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libbpf: Extend BPF_KSYSCALL documentation

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Explicitly list known quirks. Mention that socket-related syscalls can be
invoked via socketcall().

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20220726134008.256968-2-iii@linux.ibm.com
This commit is contained in:
Ilya Leoshkevich 2022-07-26 15:40:07 +02:00 committed by Daniel Borkmann
parent bd82ea52f0
commit 2d369b4b00
1 changed files with 11 additions and 4 deletions
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15
tools/lib/bpf/bpf_tracing.h
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@ -523,10 +523,17 @@ static __always_inline typeof(name(0)) ____##name(struct pt_regs *ctx, ##args)
* Original struct pt_regs * context is preserved as 'ctx' argument. This might * Original struct pt_regs * context is preserved as 'ctx' argument. This might
* be necessary when using BPF helpers like bpf_perf_event_output(). * be necessary when using BPF helpers like bpf_perf_event_output().
* *
* At the moment BPF_KSYSCALL does not handle all the calling convention * At the moment BPF_KSYSCALL does not transparently handle all the calling
* quirks for mmap(), clone() and compat syscalls transparrently. This may or * convention quirks for the following syscalls:
* may not change in the future. User needs to take extra measures to handle *
* such quirks explicitly, if necessary. * - mmap(): __ARCH_WANT_SYS_OLD_MMAP.
* - clone(): CONFIG_CLONE_BACKWARDS, CONFIG_CLONE_BACKWARDS2 and
* CONFIG_CLONE_BACKWARDS3.
* - socket-related syscalls: __ARCH_WANT_SYS_SOCKETCALL.
* - compat syscalls.
*
* This may or may not change in the future. User needs to take extra measures
* to handle such quirks explicitly, if necessary.
* *
* This macro relies on BPF CO-RE support and virtual __kconfig externs. * This macro relies on BPF CO-RE support and virtual __kconfig externs.
*/ */