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Commit 4c5023a3 authored by H. Peter Anvin's avatar H. Peter Anvin Committed by H. Peter Anvin
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x86-32: Handle exception table entries during early boot 



If we get an exception during early boot, walk the exception table to
see if we should intercept it.  The main use case for this is to allow
rdmsr_safe()/wrmsr_safe() during CPU initialization.

Since the exception table is currently sorted at runtime, and fairly
late in startup, this code walks the exception table linearly.  We
obviously don't need to worry about modules, however: none have been
loaded at this point.

This patch changes the early IDT setup to look a lot more like x86-64:
we now install handlers for all 32 exception vectors.  The output of
the early exception handler has changed somewhat as it directly
reflects the stack frame of the exception handler, and the stack frame
has been somewhat restructured.

Finally, centralize the code that can and should be run only once.

[ v2: Use early_fixup_exception() instead of linear search ]

Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1334794610-5546-6-git-send-email-hpa@zytor.com
parent 9900aa2f

arch/x86/kernel/head_32.S

+129 −94
Original line number Original line Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <asm/msr-index.h>

#include <asm/msr-index.h>

#include <asm/cpufeature.h>

#include <asm/cpufeature.h>

#include <asm/percpu.h>

#include <asm/percpu.h>

#include <asm/nops.h>





/* Physical address */

/* Physical address */

#define pa(X) ((X) - __PAGE_OFFSET)

#define pa(X) ((X) - __PAGE_OFFSET)
@@ -363,20 +364,15 @@ default_entry: 
	pushl $0

	pushl $0

	popfl

	popfl





#ifdef CONFIG_SMP

	cmpb $0, ready

	jnz checkCPUtype

#endif /* CONFIG_SMP */



/*

/*

 * start system 32-bit setup. We need to re-do some of the things done

 * start system 32-bit setup. We need to re-do some of the things done

 * in 16-bit mode for the "real" operations.

 * in 16-bit mode for the "real" operations.

 */

 */

	call setup_idt

	movl setup_once_ref,%eax



	andl %eax,%eax

checkCPUtype:

	jz 1f				# Did we do this already?



	call *%eax

	movl $-1,X86_CPUID		#  -1 for no CPUID initially

1:

	

	

/* check if it is 486 or 386. */

/* check if it is 486 or 386. */

/*

/*
@@ -384,7 +380,7 @@ checkCPUtype: 
 * apply at our cpl of 0 and the stack ought to be aligned already, and

 * apply at our cpl of 0 and the stack ought to be aligned already, and

 * we don't need to preserve eflags.

 * we don't need to preserve eflags.

 */

 */



	movl $-1,X86_CPUID	# -1 for no CPUID initially

	movb $3,X86		# at least 386

	movb $3,X86		# at least 386

	pushfl			# push EFLAGS

	pushfl			# push EFLAGS

	popl %eax		# get EFLAGS

	popl %eax		# get EFLAGS
@@ -450,21 +446,6 @@ is386: movl $2,%ecx # set MP 
	movl $(__KERNEL_PERCPU), %eax

	movl $(__KERNEL_PERCPU), %eax

	movl %eax,%fs			# set this cpu's percpu

	movl %eax,%fs			# set this cpu's percpu





#ifdef CONFIG_CC_STACKPROTECTOR

	/*

	 * The linker can't handle this by relocation.  Manually set

	 * base address in stack canary segment descriptor.

	 */

	cmpb $0,ready

	jne 1f

	movl $gdt_page,%eax

	movl $stack_canary,%ecx

	movw %cx, 8 * GDT_ENTRY_STACK_CANARY + 2(%eax)

	shrl $16, %ecx

	movb %cl, 8 * GDT_ENTRY_STACK_CANARY + 4(%eax)

	movb %ch, 8 * GDT_ENTRY_STACK_CANARY + 7(%eax)

1:

#endif

	movl $(__KERNEL_STACK_CANARY),%eax

	movl $(__KERNEL_STACK_CANARY),%eax

	movl %eax,%gs

	movl %eax,%gs
@@ -473,7 +454,6 @@ is386: movl $2,%ecx # set MP 




	cld			# gcc2 wants the direction flag cleared at all times

	cld			# gcc2 wants the direction flag cleared at all times

	pushl $0		# fake return address for unwinder

	pushl $0		# fake return address for unwinder

	movb $1, ready

	jmp *(initial_code)

	jmp *(initial_code)





/*

/*
@@ -495,81 +475,122 @@ check_x87: 
	.byte 0xDB,0xE4		/* fsetpm for 287, ignored by 387 */

	.byte 0xDB,0xE4		/* fsetpm for 287, ignored by 387 */

	ret

	ret





	

#include "verify_cpu.S"



/*

/*

 *  setup_idt

 *  setup_once

 *

 *

 *  sets up a idt with 256 entries pointing to

 *  The setup work we only want to run on the BSP.

