While the original logic already implied that the kernel part of the
guest's address space is identical on all vCPU-s (i.e. for all guest
processes), it didn't fully leverage the potential here: As long as
the top page table currently active is owned by the subject domain
(currently only Dom0), the stack dump can be done without extra
effort.
For x86-64, additionally add page table traversal so that the stack
can be dumped in all cases (unless it's invalid or user space).
I left the 32-bit variant of do_page_walk() unimplemented for the
moment as I couldn't convince myself using map_domain_page() there is
a good idea, and didn't want to introduce new fixmap entries either.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
--- 2009-06-10.orig/xen/arch/x86/traps.c 2009-06-10 10:48:29.000000000
+0200
+++ 2009-06-10/xen/arch/x86/traps.c 2009-06-10 11:15:26.000000000 +0200
@@ -129,18 +129,18 @@ boolean_param("ler", opt_ler);
#define ESP_BEFORE_EXCEPTION(regs) ((unsigned long *)regs->rsp)
#endif
-static void show_guest_stack(struct cpu_user_regs *regs)
+static void show_guest_stack(struct vcpu *v, struct cpu_user_regs *regs)
{
int i;
- struct vcpu *curr = current;
unsigned long *stack, addr;
+ unsigned long mask = STACK_SIZE;
- if ( is_hvm_vcpu(curr) )
+ if ( is_hvm_vcpu(v) )
return;
- if ( is_pv_32on64_vcpu(curr) )
+ if ( is_pv_32on64_vcpu(v) )
{
- compat_show_guest_stack(regs, debug_stack_lines);
+ compat_show_guest_stack(v, regs, debug_stack_lines);
return;
}
@@ -156,11 +156,42 @@ static void show_guest_stack(struct cpu_
printk("Guest stack trace from "__OP"sp=%p:\n ", stack);
}
+ if ( !access_ok(stack, sizeof(*stack)) )
+ {
+ printk("Guest-inaccessible memory.\n");
+ return;
+ }
+
+ if ( v != current )
+ {
+ struct vcpu *vcpu;
+
+ ASSERT(guest_kernel_mode(v, regs));
+#ifndef __x86_64__
+ addr = read_cr3();
+ for_each_vcpu( v->domain, vcpu )
+ if ( vcpu->arch.cr3 == addr )
+ break;
+#else
+ vcpu = maddr_get_owner(read_cr3()) == v->domain ? v : NULL;
+#endif
+ if ( !vcpu )
+ {
+ stack = do_page_walk(v, (unsigned long)stack);
+ if ( (unsigned long)stack < PAGE_SIZE )
+ {
+ printk("Inaccessible guest memory.\n");
+ return;
+ }
+ mask = PAGE_SIZE;
+ }
+ }
+
for ( i = 0; i < (debug_stack_lines*stack_words_per_line); i++ )
{
- if ( ((long)stack & (STACK_SIZE-BYTES_PER_LONG)) == 0 )
+ if ( (((long)stack - 1) ^ ((long)(stack + 1) - 1)) & mask )
break;
- if ( get_user(addr, stack) )
+ if ( __get_user(addr, stack) )
{
if ( i != 0 )
printk("\n ");
@@ -264,7 +295,7 @@ void show_stack(struct cpu_user_regs *re
int i;
if ( guest_mode(regs) )
- return show_guest_stack(regs);
+ return show_guest_stack(current, regs);
printk("Xen stack trace from "__OP"sp=%p:\n ", stack);
@@ -346,10 +377,8 @@ void vcpu_show_execution_state(struct vc
vcpu_pause(v); /* acceptably dangerous */
vcpu_show_registers(v);
- /* Todo: map arbitrary vcpu's top guest stack page here. */
