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With CONFIG_KPROBES_ON_FTRACE enabled on powerpc, ftrace_location_range
returns ftrace location for bpf_fentry_test1 at offset of 4 bytes from
function entry. This is because branch to _mcount function is at offset
of 4 bytes in function profile sequence.
To fix this, add entry_offset of 4 bytes while verifying the address for
kprobe entry address of bpf_fentry_test1 in verify_perf_link_info in
selftest, when CONFIG_KPROBES_ON_FTRACE is enabled.
Disassemble of bpf_fentry_test1:
c000000000e4b080 <bpf_fentry_test1>:
c000000000e4b080: a6 02 08 7c mflr r0
c000000000e4b084: b9 e2 22 4b bl c00000000007933c <_mcount>
c000000000e4b088: 01 00 63 38 addi r3,r3,1
c000000000e4b08c: b4 07 63 7c extsw r3,r3
c000000000e4b090: 20 00 80 4e blr
When CONFIG_PPC_FTRACE_OUT_OF_LINE [1] is enabled, these function profile
sequence is moved out of line with an unconditional branch at offset 0.
So, the test works without altering the offset for
'CONFIG_KPROBES_ON_FTRACE && CONFIG_PPC_FTRACE_OUT_OF_LINE' case.
Disassemble of bpf_fentry_test1:
c000000000f95190 <bpf_fentry_test1>:
c000000000f95190: 00 00 00 60 nop
c000000000f95194: 01 00 63 38 addi r3,r3,1
c000000000f95198: b4 07 63 7c extsw r3,r3
c000000000f9519c: 20 00 80 4e blr
[1] https://lore.kernel.org/all/20241030070850.1361304-13-hbathini@linux.ibm.com/
Fixes: 23cf7aa539 ("selftests/bpf: Add selftest for fill_link_info")
Signed-off-by: Saket Kumar Bhaskar <skb99@linux.ibm.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241209065720.234344-1-skb99@linux.ibm.com
62 lines
1.1 KiB
C
62 lines
1.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (C) 2023 Yafang Shao <laoar.shao@gmail.com> */
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#include "vmlinux.h"
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#include <bpf/bpf_tracing.h>
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#include <stdbool.h>
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extern bool CONFIG_X86_KERNEL_IBT __kconfig __weak;
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extern bool CONFIG_PPC_FTRACE_OUT_OF_LINE __kconfig __weak;
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extern bool CONFIG_KPROBES_ON_FTRACE __kconfig __weak;
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extern bool CONFIG_PPC64 __kconfig __weak;
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/* This function is here to have CONFIG_X86_KERNEL_IBT,
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* CONFIG_PPC_FTRACE_OUT_OF_LINE, CONFIG_KPROBES_ON_FTRACE,
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* CONFIG_PPC6 used and added to object BTF.
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*/
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int unused(void)
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{
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return CONFIG_X86_KERNEL_IBT ||
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CONFIG_PPC_FTRACE_OUT_OF_LINE ||
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CONFIG_KPROBES_ON_FTRACE ||
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CONFIG_PPC64 ? 0 : 1;
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}
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SEC("kprobe")
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int BPF_PROG(kprobe_run)
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{
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return 0;
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}
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SEC("uprobe")
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int BPF_PROG(uprobe_run)
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{
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return 0;
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}
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SEC("tracepoint")
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int BPF_PROG(tp_run)
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{
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return 0;
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}
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SEC("perf_event")
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int event_run(void *ctx)
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{
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return 0;
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}
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SEC("kprobe.multi")
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int BPF_PROG(kmulti_run)
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{
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return 0;
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}
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SEC("uprobe.multi")
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int BPF_PROG(umulti_run)
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{
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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