[PATCH] vsprintf.c: remove stack variable ksym from
From: Joe Perches
Date: Sat Mar 13 2010 - 14:54:51 EST
On Sat, 2010-03-13 at 09:44 -0800, Joe Perches wrote:
> On Sat, 2010-03-13 at 07:35 -0800, Linus Torvalds wrote:
> > On Fri, 12 Mar 2010, Andrew Morton wrote:
> > > nice.
> > But the kallsyms_lookup()/sprint_symbol() functions don't take a
> > length parameter, so we have to do the worst-case thing (which itself has
> > tons of unnecessary padding).
> Perhaps a new snprint_symbol function with the
> other kallsyms... functions changed as necessary.
Perhaps something like this:
Functions added:
kallsyms_lookup_n length limited kallsyms_lookup
snprint_symbol length limited sprint_symbol
module_address_lookup_n length limited module_address_lookup
Changes to vsprintf.c, function symbol_string:
remove stack variable ksym, just use output buffer
and length limited functions.
Compiled, untested
Signed-off-by: Joe Perches
---
include/linux/kallsyms.h | 7 ++++
include/linux/module.h | 15 ++++++++
kernel/kallsyms.c | 91 ++++++++++++++++++++++++++++++++++++++++------
kernel/module.c | 33 +++++++++++++++++
lib/vsprintf.c | 14 ++++---
5 files changed, 143 insertions(+), 17 deletions(-)
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index d8e9b3d..b1729b5 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -34,8 +34,15 @@ const char *kallsyms_lookup(unsigned long addr,
unsigned long *offset,
char **modname, char *namebuf);
+const char *kallsyms_lookup_n(unsigned long addr,
+ unsigned long *symbolsize,
+ unsigned long *offset,
+ char **modname, char *namebuf, size_t size);
+
/* Look up a kernel symbol and return it in a text buffer. */
extern int sprint_symbol(char *buffer, unsigned long address);
+/* Look up a kernel symbol and return it in a text buffer. */
+extern int snprint_symbol(char *buffer, size_t size, unsigned long address);
/* Look up a kernel symbol and print it to the kernel messages. */
extern void __print_symbol(const char *fmt, unsigned long address);
diff --git a/include/linux/module.h b/include/linux/module.h
index 5e869ff..7a65fad 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -520,6 +520,11 @@ const char *module_address_lookup(unsigned long addr,
unsigned long *offset,
char **modname,
char *namebuf);
+const char *module_address_lookup_n(unsigned long addr,
+ unsigned long *symbolsize,
+ unsigned long *offset,
+ char **modname,
+ char *namebuf, size_t size);
int lookup_module_symbol_name(unsigned long addr, char *symname);
int lookup_module_symbol_attrs(unsigned long addr, unsigned long *size, unsigned long *offset, char *modname, char *name);
@@ -598,6 +603,16 @@ static inline const char *module_address_lookup(unsigned long addr,
return NULL;
}
+/* For kallsyms to ask for address resolution. NULL means not found. */
+static inline const char *module_address_lookup_n(unsigned long addr,
+ unsigned long *symbolsize,
+ unsigned long *offset,
+ char **modname,
+ char *namebuf, size_t size)
+{
+ return NULL;
+}
+
static inline int lookup_module_symbol_name(unsigned long addr, char *symname)
{
return -ERANGE;
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 8e5288a..0516d23 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -84,9 +84,11 @@ static int is_ksym_addr(unsigned long addr)
* Expand a compressed symbol data into the resulting uncompressed string,
* given the offset to where the symbol is in the compressed stream.
*/
-static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
+static unsigned int kallsyms_expand_symbol(unsigned int off,
+ char *result, size_t size)
{
- int len, skipped_first = 0;
+ int len;
+ bool skipped_first = false;
const u8 *tptr, *data;
/* Get the compressed symbol length from the first symbol byte. */
@@ -110,16 +112,18 @@ static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
len--;
while (*tptr) {
- if (skipped_first) {
+ if (skipped_first && size > 1) {
*result = *tptr;
result++;
+ size--;
} else
- skipped_first = 1;
+ skipped_first = true;
tptr++;
}
}
- *result = '\0';
+ if (size)
+ *result = '\0';
/* Return to offset to the next symbol. */
return off;
@@ -174,7 +178,7 @@ unsigned long kallsyms_lookup_name(const char *name)
unsigned int off;
for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
- off = kallsyms_expand_symbol(off, namebuf);
+ off = kallsyms_expand_symbol(off, namebuf, sizeof(namebuf));
if (strcmp(namebuf, name) == 0)
return kallsyms_addresses[i];
@@ -193,7 +197,7 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
int ret;
for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
- off = kallsyms_expand_symbol(off, namebuf);
+ off = kallsyms_expand_symbol(off, namebuf, sizeof(namebuf));
ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
if (ret != 0)
return ret;
@@ -292,7 +296,8 @@ const char *kallsyms_lookup(unsigned long addr,
pos = get_symbol_pos(addr, symbolsize, offset);
/* Grab name */
- kallsyms_expand_symbol(get_symbol_offset(pos), namebuf);
+ kallsyms_expand_symbol(get_symbol_offset(pos),
+ namebuf, KSYM_NAME_LEN);
if (modname)
*modname = NULL;
return namebuf;
@@ -303,6 +308,38 @@ const char *kallsyms_lookup(unsigned long addr,
namebuf);
}
+/*
+ * Lookup an address (length_limited)
+ * - modname is set to NULL if it's in the kernel.
