bpf: Revert bpf_overrid_function() helper changes.

NACK'd by x86 maintainer.

Signed-off-by: David S. Miller <davem@davemloft.net>

kernel/trace/Kconfig

@@ -518,17 +518,6 @@ config FUNCTION_PROFILER
 
 	  If in doubt, say N.
 
-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
-	 set a different return value.  This is used for error injection.
-
 config FTRACE_MCOUNT_RECORD
 	def_bool y
 	depends on DYNAMIC_FTRACE

kernel/trace/bpf_trace.c

@@ -13,10 +13,6 @@
 #include <linux/filter.h>
 #include <linux/uaccess.h>
 #include <linux/ctype.h>
-#include <linux/kprobes.h>
-#include <asm/kprobes.h>
-
-#include "trace_probe.h"
 #include "trace.h"
 
 u64 bpf_get_stackid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
@@ -80,29 +76,6 @@ unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx)
 }
 EXPORT_SYMBOL_GPL(trace_call_bpf);
 
-#ifdef CONFIG_BPF_KPROBE_OVERRIDE
-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);
-	return 0;
-}
-#else
-BPF_CALL_2(bpf_override_return, struct pt_regs *, regs, unsigned long, rc)
-{
-	return -EINVAL;
-}
-#endif
-
-static const struct bpf_func_proto bpf_override_return_proto = {
-	.func		= bpf_override_return,
-	.gpl_only	= true,
-	.ret_type	= RET_INTEGER,
-	.arg1_type	= ARG_PTR_TO_CTX,
-	.arg2_type	= ARG_ANYTHING,
-};
-
 BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr)
 {
 	int ret;
@@ -578,10 +551,6 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
 		return &bpf_get_stackid_proto;
 	case BPF_FUNC_perf_event_read_value:
 		return &bpf_perf_event_read_value_proto;
-	case BPF_FUNC_override_return:
-		pr_warn_ratelimited("%s[%d] is installing a program with bpf_override_return helper that may cause unexpected behavior!",
-				    current->comm, task_pid_nr(current));
-		return &bpf_override_return_proto;
 	default:
 		return tracing_func_proto(func_id);
 	}
@@ -797,10 +766,6 @@ int perf_event_attach_bpf_prog(struct perf_event *event,
 	struct bpf_prog_array *new_array;
 	int ret = -EEXIST;
 
-	/* Kprobe override only works for ftrace based kprobes. */
-	if (prog->kprobe_override && !trace_kprobe_ftrace(event->tp_event))
-		return -EINVAL;
-
 	mutex_lock(&bpf_event_mutex);
 
 	if (event->prog)

kernel/trace/trace_kprobe.c

@@ -42,7 +42,6 @@ struct trace_kprobe {
 	(offsetof(struct trace_kprobe, tp.args) +	\
 	(sizeof(struct probe_arg) * (n)))
 
-DEFINE_PER_CPU(int, bpf_kprobe_override);
 
 static nokprobe_inline bool trace_kprobe_is_return(struct trace_kprobe *tk)
 {
@@ -88,12 +87,6 @@ static nokprobe_inline unsigned long trace_kprobe_nhit(struct trace_kprobe *tk)
 	return nhit;
 }
 
-int trace_kprobe_ftrace(struct trace_event_call *call)
-{
-	struct trace_kprobe *tk = (struct trace_kprobe *)call->data;
-	return kprobe_ftrace(&tk->rp.kp);
-}
-
 static int register_kprobe_event(struct trace_kprobe *tk);
 static int unregister_kprobe_event(struct trace_kprobe *tk);
 
@@ -1177,7 +1170,7 @@ static int kretprobe_event_define_fields(struct trace_event_call *event_call)
 #ifdef CONFIG_PERF_EVENTS
 
 /* Kprobe profile handler */
-static int
+static void
 kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
 {
 	struct trace_event_call *call = &tk->tp.call;
@@ -1186,29 +1179,12 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
 	int size, __size, dsize;
 	int rctx;
 
-	if (bpf_prog_array_valid(call)) {
-		int ret;
-
-		ret = trace_call_bpf(call, regs);
-
-		/*
-		 * We need to check and see if we modified the pc of the
-		 * pt_regs, and if so clear the kprobe and return 1 so that we
-		 * don't do the instruction skipping.  Also reset our state so
-		 * we are clean the next pass through.
-		 */
-		if (__this_cpu_read(bpf_kprobe_override)) {
-			__this_cpu_write(bpf_kprobe_override, 0);
-			reset_current_kprobe();
-			return 1;
-		}
-		if (!ret)
-			return 0;
-	}
+	if (bpf_prog_array_valid(call) && !trace_call_bpf(call, regs))
+		return;
 
 	head = this_cpu_ptr(call->perf_events);
 	if (hlist_empty(head))
-		return 0;
+		return;
 
 	dsize = __get_data_size(&tk->tp, regs);
 	__size = sizeof(*entry) + tk->tp.size + dsize;
@@ -1217,14 +1193,13 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
 
 	entry = perf_trace_buf_alloc(size, NULL, &rctx);
 	if (!entry)
-		return 0;
+		return;
 
 	entry->ip = (unsigned long)tk->rp.kp.addr;
 	memset(&entry[1], 0, dsize);
 	store_trace_args(sizeof(*entry), &tk->tp, regs, (u8 *)&entry[1], dsize);
 	perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
 			      head, NULL, NULL);
-	return 0;
 }
 NOKPROBE_SYMBOL(kprobe_perf_func);
 
@@ -1300,7 +1275,6 @@ static int kprobe_register(struct trace_event_call *event,
 static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs)
 {
 	struct trace_kprobe *tk = container_of(kp, struct trace_kprobe, rp.kp);
-	int ret = 0;
 
 	raw_cpu_inc(*tk->nhit);
 
@@ -1308,9 +1282,9 @@ static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs)
 		kprobe_trace_func(tk, regs);
 #ifdef CONFIG_PERF_EVENTS
 	if (tk->tp.flags & TP_FLAG_PROFILE)
-		ret = kprobe_perf_func(tk, regs);
+		kprobe_perf_func(tk, regs);
 #endif
-	return ret;
+	return 0;	/* We don't tweek kernel, so just return 0 */
 }
 NOKPROBE_SYMBOL(kprobe_dispatcher);
 

kernel/trace/trace_probe.h

@@ -253,7 +253,6 @@ 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);
 #else
 /* uprobes do not support symbol fetch methods */
 #define fetch_symbol_u8			NULL
@@ -279,11 +278,6 @@ alloc_symbol_cache(const char *sym, long offset)
 {
 	return NULL;
 }
-
-static inline int trace_kprobe_ftrace(struct trace_event_call *call)
-{
-	return 0;
-}
 #endif /* CONFIG_KPROBE_EVENTS */
 
 struct probe_arg {