linux-kernel - Re: [PATCHv3 perf/core 0/6] uprobe,bpf: Allow to change app registers from uprobe registers

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Message-ID: <aMSIr1oItIfWQd5R@krava>
Date: Fri, 12 Sep 2025 22:55:11 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Ihor Solodrai <ihor.solodrai@...ux.dev>
Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
	x86@...nel.org, Song Liu <songliubraving@...com>,
	Yonghong Song <yhs@...com>,
	John Fastabend <john.fastabend@...il.com>,
	Hao Luo <haoluo@...gle.com>, Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCHv3 perf/core 0/6] uprobe,bpf: Allow to change app
 registers from uprobe registers

On Fri, Sep 12, 2025 at 01:28:55PM -0700, Ihor Solodrai wrote:
> On 9/9/25 9:41 AM, Andrii Nakryiko wrote:
> > On Tue, Sep 9, 2025 at 8:39 AM Jiri Olsa <jolsa@...nel.org> wrote:
> > > 
> > > hi,
> > > we recently had several requests for tetragon to be able to change
> > > user application function return value or divert its execution through
> > > instruction pointer change.
> > > 
> > > This patchset adds support for uprobe program to change app's registers
> > > including instruction pointer.
> > > 
> > > v3 changes:
> > > - deny attach of kprobe,multi with kprobe_write_ctx set [Alexei]
> > > - added more tests for denied kprobe attachment
> > > 
> > > thanks,
> > > jirka
> > > 
> > > 
> > > ---
> > > Jiri Olsa (6):
> > >        bpf: Allow uprobe program to change context registers
> > >        uprobe: Do not emulate/sstep original instruction when ip is changed
> > >        selftests/bpf: Add uprobe context registers changes test
> > >        selftests/bpf: Add uprobe context ip register change test
> > >        selftests/bpf: Add kprobe write ctx attach test
> > >        selftests/bpf: Add kprobe multi write ctx attach test
> > > 
> > 
> > For the series:
> > 
> > Acked-by: Andrii Nakryiko <andrii@...nel.org>
> > 
> > Question is which tree will this go through? Most changes are in BPF,
> > so probably bpf-next, right?
> 
> Hi Jiri.
> 
> This series does not apply to current bpf-next, see below.
> 
> Could you please respin it with bpf-next tag?
> E.g. "[PATCH v4 bpf-next 0/6] ..."
> 

hi,
the uprobe change it needs to be on top of the optimized uprobes (tip/perf/core)
but the bpf selftests patches could be applied on bpf-next/master and disabled
in CI until tip/perf/core changes are merged in?

thanks,
jirka


> Thanks!
> 
> $ git log -1 --oneline
> a578b54a8ad2 (HEAD -> master, origin/master, origin/HEAD,
> kernel-patches/bpf-next) Merge branch
> 'bpf-report-arena-faults-to-bpf-streams'
> $ b4 am 20250909123857.315599-1-jolsa@...nel.org
> [...]
> $ git am ./v3_20250909_jolsa_uprobe_bpf_allow_to_change_app_registers_from_uprobe_registers.mbx
> Applying: bpf: Allow uprobe program to change context registers
> Applying: uprobe: Do not emulate/sstep original instruction when ip is
> changed
> error: patch failed: kernel/events/uprobes.c:2768
> error: kernel/events/uprobes.c: patch does not apply
> Patch failed at 0002 uprobe: Do not emulate/sstep original instruction when
> ip is changed
> [...]
> 
> > 
> > >   include/linux/bpf.h                                        |   1 +
> > >   kernel/events/core.c                                       |   4 +++
> > >   kernel/events/uprobes.c                                    |   7 +++++
> > >   kernel/trace/bpf_trace.c                                   |   7 +++--
> > >   tools/testing/selftests/bpf/prog_tests/attach_probe.c      |  28 +++++++++++++++++
> > >   tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c |  27 ++++++++++++++++
> > >   tools/testing/selftests/bpf/prog_tests/uprobe.c            | 156 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> > >   tools/testing/selftests/bpf/progs/kprobe_write_ctx.c       |  22 +++++++++++++
> > >   tools/testing/selftests/bpf/progs/test_uprobe.c            |  38 +++++++++++++++++++++++
> > >   9 files changed, 287 insertions(+), 3 deletions(-)
> > >   create mode 100644 tools/testing/selftests/bpf/progs/kprobe_write_ctx.c
>