[coreboot] [RFC] v3: Stack switching abstraction for C7 and later Intel processors

[Carl-Daniel Hailfinger]

On 14.10.2008 21:15, Peter Stuge wrote:
> Carl-Daniel Hailfinger wrote:
>   
>>>> I believe the stage0_main name is misleading. After all, stage0
>>>> is pure asm and lives in its own .S file.
>>>>         
>>> let's call it stage1 then and main()
>>>       
>> Works for me.
>>     
>
> I'm afraid I don't like that.
>
> Please suggest something that makes the timeline obvious.
> I think we already have other problems like this in v3.
>
> I would be OK with adding phases to stage1 e.g. but I have also
> contemplated flattening the stage/phase tree to only have stages and
> no phases - though that doesn't have to happen right now.
>   

OK, so can we settle on phases?

old -> new
stage1_main before disable_car-> stage1_phase1
disable_car and stack switch -> stage1_phase2
stage1_main after stack switch -> stage1_phase3

And yes, I'm aware that the patch below doesn't change the corresponding
asm code yet. I'll work on that as soon as we have agreed on stage1_*
naming.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net>

Index: corebootv3-stackrebuild/arch/x86/stage1.c
===================================================================
--- corebootv3-stackrebuild/arch/x86/stage1.c	(Revision 925)
+++ corebootv3-stackrebuild/arch/x86/stage1.c	(Arbeitskopie)
@@ -143,6 +143,9 @@
 	return ret;
 }
 
+void stage1_phase2(void);
+void __attribute__((stdcall)) stage1_phase3(void);
+
 /**
  * This function is called from assembler code with its argument on the
  * stack. Force the compiler to generate always correct code for this case.
@@ -154,29 +157,13 @@
  * that we are restarting after some sort of reconfiguration. Note that we could use it on geode but 
  * do not at present. 
  */
-void __attribute__((stdcall)) stage1_main(u32 bist, u32 init_detected)
+void __attribute__((stdcall)) stage1_phase1(u32 bist, u32 init_detected)
 {
 	struct global_vars globvars;
 	int ret;
 	struct mem_file archive;
-	void *entry;
 	struct node_core_id me;
-#ifdef CONFIG_PAYLOAD_ELF_LOADER
-	struct mem_file result;
-	int elfboot_mem(struct lb_memory *mem, void *where, int size);
 
-	/* Why can't we statically init this hack? */
-	unsigned char faker[64];
-	struct lb_memory *mem = (struct lb_memory*) faker;
-
-	mem->tag = LB_TAG_MEMORY;
-	mem->size = 28;
-	mem->map[0].start.lo = mem->map[0].start.hi = 0;
-	mem->map[0].size.lo = (32*1024*1024);
-	mem->map[0].size.hi = 0;
-	mem->map[0].type = LB_MEM_RAM;
-#endif /* CONFIG_PAYLOAD_ELF_LOADER */
-
 	post_code(POST_STAGE1_MAIN);
 
 	/* before we do anything, we want to stop if we do not run
@@ -234,6 +221,29 @@
 
 	printk(BIOS_DEBUG, "Done RAM init code\n");
 
+	/* Switch the stack location from CAR to RAM, rebuild the stack,
+	 * disable CAR and continue at stage1_phase3(). This is all wrapped in
+	 * stage1_phase2() to make the code easier to follow.
+	 * We will NEVER return.
+	 */
+	stage1_phase2();
+
+	/* If we reach this point, something went terribly wrong. */
+	die("The world is broken.\n");
+}
+
+/**
+ * This function is called to take care of switching and rebuilding the stack
+ * so that we can cope with processors which don't support a CAR area at low
+ * addresses where CAR could be copied to RAM without problems.
+ * After the stack has been rebuilt, we switch the stack pointer to the new
+ * location, move the printk buffer and cotinue at stage1_phase3().
+ *
+ * NOTE: switch_stack may need to be reimplemented in processor-specific asm.
+ * TODO: Reevaluate whether printk_buffer_move should come before disable_car()
+ */
+void stage1_phase2()
+{
 	/* Turn off Cache-As-Ram */
 	disable_car();
 
@@ -241,7 +251,37 @@
 	/* Move the printk buffer to PRINTK_BUF_ADDR_RAM */
 	printk_buffer_move((void *)PRINTK_BUF_ADDR_RAM, PRINTK_BUF_SIZE_RAM);
 #endif
+	stage1_phase3();
+}
 
+/**
+ * This function is the second part of the former stage1_main() after
+ * switching the stack and disabling CAR.
+ */
+void __attribute__((stdcall)) stage1_phase3()
+{
+	void *entry;
+	int ret;
+	struct mem_file archive;
+#ifdef CONFIG_PAYLOAD_ELF_LOADER
+	struct mem_file result;
+	int elfboot_mem(struct lb_memory *mem, void *where, int size);
+
+	/* Why can't we statically init this hack? */
+	unsigned char faker[64];
+	struct lb_memory *mem = (struct lb_memory*) faker;
+
+	mem->tag = LB_TAG_MEMORY;
+	mem->size = 28;
+	mem->map[0].start.lo = mem->map[0].start.hi = 0;
+	mem->map[0].size.lo = (32*1024*1024);
+	mem->map[0].size.hi = 0;
+	mem->map[0].type = LB_MEM_RAM;
+#endif /* CONFIG_PAYLOAD_ELF_LOADER */
+
+	// location and size of image.
+	init_archive(&archive);
+
 	entry = load_file_segments(&archive, "normal/stage2");
 	if (entry == (void *)-1)
 		die("FATAL: Failed loading stage2.");


-- 
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