[coreboot] [RFC] v3: Stack switching abstraction for C7 and later Intel processors
c-d.hailfinger.devel.2006 at gmx.net
Wed Oct 15 13:46:49 CEST 2008
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_*
Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net>
--- corebootv3-stackrebuild/arch/x86/stage1.c (Revision 925)
+++ corebootv3-stackrebuild/arch/x86/stage1.c (Arbeitskopie)
@@ -143,6 +143,9 @@
+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;
struct mem_file archive;
- void *entry;
struct node_core_id me;
- 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;
- struct lb_memory *mem = (struct lb_memory*) faker;
- mem->tag = LB_TAG_MEMORY;
- mem->size = 28;
- mem->map.start.lo = mem->map.start.hi = 0;
- mem->map.size.lo = (32*1024*1024);
- mem->map.size.hi = 0;
- mem->map.type = LB_MEM_RAM;
-#endif /* CONFIG_PAYLOAD_ELF_LOADER */
/* 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.
+ /* 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()
/* Turn off Cache-As-Ram */
@@ -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);
+ * 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;
+ 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;
+ struct lb_memory *mem = (struct lb_memory*) faker;
+ mem->tag = LB_TAG_MEMORY;
+ mem->size = 28;
+ mem->map.start.lo = mem->map.start.hi = 0;
+ mem->map.size.lo = (32*1024*1024);
+ mem->map.size.hi = 0;
+ mem->map.type = LB_MEM_RAM;
+#endif /* CONFIG_PAYLOAD_ELF_LOADER */
+ // location and size of image.
entry = load_file_segments(&archive, "normal/stage2");
if (entry == (void *)-1)
die("FATAL: Failed loading stage2.");
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