Commit 6cac5a92 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge
Browse files

xen/x86-64: fix breakpoints and hardware watchpoints 



Native x86-64 uses the IST mechanism to run int3 and debug traps on
an alternative stack.  Xen does not do this, and so the frames were
being misinterpreted by the ptrace code.  This change special-cases
these two exceptions by using Xen variants which run on the normal
kernel stack properly.

Impact: avoid crash or bad data when IST trap is invoked under Xen
Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
parent 6b2e8523

arch/x86/include/asm/traps.h

+3 −0
Original line number Diff line number Diff line
@@ -13,6 +13,9 @@ asmlinkage void divide_error(void); 
asmlinkage void debug(void);

asmlinkage void nmi(void);

asmlinkage void int3(void);

asmlinkage void xen_debug(void);

asmlinkage void xen_int3(void);

asmlinkage void xen_stack_segment(void);

asmlinkage void overflow(void);

asmlinkage void bounds(void);

asmlinkage void invalid_op(void);

arch/x86/kernel/entry_64.S

+5 −0
Original line number Diff line number Diff line
@@ -1379,6 +1379,11 @@ END(xen_failsafe_callback) 
paranoidzeroentry_ist debug do_debug DEBUG_STACK

paranoidzeroentry_ist int3 do_int3 DEBUG_STACK

paranoiderrorentry stack_segment do_stack_segment

#ifdef CONFIG_XEN

zeroentry xen_debug do_debug

zeroentry xen_int3 do_int3

errorentry xen_stack_segment do_stack_segment

#endif

errorentry general_protection do_general_protection

errorentry page_fault do_page_fault

#ifdef CONFIG_X86_MCE

arch/x86/xen/enlighten.c

+18 −1
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <linux/delay.h>

#include <linux/start_kernel.h>

#include <linux/sched.h>

#include <linux/kprobes.h>

#include <linux/bootmem.h>

#include <linux/module.h>

#include <linux/mm.h>
@@ -44,6 +45,7 @@ 
#include <asm/processor.h>

#include <asm/proto.h>

#include <asm/msr-index.h>

#include <asm/traps.h>

#include <asm/setup.h>

#include <asm/desc.h>

#include <asm/pgtable.h>
@@ -428,11 +430,26 @@ static void xen_write_ldt_entry(struct desc_struct *dt, int entrynum, 
static int cvt_gate_to_trap(int vector, const gate_desc *val,

			    struct trap_info *info)

{

	unsigned long addr;



	if (val->type != GATE_TRAP && val->type != GATE_INTERRUPT)

		return 0;



	info->vector = vector;

	info->address = gate_offset(*val);



	addr = gate_offset(*val);

#ifdef CONFIG_X86_64

	if (addr == (unsigned long)debug)

		addr = (unsigned long)xen_debug;

	else if (addr == (unsigned long)int3)

		addr = (unsigned long)xen_int3;

	else if (addr == (unsigned long)stack_segment)

		addr = (unsigned long)xen_stack_segment;

	else

		WARN_ON(val->ist != 0);

#endif	/* CONFIG_X86_64 */

	info->address = addr;



	info->cs = gate_segment(*val);

	info->flags = val->dpl;

	/* interrupt gates clear IF */

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