bpf: Revert bpf_overrid_function() helper changes.

NACK'd by x86 maintainer.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

arch/Kconfig

@@ -196,9 +196,6 @@ config HAVE_OPTPROBES
 config HAVE_KPROBES_ON_FTRACE
 	bool
 
-config HAVE_KPROBE_OVERRIDE
-	bool
-
 config HAVE_NMI
 	bool
 

arch/x86/Kconfig

@@ -153,7 +153,6 @@ config X86
 	select HAVE_KERNEL_XZ
 	select HAVE_KPROBES
 	select HAVE_KPROBES_ON_FTRACE
-	select HAVE_KPROBE_OVERRIDE
 	select HAVE_KRETPROBES
 	select HAVE_KVM
 	select HAVE_LIVEPATCH			if X86_64

arch/x86/include/asm/kprobes.h

@@ -67,10 +67,6 @@ 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
-
 /* Architecture specific copy of original instruction*/
 struct arch_specific_insn {
 	/* copy of the original instruction */

arch/x86/include/asm/ptrace.h

@@ -109,11 +109,6 @@ static inline unsigned long regs_return_value(struct pt_regs *regs)
 	return regs->ax;
 }
 
-static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc)
-{
-	regs->ax = rc;
-}
-
 /*
  * user_mode(regs) determines whether a register set came from user
  * mode.  On x86_32, this is true if V8086 mode was enabled OR if the

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);

include/linux/filter.h

@@ -459,8 +459,7 @@ struct bpf_prog {
 				locked:1,	/* Program image locked? */
 				gpl_compatible:1, /* Is filter GPL compatible? */
 				cb_access:1,	/* Is control block accessed? */
-				dst_needed:1,	/* Do we need dst entry? */
-				kprobe_override:1; /* Do we override a kprobe? */
+				dst_needed:1;	/* Do we need dst entry? */
 	kmemcheck_bitfield_end(meta);
 	enum bpf_prog_type	type;		/* Type of BPF program */
 	u32			len;		/* Number of filter blocks */

include/linux/trace_events.h

@@ -523,7 +523,6 @@ do {									\
 struct perf_event;
 
 DECLARE_PER_CPU(struct pt_regs, perf_trace_regs);
-DECLARE_PER_CPU(int, bpf_kprobe_override);
 
 extern int  perf_trace_init(struct perf_event *event);
 extern void perf_trace_destroy(struct perf_event *event);

include/uapi/linux/bpf.h

@@ -677,10 +677,6 @@ union bpf_attr {
  *     @buf: buf to fill
  *     @buf_size: size of the buf
  *     Return : 0 on success or negative error code
- *
- * int bpf_override_return(pt_regs, rc)
- *	@pt_regs: pointer to struct pt_regs
- *	@rc: the return value to set
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -740,8 +736,7 @@ union bpf_attr {
 	FN(xdp_adjust_meta),		\
 	FN(perf_event_read_value),	\
 	FN(perf_prog_read_value),	\
-	FN(getsockopt),			\
-	FN(override_return),
+	FN(getsockopt),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call

kernel/bpf/core.c

@@ -1326,9 +1326,6 @@ EVAL4(PROG_NAME_LIST, 416, 448, 480, 512)
 bool bpf_prog_array_compatible(struct bpf_array *array,
 			       const struct bpf_prog *fp)
 {
-	if (fp->kprobe_override)
-		return false;
-
 	if (!array->owner_prog_type) {
 		/* There's no owner yet where we could check for
 		 * compatibility.

kernel/bpf/verifier.c

@@ -4357,8 +4357,6 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
 			prog->dst_needed = 1;
 		if (insn->imm == BPF_FUNC_get_prandom_u32)
 			bpf_user_rnd_init_once();
-		if (insn->imm == BPF_FUNC_override_return)
-			prog->kprobe_override = 1;
 		if (insn->imm == BPF_FUNC_tail_call) {
 			/* If we tail call into other programs, we
 			 * cannot make any assumptions since they can

kernel/events/core.c

@@ -8171,13 +8171,6 @@ static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd)
 		return -EINVAL;
 	}
 
-	/* Kprobe override only works for kprobes, not uprobes. */
-	if (prog->kprobe_override &&
-	    !(event->tp_event->flags & TRACE_EVENT_FL_KPROBE)) {
-		bpf_prog_put(prog);
-		return -EINVAL;
-	}
-
 	if (is_tracepoint || is_syscall_tp) {
 		int off = trace_event_get_offsets(event->tp_event);
 

