From: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx>
The init_dwarf_info() function initializes "dwarf_info.dwfl" handle everytime
when it is called. The "dwarf_info.dwfl" handle should be freed once we are
done with searching of desired debuginfo and before next invocation of
init_dwarf_info().
Most of the functions (e.g get_debug_info()) that invokes init_dwarf_info()
also invokes clean_dwfl_info() to free dwfl handle. But the function
get_die_from_offset() that invokes init_dwarf_info(), does not free the dwfl
handle and hence it keeps re-reading debuginfo ELF section into memory every
time it is invoked until it starts failing with following errors:
init_dwarf_info: Can't get first elf header of /usr/lib/debug/boot/vmlinux-x.x.x
get_die_attr_type: Can't find the DIE.
init_dwarf_info: Can't get first elf header of /usr/lib/debug/boot/vmlinux-x.x.x
init_dwarf_info: Can't get first elf header of /usr/lib/debug/boot/vmlinux-x.x.x
File eppic_macro/key.c, line 32, Error: Oops! Var ref1.[keyring_name_hash]
This patch makes sure that clean_dwfl_info() is called once we are done with
the debuginfo search.
Signed-off-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
---
dwarf_info.c | 58 +++++++++++++++++++++++++++++++++++++++++++++--------
extension_eppic.c | 23 +++++++++++++++------
2 files changed, 65 insertions(+), 16 deletions(-)
diff --git a/dwarf_info.c b/dwarf_info.c
index a11b6ad..478d637 100644
--- a/dwarf_info.c
+++ b/dwarf_info.c
@@ -1347,11 +1347,14 @@ get_die_nfields(unsigned long long die_off)
tag = dwarf_tag(die);
if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
ERRMSG("DIE is not of structure or union type.\n");
+ clean_dwfl_info();
return -1;
}
- if (dwarf_child(die, &child) != 0)
+ if (dwarf_child(die, &child) != 0) {
+ clean_dwfl_info();
return -1;
+ }
/* Find the number of fields in the structure */
die = &child;
@@ -1363,6 +1366,7 @@ get_die_nfields(unsigned long long die_off)
continue;
} while (!dwarf_siblingof(die, die));
+ clean_dwfl_info();
return nfields;
}
@@ -1388,11 +1392,14 @@ get_die_member(unsigned long long die_off, int index, long *offset,
tag = dwarf_tag(die);
if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
ERRMSG("DIE is not of structure or union type.\n");
+ clean_dwfl_info();
return -1;
}
- if (dwarf_child(die, &child) != 0)
+ if (dwarf_child(die, &child) != 0) {
+ clean_dwfl_info();
return -1;
+ }
/* Find the correct field in the structure */
die = &child;
@@ -1408,6 +1415,7 @@ get_die_member(unsigned long long die_off, int index, long *offset,
if (nfields != index) {
ERRMSG("No member found at index %d.\n", index);
+ clean_dwfl_info();
return -1;
}
@@ -1416,6 +1424,13 @@ get_die_member(unsigned long long die_off, int index, long *offset,
*offset = 0;
*name = dwarf_diename(die);
+ /*
+ * Duplicate the string before we pass it to eppic layer. The
+ * original string returned by dwarf layer will become invalid
+ * after clean_dwfl_info() call.
+ */
+ if (*name)
+ *name = strdup(*name);
*m_die = dwarf_dieoffset(die);
get_die_type(die, &die_base);
@@ -1432,6 +1447,7 @@ get_die_member(unsigned long long die_off, int index, long *offset,
*/
*nbits = *fbits = 0;
+ clean_dwfl_info();
if (size < 0)
return 0;
else
@@ -1455,21 +1471,35 @@ get_die_attr_type(unsigned long long die_off, int *type_flag,
return FALSE;
}
- if (!get_die_type(&result, &result))
+ if (!get_die_type(&result, &result)) {
+ clean_dwfl_info();
return FALSE;
+ }
*die_attr_off = dwarf_dieoffset(&result);
*type_flag = dwarf_tag(&result);
+ clean_dwfl_info();
return TRUE;
}
/*
- * Get name attribute given the die offset
+ * Get name attribute given the die offset This function is called by eppic
+ * layer directly as one of the callback functions.
