Re: [PATCH v6 0/7] riscv: Add reliable stack unwinding for livepatch

On 9/29/26 3:28 PM, Martin Kaiser wrote:

Thus wrote Shuai Xue (xueshuai@linux.alibaba.com):

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Hi,

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This is v6 of the RISC-V reliable stack unwinding series for livepatch.
Wang Han has left our team, so I am taking over this series from now on.

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The series adds explicit frame-record metadata, preserves the frame
pointer through dynamic ftrace, and replaces the open-coded stack walker
with a conservative frame-pointer based unwinder. It then enables the
RISC-V livepatch capability and adds the syscall-wrapper selftest prefix.

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Changes since v5:
* Rebase onto the current riscv/for-next; no functional changes.
* Fold in the tags collected from the v5 thread:
   - Reviewed-by: Shuai Xue on 2/7, 3/7, 4/7 and 6/7
   - Acked-by: Miroslav Benes on 7/7
* Add my sign-off as the new sender.

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Since the patches are otherwise identical to v5, the v5 validation
results still apply. For reference, from the v5 cover letter:
* Built Linux 7.2.0-rc6 with riscv64-unknown-linux-gnu-gcc 15.2.0
   and binutils 2.46.
* Standard livepatch configuration built successfully, including
   Image, vmlinux, modules, compile_commands.json and GDB scripts.
* CONFIG_IRQ_STACKS=n variant linked successfully with GCC.
* QEMU 8.2.2, 1 CPU: livepatch selftests PASS: 7, SKIP: 1,
   FAIL: 0; ftrace function graph 3 passed, 0 failed, 3 unsupported.
* QEMU 8.2.2, 4 CPUs: livepatch selftests PASS: 7, SKIP: 1,
   FAIL: 0; ftrace function graph 3 passed, 0 failed, 3 unsupported.
* No BUG, WARNING, Oops, panic, unreliable stack or Call Trace found
   by the validation log scans. Expected negative livepatch errors are
   part of the selftests.

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v5 was posted in early August and has been quiet since then. I would
appreciate it if the series could be considered for the upcoming merge
window. Happy to address any remaining feedback.

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Base:
riscv/for-next 77ae27fd98f3 ("Merge tag 'printk-for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux")

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Previous versions:
v5: https://lore.kernel.org/r/20260804103626.2803112-1-wanghan@linux.alibaba.com (local)
v4 RESEND: https://lore.kernel.org/r/20260629072713.3273743-1-wanghan@linux.alibaba.com (local)
v3: https://lore.kernel.org/r/cover.194d76e3a15b.v3.riscv-livepatch.wanghan@linux.alibaba.com (local)
v2: https://lore.kernel.org/r/20260528082310.1994388-1-wanghan@linux.alibaba.com (local)
v1: https://lore.kernel.org/r/20260527123530.2593918-1-wanghan@linux.alibaba.com (local)

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Assisted-by: Qoder:Qwen-3.8-MAX-Preview

Thanks for these patches.

I tried them on a standard rv64 qemu and on a rv64 cheri system
(cheri-linux.org). The latter needed some minor tweaks, but in
both cases, I could get livepatch to work.

Reviewed-by: Martin Kaiser <redacted>
Tested-by: Martin Kaiser <redacted>

Hi Martin,

Thank you very much for testing the series and for the tags!

It is great to hear that livepatch works both on a standard rv64 QEMU
and on the rv64 CHERI system. Could you share what the minor tweaks
for CHERI were? If any of them are generic -- for example frame-record
size/alignment or pointer-width assumptions in the unwinder -- it may
be worth folding them into this series, so the cheri-linux tree has
less to carry downstream. If they are purely CHERI-specific, a pointer
to your tree would still be a useful reference.

+Palmer, Paul, gentle ping on this series.

It has been under review since late May (v1 on May 27, now in its sixth
revision) and the tags collected so far are:

  * Acked-by: Miroslav Benes [off-list ref]             (7/7, livepatch)
  * Reviewed-by: Marcos Paulo de Souza [off-list ref] (7/7)
  * Reviewed-by: Martin Kaiser [off-list ref]         (whole series)
  * Tested-by: Martin Kaiser [off-list ref]           (whole series,
    rv64 QEMU and rv64 CHERI, livepatch working on both)
  * Reviewed-by: Shuai Xue [off-list ref]   (2/7, 3/7, 4/7, 6/7)

v6 still applies cleanly onto the current riscv/for-next
(52318cf0fa6e). If it helps, I can send a v7 that folds in Martin's
Reviewed-by/Tested-by tags.

Could the series be considered for the upcoming 7.4 merge window?

Thanks,
Shuai Xue