Add 8 MB RAM support and customizable _start stub

4 files changed, 47 insertions, 25 deletions

diff --git a/libpsn00b/ldscripts/exe.ld b/libpsn00b/ldscripts/exe.ld
index 583d76a..a8dfccf 100644
--- a/libpsn00b/ldscripts/exe.ld
+++ b/libpsn00b/ldscripts/exe.ld
@@ -6,6 +6,10 @@
  * using $gp to reference them) is fully supported; the block is made up of
  * sections .sdata and .sbss. Note that GP-relative addressing is not
  * compatible with dynamic linking, as DLLs require GP to be unused.
+ *
+ * This linker script assumes main RAM is 8 MB to allow executables meant for
+ * devkits or arcade systems to be built, however the executable conversion
+ * tool (elf2x) will throw a warning if the size exceeds 2 MB.
  */
 
 /*OUTPUT_FORMAT(elf32-littlemips)*/
@@ -15,7 +19,7 @@ ENTRY(_start)
 MEMORY {
 	/* Mapped into KSEG0 */
 	KERNEL_RAM (rwx) : ORIGIN = 0x80000000, LENGTH = 0x010000
-	APP_RAM    (rwx) : ORIGIN = 0x80010000, LENGTH = 0x1f0000
+	APP_RAM    (rwx) : ORIGIN = 0x80010000, LENGTH = 0x7f0000
 }
 
 SECTIONS {
diff --git a/libpsn00b/libc/_start.s b/libpsn00b/libc/_start.s
new file mode 100644
index 0000000..56075c8
--- /dev/null
+++ b/libpsn00b/libc/_start.s
@@ -0,0 +1,18 @@
+# PSn00bSDK _start() trampoline
+# (C) 2022 spicyjpeg - MPL licensed
+#
+# This file provides a weak function that can be easily overridden to e.g. set
+# $sp or perform additional initialization before the "real" _start()
+# (_start_inner()) is called.
+
+.set noreorder
+.section .text
+
+.global _start
+.type _start, @function
+.weak _start
+_start:
+	la $gp, _gp
+
+	j  _start_inner
+	nop
diff --git a/libpsn00b/libc/start.c b/libpsn00b/libc/start.c
index fd6fe33..bfe9c9b 100644
--- a/libpsn00b/libc/start.c
+++ b/libpsn00b/libc/start.c
@@ -80,8 +80,8 @@ extern int main(int argc, const char* argv[]);
 // Even though _start() usually takes no arguments, this implementation allows
 // parent executables to pass args directly to child executables without having
 // to overwrite the arg strings in kernel RAM.
-void _start(int32_t override_argc, const char **override_argv) {
-	__asm__ volatile("la $gp, _gp;");
+void _start_inner(int32_t override_argc, const char **override_argv) {
+	//__asm__ volatile("la $gp, _gp;");
 
 	// Clear BSS 4 bytes at a time. BSS is always aligned to 4 bytes by the
 	// linker script.
diff --git a/tools/util/elf2x.c b/tools/util/elf2x.c
index 9a7c126..38ed60d 100644
--- a/tools/util/elf2x.c
+++ b/tools/util/elf2x.c
@@ -154,31 +154,31 @@ int main(int argc, char** argv) {
 
 	}
 
-	exe_tsize = (exe_haddr-exe_taddr);
-	exe_tsize += prg_heads[head.prg_entry_count-1].p_filesz;
+	exe_tsize  = (exe_haddr - exe_taddr);
+	exe_tsize += prg_heads[head.prg_entry_count - 1].p_filesz;
 
-	if( !quiet ) {
-
-		printf( "pc:%08x t_addr:%08x t_size:%d\n",
-			head.prg_entry_addr, exe_taddr, exe_tsize );
-
-	}
+	if (!quiet)
+		printf(
+			"pc:%08x t_addr:%08x t_size:%d\n",
+			head.prg_entry_addr,
+			exe_taddr,
+			exe_tsize
+		);
 
 	// Check if load address is appropriate in main RAM locations
-	if( ( ( exe_taddr>>24 ) == 0x0 ) || ( ( exe_taddr>>24 ) == 0x80 ) ||
-		( ( exe_taddr>>24 ) == 0xA0 ) ) {
-
-		if( ( exe_taddr&0x00ffffff ) < 65536 ) {
-
-			printf( "Warning: Program text address overlaps kernel area!\n" );
-
-		}
-
-	}
-
-
-	// Pad out the size to multiples of 2KB
-	exe_tsize = 2048*((exe_tsize+2047)/2048);
+	if (
+		((exe_taddr >= 0x00000000) && (exe_taddr < 0x00001000)) ||
+		((exe_taddr >= 0x80000000) && (exe_taddr < 0x80001000)) ||
+		((exe_taddr >= 0xa0000000) && (exe_taddr < 0xa0001000))
+	)
+		printf("WARNING: program text address overlaps kernel area!\n");
+
+	// Throw warning if executable is larger than 2MB
+	if (exe_tsize > 0x1f0000)
+		printf("WARNING: executable is larger than available RAM on a stock console!\n");
+
+	// Pad out the size to multiples of 2KB (CD sector size)
+	exe_tsize  = ((exe_tsize + 2047) / 2048) * 2048;
 
 	// Load the binary data
 	binary = (unsigned char*)malloc( exe_tsize );