Merge branch 'bpf: Fixes for CONFIG_X86_KERNEL_IBT'

Jiri Olsa says:

====================
Martynas reported bpf_get_func_ip returning +4 address when
CONFIG_X86_KERNEL_IBT option is enabled and I found there are
some failing bpf tests when this option is enabled.

The CONFIG_X86_KERNEL_IBT option adds endbr instruction at the
function entry, so the idea is to 'fix' entry ip for kprobe_multi
and trampoline probes, because they are placed on the function
entry.

v5 changes:
  - updated uapi/linux/bpf.h headers with comment for
    bpf_get_func_ip returning 0 [Andrii]
  - added acks

v4 changes:
  - used get_kernel_nofault to read previous instruction [Peter]
  - used movabs instruction in trampoline comment [Peter]
  - renamed fentry_ip argument in kprobe_multi_link_handler [Peter]

v3 changes:
  - using 'unused' bpf function to get IBT config option
    into selftest skeleton
  - rebased to current bpf-next/master
  - added ack/review from Masami

v2 changes:
  - change kprobes get_func_ip to return zero for kprobes
    attached within the function body [Andrii]
  - detect IBT config and properly test kprobe with offset
    [Andrii]

v1 changes:
  - read previous instruction in kprobe_multi link handler
    and adjust entry_ip for CONFIG_X86_KERNEL_IBT option
  - split first patch into 2 separate changes
  - update changelogs
====================

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 13 insertions, 12 deletions

diff --git a/tools/testing/selftests/bpf/progs/get_func_ip_test.c b/tools/testing/selftests/bpf/progs/get_func_ip_test.c
index a587aeca5ae0..8559e698b40d 100644
--- a/tools/testing/selftests/bpf/progs/get_func_ip_test.c
+++ b/tools/testing/selftests/bpf/progs/get_func_ip_test.c
@@ -2,6 +2,7 @@
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
+#include <stdbool.h>
 
 char _license[] SEC("license") = "GPL";
 
@@ -13,6 +14,16 @@ extern const void bpf_modify_return_test __ksym;
 extern const void bpf_fentry_test6 __ksym;
 extern const void bpf_fentry_test7 __ksym;
 
+extern bool CONFIG_X86_KERNEL_IBT __kconfig __weak;
+
+/* This function is here to have CONFIG_X86_KERNEL_IBT
+ * used and added to object BTF.
+ */
+int unused(void)
+{
+	return CONFIG_X86_KERNEL_IBT ? 0 : 1;
+}
+
 __u64 test1_result = 0;
 SEC("fentry/bpf_fentry_test1")
 int BPF_PROG(test1, int a)
@@ -64,21 +75,11 @@ int BPF_PROG(test5, int a, int *b, int ret)
 }
 
 __u64 test6_result = 0;
-SEC("kprobe/bpf_fentry_test6+0x5")
+SEC("?kprobe")
 int test6(struct pt_regs *ctx)
 {
 	__u64 addr = bpf_get_func_ip(ctx);
 
-	test6_result = (const void *) addr == &bpf_fentry_test6 + 5;
-	return 0;
-}
-
-__u64 test7_result = 0;
-SEC("kprobe/bpf_fentry_test7+5")
-int test7(struct pt_regs *ctx)
-{
-	__u64 addr = bpf_get_func_ip(ctx);
-
-	test7_result = (const void *) addr == &bpf_fentry_test7 + 5;
+	test6_result = (const void *) addr == 0;
 	return 0;
 }