[PATCH bpf-next 4/4] selftests/bpf: Test jumps around patches of bpf_do_misc_fixups()

[Qiliang Yuan]

bpf_do_misc_fixups() now queues its patches and applies them at once.
Check the xlated code for forward and backward jumps to a patched insn,
jumps over patches, and a may_goto whose jump leaves its own patch and
crosses another one.

Signed-off-by: Qiliang Yuan <odys.yuan@xxxxxxxxx>
---
 tools/testing/selftests/bpf/prog_tests/verifier.c  |   2 +
 .../selftests/bpf/progs/verifier_patch_list.c      | 120 +++++++++++++++++++++
 2 files changed, 122 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index 8a6d341b754ac..af107b0c1595e 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -90,6 +90,7 @@
 #include "verifier_netfilter_retcode.skel.h"
 #include "verifier_bpf_fastcall.skel.h"
 #include "verifier_or_jmp32_k.skel.h"
+#include "verifier_patch_list.skel.h"
 #include "verifier_percpu_addr.skel.h"
 #include "verifier_precision.skel.h"
 #include "verifier_prevent_map_lookup.skel.h"
@@ -273,6 +274,7 @@ void test_verifier_netfilter_ctx(void)        { RUN(verifier_netfilter_ctx); }
 void test_verifier_netfilter_retcode(void)    { RUN(verifier_netfilter_retcode); }
 void test_verifier_bpf_fastcall(void)         { RUN(verifier_bpf_fastcall); }
 void test_verifier_or_jmp32_k(void)           { RUN(verifier_or_jmp32_k); }
+void test_verifier_patch_list(void)           { RUN(verifier_patch_list); }
 void test_verifier_percpu_addr(void)          { RUN(verifier_percpu_addr); }
 void test_verifier_precision(void)            { RUN(verifier_precision); }
 void test_verifier_prevent_map_lookup(void)   { RUN(verifier_prevent_map_lookup); }
diff --git a/tools/testing/selftests/bpf/progs/verifier_patch_list.c b/tools/testing/selftests/bpf/progs/verifier_patch_list.c
new file mode 100644
index 0000000000000..268cebd179984
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_patch_list.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "../../../include/linux/filter.h"
+#include "bpf_misc.h"
+
+/*
+ * bpf_do_misc_fixups() guards each division by a register against division
+ * by zero with a 4 insn patch. Jumps to a patched insn must land on the
+ * first insn of its patch, other jumps must follow the insns they target.
+ */
+
+SEC("raw_tp")
+__description("patch list: forward jumps to and over patched insns")
+__arch_x86_64
+__arch_arm64
+__success
+__xlated("0: call")
+__xlated("1: r1 = r0")
+__xlated("2: r0 = 7")
+__xlated("3: if r1 > 0x5 goto pc+1")
+__xlated("4: r0 = 9")
+__xlated("5: if r1 != 0x0 goto pc+2")
+__xlated("6: w0 ^= w0")
+__xlated("7: goto pc+1")
+__xlated("8: r0 /= r1")
+__xlated("9: if r0 > 0x3 goto pc+4")
+__xlated("10: if r1 != 0x0 goto pc+2")
+__xlated("11: w0 ^= w0")
+__xlated("12: goto pc+1")
+__xlated("13: r0 /= r1")
+__xlated("14: exit")
+__naked void patch_list_forward(void)
+{
+	asm volatile (
+	"call %[bpf_get_prandom_u32];"
+	"r1 = r0;"
+	"r0 = 7;"
+	"if r1 > 5 goto l0_%=;"
+	"r0 = 9;"
+"l0_%=:"
+	"r0 /= r1;"
+	"if r0 > 3 goto l1_%=;"
+	"r0 /= r1;"
+"l1_%=:"
+	"exit;"
+	:
+	: __imm(bpf_get_prandom_u32)
+	: __clobber_all);
+}
+
+SEC("raw_tp")
+__description("patch list: backward jump to a patched insn")
+__arch_x86_64
+__arch_arm64
+__success
+__xlated("0: call")
+__xlated("1: r1 = r0")
+__xlated("2: r2 = 0")
+__xlated("3: if r1 != 0x0 goto pc+2")
+__xlated("4: w0 ^= w0")
+__xlated("5: goto pc+1")
+__xlated("6: r0 /= r1")
+__xlated("7: r2 += 1")
+__xlated("8: if r2 < 0x3 goto pc-6")
+__xlated("9: exit")
+__naked void patch_list_backward(void)
+{
+	asm volatile (
+	"call %[bpf_get_prandom_u32];"
+	"r1 = r0;"
+	"r2 = 0;"
+"l0_%=:"
+	"r0 /= r1;"
+	"r2 += 1;"
+	"if r2 < 3 goto l0_%=;"
+	"exit;"
+	:
+	: __imm(bpf_get_prandom_u32)
+	: __clobber_all);
+}
+
+/* The jump of may_goto leaves its own patch and crosses another one. */
+SEC("raw_tp")
+__description("patch list: may_goto between patched insns")
+__arch_x86_64
+__success
+__xlated("0: *(u64 *)(r10 -16) = 65535")
+__xlated("1: *(u64 *)(r10 -8) = 0")
+__xlated("2: call")
+__xlated("3: r1 = r0")
+__xlated("4: if r1 != 0x0 goto pc+2")
+__xlated("5: w0 ^= w0")
+__xlated("6: goto pc+1")
+__xlated("7: r0 /= r1")
+__xlated("8: r12 = *(u64 *)(r10 -16)")
+__xlated("9: if r12 == 0x0 goto pc+9")
+__xlated("...")
+__xlated("15: if r1 != 0x0 goto pc+2")
+__xlated("16: w0 ^= w0")
+__xlated("17: goto pc+1")
+__xlated("18: r0 /= r1")
+__xlated("19: exit")
+__naked void patch_list_may_goto(void)
+{
+	asm volatile (
+	"call %[bpf_get_prandom_u32];"
+	"r1 = r0;"
+	"r0 /= r1;"
+	".8byte %[may_goto];"
+	"r0 /= r1;"
+	"exit;"
+	:
+	: __imm(bpf_get_prandom_u32),
+	  __imm_insn(may_goto, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0, 0, 1 /* offset */, 0))
+	: __clobber_all);
+}
+
+char _license[] SEC("license") = "GPL";

-- 
2.43.0