From: Qiliang Yuan <odys.yuan@gmail.com>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
John Fastabend <john.fastabend@gmail.com>,
Andrii Nakryiko <andrii@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
Jiri Olsa <jolsa@kernel.org>,
Emil Tsalapatis <emil@etsalapatis.com>,
Ihor Solodrai <ihor.solodrai@linux.dev>,
Shuah Khan <shuah@kernel.org>
Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org,
Qiliang Yuan <odys.yuan@gmail.com>
Subject: [PATCH bpf-next v2 21/22] selftests/bpf: Test jumps around patches of bpf_do_misc_fixups()
Date: Fri, 30 Oct 2026 07:52:06 -0400 [thread overview]
Message-ID: <20261030-bpf-verifier-patch-batch-v2-21-55cd43439f7c@gmail.com> (raw)
In-Reply-To: <20261030-bpf-verifier-patch-batch-v2-0-55cd43439f7c@gmail.com>
bpf_do_misc_fixups() queues its patches and applies them at once,
relocating every jump through a map from old to new indices.
No test checks the xlated code of jumps that target, skip or leave such
patches, a jump that the patches push out of its 16-bit range, or an
indirect jump to a patched instruction.
Check the xlated code for forward and backward jumps to a patched
instruction, jumps over patches, and a may_goto whose jump leaves its
own patch and crosses another one. Check that a jump over 8200 guarded
divisions fails to load, and that a gotox to a guarded modulo by zero
lands on the guard.
Signed-off-by: Qiliang Yuan <odys.yuan@gmail.com>
---
tools/testing/selftests/bpf/prog_tests/verifier.c | 2 +
.../selftests/bpf/progs/verifier_patch_list.c | 175 +++++++++++++++++++++
2 files changed, 177 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index 04740ba37e918..40788891641b5 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -96,6 +96,7 @@
#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"
@@ -287,6 +288,7 @@ 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..1370cdd5e5836
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_patch_list.c
@@ -0,0 +1,175 @@
+// 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);
+}
+
+/*
+ * The conditional jump skips 8200 divisions, which their patches turn into
+ * 32800 insns, too far for its 16-bit offset.
+ */
+SEC("raw_tp")
+__description("patch list: jump pushed out of range by patches")
+__failure __msg("cannot be patched due to 16-bit range")
+__naked void patch_list_jump_out_of_range(void)
+{
+ asm volatile (" \
+ call %[bpf_get_prandom_u32]; \
+ r1 = r0; \
+ if r0 == 0 goto 0f; \
+ .rept 8200; \
+ r0 /= r1; \
+ .endr; \
+0: r0 = 0; \
+ exit; \
+" :
+ : __imm(bpf_get_prandom_u32)
+ : __clobber_all);
+}
+
+#if defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64) || defined(__TARGET_ARCH_powerpc)
+/*
+ * An indirect jump to a patched insn must land on the first insn of its
+ * patch, here the check that skips the modulo by zero.
