x86-32: Make sure the stack is set up before we use it
Since checkin ebba638ae723d8a8fc2f7abce5ec18b688b791d7 we call
verify_cpu even in 32-bit mode. Unfortunately, calling a function
means using the stack, and the stack pointer was not initialized in
the 32-bit setup code! This code initializes the stack pointer, and
simplifies the interface slightly since it is easier to rely on just a
pointer value rather than a descriptor; we need to have different
values for the segment register anyway.
This retains start_stack as a virtual address, even though a physical
address would be more convenient for 32 bits; the 64-bit code wants
the other way around...
Reported-by: Matthieu Castet <castet.matthieu@free.fr>
LKML-Reference: <4D41E86D.8060205@free.fr>
Tested-by: Kees Cook <kees.cook@canonical.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index fc293dc..767d6c4 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -85,6 +85,8 @@
*/
__HEAD
ENTRY(startup_32)
+ movl pa(stack_start),%ecx
+
/* test KEEP_SEGMENTS flag to see if the bootloader is asking
us to not reload segments */
testb $(1<<6), BP_loadflags(%esi)
@@ -99,7 +101,9 @@
movl %eax,%es
movl %eax,%fs
movl %eax,%gs
+ movl %eax,%ss
2:
+ leal -__PAGE_OFFSET(%ecx),%esp
/*
* Clear BSS first so that there are no surprises...
@@ -145,8 +149,6 @@
* _brk_end is set up to point to the first "safe" location.
* Mappings are created both at virtual address 0 (identity mapping)
* and PAGE_OFFSET for up to _end.
- *
- * Note that the stack is not yet set up!
*/
#ifdef CONFIG_X86_PAE
@@ -282,6 +284,9 @@
movl %eax,%es
movl %eax,%fs
movl %eax,%gs
+ movl pa(stack_start),%ecx
+ movl %eax,%ss
+ leal -__PAGE_OFFSET(%ecx),%esp
#endif /* CONFIG_SMP */
default_entry:
@@ -347,8 +352,8 @@
movl %eax,%cr0 /* ..and set paging (PG) bit */
ljmp $__BOOT_CS,$1f /* Clear prefetch and normalize %eip */
1:
- /* Set up the stack pointer */
- lss stack_start,%esp
+ /* Shift the stack pointer to a virtual address */
+ addl $__PAGE_OFFSET, %esp
/*
* Initialize eflags. Some BIOS's leave bits like NT set. This would
@@ -360,9 +365,7 @@
#ifdef CONFIG_SMP
cmpb $0, ready
- jz 1f /* Initial CPU cleans BSS */
- jmp checkCPUtype
-1:
+ jnz checkCPUtype
#endif /* CONFIG_SMP */
/*
@@ -470,14 +473,7 @@
cld # gcc2 wants the direction flag cleared at all times
pushl $0 # fake return address for unwinder
-#ifdef CONFIG_SMP
- movb ready, %cl
movb $1, ready
- cmpb $0,%cl # the first CPU calls start_kernel
- je 1f
- movl (stack_start), %esp
-1:
-#endif /* CONFIG_SMP */
jmp *(initial_code)
/*
@@ -670,15 +666,15 @@
#endif
.data
+.balign 4
ENTRY(stack_start)
.long init_thread_union+THREAD_SIZE
- .long __BOOT_DS
-
-ready: .byte 0
early_recursion_flag:
.long 0
+ready: .byte 0
+
int_msg:
.asciz "Unknown interrupt or fault at: %p %p %p\n"