+ *
+ * This function returns a pointer to newly allocated string which is a
+ * duplicate of original string returned from dwarf APIs. The reason for doing
+ * this is because the original string returned by dwarf layer will become
+ * invalid (freed) as soon as we close the dwarf handle through
+ * clean_dwfl_info(). This avoids the segfault when caller (eppic layer) of
+ * this function tries to access the string pointer.
+ *
+ * NOTE: It is callers responsibility to free the memory of new string.
*/
char *
get_die_name(unsigned long long die_off)
{
Dwarf_Die result;
+ char *name = NULL;
if (!die_off)
return NULL;
@@ -1479,7 +1509,11 @@ get_die_name(unsigned long long die_off)
return NULL;
}
- return dwarf_diename(&result);
+ name = dwarf_diename(&result);
+ if (name)
+ name = strdup(name);
+ clean_dwfl_info();
+ return name;
}
/*
@@ -1510,6 +1544,7 @@ int
get_die_length(unsigned long long die_off, int flag)
{
Dwarf_Die result, die_base;
+ int size = 0;
if (!die_off)
return FALSE;
@@ -1519,17 +1554,22 @@ get_die_length(unsigned long long die_off, int flag)
return FALSE;
}
- if (flag)
- return dwarf_bytesize(&result);
+ if (flag) {
+ size = dwarf_bytesize(&result);
+ goto out;
+ }
get_die_type(&result, &die_base);
if (dwarf_tag(&die_base) == DW_TAG_array_type) {
dwarf_info.array_length = 0;
get_data_array_length(&result);
- return dwarf_info.array_length;
+ size = dwarf_info.array_length;
} else {
- return dwarf_bytesize(&die_base);
+ size = dwarf_bytesize(&die_base);
}
+out:
+ clean_dwfl_info();
+ return size;
}
/*
diff --git a/extension_eppic.c b/extension_eppic.c
index a1981eb..d5e5ad0 100644
--- a/extension_eppic.c
+++ b/extension_eppic.c
@@ -121,7 +121,7 @@ drilldown(ull offset, type_t *t)
int type_flag, len = 0, t_len = 0, nidx = 0;
int fctflg = 0, ref = 0, *idxlst = 0;
ull die_off = offset, t_die_off;
- char *tstr = NULL;
+ char *tstr = NULL, *tstr_dup = NULL;
while (GET_DIE_ATTR_TYPE(die_off, &type_flag, &t_die_off)) {
switch (type_flag) {
@@ -201,9 +201,10 @@ out:
if (fctflg)
eppic_type_setfct(t, 1);
eppic_pushref(t, ref + (nidx ? 1 : 0));
- if (tstr)
- return eppic_strdup(tstr);
- return eppic_strdup("");
+ tstr_dup = (tstr) ? eppic_strdup(tstr) : eppic_strdup("");
+ /* Free the memory allocated by makedumpfile. */
+ free(tstr);
+ return tstr_dup;
}
/*
@@ -216,7 +217,7 @@ apimember(char *mname, ull idx, type_t *tm, member_t *m, ull *last_index)
int nbits = 0, fbits = 0;
long offset;
ull m_die, die_off = idx;
- char *name;
+ char *name = NULL;
nfields = GET_DIE_NFIELDS(die_off);
/*
@@ -243,8 +244,13 @@ apimember(char *mname, ull idx, type_t *tm, member_t *m, ull *last_index)
if (!mname || !mname[0] || !strcmp(mname, name)) {
eppic_member_ssize(m, size);
- if (name)
+ if (name) {
eppic_member_sname(m, name);
+ /*
+ * Free the memory allocated by makedumpfile.
+ */
+ free(name);
+ }
else
eppic_member_sname(m, "");
eppic_member_soffset(m, offset);
@@ -334,8 +340,11 @@ apigetval(char *name, ull *val, VALUE_S *value)
if (!eppic_typeislocal(stype) && eppic_type_getidx(stype) > 100) {
char *tname = GET_DIE_NAME(eppic_type_getidx(stype));
- if (tname)
+ if (tname) {
eppic_chktype(stype, tname);
+ /* Free the memory allocated by makedumpfile. */
+ free(tname);
+ }
}
return 1;
}
