Re: [BUG] broken ebba638ae723d8a8fc2f7abce5ec18b688b791d7
From: H. Peter Anvin
Date: Thu Jan 27 2011 - 21:24:40 EST
On 01/27/2011 03:00 PM, Kees Cook wrote:
Yikes, good catch.
movw $(trampoline_stack_end - r_base), %sp
movl $boot_stack_end, %eax
addl %ebp, %eax
movl %eax, %esp
what would be safe for arch/x86/kernel/head_32.S ? It uses "stack_start",
but later after paging set-up. Is the following sane to solve this?
To run it before paging is set up, you can't use stack, start; you have
to use a pointer based on physical address. You have two problems with
using stack_start: you're using a linear address to access stack_start,
and stack_start itself contains a linear address.
It's not entirely clear to me why we don't initialize %ss to __BOOT_DS
with the other segment registers, but it would make most sense to me:
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index fc293dc..c10f9ba 100644
@@ -99,7 +99,12 @@ ENTRY(startup_32)
+ movl %eax,%ss
+ * Set up an initial stack
+ movl $pa(init_thread_union+THREAD_SIZE), %esp
* Clear BSS first so that there are no surprises...
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