 *  ignore_int, interrupt gates. It doesn't actually load

 *  idt - that can be done only after paging has been enabled

 *  and the kernel moved to PAGE_OFFSET. Interrupts

 *  are enabled elsewhere, when we can be relatively

 *  sure everything is ok.

 *

 *

 *  Warning: %esi is live across this function.

 *  Warning: %esi is live across this function.

 */

 */

setup_idt:

__INIT

	lea ignore_int,%edx

setup_once:

	movl $(__KERNEL_CS << 16),%eax

	/*

	movw %dx,%ax		/* selector = 0x0010 = cs */

	 * Set up a idt with 256 entries pointing to ignore_int,

	movw $0x8E00,%dx	/* interrupt gate - dpl=0, present */

	 * interrupt gates. It doesn't actually load idt - that needs

	 * to be done on each CPU. Interrupts are enabled elsewhere,

	 * when we can be relatively sure everything is ok.

	 */





	lea idt_table,%edi

	movl $idt_table,%edi

	mov $256,%ecx

	movl $early_idt_handlers,%eax

rp_sidt:

	movl $NUM_EXCEPTION_VECTORS,%ecx

1:

	movl %eax,(%edi)

	movl %eax,(%edi)

	movl %edx,4(%edi)

	movl %eax,4(%edi)

	/* interrupt gate, dpl=0, present */

	movl $(0x8E000000 + __KERNEL_CS),2(%edi)

	addl $9,%eax

	addl $8,%edi

	addl $8,%edi

	dec %ecx

	loop 1b

	jne rp_sidt





.macro	set_early_handler handler,trapno

	movl $256 - NUM_EXCEPTION_VECTORS,%ecx

	lea \handler,%edx

	movl $ignore_int,%edx

	movl $(__KERNEL_CS << 16),%eax

	movl $(__KERNEL_CS << 16),%eax

	movw %dx,%ax

	movw %dx,%ax		/* selector = 0x0010 = cs */

	movw $0x8E00,%dx	/* interrupt gate - dpl=0, present */

	movw $0x8E00,%dx	/* interrupt gate - dpl=0, present */

	lea idt_table,%edi

2:

	movl %eax,8*\trapno(%edi)

	movl %eax,(%edi)

	movl %edx,8*\trapno+4(%edi)

	movl %edx,4(%edi)

.endm

	addl $8,%edi

	loop 2b





	set_early_handler handler=early_divide_err,trapno=0

#ifdef CONFIG_CC_STACKPROTECTOR

	set_early_handler handler=early_illegal_opcode,trapno=6

	/*

	set_early_handler handler=early_protection_fault,trapno=13

	 * Configure the stack canary. The linker can't handle this by

	set_early_handler handler=early_page_fault,trapno=14

	 * relocation.  Manually set base address in stack canary

	 * segment descriptor.

	 */

	movl $gdt_page,%eax

	movl $stack_canary,%ecx

	movw %cx, 8 * GDT_ENTRY_STACK_CANARY + 2(%eax)

	shrl $16, %ecx

	movb %cl, 8 * GDT_ENTRY_STACK_CANARY + 4(%eax)

	movb %ch, 8 * GDT_ENTRY_STACK_CANARY + 7(%eax)

#endif





	andl $0,setup_once_ref	/* Once is enough, thanks */

	ret

	ret





early_divide_err:

ENTRY(early_idt_handlers)

	xor %edx,%edx

	# 36(%esp) %eflags

	pushl $0	/* fake errcode */

	# 32(%esp) %cs

	jmp early_fault

	# 28(%esp) %eip

	# 24(%rsp) error code

	i = 0

	.rept NUM_EXCEPTION_VECTORS

	.if (EXCEPTION_ERRCODE_MASK >> i) & 1

	ASM_NOP2

	.else

	pushl $0		# Dummy error code, to make stack frame uniform

	.endif

	pushl $i		# 20(%esp) Vector number

	jmp early_idt_handler

	i = i + 1

	.endr

ENDPROC(early_idt_handlers)

	

