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selftests/bpf: Test epilogue patching when the main prog has multiple BPF_EXIT

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This patch tests the epilogue patching when the main prog has
multiple BPF_EXIT. The verifier should have patched the 2nd (and
later) BPF_EXIT with a BPF_JA that goes back to the earlier
patched epilogue instructions.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20240829210833.388152-10-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Martin KaFai Lau 2024-08-29 14:08:31 -07:00 committed by Alexei Starovoitov
parent 42fdbbde6c
commit cada0bdcc4
2 changed files with 84 additions and 0 deletions
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2
tools/testing/selftests/bpf/prog_tests/pro_epilogue.c
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@ -5,6 +5,7 @@
#include "pro_epilogue.skel.h"
#include "epilogue_tailcall.skel.h"
#include "pro_epilogue_goto_start.skel.h"
#include "epilogue_exit.skel.h"
struct st_ops_args {
__u64 a;
@ -53,6 +54,7 @@ void test_pro_epilogue(void)
{
RUN_TESTS(pro_epilogue);
RUN_TESTS(pro_epilogue_goto_start);
RUN_TESTS(epilogue_exit);
if (test__start_subtest("tailcall"))
test_tailcall();
}

82
tools/testing/selftests/bpf/progs/epilogue_exit.c Normal file
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@ -0,0 +1,82 @@
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
#include <vmlinux.h>
#include <bpf/bpf_tracing.h>
#include "bpf_misc.h"
#include "../bpf_testmod/bpf_testmod.h"
#include "../bpf_testmod/bpf_testmod_kfunc.h"
char _license[] SEC("license") = "GPL";
__success
/* save __u64 *ctx to stack */
__xlated("0: *(u64 *)(r10 -8) = r1")
/* main prog */
__xlated("1: r1 = *(u64 *)(r1 +0)")
__xlated("2: r2 = *(u64 *)(r1 +0)")
__xlated("3: r3 = 0")
__xlated("4: r4 = 1")
__xlated("5: if r2 == 0x0 goto pc+10")
__xlated("6: r0 = 0")
__xlated("7: *(u64 *)(r1 +0) = r3")
/* epilogue */
__xlated("8: r1 = *(u64 *)(r10 -8)")
__xlated("9: r1 = *(u64 *)(r1 +0)")
__xlated("10: r6 = *(u64 *)(r1 +0)")
__xlated("11: r6 += 10000")
__xlated("12: *(u64 *)(r1 +0) = r6")
__xlated("13: r0 = r6")
__xlated("14: r0 *= 2")
__xlated("15: exit")
/* 2nd part of the main prog after the first exit */
__xlated("16: *(u64 *)(r1 +0) = r4")
__xlated("17: r0 = 1")
/* Clear the r1 to ensure it does not have
* off-by-1 error and ensure it jumps back to the
* beginning of epilogue which initializes
* the r1 with the ctx ptr.
*/
__xlated("18: r1 = 0")
__xlated("19: gotol pc-12")
SEC("struct_ops/test_epilogue_exit")
__naked int test_epilogue_exit(void)
{
asm volatile (
"r1 = *(u64 *)(r1 +0);"
"r2 = *(u64 *)(r1 +0);"
"r3 = 0;"
"r4 = 1;"
"if r2 == 0 goto +3;"
"r0 = 0;"
"*(u64 *)(r1 + 0) = r3;"
"exit;"
"*(u64 *)(r1 + 0) = r4;"
"r0 = 1;"
"r1 = 0;"
"exit;"
::: __clobber_all);
}
SEC(".struct_ops.link")
struct bpf_testmod_st_ops epilogue_exit = {
.test_epilogue = (void *)test_epilogue_exit,
};
SEC("syscall")
__retval(20000)
int syscall_epilogue_exit0(void *ctx)
{
struct st_ops_args args = { .a = 1 };
return bpf_kfunc_st_ops_test_epilogue(&args);
}
SEC("syscall")
__retval(20002)
int syscall_epilogue_exit1(void *ctx)
{
struct st_ops_args args = {};
return bpf_kfunc_st_ops_test_epilogue(&args);
}