Debugging with the gdbserver has been broken for paravirtualized
guests for a while since parts of xc_ptrace.c assumes HVM guests. The
following patch fixes this along with single-stepping in attached
domains. The patch tries to separate HVM-specific address
handling. Changes:
- Functions va_to_ma32 and va_to_ma64 have been added. These translate
virtual to machine addresses through a given page directory/table
and optionally through page_array for HVM guests. These have
replaced page_array-references.
- paging_enabled now contains a check for HVM guests, and always
returns 1 for PV guests.
- Reversed logic in PTRACE_SINGLESTEP to allow stepping in attached
domains and disallow stepping in corefiles.
NOTE: I only have access to "regular" 32-bit hardware, so I've only
been able to test map_domain_va32 for PV guests. It would be nice if
other people could test it on HVM, PAE and 64-bit guests.
// Simon
Signed-off-by: Simon Kagstrom <simon.kagstrom@xxxxxx>
===File /tmp/xc_ptrace.patch================================
diff -r fc9ec6fd3400 tools/libxc/xc_ptrace.c
--- a/tools/libxc/xc_ptrace.c Mon May 08 14:56:18 2006 +0100
+++ b/tools/libxc/xc_ptrace.c Thu May 11 16:49:59 2006 +0200
@@ -100,8 +100,15 @@ static inline int
static inline int
paging_enabled(vcpu_guest_context_t *v)
{
- unsigned long cr0 = v->ctrlreg[0];
- return (cr0 & X86_CR0_PE) && (cr0 & X86_CR0_PG);
+ /* This check can be removed when Xen places the correct values in
+ * cr0 for paravirtualized guests.
+ */
+ if ( (v->flags & VGCF_HVM_GUEST) == 1 ) {
+ unsigned long cr0 = v->ctrlreg[0];
+
+ return (cr0 & X86_CR0_PE) && (cr0 & X86_CR0_PG);
+ }
+ return 1;
}
/*
@@ -157,6 +164,43 @@ static long nr_pages
static long nr_pages = 0;
static unsigned long *page_array = NULL;
+
+static unsigned long
+va_to_ma32(int cpu,
+ uint32_t *table,
+ unsigned long idx)
+{
+ unsigned long out;
+
+ /* Paravirtualized domains store machine addresses in tables while
+ * HVM domains keep pseudo-physical addresses. HVM domains
+ * therefore need one extra translation.
+ */
+ if ( (out = table[idx]) == 0)
+ return 0;
+ if ( (ctxt[cpu].flags & VGCF_HVM_GUEST) && paging_enabled(&ctxt[cpu]) )
+ out = page_array[idx] << PAGE_SHIFT;
+ return out;
+}
+
+static unsigned long
+va_to_ma64(int cpu,
+ uint64_t *table,
+ unsigned long idx)
+{
+ unsigned long out;
+
+ /* Paravirtualized domains store machine addresses in tables while
+ * HVM domains keep pseudo-physical addresses. HVM domains
+ * therefore need one extra translation.
+ */
+ if ( (out = table[idx]) == 0)
+ return 0;
+ if ( (ctxt[cpu].flags & VGCF_HVM_GUEST) && paging_enabled(&ctxt[cpu]) )
+ out = page_array[idx] << PAGE_SHIFT;
+ return out;
+}
+
static void *
map_domain_va_32(
int xc_handle,
@@ -188,10 +232,8 @@ map_domain_va_32(
if ( cr3_virt[cpu] == NULL )
return NULL;
}
- if ( (pde = cr3_virt[cpu][vtopdi(va)]) == 0 )
- return NULL;
- if ( (ctxt[cpu].flags & VGCF_HVM_GUEST) && paging_enabled(&ctxt[cpu]) )
- pde = page_array[pde >> PAGE_SHIFT] << PAGE_SHIFT;
+ if ( (pde = va_to_ma32(cpu, cr3_virt[cpu], vtopdi(va))) == 0 )
+ return NULL;
if ( pde != pde_phys[cpu] )
{
pde_phys[cpu] = pde;
@@ -203,10 +245,9 @@ map_domain_va_32(
if ( pde_virt[cpu] == NULL )
return NULL;
}
- if ( (page = pde_virt[cpu][vtopti(va)]) == 0 )
- return NULL;
- if (ctxt[cpu].flags & VGCF_HVM_GUEST)
- page = page_array[page >> PAGE_SHIFT] << PAGE_SHIFT;
+ if ( (page = va_to_ma32(cpu, pde_virt[cpu], vtopti(va))) == 0 )
+ return NULL;
+
if ( (page != page_phys[cpu]) || (perm != prev_perm[cpu]) )
{
page_phys[cpu] = page;
@@ -243,25 +284,25 @@ map_domain_va_pae(
if ( l3 == NULL )
return NULL;
