Commit 11d4c3f9 authored by H. Peter Anvin's avatar H. Peter Anvin Committed by H. Peter Anvin
Browse files

x86-32: Make sure the stack is set up before we use it 



Since checkin ebba638a 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: default avatarMatthieu Castet <castet.matthieu@free.fr>
LKML-Reference: <4D41E86D.8060205@free.fr>
Tested-by: default avatarKees Cook <kees.cook@canonical.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent f7448548

arch/x86/include/asm/smp.h

+1 −4
Original line number Diff line number Diff line
@@ -40,10 +40,7 @@ DECLARE_EARLY_PER_CPU(u16, x86_cpu_to_apicid); 
DECLARE_EARLY_PER_CPU(u16, x86_bios_cpu_apicid);



/* Static state in head.S used to set up a CPU */

extern struct {

	void *sp;

	unsigned short ss;

} stack_start;

extern unsigned long stack_start; /* Initial stack pointer address */



struct smp_ops {

	void (*smp_prepare_boot_cpu)(void);

arch/x86/kernel/acpi/sleep.c

+1 −1
Original line number Diff line number Diff line
@@ -100,7 +100,7 @@ int acpi_save_state_mem(void) 
#else /* CONFIG_64BIT */

	header->trampoline_segment = setup_trampoline() >> 4;

#ifdef CONFIG_SMP

	stack_start.sp = temp_stack + sizeof(temp_stack);

	stack_start = (unsigned long)temp_stack + sizeof(temp_stack);

	early_gdt_descr.address =

			(unsigned long)get_cpu_gdt_table(smp_processor_id());

	initial_gs = per_cpu_offset(smp_processor_id());

arch/x86/kernel/head_32.S

+13 −17
Original line number Diff line number Diff line
@@ -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"

arch/x86/kernel/smpboot.c

+2 −2
Original line number Diff line number Diff line
@@ -638,7 +638,7 @@ wakeup_secondary_cpu_via_init(int phys_apicid, unsigned long start_eip) 
	 * target processor state.

	 */

	startup_ipi_hook(phys_apicid, (unsigned long) start_secondary,

			 (unsigned long)stack_start.sp);

			 stack_start);



	/*

	 * Run STARTUP IPI loop.
@@ -785,7 +785,7 @@ do_rest: 
#endif

	early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);

	initial_code = (unsigned long)start_secondary;

	stack_start.sp = (void *) c_idle.idle->thread.sp;

	stack_start  = c_idle.idle->thread.sp;



	/* start_ip had better be page-aligned! */

	start_ip = setup_trampoline();

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