tracing/kprobe: bpf: Check error injectable event is on function entry

Check whether error injectable event is on function entry or not.
Currently it checks the event is ftrace-based kprobes or not,
but that is wrong. It should check if the event is on the entry
of target function. Since error injection will override a function
to just return with modified return value, that operation must
be done before the target function starts making stackframe.

As a side effect, bpf error injection is no need to depend on
function-tracer. It can work with sw-breakpoint based kprobe
events too.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h
index 36abb23..367d99c 100644 (file)
--- a/arch/x86/include/asm/kprobes.h
+++ b/arch/x86/include/asm/kprobes.h
@@ -67,9 +67,7 @@ extern const int kretprobe_blacklist_size;
 void arch_remove_kprobe(struct kprobe *p);
 asmlinkage void kretprobe_trampoline(void);
 
-#ifdef CONFIG_KPROBES_ON_FTRACE
-extern void arch_ftrace_kprobe_override_function(struct pt_regs *regs);
-#endif
+extern void arch_kprobe_override_function(struct pt_regs *regs);
 
 /* Architecture specific copy of original instruction*/
 struct arch_specific_insn {

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index bd36f3c..b02a377 100644 (file)
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -1183,3 +1183,17 @@ int arch_trampoline_kprobe(struct kprobe *p)
 {
        return 0;
 }
+
+asmlinkage void override_func(void);
+asm(
+       ".type override_func, @function\n"
+       "override_func:\n"
+       "       ret\n"
+       ".size override_func, .-override_func\n"
+);
+
+void arch_kprobe_override_function(struct pt_regs *regs)
+{
+       regs->ip = (unsigned long)&override_func;
+}
+NOKPROBE_SYMBOL(arch_kprobe_override_function);

diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c
index 1ea748d..8dc0161 100644 (file)
--- a/arch/x86/kernel/kprobes/ftrace.c
+++ b/arch/x86/kernel/kprobes/ftrace.c
@@ -97,17 +97,3 @@ int arch_prepare_kprobe_ftrace(struct kprobe *p)
        p->ainsn.boostable = false;
        return 0;
 }
-
-asmlinkage void override_func(void);
-asm(
-       ".type override_func, @function\n"
-       "override_func:\n"
-       "       ret\n"
-       ".size override_func, .-override_func\n"
-);
-
-void arch_ftrace_kprobe_override_function(struct pt_regs *regs)
-{
-       regs->ip = (unsigned long)&override_func;
-}
-NOKPROBE_SYMBOL(arch_ftrace_kprobe_override_function);

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index ae3a2d5..6400e1b 100644 (file)
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -533,9 +533,7 @@ config FUNCTION_PROFILER
 config BPF_KPROBE_OVERRIDE
        bool "Enable BPF programs to override a kprobed function"
        depends on BPF_EVENTS
-       depends on KPROBES_ON_FTRACE
        depends on HAVE_KPROBE_OVERRIDE
-       depends on DYNAMIC_FTRACE_WITH_REGS
        default n
        help
         Allows BPF to override the execution of a probed function and

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index f6d2327..1966ad3 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -85,7 +85,7 @@ BPF_CALL_2(bpf_override_return, struct pt_regs *, regs, unsigned long, rc)
 {
        __this_cpu_write(bpf_kprobe_override, 1);
        regs_set_return_value(regs, rc);
-       arch_ftrace_kprobe_override_function(regs);
+       arch_kprobe_override_function(regs);
        return 0;
 }
 
@@ -800,11 +800,11 @@ int perf_event_attach_bpf_prog(struct perf_event *event,
        int ret = -EEXIST;
 
        /*
-        * Kprobe override only works for ftrace based kprobes, and only if they
-        * are on the opt-in list.
+        * Kprobe override only works if they are on the function entry,
+        * and only if they are on the opt-in list.
         */
        if (prog->kprobe_override &&
-           (!trace_kprobe_ftrace(event->tp_event) ||
+           (!trace_kprobe_on_func_entry(event->tp_event) ||
             !trace_kprobe_error_injectable(event->tp_event)))
                return -EINVAL;
 

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 91f4b57..3c8deb9 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -88,13 +88,16 @@ static nokprobe_inline unsigned long trace_kprobe_nhit(struct trace_kprobe *tk)
        return nhit;
 }
 
-int trace_kprobe_ftrace(struct trace_event_call *call)
+bool trace_kprobe_on_func_entry(struct trace_event_call *call)
 {
        struct trace_kprobe *tk = (struct trace_kprobe *)call->data;
-       return kprobe_ftrace(&tk->rp.kp);
+
+       return kprobe_on_func_entry(tk->rp.kp.addr,
+                       tk->rp.kp.addr ? NULL : tk->rp.kp.symbol_name,
+                       tk->rp.kp.addr ? 0 : tk->rp.kp.offset);
 }
 
-int trace_kprobe_error_injectable(struct trace_event_call *call)
+bool trace_kprobe_error_injectable(struct trace_event_call *call)
 {
        struct trace_kprobe *tk = (struct trace_kprobe *)call->data;
        unsigned long addr;

diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 5e54d74..e101c5b 100644 (file)
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -252,8 +252,8 @@ struct symbol_cache;
 unsigned long update_symbol_cache(struct symbol_cache *sc);
 void free_symbol_cache(struct symbol_cache *sc);
 struct symbol_cache *alloc_symbol_cache(const char *sym, long offset);
-int trace_kprobe_ftrace(struct trace_event_call *call);
-int trace_kprobe_error_injectable(struct trace_event_call *call);
+bool trace_kprobe_on_func_entry(struct trace_event_call *call);
+bool trace_kprobe_error_injectable(struct trace_event_call *call);
 #else
 /* uprobes do not support symbol fetch methods */
 #define fetch_symbol_u8                        NULL
@@ -280,14 +280,14 @@ alloc_symbol_cache(const char *sym, long offset)
        return NULL;
 }
 
-static inline int trace_kprobe_ftrace(struct trace_event_call *call)
+static inline bool trace_kprobe_on_func_entry(struct trace_event_call *call)
 {
-       return 0;
+       return false;
 }
 
-static inline int trace_kprobe_error_injectable(struct trace_event_call *call)
+static inline bool trace_kprobe_error_injectable(struct trace_event_call *call)
 {
-       return 0;
+       return false;
 }
 #endif /* CONFIG_KPROBE_EVENTS */