Re: [Xen-devel] [PATCH v2 3/3] arm64: remove the rest of asm-uaccess.h

[Mark Rutland <mark.rutland@xxxxxxx>]

On Thu, Nov 21, 2019 at 09:24:06PM -0500, Pavel Tatashin wrote:
> The __uaccess_ttbr0_disable and __uaccess_ttbr0_enable,
> are the last two macros defined in asm-uaccess.h.
> 
> Replace them with C wrappers and call C functions from
> kernel_entry and kernel_exit.

For now, please leave those as-is.

I don't think we want to have out-of-line C wrappers in the middle of
the entry assembly where we don't have a complete kernel environment.
The use in entry code can also assume non-preemptibility, while the C
functions have to explcitily disable that.

We can certainly remove the includes of <asm/asm-uaccess.h> elsewhere,
and maybe fold the macros into entry.S if it's not too crowded.

Thanks,
Mark.

> 
> Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
> ---
>  arch/arm64/include/asm/asm-uaccess.h | 38 ----------------------------
>  arch/arm64/kernel/entry.S            |  6 ++---
>  arch/arm64/lib/clear_user.S          |  2 +-
>  arch/arm64/lib/copy_from_user.S      |  2 +-
>  arch/arm64/lib/copy_in_user.S        |  2 +-
>  arch/arm64/lib/copy_to_user.S        |  2 +-
>  arch/arm64/mm/cache.S                |  1 -
>  arch/arm64/mm/context.c              | 12 +++++++++
>  8 files changed, 19 insertions(+), 46 deletions(-)
>  delete mode 100644 arch/arm64/include/asm/asm-uaccess.h
> 
> diff --git a/arch/arm64/include/asm/asm-uaccess.h 
> b/arch/arm64/include/asm/asm-uaccess.h
> deleted file mode 100644
> index 8f763e5b41b1..000000000000
> --- a/arch/arm64/include/asm/asm-uaccess.h
> +++ /dev/null
> @@ -1,38 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0 */
> -#ifndef __ASM_ASM_UACCESS_H
> -#define __ASM_ASM_UACCESS_H
> -
> -#include <asm/alternative.h>
> -#include <asm/kernel-pgtable.h>
> -#include <asm/mmu.h>
> -#include <asm/sysreg.h>
> -#include <asm/assembler.h>
> -
> -/*
> - * User access enabling/disabling macros.
> - */
> -#ifdef CONFIG_ARM64_SW_TTBR0_PAN
> -     .macro  __uaccess_ttbr0_disable, tmp1
> -     mrs     \tmp1, ttbr1_el1                        // swapper_pg_dir
> -     bic     \tmp1, \tmp1, #TTBR_ASID_MASK
> -     sub     \tmp1, \tmp1, #RESERVED_TTBR0_SIZE      // reserved_ttbr0 just 
> before swapper_pg_dir
> -     msr     ttbr0_el1, \tmp1                        // set reserved 
> TTBR0_EL1
> -     isb
> -     add     \tmp1, \tmp1, #RESERVED_TTBR0_SIZE
> -     msr     ttbr1_el1, \tmp1                // set reserved ASID
> -     isb
> -     .endm
> -
> -     .macro  __uaccess_ttbr0_enable, tmp1, tmp2
> -     get_current_task \tmp1
> -     ldr     \tmp1, [\tmp1, #TSK_TI_TTBR0]   // load saved TTBR0_EL1
> -     mrs     \tmp2, ttbr1_el1
> -     extr    \tmp2, \tmp2, \tmp1, #48
> -     ror     \tmp2, \tmp2, #16
> -     msr     ttbr1_el1, \tmp2                // set the active ASID
> -     isb
> -     msr     ttbr0_el1, \tmp1                // set the non-PAN TTBR0_EL1
> -     isb
> -     .endm
> -#endif
> -#endif
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 583f71abbe98..c7b571e6d0f2 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -22,8 +22,8 @@
>  #include <asm/mmu.h>
>  #include <asm/processor.h>
>  #include <asm/ptrace.h>
