samples/bpf: add a test for bpf_override_return
This adds a basic test for bpf_override_return to verify it works. We override the main function for mounting a btrfs fs so it'll return -ENOMEM and then make sure that trying to mount a btrfs fs will fail. Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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9802d86585
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@ -12,6 +12,7 @@ hostprogs-y += tracex3
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hostprogs-y += tracex4
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hostprogs-y += tracex5
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hostprogs-y += tracex6
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hostprogs-y += tracex7
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hostprogs-y += test_probe_write_user
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hostprogs-y += trace_output
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hostprogs-y += lathist
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@ -58,6 +59,7 @@ tracex3-objs := bpf_load.o $(LIBBPF) tracex3_user.o
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tracex4-objs := bpf_load.o $(LIBBPF) tracex4_user.o
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tracex5-objs := bpf_load.o $(LIBBPF) tracex5_user.o
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tracex6-objs := bpf_load.o $(LIBBPF) tracex6_user.o
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tracex7-objs := bpf_load.o $(LIBBPF) tracex7_user.o
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load_sock_ops-objs := bpf_load.o $(LIBBPF) load_sock_ops.o
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test_probe_write_user-objs := bpf_load.o $(LIBBPF) test_probe_write_user_user.o
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trace_output-objs := bpf_load.o $(LIBBPF) trace_output_user.o
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@ -101,6 +103,7 @@ always += tracex3_kern.o
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always += tracex4_kern.o
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always += tracex5_kern.o
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always += tracex6_kern.o
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always += tracex7_kern.o
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always += sock_flags_kern.o
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always += test_probe_write_user_kern.o
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always += trace_output_kern.o
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@ -155,6 +158,7 @@ HOSTLOADLIBES_tracex3 += -lelf
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HOSTLOADLIBES_tracex4 += -lelf -lrt
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HOSTLOADLIBES_tracex5 += -lelf
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HOSTLOADLIBES_tracex6 += -lelf
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HOSTLOADLIBES_tracex7 += -lelf
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HOSTLOADLIBES_test_cgrp2_sock2 += -lelf
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HOSTLOADLIBES_load_sock_ops += -lelf
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HOSTLOADLIBES_test_probe_write_user += -lelf
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15
samples/bpf/test_override_return.sh
Executable file
15
samples/bpf/test_override_return.sh
Executable file
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@ -0,0 +1,15 @@
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#!/bin/bash
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rm -f testfile.img
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dd if=/dev/zero of=testfile.img bs=1M seek=1000 count=1
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DEVICE=$(losetup --show -f testfile.img)
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mkfs.btrfs -f $DEVICE
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mkdir tmpmnt
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./tracex7 $DEVICE
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if [ $? -eq 0 ]
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then
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echo "SUCCESS!"
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else
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echo "FAILED!"
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fi
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losetup -d $DEVICE
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samples/bpf/tracex7_kern.c
Normal file
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samples/bpf/tracex7_kern.c
Normal file
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@ -0,0 +1,16 @@
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#include <uapi/linux/ptrace.h>
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#include <uapi/linux/bpf.h>
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#include <linux/version.h>
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#include "bpf_helpers.h"
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SEC("kprobe/open_ctree")
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int bpf_prog1(struct pt_regs *ctx)
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{
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unsigned long rc = -12;
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bpf_override_return(ctx, rc);
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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u32 _version SEC("version") = LINUX_VERSION_CODE;
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samples/bpf/tracex7_user.c
Normal file
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samples/bpf/tracex7_user.c
Normal file
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@ -0,0 +1,28 @@
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <linux/bpf.h>
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#include <unistd.h>
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#include "libbpf.h"
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#include "bpf_load.h"
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int main(int argc, char **argv)
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{
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FILE *f;
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char filename[256];
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char command[256];
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int ret;
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snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
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if (load_bpf_file(filename)) {
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printf("%s", bpf_log_buf);
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return 1;
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}
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snprintf(command, 256, "mount %s tmpmnt/", argv[1]);
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f = popen(command, "r");
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ret = pclose(f);
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return ret ? 0 : 1;
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}
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@ -677,6 +677,10 @@ union bpf_attr {
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* @buf: buf to fill
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* @buf_size: size of the buf
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* Return : 0 on success or negative error code
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*
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* int bpf_override_return(pt_regs, rc)
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* @pt_regs: pointer to struct pt_regs
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* @rc: the return value to set
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*/
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#define __BPF_FUNC_MAPPER(FN) \
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FN(unspec), \
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@ -736,7 +740,8 @@ union bpf_attr {
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FN(xdp_adjust_meta), \
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FN(perf_event_read_value), \
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FN(perf_prog_read_value), \
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FN(getsockopt),
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FN(getsockopt), \
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FN(override_return),
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/* integer value in 'imm' field of BPF_CALL instruction selects which helper
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* function eBPF program intends to call
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@ -82,7 +82,8 @@ static int (*bpf_perf_event_read_value)(void *map, unsigned long long flags,
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static int (*bpf_perf_prog_read_value)(void *ctx, void *buf,
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unsigned int buf_size) =
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(void *) BPF_FUNC_perf_prog_read_value;
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static int (*bpf_override_return)(void *ctx, unsigned long rc) =
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(void *) BPF_FUNC_override_return;
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/* llvm builtin functions that eBPF C program may use to
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* emit BPF_LD_ABS and BPF_LD_IND instructions
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