From: Sami Tolvanen <samitolvanen@google.com> To: Kees Cook <keescook@chromium.org> Cc: Nathan Chancellor <nathan@kernel.org>, Nick Desaulniers <ndesaulniers@google.com>, 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>, Peter Zijlstra <peterz@infradead.org>, Sedat Dilek <sedat.dilek@gmail.com>, Mark Rutland <mark.rutland@arm.com>, Catalin Marinas <catalin.marinas@arm.com>, bpf@vger.kernel.org, linux-hardening@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Sami Tolvanen <samitolvanen@google.com> Subject: [PATCH v6 03/18] mm: add generic function_nocfi macro Date: Thu, 8 Apr 2021 11:28:28 -0700 [thread overview] Message-ID: <20210408182843.1754385-4-samitolvanen@google.com> (raw) In-Reply-To: <20210408182843.1754385-1-samitolvanen@google.com> With CONFIG_CFI_CLANG, the compiler replaces function addresses in instrumented C code with jump table addresses. This means that __pa_symbol(function) returns the physical address of the jump table entry instead of the actual function, which may not work as the jump table code will immediately jump to a virtual address that may not be mapped. To avoid this address space confusion, this change adds a generic definition for function_nocfi(), which architectures that support CFI can override. The typical implementation of would use inline assembly to take the function address, which avoids compiler instrumentation. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Mark Rutland <mark.rutland@arm.com> Tested-by: Nathan Chancellor <nathan@kernel.org> --- include/linux/mm.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 8ba434287387..22cce9c7dd05 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -124,6 +124,16 @@ extern int mmap_rnd_compat_bits __read_mostly; #define lm_alias(x) __va(__pa_symbol(x)) #endif +/* + * With CONFIG_CFI_CLANG, the compiler replaces function addresses in + * instrumented C code with jump table addresses. Architectures that + * support CFI can define this macro to return the actual function address + * when needed. + */ +#ifndef function_nocfi +#define function_nocfi(x) (x) +#endif + /* * To prevent common memory management code establishing * a zero page mapping on a read fault. -- 2.31.1.295.g9ea45b61b8-goog
WARNING: multiple messages have this Message-ID (diff)
From: Sami Tolvanen <samitolvanen@google.com> To: Kees Cook <keescook@chromium.org> Cc: Nathan Chancellor <nathan@kernel.org>, Nick Desaulniers <ndesaulniers@google.com>, 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>, Peter Zijlstra <peterz@infradead.org>, Sedat Dilek <sedat.dilek@gmail.com>, Mark Rutland <mark.rutland@arm.com>, Catalin Marinas <catalin.marinas@arm.com>, bpf@vger.kernel.org, linux-hardening@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Sami Tolvanen <samitolvanen@google.com> Subject: [PATCH v6 03/18] mm: add generic function_nocfi macro Date: Thu, 8 Apr 2021 11:28:28 -0700 [thread overview] Message-ID: <20210408182843.1754385-4-samitolvanen@google.com> (raw) In-Reply-To: <20210408182843.1754385-1-samitolvanen@google.com> With CONFIG_CFI_CLANG, the compiler replaces function addresses in instrumented C code with jump table addresses. This means that __pa_symbol(function) returns the physical address of the jump table entry instead of the actual function, which may not work as the jump table code will immediately jump to a virtual address that may not be mapped. To avoid this address space confusion, this change adds a generic definition for function_nocfi(), which architectures that support CFI can override. The typical implementation of would use inline assembly to take the function address, which avoids compiler instrumentation. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Mark Rutland <mark.rutland@arm.com> Tested-by: Nathan Chancellor <nathan@kernel.org> --- include/linux/mm.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 8ba434287387..22cce9c7dd05 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -124,6 +124,16 @@ extern int mmap_rnd_compat_bits __read_mostly; #define lm_alias(x) __va(__pa_symbol(x)) #endif +/* + * With CONFIG_CFI_CLANG, the compiler replaces function addresses in + * instrumented C code with jump table addresses. Architectures that + * support CFI can define this macro to return the actual function address + * when needed. + */ +#ifndef function_nocfi +#define function_nocfi(x) (x) +#endif + /* * To prevent common memory management code establishing * a zero page mapping on a read fault. -- 2.31.1.295.g9ea45b61b8-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-04-08 18:29 UTC|newest] Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-04-08 18:28 [PATCH v6 00/18] Add support for Clang CFI Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 01/18] add " Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 02/18] cfi: add __cficanonical Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen [this message] 2021-04-08 18:28 ` [PATCH v6 03/18] mm: add generic function_nocfi macro Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 04/18] module: ensure __cfi_check alignment Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 05/18] workqueue: use WARN_ON_FUNCTION_MISMATCH Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 06/18] kthread: " Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 07/18] kallsyms: strip ThinLTO hashes from static functions Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 08/18] bpf: disable CFI in dispatcher functions Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 09/18] treewide: Change list_sort to use const pointers Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 10/18] lkdtm: use function_nocfi Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 11/18] psci: use function_nocfi for cpu_resume Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 12/18] arm64: implement function_nocfi Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 13/18] arm64: use function_nocfi with __pa_symbol Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 14/18] arm64: add __nocfi to functions that jump to a physical address Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 15/18] arm64: add __nocfi to __apply_alternatives Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 16/18] arm64: ftrace: use function_nocfi for ftrace_call Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 17/18] KVM: arm64: Disable CFI for nVHE Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 18:28 ` [PATCH v6 18/18] arm64: allow CONFIG_CFI_CLANG to be selected Sami Tolvanen 2021-04-08 18:28 ` Sami Tolvanen 2021-04-08 22:59 ` [PATCH v6 00/18] Add support for Clang CFI Kees Cook 2021-04-08 22:59 ` Kees Cook
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