- if ( (v->domain == current->domain) &&
- guest_kernel_mode(v, &v->arch.guest_context.user_regs) )
- show_guest_stack(&v->arch.guest_context.user_regs);
+ if ( guest_kernel_mode(v, &v->arch.guest_context.user_regs) )
+ show_guest_stack(v, &v->arch.guest_context.user_regs);
vcpu_unpause(v);
}
--- 2009-06-10.orig/xen/arch/x86/x86_32/mm.c 2009-05-20 08:45:59.000000000
+0200
+++ 2009-06-10/xen/arch/x86/x86_32/mm.c 2009-06-10 11:15:26.000000000 +0200
@@ -63,6 +63,11 @@ l2_pgentry_t *virt_to_xen_l2e(unsigned l
return &idle_pg_table_l2[l2_linear_offset(v)];
}
+void *do_page_walk(struct vcpu *v, unsigned long addr)
+{
+ return NULL;
+}
+
void __init paging_init(void)
{
unsigned long v;
--- 2009-06-10.orig/xen/arch/x86/x86_64/compat/traps.c 2008-07-18
16:19:34.000000000 +0200
+++ 2009-06-10/xen/arch/x86/x86_64/compat/traps.c 2009-06-10
11:15:26.000000000 +0200
@@ -5,18 +5,46 @@
#include <compat/callback.h>
#include <compat/arch-x86_32.h>
-void compat_show_guest_stack(struct cpu_user_regs *regs, int debug_stack_lines)
+void compat_show_guest_stack(struct vcpu *v, struct cpu_user_regs *regs,
+ int debug_stack_lines)
{
- unsigned int i, *stack, addr;
+ unsigned int i, *stack, addr, mask = STACK_SIZE;
stack = (unsigned int *)(unsigned long)regs->_esp;
printk("Guest stack trace from esp=%08lx:\n ", (unsigned long)stack);
+ if ( !__compat_access_ok(v->domain, stack, sizeof(*stack)) )
+ {
+ printk("Guest-inaccessible memory.\n");
+ return;
+ }
+
+ if ( v != current )
+ {
+ struct vcpu *vcpu;
+
+ ASSERT(guest_kernel_mode(v, regs));
+ addr = read_cr3() >> PAGE_SHIFT;
+ for_each_vcpu( v->domain, vcpu )
+ if ( pagetable_get_pfn(vcpu->arch.guest_table) == addr )
+ break;
+ if ( !vcpu )
+ {
+ stack = do_page_walk(v, (unsigned long)stack);
+ if ( (unsigned long)stack < PAGE_SIZE )
+ {
+ printk("Inaccessible guest memory.\n");
+ return;
+ }
+ mask = PAGE_SIZE;
+ }
+ }
+
for ( i = 0; i < debug_stack_lines * 8; i++ )
{
- if ( (((long)stack + 3) & (STACK_SIZE - 4)) == 0 )
+ if ( (((long)stack - 1) ^ ((long)(stack + 1) - 1)) & mask )
break;
- if ( get_user(addr, stack) )
+ if ( __get_user(addr, stack) )
{
if ( i != 0 )
printk("\n ");
--- 2009-06-10.orig/xen/arch/x86/x86_64/mm.c 2009-05-20 08:45:59.000000000
+0200
+++ 2009-06-10/xen/arch/x86/x86_64/mm.c 2009-06-10 11:15:26.000000000 +0200
@@ -103,6 +103,47 @@ l2_pgentry_t *virt_to_xen_l2e(unsigned l
return l3e_to_l2e(*pl3e) + l2_table_offset(v);
}
+void *do_page_walk(struct vcpu *v, unsigned long addr)
+{
+ unsigned long mfn = pagetable_get_pfn(v->arch.guest_table);
+ l4_pgentry_t l4e, *l4t;
+ l3_pgentry_t l3e, *l3t;
+ l2_pgentry_t l2e, *l2t;
+ l1_pgentry_t l1e, *l1t;
+
+ if ( is_hvm_vcpu(v) )
+ return NULL;
+
+ l4t = mfn_to_virt(mfn);
+ l4e = l4t[l4_table_offset(addr)];
+ mfn = l4e_get_pfn(l4e);
+ if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) )
+ return NULL;
+
+ l3t = mfn_to_virt(mfn);
