linux-kernel - Re: [PATCH v5 10/16] x86/percpu/64: Remove fixed_percpu

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Message-ID: <CAFULd4ahndLYEv6+CEkFvrW6L+dRTdA0VeV=WMdHeiBUdtYtOg@mail.gmail.com>
Date: Thu, 7 Nov 2024 14:32:03 +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>, "H . Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Borislav Petkov <bp@...en8.de>, Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH v5 10/16] x86/percpu/64: Remove fixed_percpu_data

On Tue, Nov 5, 2024 at 4:58 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 ae50d5d4fa26..e1b856e2f944 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -418,14 +418,6 @@ 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 1f33d5feb050..d6102e772c7e 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -2020,10 +2020,6 @@ 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 42d1c05b0207..859ff7c0dc02 100644
> --- a/arch/x86/kernel/vmlinux.lds.S
> +++ b/arch/x86/kernel/vmlinux.lds.S
> @@ -456,7 +456,6 @@ PROVIDE(__ref_stack_chk_guard = __stack_chk_guard);
>   */
>  #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 8b5e2bc3d241..a661a6bab4cf 100644
> --- a/arch/x86/tools/relocs.c
> +++ b/arch/x86/tools/relocs.c
> @@ -829,7 +829,6 @@ 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)
> --
> 2.47.0
>