	/* This is global to keep gas from relaxing the jumps */

ENTRY(early_idt_handler)

	cld

	cmpl $2,%ss:early_recursion_flag

	je hlt_loop

	incl %ss:early_recursion_flag





early_illegal_opcode:

	push %eax		# 16(%esp)

	movl $6,%edx

	push %ecx		# 12(%esp)

	pushl $0	/* fake errcode */

	push %edx		#  8(%esp)

	jmp early_fault

	push %ds		#  4(%esp)

	push %es		#  0(%esp)

	movl $(__KERNEL_DS),%eax

	movl %eax,%ds

	movl %eax,%es





early_protection_fault:

	cmpl $(__KERNEL_CS),32(%esp)

	movl $13,%edx

	jne 10f

	jmp early_fault





early_page_fault:

	leal 28(%esp),%eax	# Pointer to %eip

	movl $14,%edx

	call early_fixup_exception

	jmp early_fault

	andl %eax,%eax

	jnz ex_entry		/* found an exception entry */





early_fault:

10:

	cld

#ifdef CONFIG_PRINTK

#ifdef CONFIG_PRINTK

	pusha

	xorl %eax,%eax

	movl $(__KERNEL_DS),%eax

	movw %ax,2(%esp)	/* clean up the segment values on some cpus */

	movl %eax,%ds

	movw %ax,6(%esp)

	movl %eax,%es

	movw %ax,34(%esp)

	cmpl $2,early_recursion_flag

	leal  40(%esp),%eax

	je hlt_loop

	pushl %eax		/* %esp before the exception */

	incl early_recursion_flag

	pushl %ebx

	pushl %ebp

	pushl %esi

	pushl %edi

	movl %cr2,%eax

	movl %cr2,%eax

	pushl %eax

	pushl %eax

	pushl %edx		/* trapno */

	pushl (20+6*4)(%esp)	/* trapno */

	pushl $fault_msg

	pushl $fault_msg

	call printk

	call printk

#endif

#endif
@@ -578,6 +599,17 @@ hlt_loop: 
	hlt

	hlt

	jmp hlt_loop

	jmp hlt_loop





ex_entry:

	pop %es

	pop %ds

	pop %edx

	pop %ecx

	pop %eax

	addl $8,%esp		/* drop vector number and error code */

	decl %ss:early_recursion_flag

	iret

ENDPROC(early_idt_handler)



/* This is the default interrupt "handler" :-) */

/* This is the default interrupt "handler" :-) */

	ALIGN

	ALIGN

ignore_int:

ignore_int:
@@ -611,13 +643,18 @@ ignore_int: 
	popl %eax

	popl %eax

#endif

#endif

	iret

	iret



ENDPROC(ignore_int)

#include "verify_cpu.S"

__INITDATA

	.align 4

early_recursion_flag:

	.long 0





__REFDATA

__REFDATA

	.align 4

	.align 4

ENTRY(initial_code)

ENTRY(initial_code)

	.long i386_start_kernel

	.long i386_start_kernel

ENTRY(setup_once_ref)

	.long setup_once





/*

/*

 * BSS section

 * BSS section
@@ -670,22 +707,19 @@ ENTRY(initial_page_table) 
ENTRY(stack_start)

ENTRY(stack_start)

	.long init_thread_union+THREAD_SIZE

	.long init_thread_union+THREAD_SIZE





early_recursion_flag:

__INITRODATA

	.long 0



ready:	.byte 0



int_msg:

int_msg:

	.asciz "Unknown interrupt or fault at: %p %p %p\n"

	.asciz "Unknown interrupt or fault at: %p %p %p\n"





fault_msg:

fault_msg:

/* fault info: */

/* fault info: */

	.ascii "BUG: Int %d: CR2 %p\n"

	.ascii "BUG: Int %d: CR2 %p\n"

/* pusha regs: */

/* regs pushed in early_idt_handler: */

	.ascii "     EDI %p  ESI %p  EBP %p  ESP %p\n"

	.ascii "     EDI %p  ESI %p  EBP %p  EBX %p\n"

	.ascii "     EBX %p  EDX %p  ECX %p  EAX %p\n"

	.ascii "     ESP %p   ES %p   DS %p\n"

	.ascii "     EDX %p  ECX %p  EAX %p\n"

/* fault frame: */

/* fault frame: */

	.ascii "     err %p  EIP %p   CS %p  flg %p\n"

	.ascii "     vec %p  err %p  EIP %p   CS %p  flg %p\n"

	.ascii "Stack: %p %p %p %p %p %p %p %p\n"

	.ascii "Stack: %p %p %p %p %p %p %p %p\n"

	.ascii "       %p %p %p %p %p %p %p %p\n"

	.ascii "       %p %p %p %p %p %p %p %p\n"

	.asciz "       %p %p %p %p %p %p %p %p\n"

	.asciz "       %p %p %p %p %p %p %p %p\n"
@@ -699,6 +733,7 @@ fault_msg: 
 * segment size, and 32-bit linear address value:

 * segment size, and 32-bit linear address value:

 */

 */





	.data

.globl boot_gdt_descr

.globl boot_gdt_descr

.globl idt_descr

.globl idt_descr