Commit c29c775a authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

x86/entry: Convert double fault exception to IDTENTRY_DF 



Convert #DF to IDTENTRY_DF
  - Implement the C entry point with DEFINE_IDTENTRY_DF
  - Emit the ASM stub with DECLARE_IDTENTRY_DF on 64bit
  - Remove the ASM idtentry in 64bit
  - Adjust the 32bit shim code
  - Fixup the XEN/PV code
  - Remove the old prototypes

No functional change.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarAlexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Acked-by: default avatarAndy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505135315.583415264@linutronix.de
parent 6a8dfa8e

arch/x86/entry/entry_32.S

+2 −2
Original line number Diff line number Diff line
@@ -1488,7 +1488,7 @@ ret_to_user: 
	jmp	restore_all_switch_stack

SYM_CODE_END(handle_exception)



SYM_CODE_START(double_fault)

SYM_CODE_START(asm_exc_double_fault)

1:

	/*

	 * This is a task gate handler, not an interrupt gate handler.
@@ -1526,7 +1526,7 @@ SYM_CODE_START(double_fault) 
1:

	hlt

	jmp 1b

SYM_CODE_END(double_fault)

SYM_CODE_END(asm_exc_double_fault)



/*

 * NMI is doubly nasty.  It can happen on the first instruction of

arch/x86/entry/entry_64.S

+1 −9
Original line number Diff line number Diff line
@@ -680,15 +680,9 @@ SYM_CODE_START(\asmsym) 
	call	paranoid_entry

	UNWIND_HINT_REGS



	/* Read CR2 early */

	GET_CR2_INTO(%r12);



	TRACE_IRQS_OFF



	movq	%rsp, %rdi		/* pt_regs pointer into first argument */

	movq	ORIG_RAX(%rsp), %rsi	/* get error code into 2nd argument*/

	movq	$-1, ORIG_RAX(%rsp)	/* no syscall to restart */

	movq	%r12, %rdx		/* Move CR2 into 3rd argument */

	call	\cfunc



	jmp	paranoid_exit
@@ -918,7 +912,7 @@ SYM_INNER_LABEL(native_irq_return_iret, SYM_L_GLOBAL) 
	/*

	 * This may fault.  Non-paranoid faults on return to userspace are

	 * handled by fixup_bad_iret.  These include #SS, #GP, and #NP.

	 * Double-faults due to espfix64 are handled in do_double_fault.

	 * Double-faults due to espfix64 are handled in exc_double_fault.

	 * Other faults here are fatal.

	 */

	iretq
@@ -1073,8 +1067,6 @@ apicinterrupt IRQ_WORK_VECTOR irq_work_interrupt smp_irq_work_interrupt 


idtentry	X86_TRAP_PF		page_fault		do_page_fault			has_error_code=1



idtentry_df	X86_TRAP_DF		double_fault		do_double_fault



#ifdef CONFIG_XEN_PV

idtentry	512 /* dummy */		hypervisor_callback	xen_do_hypervisor_callback	has_error_code=0

#endif

arch/x86/include/asm/idtentry.h

+3 −0
Original line number Diff line number Diff line
@@ -368,4 +368,7 @@ DECLARE_IDTENTRY_XEN(X86_TRAP_NMI, nmi); 
DECLARE_IDTENTRY_DEBUG(X86_TRAP_DB,	exc_debug);

DECLARE_IDTENTRY_XEN(X86_TRAP_DB,	debug);



/* #DF */

DECLARE_IDTENTRY_DF(X86_TRAP_DF,	exc_double_fault);



#endif

arch/x86/include/asm/traps.h

+0 −5
Original line number Diff line number Diff line
@@ -11,18 +11,13 @@ 


#define dotraplinkage __visible



#ifdef CONFIG_X86_64

asmlinkage void double_fault(void);

#endif

asmlinkage void page_fault(void);

asmlinkage void async_page_fault(void);



#if defined(CONFIG_X86_64) && defined(CONFIG_XEN_PV)

asmlinkage void xen_double_fault(void);

asmlinkage void xen_page_fault(void);

#endif



dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsigned long cr2);

dotraplinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address);



#ifdef CONFIG_X86_64

arch/x86/kernel/doublefault_32.c

+4 −6
Original line number Diff line number Diff line
@@ -10,7 +10,6 @@ 
#include <asm/desc.h>

#include <asm/traps.h>



extern void double_fault(void);

#define ptr_ok(x) ((x) > PAGE_OFFSET && (x) < PAGE_OFFSET + MAXMEM)



#define TSS(x) this_cpu_read(cpu_tss_rw.x86_tss.x)
@@ -21,7 +20,7 @@ static void set_df_gdt_entry(unsigned int cpu); 
 * Called by double_fault with CR0.TS and EFLAGS.NT cleared.  The CPU thinks

 * we're running the doublefault task.  Cannot return.

 */

asmlinkage notrace void __noreturn doublefault_shim(void)

asmlinkage noinstr void __noreturn doublefault_shim(void)

{

	unsigned long cr2;

	struct pt_regs regs;
@@ -40,7 +39,7 @@ asmlinkage notrace void __noreturn doublefault_shim(void) 
	 * Fill in pt_regs.  A downside of doing this in C is that the unwinder

	 * won't see it (no ENCODE_FRAME_POINTER), so a nested stack dump

	 * won't successfully unwind to the source of the double fault.

	 * The main dump from do_double_fault() is fine, though, since it

	 * The main dump from exc_double_fault() is fine, though, since it

	 * uses these regs directly.

	 *

	 * If anyone ever cares, this could be moved to asm.
@@ -70,7 +69,7 @@ asmlinkage notrace void __noreturn doublefault_shim(void) 
	regs.cx		= TSS(cx);

	regs.bx		= TSS(bx);



	do_double_fault(&regs, 0, cr2);

	exc_double_fault(&regs, 0, cr2);



	/*

	 * x86_32 does not save the original CR3 anywhere on a task switch.
@@ -84,7 +83,6 @@ asmlinkage notrace void __noreturn doublefault_shim(void) 
	 */

	panic("cannot return from double fault\n");

}

NOKPROBE_SYMBOL(doublefault_shim);



DEFINE_PER_CPU_PAGE_ALIGNED(struct doublefault_stack, doublefault_stack) = {

	.tss = {
@@ -95,7 +93,7 @@ DEFINE_PER_CPU_PAGE_ALIGNED(struct doublefault_stack, doublefault_stack) = { 
		.ldt		= 0,

	.io_bitmap_base	= IO_BITMAP_OFFSET_INVALID,



		.ip		= (unsigned long) double_fault,

		.ip		= (unsigned long) asm_exc_double_fault,

		.flags		= X86_EFLAGS_FIXED,

		.es		= __USER_DS,

		.cs		= __KERNEL_CS,

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