+ */
+SEC("socket")
+__description("patch list: indirect jump to a patched insn")
+__success __retval(7)
+__naked void patch_list_indirect(void)
+{
+ asm volatile (" \
+ .pushsection .jumptables,\"\",@progbits; \
+jt0_%=: \
+ .quad l0_%= - socket; \
+ .size jt0_%=, 8; \
+ .global jt0_%=; \
+ .popsection; \
+ r1 = 0; \
+ r6 = 7; \
+ r0 = jt0_%= ll; \
+ r0 = *(u64 *)(r0 + 0); \
+ .8byte %[gotox_r0]; \
+l0_%=: \
+ r6 %%= r1; \
+ r0 = r6; \
+ exit; \
+" :
+ : __imm_insn(gotox_r0, BPF_RAW_INSN(BPF_JMP | BPF_JA | BPF_X, BPF_REG_0, 0, 0, 0))
+ : __clobber_all);
+}
+#endif
+
+char _license[] SEC("license") = "GPL";
--
2.43.0
next prev parent reply other threads:[~2026-10-30 11:54 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-30 11:51 [PATCH bpf-next v2 00/22] bpf: Replace bpf_patch_insn_data() with a list of deferred patches Qiliang Yuan
2026-10-30 11:51 ` [PATCH bpf-next v2 01/22] bpf: Add a list of deferred instruction patches Qiliang Yuan
2026-10-30 11:51 ` [PATCH bpf-next v2 02/22] bpf: Remap the verifier state through the patch list Qiliang Yuan
2026-10-30 12:44 ` bot+bpf-ci
2026-10-30 11:51 ` [PATCH bpf-next v2 03/22] bpf: Apply single-instruction patches of the verifier in place Qiliang Yuan
2026-10-30 11:51 ` [PATCH bpf-next v2 04/22] bpf: Queue the rewrites of bpf_do_misc_fixups() Qiliang Yuan
2026-10-30 11:51 ` [PATCH bpf-next v2 05/22] bpf: Expand a backward may_goto to gotol when patches push it out of range Qiliang Yuan
2026-10-30 12:59 ` bot+bpf-ci
2026-10-30 11:51 ` [PATCH bpf-next v2 06/22] bpf: Drop the constant delta from bpf_do_misc_fixups() Qiliang Yuan
2026-10-30 11:51 ` [PATCH bpf-next v2 07/22] bpf: Let the patch list remove instructions Qiliang Yuan
2026-10-30 12:11 ` sashiko-bot
2026-10-30 11:51 ` [PATCH bpf-next v2 08/22] bpf: Remove dead code through the patch list Qiliang Yuan
2026-10-30 11:51 ` [PATCH bpf-next v2 09/22] bpf: Strip nops " Qiliang Yuan
2026-10-30 12:45 ` bot+bpf-ci
2026-10-30 11:51 ` [PATCH bpf-next v2 10/22] bpf: Batch the patches of bpf_opt_subreg_zext_lo32_rnd_hi32() Qiliang Yuan
2026-10-30 11:51 ` [PATCH bpf-next v2 11/22] bpf: Allow patching an instruction twice through the patch list Qiliang Yuan
2026-10-30 11:51 ` [PATCH bpf-next v2 12/22] bpf: Teach the patch list to insert in front of an instruction Qiliang Yuan
2026-10-30 12:44 ` bot+bpf-ci
2026-10-30 11:51 ` [PATCH bpf-next v2 13/22] bpf: Allow inserting in front of a queued patch Qiliang Yuan
2026-10-30 11:51 ` [PATCH bpf-next v2 14/22] bpf: Move bpf_convert_ctx_accesses() to the patch list Qiliang Yuan
2026-10-30 12:24 ` sashiko-bot
2026-10-30 11:52 ` [PATCH bpf-next v2 15/22] bpf: Insert the may_goto counter setup through " Qiliang Yuan
2026-10-30 11:52 ` [PATCH bpf-next v2 16/22] bpf: Append the hidden subprog " Qiliang Yuan
2026-10-30 11:52 ` [PATCH bpf-next v2 17/22] bpf: Inline bpf_loop() calls " Qiliang Yuan
2026-10-30 11:52 ` [PATCH bpf-next v2 18/22] bpf: Apply the patch list without a verifier env Qiliang Yuan
2026-10-30 11:52 ` [PATCH bpf-next v2 19/22] bpf: Blind constants through the patch list Qiliang Yuan
2026-10-30 12:44 ` bot+bpf-ci
2026-10-30 11:52 ` [PATCH bpf-next v2 20/22] bpf: Remove the old instruction patching code Qiliang Yuan
2026-10-30 11:52 ` Qiliang Yuan [this message]
2026-10-30 11:52 ` [PATCH bpf-next v2 22/22] selftests/bpf: Cover a backward may_goto pushed out of range by patches Qiliang Yuan
2026-10-30 12:13 ` sashiko-bot
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