linux-kernel - Re: [PATCH 04/13] Kbuild: Rust support

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Message-ID: <20210419195850.GV7604@twin.jikos.cz>
Date:   Mon, 19 Apr 2021 21:58:51 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rust-for-linux@...r.kernel.org,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Geoffrey Thomas <geofft@...reload.com>,
        Finn Behrens <me@...enk.de>,
        Adam Bratschi-Kaye <ark.email@...il.com>,
        Wedson Almeida Filho <wedsonaf@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH 04/13] Kbuild: Rust support

On Fri, Apr 16, 2021 at 07:34:51PM +0200, Miguel Ojeda wrote:
> On Fri, Apr 16, 2021 at 3:38 PM Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > So if I read all this right, rust compiles to .o and, like any other .o
> > file is then fed into objtool (for x86_64). Did you have any problems
> > with objtool? Does it generate correct ORC unwind information?
> 
> I opened an issue a while ago to take a closer look at the ORC
> unwinder etc., so it is in my radar (thanks for raising it up,
> nevertheless!).
> 
> Currently, causing a panic in a nested non-inlined function (f -> g ->
> h) in one of the samples with the ORC unwinder enabled gives me
> something like:
> 
> [    0.903456]  rust_begin_unwind+0x9/0x10
> [    0.903456]  ? _RNvNtCsbDqzXfLQacH_4core9panicking9panic_fmt+0x29/0x30
> [    0.903456]  ? _RNvNtCsbDqzXfLQacH_4core9panicking5panic+0x44/0x50
> [    0.903456]  ? _RNvCsbDqzXfLQacH_12rust_minimal1h+0x1c/0x20
> [    0.903456]  ? _RNvCsbDqzXfLQacH_12rust_minimal1g+0x9/0x10
> [    0.903456]  ? _RNvCsbDqzXfLQacH_12rust_minimal1f+0x9/0x10
> [    0.903456]  ?
> _RNvXCsbDqzXfLQacH_12rust_minimalNtB2_11RustMinimalNtCsbDqzXfLQacH_6kernel12KernelModule4init+0x73/0x80
> [    0.903456]  ? _RNvXsa_NtCsbDqzXfLQacH_4core3fmtbNtB5_5Debug3fmt+0x30/0x30
> [    0.903456]  ? __rust_minimal_init+0x11/0x20

Are there plans to unmangle the symbols when printing stacks? c++filt
says:

  rust_begin_unwind+0x9/0x10
  ? core[8787f43e282added]::panicking::panic_fmt+0x29/0x30
  ? core[8787f43e282added]::panicking::panic+0x44/0x50
  ? rust_minimal[8787f43e282added]::h+0x1c/0x20
  ? rust_minimal[8787f43e282added]::g+0x9/0x10
  ? rust_minimal[8787f43e282added]::f+0x9/0x10
  ? <rust_minimal[8787f43e282added]::RustMinimal as kernel[8787f43e282added]::KernelModule>::init+0x73/0x80
  ? <bool as core[8787f43e282added]::fmt::Debug>::fmt+0x30/0x30
  ? __rust_minimal_init+0x11/0x20

for simple functions it's barely parseable but the following is hardly
readable

> _RNvXs5_NtCsbDqzXfLQacH_11rust_binder11range_allocNtB5_15DescriptorStateNtNtCsbDqzXfLQacH_4core3fmt5Debug3fmt+0x60/0x60

translates to

  <rust_binder[8787f43e282added]::range_alloc::DescriptorState as core[8787f43e282added]::fmt::Debug>::fmt