+ l3e = l3t[l3_table_offset(addr)];
+ mfn = l3e_get_pfn(l3e);
+ if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) || !mfn_valid(mfn) )
+ if ( (l3e_get_flags(l3e) & _PAGE_PSE) )
+ return mfn_to_virt(mfn) + (addr & ((1UL << L3_PAGETABLE_SHIFT) - 1));
+
+ l2t = mfn_to_virt(mfn);
+ l2e = l2t[l2_table_offset(addr)];
+ mfn = l2e_get_pfn(l2e);
+ if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) || !mfn_valid(mfn) )
+ return NULL;
+ if ( (l2e_get_flags(l2e) & _PAGE_PSE) )
+ return mfn_to_virt(mfn) + (addr & ((1UL << L2_PAGETABLE_SHIFT) - 1));
+
+ l1t = mfn_to_virt(mfn);
+ l1e = l1t[l1_table_offset(addr)];
+ mfn = l1e_get_pfn(l1e);
+ if ( !(l1e_get_flags(l1e) & _PAGE_PRESENT) || !mfn_valid(mfn) )
+ return NULL;
+
+ return mfn_to_virt(mfn) + (addr & ~PAGE_MASK);
+}
+
void __init paging_init(void)
{
unsigned long i, mpt_size, va;
--- 2009-06-10.orig/xen/include/asm-x86/mm.h 2009-06-05 11:59:48.000000000
+0200
+++ 2009-06-10/xen/include/asm-x86/mm.h 2009-06-10 11:15:26.000000000 +0200
@@ -475,6 +475,7 @@ int new_guest_cr3(unsigned long pfn);
void make_cr3(struct vcpu *v, unsigned long mfn);
void update_cr3(struct vcpu *v);
void propagate_page_fault(unsigned long addr, u16 error_code);
+void *do_page_walk(struct vcpu *v, unsigned long addr);
int __sync_lazy_execstate(void);
--- 2009-06-10.orig/xen/include/asm-x86/processor.h 2009-03-16
16:09:07.000000000 +0100
+++ 2009-06-10/xen/include/asm-x86/processor.h 2009-06-10 11:15:26.000000000
+0200
@@ -536,9 +536,9 @@ void show_page_walk(unsigned long addr);
asmlinkage void fatal_trap(int trapnr, struct cpu_user_regs *regs);
#ifdef CONFIG_COMPAT
-void compat_show_guest_stack(struct cpu_user_regs *, int lines);
+void compat_show_guest_stack(struct vcpu *, struct cpu_user_regs *, int lines);
#else
-#define compat_show_guest_stack(regs, lines) ((void)0)
+#define compat_show_guest_stack(vcpu, regs, lines) ((void)0)
#endif
extern void mtrr_ap_init(void);
--- 2009-06-10.orig/xen/include/asm-x86/x86_64/uaccess.h 2008-06-16
10:43:34.000000000 +0200
+++ 2009-06-10/xen/include/asm-x86/x86_64/uaccess.h 2009-06-10
11:15:26.000000000 +0200
@@ -27,11 +27,14 @@ DECLARE_PER_CPU(char, compat_arg_xlat[CO
#define array_access_ok(addr, count, size) \
(access_ok(addr, (count)*(size)))
-#define __compat_addr_ok(addr) \
- ((unsigned long)(addr) < HYPERVISOR_COMPAT_VIRT_START(current->domain))
+#define __compat_addr_ok(d, addr) \
+ ((unsigned long)(addr) < HYPERVISOR_COMPAT_VIRT_START(d))
+
+#define __compat_access_ok(d, addr, size) \
+ __compat_addr_ok(d, (unsigned long)(addr) + ((size) ? (size) - 1 : 0))
#define compat_access_ok(addr, size) \
- __compat_addr_ok((unsigned long)(addr) + ((size) ? (size) - 1 : 0))
+ __compat_access_ok(current->domain, addr, size)
#define compat_array_access_ok(addr,count,size) \
(likely((count) < (~0U / (size))) && \
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