[PATCH 4/8] ftrace: Store direct called addresses in their ops

Florent Revest
2023-02-01T16:37:23Z

All direct calls are now registered using the register_ftrace_direct API
so each ops can jump to only one direct-called trampoline.

By storing the direct called trampoline address directly in the ops we
can save one hashmap lookup in the direct call ops and implement arm64
direct calls on top of call ops.

Signed-off-by: Florent Revest <revest@chromium.org>
---
include/linux/ftrace.h | 3 +++
kernel/trace/ftrace.c | 6 ++++--
2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index a7dbd307c3a4..84f717f8959e 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -321,6 +321,9 @@ struct ftrace_ops {
unsigned long trampoline_size;
struct list_head list;
ftrace_ops_func_t ops_func;
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+ unsigned long direct_call;
+#endif
#endif
};

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index cb77a0a208c7..b0426de11c45 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2577,9 +2577,8 @@ ftrace_add_rec_direct(unsigned long ip, unsigned long addr,
static void call_direct_funcs(unsigned long ip, unsigned long pip,
struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
- unsigned long addr;
+ unsigned long addr = ops->direct_call;

- addr = ftrace_find_rec_direct(ip);
if (!addr)
return;

@@ -5375,6 +5374,7 @@ int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
ops->func = call_direct_funcs;
ops->flags = MULTI_FLAGS;
ops->trampoline = FTRACE_REGS_ADDR;
+ ops->direct_call = addr;

err = register_ftrace_function_nolock(ops);

@@ -5445,6 +5445,7 @@ __modify_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
/* Enable the tmp_ops to have the same functions as the direct ops */
ftrace_ops_init(&tmp_ops);
tmp_ops.func_hash = ops->func_hash;
+ tmp_ops.direct_call = addr;

err = register_ftrace_function_nolock(&tmp_ops);
if (err)
@@ -5466,6 +5467,7 @@ __modify_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
entry->direct = addr;
}
}
+ ops->direct_call = addr;

mutex_unlock(&ftrace_lock);

--
2.39.1.519.gcb327c4b5f-goog