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Commit b556b35e authored by Jan Beulich's avatar Jan Beulich Committed by Linus Torvalds
Browse files

[PATCH] x86_64: Move int 3 handler to debug stack and allow to increase it. 



This
- switches the INT3 handler to run on an IST stack (to cope with
  breakpoints set by a kernel debugger on places where the kernel's
  %gs base hasn't been set up, yet); the IST stack used is shared with
  the INT1 handler's
[AK: this also allows setting a kprobe on the interrupt/exception entry
points]
- allows nesting of INT1/INT3 handlers so that one can, with a kernel
  debugger, debug (at least) the user-mode portions of the INT1/INT3
  handling; the nesting isn't actively enabled here since a kernel-
  debugger-free kernel doesn't need it

Signed-Off-By: default avatarJan Beulich <jbeulich@novell.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent ed8388a5

arch/x86_64/kernel/asm-offsets.c

+4 −0
Original line number Diff line number Diff line
@@ -64,5 +64,9 @@ int main(void) 
	DEFINE(pbe_address, offsetof(struct pbe, address));

	DEFINE(pbe_orig_address, offsetof(struct pbe, orig_address));

	DEFINE(pbe_next, offsetof(struct pbe, next));

	BLANK();

#if DEBUG_STKSZ > EXCEPTION_STKSZ

	DEFINE(DEBUG_IST, DEBUG_STACK);

#endif

	return 0;

}

arch/x86_64/kernel/entry.S

+22 −4
Original line number Diff line number Diff line
@@ -673,7 +673,10 @@ ENTRY(spurious_interrupt) 


	/* error code is on the stack already */

	/* handle NMI like exceptions that can happen everywhere */

	.macro paranoidentry sym

#ifndef DEBUG_IST

# define DEBUG_IST 0

#endif

	.macro paranoidentry sym, ist=0

	SAVE_ALL

	cld

	movl $1,%ebx
@@ -683,10 +686,20 @@ ENTRY(spurious_interrupt) 
	js    1f

	swapgs

	xorl  %ebx,%ebx

1:	movq %rsp,%rdi

1:

	.if \ist

	movq	%gs:pda_data_offset, %rbp

	.endif

	movq %rsp,%rdi

	movq ORIG_RAX(%rsp),%rsi

	movq $-1,ORIG_RAX(%rsp)

	.if \ist

	subq	$EXCEPTION_STACK_SIZE, per_cpu__init_tss + TSS_ist + (\ist - 1) * 8(%rbp)

	.endif

	call \sym

	.if \ist

	addq	$EXCEPTION_STACK_SIZE, per_cpu__init_tss + TSS_ist + (\ist - 1) * 8(%rbp)

	.endif

	cli

	.endm
@@ -904,7 +917,7 @@ KPROBE_ENTRY(debug) 
 	INTR_FRAME

	pushq $0

	CFI_ADJUST_CFA_OFFSET 8		

	paranoidentry do_debug

	paranoidentry do_debug, DEBUG_IST

	jmp paranoid_exit

	CFI_ENDPROC

	.previous .text
@@ -959,7 +972,12 @@ paranoid_schedule: 
	CFI_ENDPROC



KPROBE_ENTRY(int3)

	zeroentry do_int3	

 	INTR_FRAME

 	pushq $0

 	CFI_ADJUST_CFA_OFFSET 8

 	paranoidentry do_int3, DEBUG_IST

 	jmp paranoid_exit

 	CFI_ENDPROC

	.previous .text



ENTRY(overflow)

arch/x86_64/kernel/setup64.c

+18 −4
Original line number Diff line number Diff line
@@ -145,7 +145,7 @@ void pda_init(int cpu) 
	pda->irqstackptr += IRQSTACKSIZE-64;

} 



char boot_exception_stacks[N_EXCEPTION_STACKS * EXCEPTION_STKSZ] 

char boot_exception_stacks[(N_EXCEPTION_STACKS - 2) * EXCEPTION_STKSZ + DEBUG_STKSZ]

__attribute__((section(".bss.page_aligned")));



/* May not be marked __init: used by software suspend */
@@ -236,13 +236,27 @@ void __cpuinit cpu_init (void) 
	 */

	for (v = 0; v < N_EXCEPTION_STACKS; v++) {

		if (cpu) {

			estacks = (char *)__get_free_pages(GFP_ATOMIC, 

						   EXCEPTION_STACK_ORDER);

			static const unsigned int order[N_EXCEPTION_STACKS] = {

				[0 ... N_EXCEPTION_STACKS - 1] = EXCEPTION_STACK_ORDER,

				[DEBUG_STACK - 1] = DEBUG_STACK_ORDER

			};



			estacks = (char *)__get_free_pages(GFP_ATOMIC, order[v]);

			if (!estacks)

				panic("Cannot allocate exception stack %ld %d\n",

				      v, cpu); 