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 {

samples/bpf/Makefile

@@ -15,7 +15,6 @@ hostprogs-y += tracex3
 hostprogs-y += tracex4
 hostprogs-y += tracex5
 hostprogs-y += tracex6
-hostprogs-y += tracex7
 hostprogs-y += test_probe_write_user
 hostprogs-y += trace_output
 hostprogs-y += lathist
@@ -62,7 +61,6 @@ tracex3-objs := bpf_load.o $(LIBBPF) tracex3_user.o
 tracex4-objs := bpf_load.o $(LIBBPF) tracex4_user.o
 tracex5-objs := bpf_load.o $(LIBBPF) tracex5_user.o
 tracex6-objs := bpf_load.o $(LIBBPF) tracex6_user.o
-tracex7-objs := bpf_load.o $(LIBBPF) tracex7_user.o
 load_sock_ops-objs := bpf_load.o $(LIBBPF) load_sock_ops.o
 test_probe_write_user-objs := bpf_load.o $(LIBBPF) test_probe_write_user_user.o
 trace_output-objs := bpf_load.o $(LIBBPF) trace_output_user.o
@@ -106,7 +104,6 @@ always += tracex3_kern.o
 always += tracex4_kern.o
 always += tracex5_kern.o
 always += tracex6_kern.o
-always += tracex7_kern.o
 always += sock_flags_kern.o
 always += test_probe_write_user_kern.o
 always += trace_output_kern.o
@@ -161,7 +158,6 @@ HOSTLOADLIBES_tracex3 += -lelf
 HOSTLOADLIBES_tracex4 += -lelf -lrt
 HOSTLOADLIBES_tracex5 += -lelf
 HOSTLOADLIBES_tracex6 += -lelf
-HOSTLOADLIBES_tracex7 += -lelf
 HOSTLOADLIBES_test_cgrp2_sock2 += -lelf
 HOSTLOADLIBES_load_sock_ops += -lelf
 HOSTLOADLIBES_test_probe_write_user += -lelf

samples/bpf/test_override_return.sh

-#!/bin/bash
-
-rm -f testfile.img
-dd if=/dev/zero of=testfile.img bs=1M seek=1000 count=1
-DEVICE=$(losetup --show -f testfile.img)
-mkfs.btrfs -f $DEVICE
-mkdir tmpmnt
-./tracex7 $DEVICE
-if [ $? -eq 0 ]
-then
-	echo "SUCCESS!"
-else
-	echo "FAILED!"
-fi
-losetup -d $DEVICE

samples/bpf/tracex7_kern.c

-#include <uapi/linux/ptrace.h>
-#include <uapi/linux/bpf.h>
-#include <linux/version.h>
-#include "bpf_helpers.h"
-
-SEC("kprobe/open_ctree")
-int bpf_prog1(struct pt_regs *ctx)
-{
-	unsigned long rc = -12;
-
-	bpf_override_return(ctx, rc);
-	return 0;
-}
-
-char _license[] SEC("license") = "GPL";
-u32 _version SEC("version") = LINUX_VERSION_CODE;

samples/bpf/tracex7_user.c

-#define _GNU_SOURCE
-
-#include <stdio.h>
-#include <linux/bpf.h>
-#include <unistd.h>
-#include "libbpf.h"
-#include "bpf_load.h"
-
-int main(int argc, char **argv)
-{
-	FILE *f;
-	char filename[256];
-	char command[256];
-	int ret;
-
-	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
-
-	if (load_bpf_file(filename)) {
-		printf("%s", bpf_log_buf);
-		return 1;
-	}
-
-	snprintf(command, 256, "mount %s tmpmnt/", argv[1]);
-	f = popen(command, "r");
-	ret = pclose(f);
-
-	return ret ? 0 : 1;
-}

tools/include/uapi/linux/bpf.h

@@ -677,10 +677,6 @@ union bpf_attr {
  *     @buf: buf to fill
  *     @buf_size: size of the buf
  *     Return : 0 on success or negative error code
- *
- * int bpf_override_return(pt_regs, rc)
- *	@pt_regs: pointer to struct pt_regs
- *	@rc: the return value to set
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -740,8 +736,7 @@ union bpf_attr {
 	FN(xdp_adjust_meta),		\
 	FN(perf_event_read_value),	\
 	FN(perf_prog_read_value),	\
-	FN(getsockopt),			\
-	FN(override_return),
+	FN(getsockopt),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call

tools/testing/selftests/bpf/bpf_helpers.h

@@ -82,8 +82,7 @@ static int (*bpf_perf_event_read_value)(void *map, unsigned long long flags,
 static int (*bpf_perf_prog_read_value)(void *ctx, void *buf,
 				       unsigned int buf_size) =
 	(void *) BPF_FUNC_perf_prog_read_value;
-static int (*bpf_override_return)(void *ctx, unsigned long rc) =
-	(void *) BPF_FUNC_override_return;
+
 
 /* llvm builtin functions that eBPF C program may use to
  * emit BPF_LD_ABS and BPF_LD_IND instructions