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    SubjectRe: [RFC PATCH v2 20/31] function_graph: Add a new exit handler with parent_ip and ftrace_regs
    On Wed,  8 Nov 2023 23:28:11 +0900
    "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:

    > From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
    >
    > Add a new return handler to fgraph_ops as 'retregfunc' which takes
    > parent_ip and ftrace_regs instead of ftrace_graph_ret. This handler
    > is available only if the arch support CONFIG_HAVE_FUNCTION_GRAPH_FREGS.
    > Note that the 'retfunc' and 'reregfunc' are mutual exclusive.
    > You can set only one of them.
    >
    > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
    > ---
    > arch/x86/include/asm/ftrace.h | 2 +
    > include/linux/ftrace.h | 10 +++++-
    > kernel/trace/Kconfig | 5 ++-
    > kernel/trace/fgraph.c | 74 +++++++++++++++++++++++++++--------------
    > 4 files changed, 63 insertions(+), 28 deletions(-)
    >
    > diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
    > index fc60974a1d89..4701d009c215 100644
    > --- a/arch/x86/include/asm/ftrace.h
    > +++ b/arch/x86/include/asm/ftrace.h
    > @@ -72,6 +72,8 @@ arch_ftrace_get_regs(struct ftrace_regs *fregs)
    > override_function_with_return(&(fregs)->regs)
    > #define ftrace_regs_query_register_offset(name) \
    > regs_query_register_offset(name)
    > +#define ftrace_regs_get_frame_pointer(fregs) \
    > + frame_pointer(&(fregs)->regs)
    >
    > struct ftrace_ops;
    > #define ftrace_graph_func ftrace_graph_func
    > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
    > index c91b234949d5..8efccd911d41 100644
    > --- a/include/linux/ftrace.h
    > +++ b/include/linux/ftrace.h
    > @@ -43,7 +43,9 @@ struct dyn_ftrace;
    >
    > char *arch_ftrace_match_adjust(char *str, const char *search);
    >
    > -#ifdef CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
    > +#ifdef CONFIG_HAVE_FUNCTION_GRAPH_FREGS
    > +unsigned long ftrace_return_to_handler(struct ftrace_regs *fregs);
    > +#elif defined(CONFIG_HAVE_FUNCTION_GRAPH_RETVAL)
    > struct fgraph_ret_regs;
    > unsigned long ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs);
    > #else
    > @@ -156,6 +158,7 @@ struct ftrace_regs {
    > #define ftrace_regs_set_instruction_pointer(fregs, ip) do { } while (0)
    > #endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
    >
    > +
    > static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs)
    > {
    > if (!fregs)
    > @@ -1066,6 +1069,10 @@ typedef int (*trace_func_graph_regs_ent_t)(unsigned long func,
    > unsigned long parent_ip,
    > struct ftrace_regs *fregs,
    > struct fgraph_ops *); /* entry w/ regs */
    > +typedef void (*trace_func_graph_regs_ret_t)(unsigned long func,
    > + unsigned long parent_ip,
    > + struct ftrace_regs *,
    > + struct fgraph_ops *); /* return w/ regs */
    >
    > extern int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace, struct fgraph_ops *gops);
    >
    > @@ -1075,6 +1082,7 @@ struct fgraph_ops {
    > trace_func_graph_ent_t entryfunc;
    > trace_func_graph_ret_t retfunc;
    > trace_func_graph_regs_ent_t entryregfunc;
    > + trace_func_graph_regs_ret_t retregfunc;
    > struct ftrace_ops ops; /* for the hash lists */
    > void *private;
    > int idx;
    > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
    > index 61c541c36596..308b3bec01b1 100644
    > --- a/kernel/trace/Kconfig
    > +++ b/kernel/trace/Kconfig
    > @@ -34,6 +34,9 @@ config HAVE_FUNCTION_GRAPH_TRACER
    > config HAVE_FUNCTION_GRAPH_RETVAL
    > bool
    >
    > +config HAVE_FUNCTION_GRAPH_FREGS
    > + bool
    > +
    > config HAVE_DYNAMIC_FTRACE
    > bool
    > help
    > @@ -232,7 +235,7 @@ config FUNCTION_GRAPH_TRACER
    >
    > config FUNCTION_GRAPH_RETVAL
    > bool "Kernel Function Graph Return Value"
    > - depends on HAVE_FUNCTION_GRAPH_RETVAL
    > + depends on HAVE_FUNCTION_GRAPH_RETVAL || HAVE_FUNCTION_GRAPH_FREGS
    > depends on FUNCTION_GRAPH_TRACER
    > default n
    > help
    > diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
    > index 6567b18c6c54..cf240914ef9b 100644
    > --- a/kernel/trace/fgraph.c
    > +++ b/kernel/trace/fgraph.c
    > @@ -623,8 +623,7 @@ int function_graph_enter_regs(unsigned long ret, unsigned long func,
    >
    > /* Retrieve a function return address to the trace stack on thread info.*/
    > static struct ftrace_ret_stack *
    > -ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
    > - unsigned long frame_pointer)
    > +ftrace_pop_return_trace(unsigned long *ret, unsigned long frame_pointer)
    > {
    > struct ftrace_ret_stack *ret_stack;
    > int index;
    > @@ -669,10 +668,6 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
    > #endif
    >
    > *ret = ret_stack->ret;
    > - trace->func = ret_stack->func;
    > - trace->calltime = ret_stack->calltime;
    > - trace->overrun = atomic_read(&current->trace_overrun);
    > - trace->depth = current->curr_ret_depth;
    > /*
    > * We still want to trace interrupts coming in if
    > * max_depth is set to 1. Make sure the decrement is
    > @@ -711,22 +706,43 @@ static struct notifier_block ftrace_suspend_notifier = {
    > /* fgraph_ret_regs is not defined without CONFIG_FUNCTION_GRAPH_RETVAL */
    > struct fgraph_ret_regs;
    >
    > +static void fgraph_call_retfunc(struct ftrace_regs *fregs,
    > + struct fgraph_ret_regs *ret_regs,
    > + struct ftrace_ret_stack *ret_stack,
    > + struct fgraph_ops *gops)
    > +{
    > + struct ftrace_graph_ret trace;
    > +
    > + trace.func = ret_stack->func;
    > + trace.calltime = ret_stack->calltime;
    > + trace.overrun = atomic_read(&current->trace_overrun);
    > + trace.depth = current->curr_ret_depth;
    > + trace.rettime = trace_clock_local();
    > +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
    > + if (fregs)
    > + trace.retval = ftrace_regs_return_value(fregs);
    > + else
    > + trace.retval = fgraph_ret_regs_return_value(ret_regs);
    > +#endif
    > + gops->retfunc(&trace, gops);
    > +}
    > +
    > /*
    > * Send the trace to the ring-buffer.
    > * @return the original return address.
    > */
    > -static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs,
    > +static unsigned long __ftrace_return_to_handler(struct ftrace_regs *fregs,
    > + struct fgraph_ret_regs *ret_regs,
    > unsigned long frame_pointer)
    > {
    > struct ftrace_ret_stack *ret_stack;
    > - struct ftrace_graph_ret trace;
    > - unsigned long ret;
    > + struct fgraph_ops *gops;
    > int curr_ret_stack;
    > + unsigned long ret;
    > int stop_at;
    > int index;
    > - int idx;
    >
    > - ret_stack = ftrace_pop_return_trace(&trace, &ret, frame_pointer);
    > + ret_stack = ftrace_pop_return_trace(&ret, frame_pointer);
    >
    > if (unlikely(!ret_stack)) {
    > ftrace_graph_stop();
    > @@ -735,11 +751,6 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
    > return (unsigned long)panic;
    > }
    >
    > - trace.rettime = trace_clock_local();
    > -#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
    > - trace.retval = fgraph_ret_regs_return_value(ret_regs);
    > -#endif
    > -