> +#include <asm/kernel-pgtable.h>
>  #include <asm/thread_info.h>
> -#include <asm/asm-uaccess.h>
>  #include <asm/unistd.h>
>  
>  /*
> @@ -219,7 +219,7 @@ alternative_else_nop_endif
>       and     x23, x23, #~PSR_PAN_BIT         // Clear the emulated PAN in 
> the saved SPSR
>       .endif
>  
> -     __uaccess_ttbr0_disable x21
> +     bl __uaccess_ttbr0_disable_c
>  1:
>  #endif
>  
> @@ -293,7 +293,7 @@ alternative_else_nop_endif
>       tbnz    x22, #22, 1f                    // Skip re-enabling TTBR0 
> access if the PSR_PAN_BIT is set
>       .endif
>  
> -     __uaccess_ttbr0_enable x0, x1
> +     bl      __uaccess_ttbr0_enable_c
>  
>       .if     \el == 0
>       /*
> diff --git a/arch/arm64/lib/clear_user.S b/arch/arm64/lib/clear_user.S
> index aeafc03e961a..b0b4a86a09e2 100644
> --- a/arch/arm64/lib/clear_user.S
> +++ b/arch/arm64/lib/clear_user.S
> @@ -6,7 +6,7 @@
>   */
>  #include <linux/linkage.h>
>  
> -#include <asm/asm-uaccess.h>
> +#include <asm/alternative.h>
>  #include <asm/assembler.h>
>  
>       .text
> diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S
> index ebb3c06cbb5d..142bc7505518 100644
> --- a/arch/arm64/lib/copy_from_user.S
> +++ b/arch/arm64/lib/copy_from_user.S
> @@ -5,7 +5,7 @@
>  
>  #include <linux/linkage.h>
>  
> -#include <asm/asm-uaccess.h>
> +#include <asm/alternative.h>
>  #include <asm/assembler.h>
>  #include <asm/cache.h>
>  
> diff --git a/arch/arm64/lib/copy_in_user.S b/arch/arm64/lib/copy_in_user.S
> index 3d8153a1ebce..04dc48ca26f7 100644
> --- a/arch/arm64/lib/copy_in_user.S
> +++ b/arch/arm64/lib/copy_in_user.S
> @@ -7,7 +7,7 @@
>  
>  #include <linux/linkage.h>
>  
> -#include <asm/asm-uaccess.h>
> +#include <asm/alternative.h>
>  #include <asm/assembler.h>
>  #include <asm/cache.h>
>  
> diff --git a/arch/arm64/lib/copy_to_user.S b/arch/arm64/lib/copy_to_user.S
> index 357eae2c18eb..8f3218ae88ab 100644
> --- a/arch/arm64/lib/copy_to_user.S
> +++ b/arch/arm64/lib/copy_to_user.S
> @@ -5,7 +5,7 @@
>  
>  #include <linux/linkage.h>
>  
> -#include <asm/asm-uaccess.h>
> +#include <asm/alternative.h>
>  #include <asm/assembler.h>
>  #include <asm/cache.h>
>  
> diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S
> index 408d317a47d2..7940d6ef5da5 100644
> --- a/arch/arm64/mm/cache.S
> +++ b/arch/arm64/mm/cache.S
> @@ -12,7 +12,6 @@
>  #include <asm/assembler.h>
>  #include <asm/cpufeature.h>
>  #include <asm/alternative.h>
> -#include <asm/asm-uaccess.h>
>  
>  /*
>   *   __arch_flush_icache_range(start,end)
> diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
> index b5e329fde2dd..4fc32c504dea 100644
> --- a/arch/arm64/mm/context.c
> +++ b/arch/arm64/mm/context.c
> @@ -237,6 +237,18 @@ void check_and_switch_context(struct mm_struct *mm, 
> unsigned int cpu)
>               cpu_switch_mm(mm->pgd, mm);
>  }
>  
> +#ifdef CONFIG_ARM64_SW_TTBR0_PAN
> +asmlinkage void __uaccess_ttbr0_enable_c(void)
> +{
> +     __uaccess_ttbr0_enable();
> +}
> +
> +asmlinkage void __uaccess_ttbr0_disable_c(void)
> +{
> +     __uaccess_ttbr0_disable();
> +}
> +#endif
> +
>  /* Errata workaround post TTBRx_EL1 update. */
>  asmlinkage void post_ttbr_update_workaround(void)
>  {
> -- 
> 2.24.0
> 

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