Commit af9bd3e3 authored by Daniel T. Lee's avatar Daniel T. Lee Committed by Daniel Borkmann
Browse files

samples: bpf: Fix bpf programs with kprobe/sys_connect event 



Currently, BPF programs with kprobe/sys_connect does not work properly.

Commit 34745aed ("samples/bpf: fix kprobe attachment issue on x64")
This commit modifies the bpf_load behavior of kprobe events in the x64
architecture. If the current kprobe event target starts with "sys_*",
add the prefix "__x64_" to the front of the event.

Appending "__x64_" prefix with kprobe/sys_* event was appropriate as a
solution to most of the problems caused by the commit below.

    commit d5a00528 ("syscalls/core, syscalls/x86: Rename struct
    pt_regs-based sys_*() to __x64_sys_*()")

However, there is a problem with the sys_connect kprobe event that does
not work properly. For __sys_connect event, parameters can be fetched
normally, but for __x64_sys_connect, parameters cannot be fetched.

    ffffffff818d3520 <__x64_sys_connect>:
    ffffffff818d3520: e8 fb df 32 00        callq   0xffffffff81c01520
    <__fentry__>
    ffffffff818d3525: 48 8b 57 60           movq    96(%rdi), %rdx
    ffffffff818d3529: 48 8b 77 68           movq    104(%rdi), %rsi
    ffffffff818d352d: 48 8b 7f 70           movq    112(%rdi), %rdi
    ffffffff818d3531: e8 1a ff ff ff        callq   0xffffffff818d3450
    <__sys_connect>
    ffffffff818d3536: 48 98                 cltq
    ffffffff818d3538: c3                    retq
    ffffffff818d3539: 0f 1f 80 00 00 00 00  nopl    (%rax)

As the assembly code for __x64_sys_connect shows, parameters should be
fetched and set into rdi, rsi, rdx registers prior to calling
__sys_connect.

Because of this problem, this commit fixes the sys_connect event by
first getting the value of the rdi register and then the value of the
rdi, rsi, and rdx register through an offset based on that value.

Fixes: 34745aed ("samples/bpf: fix kprobe attachment issue on x64")
Signed-off-by: default avatarDaniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200707184855.30968-2-danieltimlee@gmail.com
parent 65ffd797

samples/bpf/map_perf_test_kern.c

+6 −3
Original line number Diff line number Diff line
@@ -11,6 +11,8 @@ 
#include <bpf/bpf_helpers.h>

#include "bpf_legacy.h"

#include <bpf/bpf_tracing.h>

#include <bpf/bpf_core_read.h>

#include "trace_common.h"



#define MAX_ENTRIES 1000

#define MAX_NR_CPUS 1024
@@ -154,9 +156,10 @@ int stress_percpu_hmap_alloc(struct pt_regs *ctx) 
	return 0;

}



SEC("kprobe/sys_connect")

SEC("kprobe/" SYSCALL(sys_connect))

int stress_lru_hmap_alloc(struct pt_regs *ctx)

{

	struct pt_regs *real_regs = (struct pt_regs *)PT_REGS_PARM1_CORE(ctx);

	char fmt[] = "Failed at stress_lru_hmap_alloc. ret:%dn";

	union {

		u16 dst6[8];
@@ -175,8 +178,8 @@ int stress_lru_hmap_alloc(struct pt_regs *ctx) 
	long val = 1;

	u32 key = 0;



	in6 = (struct sockaddr_in6 *)PT_REGS_PARM2(ctx);

	addrlen = (int)PT_REGS_PARM3(ctx);

	in6 = (struct sockaddr_in6 *)PT_REGS_PARM2_CORE(real_regs);

	addrlen = (int)PT_REGS_PARM3_CORE(real_regs);



	if (addrlen != sizeof(*in6))

		return 0;

samples/bpf/test_map_in_map_kern.c

+6 −3
Original line number Diff line number Diff line
@@ -13,6 +13,8 @@ 
#include <bpf/bpf_helpers.h>

#include "bpf_legacy.h"

#include <bpf/bpf_tracing.h>

#include <bpf/bpf_core_read.h>

#include "trace_common.h"



#define MAX_NR_PORTS 65536
@@ -102,9 +104,10 @@ static __always_inline int do_inline_hash_lookup(void *inner_map, u32 port) 
	return result ? *result : -ENOENT;

}



SEC("kprobe/sys_connect")

SEC("kprobe/" SYSCALL(sys_connect))

int trace_sys_connect(struct pt_regs *ctx)

{

	struct pt_regs *real_regs = (struct pt_regs *)PT_REGS_PARM1_CORE(ctx);

	struct sockaddr_in6 *in6;

	u16 test_case, port, dst6[8];

	int addrlen, ret, inline_ret, ret_key = 0;
@@ -112,8 +115,8 @@ int trace_sys_connect(struct pt_regs *ctx) 
	void *outer_map, *inner_map;

	bool inline_hash = false;



	in6 = (struct sockaddr_in6 *)PT_REGS_PARM2(ctx);

	addrlen = (int)PT_REGS_PARM3(ctx);

	in6 = (struct sockaddr_in6 *)PT_REGS_PARM2_CORE(real_regs);

	addrlen = (int)PT_REGS_PARM3_CORE(real_regs);



	if (addrlen != sizeof(*in6))

		return 0;

samples/bpf/test_probe_write_user_kern.c

+6 −3
Original line number Diff line number Diff line
@@ -10,6 +10,8 @@ 
#include <linux/version.h>

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>

#include <bpf/bpf_core_read.h>

#include "trace_common.h"



struct bpf_map_def SEC("maps") dnat_map = {

	.type = BPF_MAP_TYPE_HASH,
@@ -26,13 +28,14 @@ struct bpf_map_def SEC("maps") dnat_map = { 
 * This example sits on a syscall, and the syscall ABI is relatively stable

 * of course, across platforms, and over time, the ABI may change.

 */

SEC("kprobe/sys_connect")

SEC("kprobe/" SYSCALL(sys_connect))

int bpf_prog1(struct pt_regs *ctx)

{

	struct pt_regs *real_regs = (struct pt_regs *)PT_REGS_PARM1_CORE(ctx);

	void *sockaddr_arg = (void *)PT_REGS_PARM2_CORE(real_regs);

	int sockaddr_len = (int)PT_REGS_PARM3_CORE(real_regs);

	struct sockaddr_in new_addr, orig_addr = {};

	struct sockaddr_in *mapped_addr;

	void *sockaddr_arg = (void *)PT_REGS_PARM2(ctx);

	int sockaddr_len = (int)PT_REGS_PARM3(ctx);



	if (sockaddr_len > sizeof(orig_addr))

		return 0;

CRA Git | Maintained and supported by SUSTech CRA and CCSE