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ftrace: Store direct called addresses in their ops

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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.

Link: https://lkml.kernel.org/r/20230321140424.345218-6-revest@chromium.org

Signed-off-by: Florent Revest <revest@chromium.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Florent Revest 2023-03-21 15:04:22 +01:00 • committed by Steven Rostedt (Google)
parent da8bdfbd42
commit dbaccb618f
2 changed files with 8 additions and 2 deletions
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3
include/linux/ftrace.h
View file

@ -321,6 +321,9 @@ struct ftrace_ops {
unsigned long trampoline_size; unsigned long trampoline_size;
struct list_head list; struct list_head list;
ftrace_ops_func_t ops_func; ftrace_ops_func_t ops_func;
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
unsigned long direct_call;
#endif
#endif #endif
}; };

7
kernel/trace/ftrace.c
View file

@ -2583,9 +2583,8 @@ ftrace_add_rec_direct(unsigned long ip, unsigned long addr,
static void call_direct_funcs(unsigned long ip, unsigned long pip, static void call_direct_funcs(unsigned long ip, unsigned long pip,
struct ftrace_ops *ops, struct ftrace_regs *fregs) struct ftrace_ops *ops, struct ftrace_regs *fregs)
{ {
unsigned long addr; unsigned long addr = READ_ONCE(ops->direct_call);
addr = ftrace_find_rec_direct(ip);
if (!addr) if (!addr)
return; return;
@ -5381,6 +5380,7 @@ int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
ops->func = call_direct_funcs; ops->func = call_direct_funcs;
ops->flags = MULTI_FLAGS; ops->flags = MULTI_FLAGS;
ops->trampoline = FTRACE_REGS_ADDR; ops->trampoline = FTRACE_REGS_ADDR;
ops->direct_call = addr;
err = register_ftrace_function_nolock(ops); err = register_ftrace_function_nolock(ops);
@ -5455,6 +5455,7 @@ __modify_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
/* Enable the tmp_ops to have the same functions as the direct ops */ /* Enable the tmp_ops to have the same functions as the direct ops */
ftrace_ops_init(&tmp_ops); ftrace_ops_init(&tmp_ops);
tmp_ops.func_hash = ops->func_hash; tmp_ops.func_hash = ops->func_hash;
tmp_ops.direct_call = addr;
err = register_ftrace_function_nolock(&tmp_ops); err = register_ftrace_function_nolock(&tmp_ops);
if (err) if (err)
@ -5476,6 +5477,8 @@ __modify_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
entry->direct = addr; entry->direct = addr;
} }
} }
/* Prevent store tearing if a trampoline concurrently accesses the value */
WRITE_ONCE(ops->direct_call, addr);
mutex_unlock(&ftrace_lock); mutex_unlock(&ftrace_lock);