From: Sami Tolvanen <samitolvanen@google.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Kees Cook <keescook@chromium.org>,
Nathan Chancellor <nathan@kernel.org>,
Masahiro Yamada <masahiroy@kernel.org>,
Will Deacon <will@kernel.org>, Jessica Yu <jeyu@kernel.org>,
Arnd Bergmann <arnd@arndb.de>, Tejun Heo <tj@kernel.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
Christoph Hellwig <hch@infradead.org>, bpf <bpf@vger.kernel.org>,
linux-hardening@vger.kernel.org,
linux-arch <linux-arch@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
PCI <linux-pci@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 07/17] kallsyms: strip ThinLTO hashes from static functions
Date: Thu, 18 Mar 2021 14:41:03 -0700 [thread overview]
Message-ID: <CABCJKueWJ0we0K+gw39=bF-uaz36dQ11uTsE+a5pAb6GrM-+5g@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdkETA4OU5d_f_8eCeXgo4juagHuPWo6Fd4jg7C1cWqoYA@mail.gmail.com>
On Thu, Mar 18, 2021 at 12:00 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Thu, Mar 18, 2021 at 10:11 AM Sami Tolvanen <samitolvanen@google.com> wrote:
> >
> > With CONFIG_CFI_CLANG and ThinLTO, Clang appends a hash to the names
> > of all static functions not marked __used. This can break userspace
> > tools that don't expect the function name to change, so strip out the
> > hash from the output.
> >
> > Suggested-by: Jack Pham <jackp@codeaurora.org>
> > Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> > Reviewed-by: Kees Cook <keescook@chromium.org>
> > ---
> > kernel/kallsyms.c | 54 ++++++++++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 49 insertions(+), 5 deletions(-)
> >
> > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> > index 8043a90aa50e..17d3a704bafa 100644
> > --- a/kernel/kallsyms.c
> > +++ b/kernel/kallsyms.c
> > @@ -161,6 +161,26 @@ static unsigned long kallsyms_sym_address(int idx)
> > return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
> > }
> >
> > +#if defined(CONFIG_CFI_CLANG) && defined(CONFIG_LTO_CLANG_THIN)
> > +/*
> > + * LLVM appends a hash to static function names when ThinLTO and CFI are
> > + * both enabled, which causes confusion and potentially breaks user space
>
> Might be nice to add an example, something along the lines of:
> ie. foo() becomes foo$asfdasdfasdfasdf()
Agreed, I'll update the comment in v3.
>
> > + * tools, so we will strip the postfix from expanded symbol names.
>
> s/postfix/suffix/ ?
Ack.
>
> > + */
> > +static inline char *cleanup_symbol_name(char *s)
> > +{
> > + char *res = NULL;
> > +
> > + res = strrchr(s, '$');
> > + if (res)
> > + *res = '\0';
> > +
> > + return res;
> > +}
> > +#else
> > +static inline char *cleanup_symbol_name(char *s) { return NULL; }
> > +#endif
>
> Might be nicer to return a `bool` and have the larger definition
> `return res != NULL`). Not sure what a caller would do with `res` if
> it was not `NULL`?
Sure, I'll change this to bool.
Sami
next prev parent reply other threads:[~2021-03-18 21:42 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-18 17:10 [PATCH v2 00/17] Add support for Clang CFI Sami Tolvanen
2021-03-18 17:10 ` [PATCH v2 01/17] add " Sami Tolvanen
2021-03-18 22:29 ` Peter Zijlstra
2021-03-18 23:48 ` Sami Tolvanen
2021-03-19 12:26 ` Peter Zijlstra
2021-03-19 13:52 ` Paul E. McKenney
2021-03-19 16:17 ` Sami Tolvanen
2021-03-19 17:03 ` Paul E. McKenney
2021-03-18 17:10 ` [PATCH v2 02/17] cfi: add __cficanonical Sami Tolvanen
2021-03-18 17:49 ` Nick Desaulniers
2021-03-18 17:10 ` [PATCH v2 03/17] mm: add generic __va_function and __pa_function macros Sami Tolvanen
2021-03-18 17:10 ` [PATCH v2 04/17] module: ensure __cfi_check alignment Sami Tolvanen
2021-03-18 19:27 ` Nick Desaulniers
2021-03-18 21:43 ` Sami Tolvanen
2021-03-18 17:10 ` [PATCH v2 05/17] workqueue: use WARN_ON_FUNCTION_MISMATCH Sami Tolvanen
2021-03-18 18:50 ` Nick Desaulniers
2021-03-18 21:38 ` Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 06/17] kthread: " Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 07/17] kallsyms: strip ThinLTO hashes from static functions Sami Tolvanen
2021-03-18 19:00 ` Nick Desaulniers
2021-03-18 21:41 ` Sami Tolvanen [this message]
2021-03-18 17:11 ` [PATCH v2 08/17] bpf: disable CFI in dispatcher functions Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 09/17] lib/list_sort: fix function type mismatches Sami Tolvanen
2021-03-18 18:31 ` Nick Desaulniers
2021-03-18 21:31 ` Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 10/17] lkdtm: use __va_function Sami Tolvanen
2021-03-18 18:43 ` Nick Desaulniers
2021-03-18 18:45 ` Nick Desaulniers
2021-03-18 17:11 ` [PATCH v2 11/17] psci: use __pa_function for cpu_resume Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 12/17] arm64: implement __va_function Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 13/17] arm64: use __pa_function Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 14/17] arm64: add __nocfi to functions that jump to a physical address Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 15/17] arm64: add __nocfi to __apply_alternatives Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 16/17] KVM: arm64: Disable CFI for nVHE Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 17/17] arm64: allow CONFIG_CFI_CLANG to be selected Sami Tolvanen
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