		}

		switch (v + 1) {

#if DEBUG_STKSZ > EXCEPTION_STKSZ

		case DEBUG_STACK:

			cpu_pda[cpu].debugstack = (unsigned long)estacks;

			estacks += DEBUG_STKSZ;

			break;

#endif

		default:

			estacks += EXCEPTION_STKSZ;

			break;

		}

		t->ist[v] = (unsigned long)estacks;

	}

arch/x86_64/kernel/traps.c

+32 −3
Original line number Diff line number Diff line
@@ -121,19 +121,31 @@ int printk_address(unsigned long address) 
static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,

					unsigned *usedp, const char **idp)

{

	static const char ids[N_EXCEPTION_STACKS][8] = {

	static char ids[][8] = {

		[DEBUG_STACK - 1] = "#DB",

		[NMI_STACK - 1] = "NMI",

		[DOUBLEFAULT_STACK - 1] = "#DF",

		[STACKFAULT_STACK - 1] = "#SS",

		[MCE_STACK - 1] = "#MC",

#if DEBUG_STKSZ > EXCEPTION_STKSZ

		[N_EXCEPTION_STACKS ... N_EXCEPTION_STACKS + DEBUG_STKSZ / EXCEPTION_STKSZ - 2] = "#DB[?]"

#endif

	};

	unsigned k;



	for (k = 0; k < N_EXCEPTION_STACKS; k++) {

		unsigned long end;



		switch (k + 1) {

#if DEBUG_STKSZ > EXCEPTION_STKSZ

		case DEBUG_STACK:

			end = cpu_pda[cpu].debugstack + DEBUG_STKSZ;

			break;

#endif

		default:

			end = per_cpu(init_tss, cpu).ist[k];

			break;

		}

		if (stack >= end)

			continue;

		if (stack >= end - EXCEPTION_STKSZ) {
@@ -143,6 +155,22 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack, 
			*idp = ids[k];

			return (unsigned long *)end;

		}

#if DEBUG_STKSZ > EXCEPTION_STKSZ

		if (k == DEBUG_STACK - 1 && stack >= end - DEBUG_STKSZ) {

			unsigned j = N_EXCEPTION_STACKS - 1;



			do {

				++j;

				end -= EXCEPTION_STKSZ;

				ids[j][4] = '1' + (j - N_EXCEPTION_STACKS);

			} while (stack < end - EXCEPTION_STKSZ);

			if (*usedp & (1U << j))

				break;

			*usedp |= 1U << j;

			*idp = ids[j];

			return (unsigned long *)end;

		}

#endif

	}

	return NULL;

}
@@ -613,6 +641,7 @@ asmlinkage void default_do_nmi(struct pt_regs *regs) 
		io_check_error(reason, regs);

}



/* runs on IST stack. */

asmlinkage void __kprobes do_int3(struct pt_regs * regs, long error_code)

{

	if (notify_die(DIE_INT3, "int3", regs, error_code, 3, SIGTRAP) == NOTIFY_STOP) {
@@ -894,7 +923,7 @@ void __init trap_init(void) 
	set_intr_gate(0,&divide_error);

	set_intr_gate_ist(1,&debug,DEBUG_STACK);

	set_intr_gate_ist(2,&nmi,NMI_STACK);

	set_system_gate(3,&int3);

 	set_system_gate_ist(3,&int3,DEBUG_STACK); /* int3 can be called from all */

	set_system_gate(4,&overflow);	/* int4 can be called from all */

	set_intr_gate(5,&bounds);

	set_intr_gate(6,&invalid_op);

include/asm-x86_64/desc.h

+5 −0
Original line number Diff line number Diff line
@@ -114,6 +114,11 @@ static inline void set_system_gate(int nr, void *func) 
	_set_gate(&idt_table[nr], GATE_INTERRUPT, (unsigned long) func, 3, 0); 

} 



static inline void set_system_gate_ist(int nr, void *func, unsigned ist)

{

	_set_gate(&idt_table[nr], GATE_INTERRUPT, (unsigned long) func, 3, ist);

}



static inline void set_tssldt_descriptor(void *ptr, unsigned long tss, unsigned type, 

					 unsigned size) 

{