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Date: Thu, 30 Oct 2014 13:00:41 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: "H. Peter Anvin" <hpa@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Jiri Kosina <jkosina@...e.cz>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Vojtech Pavlik <vojtech@...e.cz>,
Seth Jennings <sjenning@...hat.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [for-next][PATCH 2/4] ftrace/x86: Show trampoline call function
in enabled_functions
H. Peter,
Can you give me your acked-by for this?
Thanks,
-- Steve
On Mon, 27 Oct 2014 14:27:04 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
>
> The file /sys/kernel/debug/tracing/eneabled_functions is used to debug
> ftrace function hooks. Add to the output what function is being called
> by the trampoline if the arch supports it.
>
> Add support for this feature in x86_64.
>
> Cc: H. Peter Anvin <hpa@...ux.intel.com>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> ---
> arch/x86/kernel/ftrace.c | 98 ++++++++++++++++++++++++++++++++++++++++++------
> kernel/trace/ftrace.c | 22 ++++++++++-
> 2 files changed, 106 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> index e4d48f6cad86..ca17c20a1010 100644
> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -48,7 +48,7 @@ int ftrace_arch_code_modify_post_process(void)
> union ftrace_code_union {
> char code[MCOUNT_INSN_SIZE];
> struct {
> - char e8;
> + unsigned char e8;
> int offset;
> } __attribute__((packed));
> };
> @@ -797,12 +797,26 @@ static unsigned long create_trampoline(struct ftrace_ops *ops)
> return (unsigned long)trampoline;
> }
>
> +static unsigned long calc_trampoline_call_offset(bool save_regs)
> +{
> + unsigned long start_offset;
> + unsigned long call_offset;
> +
> + if (save_regs) {
> + start_offset = (unsigned long)ftrace_regs_caller;
> + call_offset = (unsigned long)ftrace_regs_call;
> + } else {
> + start_offset = (unsigned long)ftrace_caller;
> + call_offset = (unsigned long)ftrace_call;
> + }
> +
> + return call_offset - start_offset;
> +}
> +
> void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
> {
> ftrace_func_t func;
> unsigned char *new;
> - unsigned long start_offset;
> - unsigned long call_offset;
> unsigned long offset;
> unsigned long ip;
> int ret;
> @@ -820,15 +834,7 @@ void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
> return;
> }
>
> - if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
> - start_offset = (unsigned long)ftrace_regs_caller;
> - call_offset = (unsigned long)ftrace_regs_call;
> - } else {
> - start_offset = (unsigned long)ftrace_caller;
> - call_offset = (unsigned long)ftrace_call;
> - }
> -
> - offset = call_offset - start_offset;
> + offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
> ip = ops->trampoline + offset;
>
> func = ftrace_ops_get_func(ops);
> @@ -840,6 +846,74 @@ void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
> /* The update should never fail */
> WARN_ON(ret);
> }
> +
> +/* Return the address of the function the trampoline calls */
> +static void *addr_from_call(void *ptr)
> +{
> + union ftrace_code_union calc;
> + int ret;
> +
> + ret = probe_kernel_read(&calc, ptr, MCOUNT_INSN_SIZE);
> + if (WARN_ON_ONCE(ret < 0))
> + return NULL;
> +
> + /* Make sure this is a call */
> + if (WARN_ON_ONCE(calc.e8 != 0xe8)) {
> + pr_warn("Expected e8, got %x\n", calc.e8);
> + return NULL;
> + }
> +
> + return ptr + MCOUNT_INSN_SIZE + calc.offset;
> +}
> +
> +void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
> + unsigned long frame_pointer);
> +
> +/*
> + * If the ops->trampoline was not allocated, then it probably
> + * has a static trampoline func, or is the ftrace caller itself.
> + */
> +static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
> +{
> + unsigned long offset;
> + bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
> + void *ptr;
> +
> + if (ops && ops->trampoline) {
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> + /*
> + * We only know about function graph tracer setting as static
> + * trampoline.
> + */
> + if (ops->trampoline == FTRACE_GRAPH_ADDR)
> + return (void *)prepare_ftrace_return;
> +#endif
> + return NULL;
> + }
> +
> + offset = calc_trampoline_call_offset(save_regs);
> +
> + if (save_regs)
> + ptr = (void *)FTRACE_REGS_ADDR + offset;
> + else
> + ptr = (void *)FTRACE_ADDR + offset;
> +
> + return addr_from_call(ptr);
> +}
> +
> +void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
> +{
> + unsigned long offset;
> +
> + /* If we didn't allocate this trampoline, consider it static */
> + if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
> + return static_tramp_func(ops, rec);
> +
> + offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
> + return addr_from_call((void *)ops->trampoline + offset);
> +}
> +
> +
> #endif /* CONFIG_X86_64 */
> #endif /* CONFIG_DYNAMIC_FTRACE */
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 15f85eac7e95..422e1f8300b1 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -2952,6 +2952,22 @@ static void t_stop(struct seq_file *m, void *p)
> mutex_unlock(&ftrace_lock);
> }
>
> +void * __weak
> +arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
> +{
> + return NULL;
> +}
> +
> +static void add_trampoline_func(struct seq_file *m, struct ftrace_ops *ops,
> + struct dyn_ftrace *rec)
> +{
> + void *ptr;
> +
> + ptr = arch_ftrace_trampoline_func(ops, rec);
> + if (ptr)
> + seq_printf(m, " ->%pS", ptr);
> +}
> +
> static int t_show(struct seq_file *m, void *v)
> {
> struct ftrace_iterator *iter = m->private;
> @@ -2975,19 +2991,21 @@ static int t_show(struct seq_file *m, void *v)
>
> seq_printf(m, "%ps", (void *)rec->ip);
> if (iter->flags & FTRACE_ITER_ENABLED) {
> + struct ftrace_ops *ops = NULL;
> +
> seq_printf(m, " (%ld)%s",
> ftrace_rec_count(rec),
> rec->flags & FTRACE_FL_REGS ? " R" : " ");
> if (rec->flags & FTRACE_FL_TRAMP_EN) {
> - struct ftrace_ops *ops;
> -
> ops = ftrace_find_tramp_ops_any(rec);
> if (ops)
> seq_printf(m, "\ttramp: %pS",
> (void *)ops->trampoline);
> else
> seq_printf(m, "\ttramp: ERROR!");
> +
> }
> + add_trampoline_func(m, ops, rec);
> }
>
> seq_printf(m, "\n");
--
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