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authorDaniel T. Lee <danieltimlee@gmail.com>2020-07-07 21:48:52 +0300
committerDaniel Borkmann <daniel@iogearbox.net>2020-07-08 02:32:14 +0300
commitaf9bd3e3331b8af42b6606c75797d041ab39380c (patch)
treee4912c10f7f5680424b6d48fbfa0c0c5c98f20ba /samples/bpf/test_probe_write_user_kern.c
parent65ffd797861a44ff97081de1db01e4aef716ed46 (diff)
downloadlinux-af9bd3e3331b8af42b6606c75797d041ab39380c.tar.xz
samples: bpf: Fix bpf programs with kprobe/sys_connect event
Currently, BPF programs with kprobe/sys_connect does not work properly. Commit 34745aed515c ("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 d5a00528b58c ("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: 34745aed515c ("samples/bpf: fix kprobe attachment issue on x64") Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Andrii Nakryiko <andriin@fb.com> Link: https://lore.kernel.org/bpf/20200707184855.30968-2-danieltimlee@gmail.com
Diffstat (limited to 'samples/bpf/test_probe_write_user_kern.c')
-rw-r--r--samples/bpf/test_probe_write_user_kern.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/samples/bpf/test_probe_write_user_kern.c b/samples/bpf/test_probe_write_user_kern.c
index f033f36a13a3..fd651a65281e 100644
--- a/samples/bpf/test_probe_write_user_kern.c
+++ b/samples/bpf/test_probe_write_user_kern.c
@@ -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;