It is about the bug in the gnu linker. It seems to be ridiculous.
It can be tested by a small program.

In the ld script, if the expression is located in a section, like
   .stack . : {
        EXPRESSION;
   }
the symbol and constant can not be in the expression at the same time,
like:
      . = CONFIG_STACK_SIZE * 2;
or:
      CONFIG_RAMBASE<0x100000 ? xxxxx : yyyyy;

This bug leads to the fact that we can not allocate enough space of
stack for each core. Then the data in the memory will be covered by AP
stack which doesnt know anything.

That is the fact I can find. It is a bug in the linker. But we can not
fix each linker on coreboot developer, not to mention the fact I have
no idea how to submit the bug. The bug will be fixed in the
future. But when the fixed linker will come into our machine? So I
believe we need the workaround patch to avoid this problem.

Signed-off-by: Zheng Bao <zheng.bao@amd.com>


Index: src/arch/i386/coreboot_ram.ld
===================================================================
--- src/arch/i386/coreboot_ram.ld	(revision 5165)
+++ src/arch/i386/coreboot_ram.ld	(working copy)
@@ -101,11 +101,11 @@
 	_end = .;
 	. = ALIGN(CONFIG_STACK_SIZE);
 	_stack = .;
-	.stack . : {
-		/* Reserve a stack for each possible cpu */
-		/* the stack for ap will be put after pgtbl in 1M to CONFIG_RAMTOP range when VGA and ROM_RUN and CONFIG_RAMTOP>1M*/
-		. = ((CONFIG_CONSOLE_VGA || CONFIG_PCI_ROM_RUN)&&(CONFIG_RAMBASE<0x100000)&&(CONFIG_RAMTOP>0x100000) ) ? CONFIG_STACK_SIZE : (CONFIG_MAX_CPUS*CONFIG_STACK_SIZE);
-	}
+	/* Reserve a stack for each possible cpu */
+	/* the stack for ap will be put after pgtbl in 1M to CONFIG_RAMTOP range when VGA and ROM_RUN and CONFIG_RAMTOP>1M*/
+	/* TODO: workaround for the bug of GNU linker. When the bug is fixed
+	 * on almost every machine, Please change it back */
+	. += ((CONFIG_CONSOLE_VGA || CONFIG_PCI_ROM_RUN)&&(CONFIG_RAMBASE<0x100000)&&(CONFIG_RAMTOP>0x100000) ) ? CONFIG_STACK_SIZE : (CONFIG_MAX_CPUS*CONFIG_STACK_SIZE);
 	_estack = .;
         _heap = .;
         .heap . : {