    So, here we need

    if (fregs)
    ftrace_regs_set_instruction_pointer(fregs, ret);

    set return address to the instruction pointer.

    Thank you,

    > curr_ret_stack = current->curr_ret_stack;
    > index = get_ret_stack_index(current, curr_ret_stack - 1);
    >
    > @@ -752,8 +763,11 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
    > val = current->ret_stack[curr_ret_stack - 1];
    > switch (__get_type(val)) {
    > case FGRAPH_TYPE_ARRAY:
    > - idx = __get_array(val);
    > - fgraph_array[idx]->retfunc(&trace, fgraph_array[idx]);
    > + gops = fgraph_array[__get_array(val)];
    > + if (gops->retregfunc)
    > + gops->retregfunc(ret_stack->func, ret, fregs, gops);
    > + else
    > + fgraph_call_retfunc(fregs, ret_regs, ret_stack, gops);
    > curr_ret_stack -= __get_index(val);
    > break;
    > case FGRAPH_TYPE_RESERVED:
    > @@ -777,20 +791,22 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
    > return ret;
    > }
    >
    > -/*
    > - * After all architecures have selected HAVE_FUNCTION_GRAPH_RETVAL, we can
    > - * leave only ftrace_return_to_handler(ret_regs).
    > - */
    > -#ifdef CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
    > +#ifdef CONFIG_HAVE_FUNCTION_GRAPH_FREGS
    > +unsigned long ftrace_return_to_handler(struct ftrace_regs *fregs)
    > +{
    > + return __ftrace_return_to_handler(fregs, NULL,
    > + ftrace_regs_get_frame_pointer(fregs));
    > +}
    > +#elif defined(CONFIG_HAVE_FUNCTION_GRAPH_RETVAL)
    > unsigned long ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs)
    > {
    > - return __ftrace_return_to_handler(ret_regs,
    > + return __ftrace_return_to_handler(NULL, ret_regs,
    > fgraph_ret_regs_frame_pointer(ret_regs));
    > }
    > #else
    > unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
    > {
    > - return __ftrace_return_to_handler(NULL, frame_pointer);
    > + return __ftrace_return_to_handler(NULL, NULL, frame_pointer);
    > }
    > #endif
    >
    > @@ -1131,9 +1147,15 @@ int register_ftrace_graph(struct fgraph_ops *gops)
    > int ret = 0;
    > int i;
    >
    > - if (gops->entryfunc && gops->entryregfunc)
    > + if ((gops->entryfunc && gops->entryregfunc) ||
    > + (gops->retfunc && gops->retregfunc))
    > return -EINVAL;
    >
    > +#ifndef CONFIG_HAVE_FUNCTION_GRAPH_FREGS
    > + if (gops->retregfunc)
    > + return -EOPNOTSUPP;
    > +#endif
    > +
    > mutex_lock(&ftrace_lock);
    >
    > if (!gops->ops.func) {
    >


    --
    Masami Hiramatsu (Google) <mhiramat@kernel.org>

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