linux-kernel - Re: [PATCH v9 11/26] efi: Let architectures decide the flags that should be saved/restored

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Date:   Mon, 21 Jan 2019 16:42:48 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Julien Thierry <julien.thierry@....com>
Cc:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Christoffer Dall <christoffer.dall@....com>,
        James Morse <james.morse@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [PATCH v9 11/26] efi: Let architectures decide the flags that
 should be saved/restored

On Mon, 21 Jan 2019 at 16:34, Julien Thierry <julien.thierry@....com> wrote:
>
> Currently, irqflags are saved before calling runtime services and
> checked for mismatch on return.
>
> Provide a pair of overridable macros to save and restore (if needed) the
> state that need to be preserved on return from a runtime service.
> This allows to check for flags that are not necesarly related to
> irqflags.
>
> Signed-off-by: Julien Thierry <julien.thierry@....com>
> Acked-by: Catalin Marinas <catalin.marinas@....com>
> Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> Cc: linux-efi@...r.kernel.org
> ---
>  drivers/firmware/efi/runtime-wrappers.c | 17 +++++++++++++++--
>  include/linux/efi.h                     |  5 +++--
>  2 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
> index 8903b9c..2f4b68b 100644
> --- a/drivers/firmware/efi/runtime-wrappers.c
> +++ b/drivers/firmware/efi/runtime-wrappers.c
> @@ -89,11 +89,24 @@
>         efi_rts_work.status;                                            \
>  })
>
> +#ifndef arch_efi_save_flags
> +#define arch_efi_save_flags(state_flags)       local_save_flags(state_flags)
> +#define arch_efi_restore_flags(state_flags)    local_irq_restore(state_flags)
> +#endif
> +
> +inline unsigned long efi_call_virt_save_flags(void)

If you drop the 'inline' here,

Acked-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>

> +{
> +       unsigned long flags;
> +
> +       arch_efi_save_flags(flags);
> +       return flags;
> +}
> +
>  void efi_call_virt_check_flags(unsigned long flags, const char *call)
>  {
>         unsigned long cur_flags, mismatch;
>
> -       local_save_flags(cur_flags);
> +       cur_flags = efi_call_virt_save_flags();
>
>         mismatch = flags ^ cur_flags;
>         if (!WARN_ON_ONCE(mismatch & ARCH_EFI_IRQ_FLAGS_MASK))
> @@ -102,7 +115,7 @@ void efi_call_virt_check_flags(unsigned long flags, const char *call)
>         add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_NOW_UNRELIABLE);
>         pr_err_ratelimited(FW_BUG "IRQ flags corrupted (0x%08lx=>0x%08lx) by EFI %s\n",
>                            flags, cur_flags, call);
> -       local_irq_restore(flags);
> +       arch_efi_restore_flags(flags);
>  }
>
>  /*
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index 45ff763..bd80b7e 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -1607,6 +1607,7 @@ efi_status_t efi_setup_gop(efi_system_table_t *sys_table_arg,
>
>  bool efi_runtime_disabled(void);
>  extern void efi_call_virt_check_flags(unsigned long flags, const char *call);
> +extern unsigned long efi_call_virt_save_flags(void);
>
>  enum efi_secureboot_mode {
>         efi_secureboot_mode_unset,
> @@ -1652,7 +1653,7 @@ enum efi_secureboot_mode {
>                                                                         \
>         arch_efi_call_virt_setup();                                     \
>                                                                         \
> -       local_save_flags(__flags);                                      \
> +       __flags = efi_call_virt_save_flags();                           \
>         __s = arch_efi_call_virt(p, f, args);                           \
>         efi_call_virt_check_flags(__flags, __stringify(f));             \
>                                                                         \
> @@ -1667,7 +1668,7 @@ enum efi_secureboot_mode {
>                                                                         \
>         arch_efi_call_virt_setup();                                     \
>                                                                         \
> -       local_save_flags(__flags);                                      \
> +       __flags = efi_call_virt_save_flags();                           \
>         arch_efi_call_virt(p, f, args);                                 \
>         efi_call_virt_check_flags(__flags, __stringify(f));             \
>                                                                         \
> --
> 1.9.1
>