boot: Move PIC challenge to 1BL low ROM, before 2BL RAM copy

XboxDev · Oct 7, 2022 · 1a258b1 · 1a258b1
1 parent f1ad8cf
commit 1a258b1
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Showing 4 changed files with 40 additions and 14 deletions.
diff --git a/boot_rom/2bBootStartBios.c b/boot_rom/2bBootStartBios.c
@@ -261,12 +261,9 @@ void BootStartBiosLoader(void)
 	SHA1Input(&context,(void*)(PROGRAMM_Memory_2bl+20),bootloadersize-20);
 	SHA1Result(&context,SHA1_result);
 
-        if (memcmp(&bootloaderChecksum[0],&SHA1_result[0],20)==0) {
-		// HEHE, the Image we copy'd into ram is SHA-1 hash identical, this is Optimum
-		BootPerformPicChallengeResponseAction();
-
-	} else {
-		// Bad, the checksum does not match, but we can nothing do now, we wait until PIC kills us
+        if (memcmp(&bootloaderChecksum[0],&SHA1_result[0],20)) {
+		// Bad, the checksum does not match, we did not get a valid image to RAM, we stop and display an error
+		setLED("rrrr");
 		while(1);
 	}
 
@@ -358,9 +355,6 @@ void BootStartBiosLoader(void)
 		// We are not Longer here
 	}
 
-	// Bad, we did not get a valid im age to RAM, we stop and display a error
-	//setLED("rrrr");
-
 	setLED("oooo");
 
 //	I2CTransmitWord(0x10, 0x1901); // no reset on eject

diff --git a/boot_rom/2bBootStartup.S b/boot_rom/2bBootStartup.S
@@ -211,6 +211,11 @@
 
         cld
 
+	// Set the stack pointer to give us a valid stack
+	movl $0x1ffff0, %esp
+
+	call	pic_challenge_response
+
 	// copy everything into RAM
 
 	mov 	$_ram_location, %edi
@@ -309,9 +314,6 @@ reload_cs:
 	mov %eax, %fs
 	mov %eax, %gs
 
-	// Set the stack pointer to give us a valid stack
-	movl $0x1ffff0, %esp
-
 	// Clear out .bss
 	xor %eax, %eax
 	mov $BSS_SIZE_L, %ecx

diff --git a/boot_rom/2bPicResponseAction.c b/boot_rom/2bPicResponseAction.c
@@ -84,7 +84,7 @@ int I2CTransmitWord(u8 bPicAddressI2cFormat, u16 wDataToWrite)
 	}
 	return ERR_I2C_ERROR_BUS;
 }
-
+#if 0
 // ----------------------------  PIC challenge/response -----------------------------------------------------------
 //
 // given four bytes, returns a u16
@@ -143,6 +143,35 @@ int BootPerformPicChallengeResponseAction()
 	// continues as part of video setup....
 	return ERR_SUCCESS;
 }
+#endif
+void pic_challenge_response(void)
+{
+    register u8 x1c, x1d, x1e, x1f;
+    register u8 b1, b2, b3, b4;
+    register int i;
+
+    smbus_set_addr(0x21); /* set PIC address; read command */
+    x1c = smbus_read(0x1c);
+    x1d = smbus_read(0x1d);
+    x1e = smbus_read(0x1e);
+    x1f = smbus_read(0x1f);
+
+    b1  = 0x33;
+    b2  = 0xed;
+    b3  = x1c << 2;
+    b3 ^= x1d + 0x39;
+    b3 ^= x1e >> 2;
+    b3 ^= x1f + 0x63;
+    b4  = x1c + 0x0b;
+    b4 ^= x1d >> 2;
+    b4 ^= x1e + 0x1b;
+
+    for (i = 0; i < 4; b1 += b2 ^ b3, b2 += b1 ^ b4, ++i);
+
+    smbus_set_addr(0x20); /* set PIC address; write command */
+    smbus_write(0x20, b1);
+    smbus_write(0x21, b2);
+}
 
 extern int I2cSetFrontpanelLed(u8 b)
 {

diff --git a/boot_rom/2bload.h b/boot_rom/2bload.h
@@ -168,7 +168,8 @@ static INLINE u8 smbus_read(u8 cmd)
 }
 
 // boot process
-int BootPerformPicChallengeResponseAction(void);
+//int BootPerformPicChallengeResponseAction(void);
+void pic_challenge_response(void) __attribute__((section(".low_rom"),aligned(16)));
 // LED control (see associated enum above)
 int I2cSetFrontpanelLed(u8 b);
 int I2cResetFrontpanelLed(void);