On Mon, 23 Dec 2024 15:13:48 -0500 Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > From: Sven Schnelle <svens@xxxxxxxxxxxxx> > > Add a function to decode argument types with the help of BTF. Will > be used to display arguments in the function and function graph > tracer. > > It can only handle simply arguments and up to FTRACE_REGS_MAX_ARGS number > of arguments. When it hits a max, it will print ", ...": > > page_to_skb(vi=0xffff8d53842dc980, rq=0xffff8d53843a0800, page=0xfffffc2e04337c00, offset=6160, len=64, truesize=1536, ...) > > And if it hits an argument that is not recognized, it will print the raw > value and the type of argument it is: > > make_vfsuid(idmap=0xffffffff87f99db8, fs_userns=0xffffffff87e543c0, kuid=0x0 (STRUCT)) > __pti_set_user_pgtbl(pgdp=0xffff8d5384ab47f8, pgd=0x110e74067 (STRUCT)) > > Co-developed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> > Signed-off-by: Sven Schnelle <svens@xxxxxxxxxxxxx> > Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> > --- > Changes since v1: https://lore.kernel.org/20240904065908.1009086-5-svens@xxxxxxxxxxxxx > > - Added Config option FUNCTION_TRACE_ARGS to this patch > (unconditional if dependencies are met) > > - Changed the print_function_args() function to take an array of > unsigned long args and not the ftrace_regs pointer. The ftrace_regs > should be opaque from generic code. > > - Have the function print the name of an BTF type that is not supported. > > - Added FTRACE_REGS_MAX_ARGS as the number of arguments saved in > the event and printed out. > > - Print "...," if the number of arguments goes past FTRACE_REGS_MAX_ARGS. > > include/linux/ftrace_regs.h | 5 +++ > kernel/trace/Kconfig | 6 +++ > kernel/trace/trace_output.c | 78 +++++++++++++++++++++++++++++++++++++ > kernel/trace/trace_output.h | 9 +++++ > 4 files changed, 98 insertions(+) > > diff --git a/include/linux/ftrace_regs.h b/include/linux/ftrace_regs.h > index bbc1873ca6b8..15627ceea9bc 100644 > --- a/include/linux/ftrace_regs.h > +++ b/include/linux/ftrace_regs.h > @@ -35,4 +35,9 @@ struct ftrace_regs; > > #endif /* HAVE_ARCH_FTRACE_REGS */ > > +/* This can be overridden by the architectures */ > +#ifndef FTRACE_REGS_MAX_ARGS > +# define FTRACE_REGS_MAX_ARGS 6 > +#endif > + > #endif /* _LINUX_FTRACE_REGS_H */ > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > index d570b8b9c0a9..60412c1012ef 100644 > --- a/kernel/trace/Kconfig > +++ b/kernel/trace/Kconfig > @@ -263,6 +263,12 @@ config FUNCTION_GRAPH_RETADDR > the function is called. This feature is off by default, and you can > enable it via the trace option funcgraph-retaddr. > > +config FUNCTION_TRACE_ARGS > + bool > + depends on HAVE_FUNCTION_ARG_ACCESS_API > + depends on DEBUG_INFO_BTF For using the BTF APIs, we also needs BPF_SYSCALL (DEBUG_INFO_BTF just compiles the BTF info into the kernel binary.) Others looks good to me. Revewied-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> Thanks! > + default y > + > config DYNAMIC_FTRACE > bool "enable/disable function tracing dynamically" > depends on FUNCTION_TRACER > diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c > index da748b7cbc4d..40d6c7a9e0c4 100644 > --- a/kernel/trace/trace_output.c > +++ b/kernel/trace/trace_output.c > @@ -12,8 +12,11 @@ > #include <linux/sched/clock.h> > #include <linux/sched/mm.h> > #include <linux/idr.h> > +#include <linux/btf.h> > +#include <linux/bpf.h> > > #include "trace_output.h" > +#include "trace_btf.h" > > /* must be a power of 2 */ > #define EVENT_HASHSIZE 128 > @@ -680,6 +683,81 @@ int trace_print_lat_context(struct trace_iterator *iter) > return !trace_seq_has_overflowed(s); > } > > +#ifdef CONFIG_FUNCTION_TRACE_ARGS > +void print_function_args(struct trace_seq *s, unsigned long *args, > + unsigned long func) > +{ > + const struct btf_param *param; > + const struct btf_type *t; > + const char *param_name; > + char name[KSYM_NAME_LEN]; > + unsigned long arg; > + struct btf *btf; > + s32 tid, nr = 0; > + int i; > + > + trace_seq_printf(s, "("); > + > + if (!args) > + goto out; > + if (lookup_symbol_name(func, name)) > + goto out; > + > + btf = bpf_get_btf_vmlinux(); > + if (IS_ERR_OR_NULL(btf)) > + goto out; > + > + t = btf_find_func_proto(name, &btf); > + if (IS_ERR_OR_NULL(t)) > + goto out; > + > + param = btf_get_func_param(t, &nr); > + if (!param) > + goto out_put; > + > + for (i = 0; i < nr; i++) { > + /* This only prints what the arch allows (6 args by default) */ > + if (i == FTRACE_REGS_MAX_ARGS) { > + trace_seq_puts(s, "..."); > + break; > + } > + > + arg = args[i]; > + > + param_name = btf_name_by_offset(btf, param[i].name_off); > + if (param_name) > + trace_seq_printf(s, "%s=", param_name); > + t = btf_type_skip_modifiers(btf, param[i].type, &tid); > + > + switch (t ? BTF_INFO_KIND(t->info) : BTF_KIND_UNKN) { > + case BTF_KIND_UNKN: > + trace_seq_putc(s, '?'); > + /* Still print unknown type values */ > + fallthrough; > + case BTF_KIND_PTR: > + trace_seq_printf(s, "0x%lx", arg); > + break; > + case BTF_KIND_INT: > + trace_seq_printf(s, "%ld", arg); > + break; > + case BTF_KIND_ENUM: > + trace_seq_printf(s, "%ld", arg); > + break; > + default: > + /* This does not handle complex arguments */ > + trace_seq_printf(s, "0x%lx (%s)", arg, btf_type_str(t)); > + break; > + } > + if (i < nr - 1) > + trace_seq_printf(s, ", "); > + } > +out_put: > + btf_put(btf); > +out: > + trace_seq_printf(s, ")"); > +} > +#endif > + > /** > * ftrace_find_event - find a registered event > * @type: the type of event to look for > diff --git a/kernel/trace/trace_output.h b/kernel/trace/trace_output.h > index dca40f1f1da4..2e305364f2a9 100644 > --- a/kernel/trace/trace_output.h > +++ b/kernel/trace/trace_output.h > @@ -41,5 +41,14 @@ extern struct rw_semaphore trace_event_sem; > #define SEQ_PUT_HEX_FIELD(s, x) \ > trace_seq_putmem_hex(s, &(x), sizeof(x)) > > +#ifdef CONFIG_FUNCTION_TRACE_ARGS > +void print_function_args(struct trace_seq *s, unsigned long *args, > + unsigned long func); > +#else > +static inline void print_function_args(struct trace_seq *s, unsigned long *args, > + unsigned long func) { > + trace_seq_puts(s, "()"); > +} > +#endif > #endif > > -- > 2.45.2 > > -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