+ * - We guarantee that the returned name is valid until we reschedule even if.
+ * It resides in a module.
+ * - We also guarantee that modname will be valid until rescheduled.
+ */
+const char *kallsyms_lookup_n(unsigned long addr,
+ unsigned long *symbolsize,
+ unsigned long *offset,
+ char **modname, char *namebuf, size_t size)
+{
+ if (size)
+ namebuf[size - 1] = 0;
+ namebuf[0] = 0;
+
+ if (is_ksym_addr(addr)) {
+ unsigned long pos;
+
+ pos = get_symbol_pos(addr, symbolsize, offset);
+ /* Grab name */
+ kallsyms_expand_symbol(get_symbol_offset(pos), namebuf, size);
+ if (modname)
+ *modname = NULL;
+ return namebuf;
+ }
+
+ /* See if it's in a module. */
+ return module_address_lookup_n(addr, symbolsize, offset, modname,
+ namebuf, size);
+}
+
int lookup_symbol_name(unsigned long addr, char *symname)
{
symname[0] = '\0';
@@ -313,7 +350,8 @@ int lookup_symbol_name(unsigned long addr, char *symname)
pos = get_symbol_pos(addr, NULL, NULL);
/* Grab name */
- kallsyms_expand_symbol(get_symbol_offset(pos), symname);
+ kallsyms_expand_symbol(get_symbol_offset(pos),
+ symname, KSYM_NAME_LEN);
return 0;
}
/* See if it's in a module. */
@@ -331,7 +369,8 @@ int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
pos = get_symbol_pos(addr, size, offset);
/* Grab name */
- kallsyms_expand_symbol(get_symbol_offset(pos), name);
+ kallsyms_expand_symbol(get_symbol_offset(pos),
+ name, KSYM_NAME_LEN);
modname[0] = '\0';
return 0;
}
@@ -340,6 +379,36 @@ int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
}
/* Look up a kernel symbol and return it in a text buffer. */
+int snprint_symbol(char *buffer, size_t size, unsigned long address)
+{
+ char *modname;
+ const char *name;
+ unsigned long offset, ksize;
+ int len;
+
+ name = kallsyms_lookup_n(address, &ksize, &offset, &modname,
+ buffer, size);
+ if (!name)
+ return snprintf(buffer, size, "0x%lx", address);
+
+ if (name != buffer)
+ strncpy(buffer, name, size);
+ len = strlen(buffer);
+ buffer += len;
+
+ if (modname)
+ len += snprintf(buffer, size - len,
+ "+%#lx/%#lx [%s]", offset, ksize, modname);
+ else
+ len += snprintf(buffer, size - len,
+ "+%#lx/%#lx", offset, ksize);
+
+ return len;
+}
+EXPORT_SYMBOL_GPL(snprint_symbol);
+
+
+/* Look up a kernel symbol and return it in a text buffer. */
int sprint_symbol(char *buffer, unsigned long address)
{
char *modname;
@@ -407,7 +476,7 @@ static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
iter->type = kallsyms_get_symbol_type(off);
- off = kallsyms_expand_symbol(off, iter->name);
+ off = kallsyms_expand_symbol(off, iter->name, sizeof(iter->name));
return off - iter->nameoff;
}
diff --git a/kernel/module.c b/kernel/module.c
index c968d36..17a879a 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2607,6 +2607,39 @@ const char *module_address_lookup(unsigned long addr,
return ret;
}
+/* For kallsyms to ask for address resolution. NULL means not found. Careful
+ * not to lock to avoid deadlock on oopses, simply disable preemption. */
+const char *module_address_lookup_n(unsigned long addr,
+ unsigned long *ksize,
+ unsigned long *offset,
+ char **modname,
+ char *namebuf, size_t size)
+{
+ struct module *mod;
+ const char *ret = NULL;
+
+ preempt_disable();
+ list_for_each_entry_rcu(mod, &modules, list) {
+ if (within_module_init(addr, mod) ||
+ within_module_core(addr, mod)) {
+ if (modname)
+ *modname = mod->name;
+ ret = get_ksymbol(mod, addr, ksize, offset);
+ break;
+ }
+ }
+ /* Make a copy in here where it's safe */
+ if (ret) {
+ if (size) {
+ strncpy(namebuf, ret, size - 1);
+ namebuf[size - 1] = 0;
+ }
+ ret = namebuf;
+ }
+ preempt_enable();
+ return ret;
+}
+
int lookup_module_symbol_name(unsigned long addr, char *symname)
{
struct module *mod;
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 0d461c7..dab6354 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -571,13 +571,15 @@ static char *symbol_string(char *buf, char *end, void *ptr,
{
unsigned long value = (unsigned long) ptr;
#ifdef CONFIG_KALLSYMS
- char sym[KSYM_SYMBOL_LEN];
- if (ext != 'f' && ext != 's')
- sprint_symbol(sym, value);
- else
- kallsyms_lookup(value, NULL, NULL, NULL, sym);
+ /* Cap ending position to spec.field_width if specified */
+ if (spec.field_width > 0 && (end - buf) > spec.field_width)
+ end = buf + spec.field_width;
- return string(buf, end, sym, spec);
+ if (ext != 'f' && ext != 's')
+ return buf + snprint_symbol(buf, end - buf, value);
+
+ kallsyms_lookup_n(value, NULL, NULL, NULL, buf, end - buf);
+ return buf + strlen(buf);
#else
spec.field_width = 2 * sizeof(void *);
spec.flags |= SPECIAL | SMALL | ZEROPAD;
--
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