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Subject[PATCH V2 06/13] ftrace: Add symbols for ftrace trampolines
Date
Symbols are needed for tools to describe instruction addresses. Pages
allocated for ftrace's purposes need symbols to be created for them.
Add such symbols to be visible via /proc/kallsyms.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
arch/x86/kernel/ftrace.c | 26 ++++++++++----------
include/linux/ftrace.h | 15 ++++++++----
kernel/trace/ftrace.c | 52 +++++++++++++++++++++++++++++++++++++++-
3 files changed, 76 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 108ee96f8b66..76920ce85b9c 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -307,9 +307,9 @@ union ftrace_op_code_union {

#define RET_SIZE 1

-static unsigned long
-create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
+static void create_trampoline(struct ftrace_ops *ops)
{
+ unsigned int tramp_size;
unsigned long start_offset;
unsigned long end_offset;
unsigned long op_offset;
@@ -347,10 +347,10 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
*/
trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
if (!trampoline)
- return 0;
+ return;

- *tramp_size = size + RET_SIZE + sizeof(void *);
- npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);
+ tramp_size = size + RET_SIZE + sizeof(void *);
+ npages = DIV_ROUND_UP(tramp_size, PAGE_SIZE);

/* Copy ftrace_caller onto the trampoline memory */
ret = probe_kernel_read(trampoline, (void *)start_offset, size);
@@ -403,15 +403,18 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)

/* ALLOC_TRAMP flags lets us know we created it */
ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
+ ops->trampoline = (unsigned long)trampoline;
+ ops->trampoline_size = tramp_size;
+
+ ftrace_add_trampoline_to_kallsyms(ops);

set_vm_flush_reset_perms(trampoline);

set_memory_ro((unsigned long)trampoline, npages);
set_memory_x((unsigned long)trampoline, npages);
- return (unsigned long)trampoline;
+ return;
fail:
tramp_free(trampoline);
- return 0;
}

static unsigned long calc_trampoline_call_offset(bool save_regs)
@@ -435,14 +438,10 @@ void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
ftrace_func_t func;
unsigned long offset;
unsigned long ip;
- unsigned int size;
const char *new;

if (!ops->trampoline) {
- ops->trampoline = create_trampoline(ops, &size);
- if (!ops->trampoline)
- return;
- ops->trampoline_size = size;
+ create_trampoline(ops);
return;
}

@@ -535,6 +534,9 @@ void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
return;

+ ftrace_remove_trampoline_from_kallsyms(ops);
+ synchronize_rcu();
+
tramp_free((void *)ops->trampoline);
ops->trampoline = 0;
}
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index db95244a62d4..70dea4785443 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -58,9 +58,6 @@ struct ftrace_direct_func;
const char *
ftrace_mod_address_lookup(unsigned long addr, unsigned long *size,
unsigned long *off, char **modname, char *sym);
-int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value,
- char *type, char *name,
- char *module_name, int *exported);
#else
static inline const char *
ftrace_mod_address_lookup(unsigned long addr, unsigned long *size,
@@ -68,6 +65,13 @@ ftrace_mod_address_lookup(unsigned long addr, unsigned long *size,
{
return NULL;
}
+#endif
+
+#if defined(CONFIG_FUNCTION_TRACER) && defined(CONFIG_DYNAMIC_FTRACE)
+int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value,
+ char *type, char *name,
+ char *module_name, int *exported);
+#else
static inline int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value,
char *type, char *name,
char *module_name, int *exported)
@@ -76,7 +80,6 @@ static inline int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *val
}
#endif

-
#ifdef CONFIG_FUNCTION_TRACER

extern int ftrace_enabled;
@@ -179,6 +182,9 @@ struct ftrace_ops_hash {

void ftrace_free_init_mem(void);
void ftrace_free_mem(struct module *mod, void *start, void *end);
+#define FTRACE_TRAMPOLINE_SYM "ftrace_trampoline"
+void ftrace_add_trampoline_to_kallsyms(struct ftrace_ops *ops);
+void ftrace_remove_trampoline_from_kallsyms(struct ftrace_ops *ops);
#else
static inline void ftrace_free_init_mem(void) { }
static inline void ftrace_free_mem(struct module *mod, void *start, void *end) { }
@@ -207,6 +213,7 @@ struct ftrace_ops {
struct ftrace_ops_hash old_hash;
unsigned long trampoline;
unsigned long trampoline_size;
+ struct list_head list;
#endif
};

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 9bf1f2cd515e..697ab4759f0c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6174,6 +6174,41 @@ struct ftrace_mod_map {
unsigned int num_funcs;
};

+/* List of trace_ops that have allocated trampolines */
+static LIST_HEAD(ftrace_ops_trampoline_list);
+
+void ftrace_add_trampoline_to_kallsyms(struct ftrace_ops *ops)
+{
+ lockdep_assert_held(&ftrace_lock);
+ list_add_rcu(&ops->list, &ftrace_ops_trampoline_list);
+}
+
+void ftrace_remove_trampoline_from_kallsyms(struct ftrace_ops *ops)
+{
+ lockdep_assert_held(&ftrace_lock);
+ list_del_rcu(&ops->list);
+}
+
+int ftrace_get_trampoline_kallsym(unsigned int symnum, unsigned long *value,
+ char *type, char *name, char *module_name,
+ int *exported)
+{
+ struct ftrace_ops *op;
+
+ list_for_each_entry_rcu(op, &ftrace_ops_trampoline_list, list) {
+ if (!op->trampoline || symnum--)
+ continue;
+ *value = op->trampoline;
+ *type = 't';
+ strlcpy(name, FTRACE_TRAMPOLINE_SYM, KSYM_NAME_LEN);
+ strlcpy(module_name, "ftrace", MODULE_NAME_LEN);
+ *exported = 0;
+ return 0;
+ }
+
+ return -ERANGE;
+}
+
#ifdef CONFIG_MODULES

#define next_to_ftrace_page(p) container_of(p, struct ftrace_page, next)
@@ -6510,6 +6545,7 @@ int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value,
{
struct ftrace_mod_map *mod_map;
struct ftrace_mod_func *mod_func;
+ int ret;

preempt_disable();
list_for_each_entry_rcu(mod_map, &ftrace_mod_maps, list) {
@@ -6536,8 +6572,10 @@ int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value,
WARN_ON(1);
break;
}
+ ret = ftrace_get_trampoline_kallsym(symnum, value, type, name,
+ module_name, exported);
preempt_enable();
- return -ERANGE;
+ return ret;
}

#else
@@ -6549,6 +6587,18 @@ allocate_ftrace_mod_map(struct module *mod,
{
return NULL;
}
+int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value,
+ char *type, char *name, char *module_name,
+ int *exported)
+{
+ int ret;
+
+ preempt_disable();
+ ret = ftrace_get_trampoline_kallsym(symnum, value, type, name,
+ module_name, exported);
+ preempt_enable();
+ return ret;
+}
#endif /* CONFIG_MODULES */

struct ftrace_init_func {
--
2.17.1
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