linux-kernel - Re: [PATCH v4 2/4] x86: Handle KCOV _

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <aIiGHmw8IJb9vsM5@kernel.org>
Date: Tue, 29 Jul 2025 11:28:14 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Kees Cook <kees@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>, 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>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Hans de Goede <hdegoede@...hat.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>, Masami Hiramatsu <mhiramat@...nel.org>,
	Michal Wilczynski <michal.wilczynski@...el.com>,
	Juergen Gross <jgross@...e.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Roger Pau Monne <roger.pau@...rix.com>,
	David Woodhouse <dwmw@...zon.co.uk>,
	Usama Arif <usama.arif@...edance.com>,
	"Guilherme G. Piccoli" <gpiccoli@...lia.com>,
	Thomas Huth <thuth@...hat.com>, Brian Gerst <brgerst@...il.com>,
	kvm@...r.kernel.org, ibm-acpi-devel@...ts.sourceforge.net,
	platform-driver-x86@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	linux-mm@...ck.org, Will Deacon <will@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Gavin Shan <gshan@...hat.com>,
	"Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
	James Morse <james.morse@....com>,
	Oza Pawandeep <quic_poza@...cinc.com>,
	Anshuman Khandual <anshuman.khandual@....com>,
	Hans de Goede <hansg@...nel.org>,
	"Kirill A. Shutemov" <kas@...nel.org>,
	Marco Elver <elver@...gle.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Hou Wenlong <houwenlong.hwl@...group.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Masahiro Yamada <masahiroy@...nel.org>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Luis Chamberlain <mcgrof@...nel.org>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas.schier@...ux.dev>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Andy Lutomirski <luto@...nel.org>, Baoquan He <bhe@...hat.com>,
	Alexander Graf <graf@...zon.com>,
	Changyuan Lyu <changyuanl@...gle.com>,
	Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Jan Beulich <jbeulich@...e.com>, Boqun Feng <boqun.feng@...il.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Bibo Mao <maobibo@...ngson.cn>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, kasan-dev@...glegroups.com,
	linux-kbuild@...r.kernel.org, linux-hardening@...r.kernel.org,
	kexec@...ts.infradead.org, linux-security-module@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: Re: [PATCH v4 2/4] x86: Handle KCOV __init vs inline mismatches

On Wed, Jul 23, 2025 at 10:50:26PM -0700, Kees Cook wrote:
> GCC appears to have kind of fragile inlining heuristics, in the
> sense that it can change whether or not it inlines something based on
> optimizations. It looks like the kcov instrumentation being added (or in
> this case, removed) from a function changes the optimization results,
> and some functions marked "inline" are _not_ inlined. In that case,
> we end up with __init code calling a function not marked __init, and we
> get the build warnings I'm trying to eliminate in the coming patch that
> adds __no_sanitize_coverage to __init functions:
> 
> WARNING: modpost: vmlinux: section mismatch in reference: xbc_exit+0x8 (section: .text.unlikely) -> _xbc_exit (section: .init.text)
> WARNING: modpost: vmlinux: section mismatch in reference: real_mode_size_needed+0x15 (section: .text.unlikely) -> real_mode_blob_end (section: .init.data)
> WARNING: modpost: vmlinux: section mismatch in reference: __set_percpu_decrypted+0x16 (section: .text.unlikely) -> early_set_memory_decrypted (section: .init.text)
> WARNING: modpost: vmlinux: section mismatch in reference: memblock_alloc_from+0x26 (section: .text.unlikely) -> memblock_alloc_try_nid (section: .init.text)
> WARNING: modpost: vmlinux: section mismatch in reference: acpi_arch_set_root_pointer+0xc (section: .text.unlikely) -> x86_init (section: .init.data)
> WARNING: modpost: vmlinux: section mismatch in reference: acpi_arch_get_root_pointer+0x8 (section: .text.unlikely) -> x86_init (section: .init.data)
> WARNING: modpost: vmlinux: section mismatch in reference: efi_config_table_is_usable+0x16 (section: .text.unlikely) -> xen_efi_config_table_is_usable (section: .init.text)
> 
> This problem is somewhat fragile (though using either __always_inline
> or __init will deterministically solve it), but we've tripped over
> this before with GCC and the solution has usually been to just use
> __always_inline and move on.
> 
> For x86 this means forcing several functions to be inline with
> __always_inline.
> 
> Signed-off-by: Kees Cook <kees@...nel.org>

For memblock bit:

Acked-by: Mike Rapoport (Microsoft) <rppt@...nel.org>

-- 
Sincerely yours,
Mike.