- l2p = l3[l3_table_offset_pae(va)] >> PAGE_SHIFT;
- l2p = page_array[l2p];
- l2 = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, PROT_READ,
l2p);
+ if ( ( l2p = va_to_ma64(cpu, l3, l3_table_offset_pae(va)) ) == 0 )
+ return NULL;
+ l2 = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, PROT_READ,
l2p >> PAGE_SHIFT);
munmap(l3, PAGE_SIZE);
if ( l2 == NULL )
return NULL;
- l1p = l2[l2_table_offset_pae(va)] >> PAGE_SHIFT;
- l1p = page_array[l1p];
- l1 = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, perm, l1p);
+ if ( ( l1p = va_to_ma64(cpu, l2, l2_table_offset_pae(va)) ) == 0 )
+ return NULL;
+ l1 = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, perm, l1p
>> PAGE_SHIFT);
munmap(l2, PAGE_SIZE);
if ( l1 == NULL )
return NULL;
- p = l1[l1_table_offset_pae(va)] >> PAGE_SHIFT;
- p = page_array[p];
+ if ( ( p = va_to_ma64(cpu, l1, l1_table_offset_pae(va)) ) == 0 )
+ return NULL;
if ( v != NULL )
munmap(v, PAGE_SIZE);
- v = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, perm, p);
+ v = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, perm, p >>
PAGE_SHIFT);
munmap(l1, PAGE_SIZE);
if ( v == NULL )
return NULL;
@@ -289,38 +330,41 @@ map_domain_va_64(
if ( l4 == NULL )
return NULL;
- l3p = l4[l4_table_offset(va)] >> PAGE_SHIFT;
- l3p = page_array[l3p];
- l3 = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, PROT_READ,
l3p);
+ if ( ( l3p = va_to_ma64(cpu, l4, l4_table_offset(va)) ) == 0 )
+ return NULL;
+ l3 = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, PROT_READ,
l3p >> PAGE_SHIFT);
munmap(l4, PAGE_SIZE);
if ( l3 == NULL )
return NULL;
- l2p = l3[l3_table_offset(va)] >> PAGE_SHIFT;
- l2p = page_array[l2p];
- l2 = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, PROT_READ,
l2p);
+ if ( ( l2p = va_to_ma64(cpu, l3, l3_table_offset(va)) ) == 0 )
+ return NULL;
+ l2 = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, PROT_READ,
l2p >> PAGE_SHIFT);
munmap(l3, PAGE_SIZE);
if ( l2 == NULL )
return NULL;
l1 = NULL;
- l1e = l2[l2_table_offset(va)];
+ if ( ( l1e = va_to_ma64(cpu, l2, l2_table_offset(va)) ) == 0 )
+ return NULL;
l1p = l1e >> PAGE_SHIFT;
if (l1e & 0x80) { /* 2M pages */
p = (l1p + l1_table_offset(va));
+ if ( (ctxt[cpu].flags & VGCF_HVM_GUEST))
+ p = page_array[p] << PAGE_SHIFT;
} else { /* 4K pages */
- l1p = page_array[l1p];
- l1 = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, perm,
l1p);
+ if ( ( l1p = va_to_ma64(cpu, l1e, l1_table_offset(va)) ) == 0 )
+ return NULL;
+ l1 = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, perm,
l1p >> PAGE_SHIFT);
munmap(l2, PAGE_SIZE);
if ( l1 == NULL )
return NULL;
- p = l1[l1_table_offset(va)] >> PAGE_SHIFT;
- }
- p = page_array[p];
+ p = va_to_ma64(cpu, l1, l1_table_offset(va));
+ }
if ( v != NULL )
munmap(v, PAGE_SIZE);
- v = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, perm, p);
+ v = xc_map_foreign_range(xc_handle, current_domid, PAGE_SIZE, perm, p >>
PAGE_SHIFT);
if (l1)
munmap(l1, PAGE_SIZE);
if ( v == NULL )
@@ -381,7 +425,7 @@ map_domain_va(
if ( v != NULL )
munmap(v, PAGE_SIZE);
- page = page_array[va >> PAGE_SHIFT] << PAGE_SHIFT;
+ page = va_to_ma32(cpu, (uint32_t*)page_array, va);
v = xc_map_foreign_range( xc_handle, current_domid, PAGE_SIZE,
perm, page >> PAGE_SHIFT);
@@ -526,7 +570,7 @@ xc_ptrace(
break;
case PTRACE_SINGLESTEP:
- if (!current_isfile)
+ if (current_isfile)
goto out_unspported; /* XXX not yet supported */
/* XXX we can still have problems if the user switches threads
* during single-stepping - but that just seems retarded
============================================================
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