28 @@ $(PS2SDKSRC)/tools/bin2c/bin/bin2c: $(PS2SDKSRC)/tools/bin2c
 src/loader/bin/loader.elf:
 	$(MAKEREC) src/loader
 
+src/loader/bin_noreset/loader.elf:
+	$(MAKEREC) src/loader EE_BIN_DIR=bin_noreset/ EE_OBJS_DIR=obj_noreset/ LOADER_SKIP_IOP_RESET=1
+
 $(EE_OBJS_DIR)loader.c: src/loader/bin/loader.elf $(PS2SDKSRC)/tools/bin2c/bin/bin2c
 	$(PS2SDKSRC)/tools/bin2c/bin/bin2c $< $@ loader_elf
 
+$(EE_OBJS_DIR)loader_noreset.c: src/loader/bin_noreset/loader.elf $(PS2SDKSRC)/tools/bin2c/bin/bin2c
+	$(PS2SDKSRC)/tools/bin2c/bin/bin2c $< $@ loader_noreset_elf
+
 $(EE_OBJS_DIR)loader.o: $(EE_OBJS_DIR)loader.c
 	$(DIR_GUARD)
 	$(EE_C_COMPILE) $< -c -o $@
 
+$(EE_OBJS_DIR)loader_noreset.o: $(EE_OBJS_DIR)loader_noreset.c
+	$(DIR_GUARD)
+	$(EE_C_COMPILE) $< -c -o $@
+
 clean::
 	$(MAKEREC) src/loader clean
+	$(MAKEREC) src/loader EE_BIN_DIR=bin_noreset/ EE_OBJS_DIR=obj_noreset/ clean
 
 .NOTPARALLEL:: \
 	$(PS2SDKSRC)/tools/bin2c/bin/bin2c \
-	src/loader/bin/loader.elf
+	src/loader/bin/loader.elf \
+	src/loader/bin_noreset/loader.elf

ee/elf-loader/include/elf-loader.h

@@ -50,6 +50,13 @@ extern int LoadELFFromFile(const char *filename, int argc, char *argv[]);
  */
 extern int LoadELFFromFileWithPartition(const char *filename, const char *partition, int argc, char *argv[]);
 
+/** As LoadELFFromFileWithPartition, but the loader does NOT reset the IOP
+ *  before handing off. Storage modules stay resident, so the launched ELF's
+ *  own loader can read from the device it was booted from. The launched ELF
+ *  is responsible for any IOP reset it needs.
+ */
+extern int LoadELFFromFileWithPartitionNoReset(const char *filename, const char *partition, int argc, char *argv[]);
+
 #ifdef __cplusplus
 }
 #endif

ee/elf-loader/src/elf.c

@@ -21,6 +21,9 @@
 extern u8 loader_elf[];
 extern int size_loader_elf;
 
+extern u8 loader_noreset_elf[];
+extern int size_loader_noreset_elf;
+
 // ELF-loading stuff
 #define ELF_MAGIC 0x464c457f
 #define ELF_PT_LOAD 1
@@ -54,8 +57,7 @@ static void wipe_bramMem(void) {
 #endif
 }
 
-int LoadELFFromFileWithPartition(const char *filename, const char *partition, int argc, char *argv[]) {
-	u8 *boot_elf;
+static int LoadELFFromFileCommon(u8 *boot_elf, const char *filename, const char *partition, int argc, char *argv[]) {
 	elf_header_t *eh;
 	elf_pheader_t *eph;
 	void *pdata;
@@ -76,9 +78,8 @@ int LoadELFFromFileWithPartition(const char *filename, const char *partition, in
 	for (i = 0; i < argc; i++) {
 		new_argv[i + 2] = argv[i];
 	}
-
-	/* NB: LOADER.ELF is embedded  */
-	boot_elf = (u8 *)loader_elf;
+
+	/* NB: the selected loader stub is embedded */
 	eh = (elf_header_t *)boot_elf;
 	if (_lw((u32)&eh->ident) != ELF_MAGIC)
 		__builtin_trap();
@@ -105,6 +106,16 @@ int LoadELFFromFileWithPartition(const char *filename, const char *partition, in
 	return ExecPS2((void *)eh->entry, NULL, new_argc, new_argv);
 }
 
+int LoadELFFromFileWithPartition(const char *filename, const char *partition, int argc, char *argv[])
+{
+	return LoadELFFromFileCommon(loader_elf, filename, partition, argc, argv);
+}
+
+int LoadELFFromFileWithPartitionNoReset(const char *filename, const char *partition, int argc, char *argv[])
+{
+	return LoadELFFromFileCommon(loader_noreset_elf, filename, partition, argc, argv);
+}
+
 int LoadELFFromFile(const char *filename, int argc, char *argv[])
 {
 	return LoadELFFromFileWithPartition(filename, NULL, argc, argv);

ee/elf-loader/src/loader/Makefile

@@ -21,6 +21,11 @@ ifneq (x$(LOADER_ENABLE_DEBUG_COLORS), x0)
 EE_CFLAGS += -DLOADER_ENABLE_DEBUG_COLORS
 endif
 
+# Skip the IOP reset before handing off (keeps storage modules resident so the launched ELF's own loader can still read from the boot device)
+ifeq ($(LOADER_SKIP_IOP_RESET), 1)
+EE_CFLAGS += -DLOADER_SKIP_IOP_RESET
+endif
+
 include $(PS2SDKSRC)/Defs.make
 include $(PS2SDKSRC)/ee/Rules.bin.make
 include $(PS2SDKSRC)/ee/Rules.make

ee/elf-loader/src/loader/src/loader.c

@@ -122,6 +122,7 @@ int main(int argc, char *argv[])
 	if (ret == 0 && elfdata.epc != 0) {
 		SET_GS_BGCOLOUR(YELLOW_BG);
 
+#ifndef LOADER_SKIP_IOP_RESET
 		// Let's reset IOP because ELF was already loaded in memory
 		while(!SifIopReset(NULL, 0)){};
 		while (!SifIopSync()) {};
@@ -136,6 +137,7 @@ int main(int argc, char *argv[])
         SifLoadModule("rom0:MCSERV", 0, NULL);
         SifLoadFileExit();
         sceSifExitRpc();
+#endif
 
 		SET_GS_BGCOLOUR(BROWN_BG);