linux-kernel - Re: [PATCH v4 10/16] x86/percpu/64: Remove fixed_percpu

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Date: Sat, 23 Mar 2024 18:14:56 +0100
From: Uros Bizjak <ubizjak@...il.com>
To: Brian Gerst <brgerst@...il.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, 
	Ingo Molnar <mingo@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, 
	"H . Peter Anvin" <hpa@...or.com>, David.Laight@...lab.com
Subject: Re: [PATCH v4 10/16] x86/percpu/64: Remove fixed_percpu_data

On Fri, Mar 22, 2024 at 5:52 PM Brian Gerst <brgerst@...il.com> wrote:
>
> Now that the stack protector canary value is a normal percpu variable,
> fixed_percpu_data is unused and can be removed.
>
> Signed-off-by: Brian Gerst <brgerst@...il.com>

Reviewed-by: Uros Bizjak <ubizjak@...il.com>

> ---
>  arch/x86/include/asm/processor.h | 8 --------
>  arch/x86/kernel/cpu/common.c     | 4 ----
>  arch/x86/kernel/vmlinux.lds.S    | 1 -
>  arch/x86/tools/relocs.c          | 1 -
>  4 files changed, 14 deletions(-)
>
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 40d6add8ff31..1f15a7bee876 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -386,14 +386,6 @@ struct irq_stack {
>  } __aligned(IRQ_STACK_SIZE);
>
>  #ifdef CONFIG_X86_64
> -struct fixed_percpu_data {
> -       char            gs_base[40];
> -       unsigned long   reserved;
> -};
> -
> -DECLARE_PER_CPU_FIRST(struct fixed_percpu_data, fixed_percpu_data) __visible;
> -DECLARE_INIT_PER_CPU(fixed_percpu_data);
> -
>  static inline unsigned long cpu_kernelmode_gs_base(int cpu)
>  {
>  #ifdef CONFIG_SMP
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index f49e8f5b858d..395a8831d507 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -1997,10 +1997,6 @@ EXPORT_PER_CPU_SYMBOL(pcpu_hot);
>  EXPORT_PER_CPU_SYMBOL(const_pcpu_hot);
>
>  #ifdef CONFIG_X86_64
> -DEFINE_PER_CPU_FIRST(struct fixed_percpu_data,
> -                    fixed_percpu_data) __aligned(PAGE_SIZE) __visible;
> -EXPORT_PER_CPU_SYMBOL_GPL(fixed_percpu_data);
> -
>  static void wrmsrl_cstar(unsigned long val)
>  {
>         /*
> diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
> index 0b152f96c24e..667202ebd37f 100644
> --- a/arch/x86/kernel/vmlinux.lds.S
> +++ b/arch/x86/kernel/vmlinux.lds.S
> @@ -473,7 +473,6 @@ SECTIONS
>   */
>  #define INIT_PER_CPU(x) init_per_cpu__##x = ABSOLUTE(x)
>  INIT_PER_CPU(gdt_page);
> -INIT_PER_CPU(fixed_percpu_data);
>  INIT_PER_CPU(irq_stack_backing_store);
>
>  #ifdef CONFIG_MITIGATION_UNRET_ENTRY
> diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
> index 016650ddaf7f..65e6f3d6d890 100644
> --- a/arch/x86/tools/relocs.c
> +++ b/arch/x86/tools/relocs.c
> @@ -834,7 +834,6 @@ static void percpu_init(void)
>   *     __per_cpu_load
>   *
>   * The "gold" linker incorrectly associates:
> - *     init_per_cpu__fixed_percpu_data
>   *     init_per_cpu__gdt_page
>   */
>  static int is_percpu_sym(ElfW(Sym) *sym, const char *symname)
> --
> 2.44.0
>