linux-kernel - Re: [PATCH v6 33/33] kselftest/riscv: kselftest for user mode cfi

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Message-ID: <CANXhq0rH_07JRGbBnMTntPxhOQcXzxrcRJ0WAN7T6oQX7DaNoQ@mail.gmail.com>
Date: Mon, 14 Oct 2024 22:33:50 +0800
From: Zong Li <zong.li@...ive.com>
To: Deepak Gupta <debug@...osinc.com>
Cc: Mark Brown <broonie@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	"Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Conor Dooley <conor@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Arnd Bergmann <arnd@...db.de>, 
	Christian Brauner <brauner@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Oleg Nesterov <oleg@...hat.com>, Eric Biederman <ebiederm@...ssion.com>, Kees Cook <kees@...nel.org>, 
	Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, 
	linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org, 
	linux-arch@...r.kernel.org, linux-doc@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, alistair.francis@....com, 
	richard.henderson@...aro.org, jim.shu@...ive.com, andybnac@...il.com, 
	kito.cheng@...ive.com, charlie@...osinc.com, atishp@...osinc.com, 
	evan@...osinc.com, cleger@...osinc.com, alexghiti@...osinc.com, 
	samitolvanen@...gle.com, rick.p.edgecombe@...el.com
Subject: Re: [PATCH v6 33/33] kselftest/riscv: kselftest for user mode cfi

On Sat, Oct 12, 2024 at 3:46 AM Deepak Gupta <debug@...osinc.com> wrote:
>
> On Fri, Oct 11, 2024 at 07:43:30PM +0800, Zong Li wrote:
> >On Fri, Oct 11, 2024 at 6:18 PM Mark Brown <broonie@...nel.org> wrote:
> >>
> >> On Fri, Oct 11, 2024 at 01:44:55PM +0800, Zong Li wrote:
> >> > On Wed, Oct 9, 2024 at 7:46 AM Deepak Gupta <debug@...osinc.com> wrote:
> >>
> >> > > +       if (si->si_code == SEGV_CPERR) {
> >>
> >> > Hi Deepak,
> >> > I got some errors when building this test, I suppose they should be
> >> > fixed in the next version.
> >>
> >> > riscv_cfi_test.c: In function 'sigsegv_handler':
> >> > riscv_cfi_test.c:17:28: error: 'SEGV_CPERR' undeclared (first use in
> >> > this function); did you mean 'SEGV_ACCERR'?
> >> >    17 |         if (si->si_code == SEGV_CPERR) {
> >> >       |                            ^~~~~~~~~~
> >> >       |                            SEGV_ACCERR
> >> >
> >>
> >> Did you run "make headers_install" prior to building kselftest to get
> >> the current kernel's headers available for userspace builds?
> >
> >Yes, I have run "make header" and "make header_install" before
> >building the kselftest. This error happens when I cross compiled it,
> >perhaps I can help to check if it is missing some header files or
> >header search path.
>
> That's wierd.
>
> It doesn't fail for me even if I do not do `make headers_install`. But I am
> building kernel and selftests with toolchain which supports shadow stack and
> landing pad. It's defined in `siginfo.h`. When I built toolchain, I did point
> it at the latest kernel headers. May be that's the trick.
>
> """
>
> $ grep -nir SEGV_CPERR /scratch/debug/linux/kbuild/usr/include/*
> /scratch/debug/linux/kbuild/usr/include/asm-generic/siginfo.h:240:#define SEGV_CPERR    10      /* Control protection fault */
>
> $ grep -nir SEGV_CPERR /scratch/debug/open_src/sifive_cfi_toolchain/INSTALL_Sept18/sysroot/usr/*
> /scratch/debug/open_src/sifive_cfi_toolchain/INSTALL_Sept18/sysroot/usr/include/asm-generic/siginfo.h:240:#define SEGV_CPERR    10      /* Control protection fault */
> /scratch/debug/open_src/sifive_cfi_toolchain/INSTALL_Sept18/sysroot/usr/include/bits/siginfo-consts.h:139:  SEGV_CPERR                  /* Control protection fault.  */
> /scratch/debug/open_src/sifive_cfi_toolchain/INSTALL_Sept18/sysroot/usr/include/bits/siginfo-consts.h:140:#  define SEGV_CPERR  SEGV_CPERR
>
> """

In my case, because the test files don't explicitly include siginfo.h,
I assume it's expected that siginfo.h will be included through
signal.h. Regarding the header search path, it will eventually locate
signal.h in toolchain_path/sysroot/usr/include/. In my
toolchain_path/sysroot/usr/include/signal.h, it doesn't include any
signal.h; instead, signal.h will be included from
toolchain_path/sysroot/usr/include/linux/signal.h or
kernel_src/usr/include/linux/signal.h rather than
toolchain/sysroot/usr/include/signal.h. I think that is why I lost the
SEGV_CPERR definition. Is there any difference with you?

>