From 11d4c3f9b671720e80353dd7e433ff2bf65e9500 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Fri, 4 Feb 2011 16:14:11 -0800 Subject: 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 LKML-Reference: <4D41E86D.8060205@free.fr> Tested-by: Kees Cook Signed-off-by: H. Peter Anvin --- arch/x86/kernel/head_32.S | 30 +++++++++++++----------------- 1 file changed, 13 insertions(+), 17 deletions(-) (limited to 'arch/x86/kernel/head_32.S') diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index fc293dc8dc35..767d6c43de37 100644 --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -85,6 +85,8 @@ RESERVE_BRK(pagetables, INIT_MAP_SIZE) */ __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 @@ ENTRY(startup_32) 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 @@ ENTRY(startup_32) * _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 @@ ENTRY(startup_32_smp) 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 @@ default_entry: 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 @@ default_entry: #ifdef CONFIG_SMP cmpb $0, ready - jz 1f /* Initial CPU cleans BSS */ - jmp checkCPUtype -1: + jnz checkCPUtype #endif /* CONFIG_SMP */ /* @@ -470,14 +473,7 @@ is386: movl $2,%ecx # set MP 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 @@ ENTRY(initial_page_table) #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" -- cgit v1.2.3