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]
Date:   Mon, 7 Oct 2019 14:34:26 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] arm64: fix alternatives with LLVM's integrated assembler

On Mon, Oct 7, 2019 at 2:14 PM 'Sami Tolvanen' via Clang Built Linux
<clang-built-linux@...glegroups.com> wrote:
>
> LLVM's integrated assembler fails with the following error when
> building KVM:
>
>   <inline asm>:12:6: error: expected absolute expression
>    .if kvm_update_va_mask == 0
>        ^
>   <inline asm>:21:6: error: expected absolute expression
>    .if kvm_update_va_mask == 0
>        ^
>   <inline asm>:24:2: error: unrecognized instruction mnemonic
>           NOT_AN_INSTRUCTION
>           ^
>   LLVM ERROR: Error parsing inline asm
>
> These errors come from ALTERNATIVE_CB and __ALTERNATIVE_CFG,
> which test for the existence of the callback parameter in inline
> assembly using the following expression:
>
>   " .if " __stringify(cb) " == 0\n"
>
> This works with GNU as, but isn't supported by LLVM. This change
> splits __ALTERNATIVE_CFG and ALTINSTR_ENTRY into separate macros
> to fix the LLVM build.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/472
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> ---
>  arch/arm64/include/asm/alternative.h | 32 ++++++++++++++++++----------
>  1 file changed, 21 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
> index b9f8d787eea9..324e7d5ab37e 100644
> --- a/arch/arm64/include/asm/alternative.h
> +++ b/arch/arm64/include/asm/alternative.h
> @@ -35,13 +35,16 @@ void apply_alternatives_module(void *start, size_t length);
>  static inline void apply_alternatives_module(void *start, size_t length) { }
>  #endif
>
> -#define ALTINSTR_ENTRY(feature,cb)                                           \
> +#define ALTINSTR_ENTRY(feature)                                                      \
>         " .word 661b - .\n"                             /* label           */ \
> -       " .if " __stringify(cb) " == 0\n"                                     \
>         " .word 663f - .\n"                             /* new instruction */ \
> -       " .else\n"                                                            \
> +       " .hword " __stringify(feature) "\n"            /* feature bit     */ \
> +       " .byte 662b-661b\n"                            /* source len      */ \
> +       " .byte 664f-663f\n"                            /* replacement len */
> +
> +#define ALTINSTR_ENTRY_CB(feature, cb)                                       \
> +       " .word 661b - .\n"                             /* label           */ \
>         " .word " __stringify(cb) "- .\n"               /* callback */        \
> -       " .endif\n"                                                           \
>         " .hword " __stringify(feature) "\n"            /* feature bit     */ \
>         " .byte 662b-661b\n"                            /* source len      */ \
>         " .byte 664f-663f\n"                            /* replacement len */
> @@ -62,15 +65,14 @@ static inline void apply_alternatives_module(void *start, size_t length) { }
>   *
>   * Alternatives with callbacks do not generate replacement instructions.
>   */
> -#define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled, cb)        \
> +#define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled)    \
>         ".if "__stringify(cfg_enabled)" == 1\n"                         \
>         "661:\n\t"                                                      \
>         oldinstr "\n"                                                   \
>         "662:\n"                                                        \
>         ".pushsection .altinstructions,\"a\"\n"                         \
> -       ALTINSTR_ENTRY(feature,cb)                                      \
> +       ALTINSTR_ENTRY(feature)                                         \
>         ".popsection\n"                                                 \
> -       " .if " __stringify(cb) " == 0\n"                               \
>         ".pushsection .altinstr_replacement, \"a\"\n"                   \
>         "663:\n\t"                                                      \
>         newinstr "\n"                                                   \
> @@ -78,17 +80,25 @@ static inline void apply_alternatives_module(void *start, size_t length) { }
>         ".popsection\n\t"                                               \
>         ".org   . - (664b-663b) + (662b-661b)\n\t"                      \
>         ".org   . - (662b-661b) + (664b-663b)\n"                        \
> -       ".else\n\t"                                                     \
> +       ".endif\n"
> +
> +#define __ALTERNATIVE_CFG_CB(oldinstr, feature, cfg_enabled, cb)       \
> +       ".if "__stringify(cfg_enabled)" == 1\n"                         \
> +       "661:\n\t"                                                      \
> +       oldinstr "\n"                                                   \
> +       "662:\n"                                                        \
> +       ".pushsection .altinstructions,\"a\"\n"                         \
> +       ALTINSTR_ENTRY_CB(feature, cb)                                  \
> +       ".popsection\n"                                                 \
>         "663:\n\t"                                                      \
>         "664:\n\t"                                                      \
> -       ".endif\n"                                                      \
>         ".endif\n"
>
>  #define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...)        \
> -       __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg), 0)
> +       __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg))
>
>  #define ALTERNATIVE_CB(oldinstr, cb) \
> -       __ALTERNATIVE_CFG(oldinstr, "NOT_AN_INSTRUCTION", ARM64_CB_PATCH, 1, cb)
> +       __ALTERNATIVE_CFG_CB(oldinstr, ARM64_CB_PATCH, 1, cb)
>  #else
>
>  #include <asm/assembler.h>


Should the definition of the ALTERNATIVE macro
(arch/arm64/include/asm/alternative.h#L295) also be updated in this
patch to not pass `1` as the final parameter? Otherwise with this
patch and your LSE one
(https://lore.kernel.org/lkml/20191007201452.208067-1-samitolvanen@google.com/T/#u)
I get one error on linux-next that looks related:
$ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make CC=clang AS=clang
-j71 arch/arm64/kvm/
...
arch/arm64/kvm/hyp/entry.S:109:87: error: too many positional arguments
 alternative_insn nop, .inst (0xd500401f | ((0) << 16 | (4) << 5) |
((!!1) << 8)), 4, 1

               ^

Since __ALTERNATIVE_CFG now takes one less arg, with your patch?

-- 
Thanks,
~Nick Desaulniers

Powered by blists - more mailing lists