Also found by afl-fuzz on the varlocs testcase.
DW_FORM_data16 is constant from according to the DWARF5 spec.
But since it is 128bits it isn't really representable as Dwarf_Word.
So we treat it as block form. But we cannot treat it as an expression
block. Make sure readelf prints it as a regular block and that
dwarf_getlocation[s|_addr] doesn't treat it as location expression.
Signed-off-by: Mark Wielaard <m...@klomp.org>
---
libdw/dwarf_getlocation.c | 44 +++++++++++++++++++++++++++++++-------------
src/ChangeLog | 5 +++++
src/readelf.c | 15 ++++++++++-----
3 files changed, 46 insertions(+), 18 deletions(-)
diff --git a/libdw/dwarf_getlocation.c b/libdw/dwarf_getlocation.c
index 7f294fe..fc59a2a 100644
--- a/libdw/dwarf_getlocation.c
+++ b/libdw/dwarf_getlocation.c
@@ -174,6 +174,8 @@ check_constant_offset (Dwarf_Attribute *attr,
default:
return 1;
+ /* Note, we don't regard DW_FORM_data16 as a constant form,
+ even though technically it is according to the standard. */
case DW_FORM_data1:
case DW_FORM_data2:
case DW_FORM_data4:
@@ -665,7 +667,13 @@ dwarf_getlocation (Dwarf_Attribute *attr, Dwarf_Op
**llbuf, size_t *listlen)
if (result != 1)
return result;
- /* If it has a block form, it's a single location expression. */
+ /* If it has a block form, it's a single location expression.
+ Except for DW_FORM_data16, which is a 128bit constant. */
+ if (attr->form == DW_FORM_data16)
+ {
+ __libdw_seterrno (DWARF_E_NO_BLOCK);
+ return -1;
+ }
Dwarf_Block block;
if (INTUSE(dwarf_formblock) (attr, &block) != 0)
return -1;
@@ -863,9 +871,11 @@ dwarf_getlocation_addr (Dwarf_Attribute *attr, Dwarf_Addr
address,
if (llbufs == NULL)
maxlocs = SIZE_MAX;
- /* If it has a block form, it's a single location expression. */
+ /* If it has a block form, it's a single location expression.
+ Except for DW_FORM_data16, which is a 128bit constant. */
Dwarf_Block block;
- if (INTUSE(dwarf_formblock) (attr, &block) == 0)
+ if (attr->form != DW_FORM_data16
+ && INTUSE(dwarf_formblock) (attr, &block) == 0)
{
if (maxlocs == 0)
return 0;
@@ -876,11 +886,14 @@ dwarf_getlocation_addr (Dwarf_Attribute *attr, Dwarf_Addr
address,
return listlens[0] == 0 ? 0 : 1;
}
- int error = INTUSE(dwarf_errno) ();
- if (unlikely (error != DWARF_E_NO_BLOCK))
+ if (attr->form != DW_FORM_data16)
{
- __libdw_seterrno (error);
- return -1;
+ int error = INTUSE(dwarf_errno) ();
+ if (unlikely (error != DWARF_E_NO_BLOCK))
+ {
+ __libdw_seterrno (error);
+ return -1;
+ }
}
int result = check_constant_offset (attr, &llbufs[0], &listlens[0]);
@@ -938,9 +951,11 @@ dwarf_getlocations (Dwarf_Attribute *attr, ptrdiff_t
offset, Dwarf_Addr *basep,
if (offset == 0)
{
- /* If it has a block form, it's a single location expression. */
+ /* If it has a block form, it's a single location expression.
+ Except for DW_FORM_data16, which is a 128bit constant. */
Dwarf_Block block;
- if (INTUSE(dwarf_formblock) (attr, &block) == 0)
+ if (attr->form != DW_FORM_data16
+ && INTUSE(dwarf_formblock) (attr, &block) == 0)
{
if (getlocation (attr->cu, &block, expr, exprlen,
cu_sec_idx (attr->cu)) != 0)
@@ -952,11 +967,14 @@ dwarf_getlocations (Dwarf_Attribute *attr, ptrdiff_t
offset, Dwarf_Addr *basep,
return 1;
}
- int error = INTUSE(dwarf_errno) ();
- if (unlikely (error != DWARF_E_NO_BLOCK))
+ if (attr->form != DW_FORM_data16)
{
- __libdw_seterrno (error);
- return -1;
+ int error = INTUSE(dwarf_errno) ();
+ if (unlikely (error != DWARF_E_NO_BLOCK))
+ {
+ __libdw_seterrno (error);
+ return -1;
+ }
}
int result = check_constant_offset (attr, expr, exprlen);
diff --git a/src/ChangeLog b/src/ChangeLog
index 8fb418a..9b119b6 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2018-06-15 Mark Wielaard <m...@klomp.org>
+
+ * readelf.c (attr_callback): Only print block as expressions if it
+ isn't DW_FORM_data16.
+
2018-06-16 Mark Wielaard <m...@klomp.org>
* readelf.c (print_debug_loc_section): Make sure next_off doesn't
diff --git a/src/readelf.c b/src/readelf.c
index 2e7378e..4172046 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -7483,11 +7483,16 @@ attr_callback (Dwarf_Attribute *attrp, void *arg)
case DW_AT_GNU_call_site_data_value:
case DW_AT_GNU_call_site_target:
case DW_AT_GNU_call_site_target_clobbered:
- putchar ('\n');
- print_ops (cbargs->dwflmod, cbargs->dbg,
- 12 + level * 2, 12 + level * 2,
- cbargs->version, cbargs->addrsize, cbargs->offset_size,
- attrp->cu, block.length, block.data);
+ if (form != DW_FORM_data16)
+ {
+ putchar ('\n');
+ print_ops (cbargs->dwflmod, cbargs->dbg,
+ 12 + level * 2, 12 + level * 2,
+ cbargs->version, cbargs->addrsize, cbargs->offset_size,
+ attrp->cu, block.length, block.data);
+ }
+ else
+ print_block (block.length, block.data);
break;
}
break;
--
1.8.3.1
