Re: [PATCH] x86/asm: Merge KSTK_ESP() implementations

[H. Peter Anvin]

On March 3, 2025 10:31:11 AM PST, Brian Gerst <brgerst@xxxxxxxxx> wrote:
>Commit 263042e4630a ("Save user RSP in pt_regs->sp on SYSCALL64
>fastpath") simplified the 64-bit implementation of KSTK_ESP() which is
>now identical to 32-bit.  Merge them into a common definition.
>
>No functional change.
>
>Signed-off-by: Brian Gerst <brgerst@xxxxxxxxx>
>---
> arch/x86/include/asm/processor.h | 5 +----
> arch/x86/kernel/process_64.c     | 5 -----
> 2 files changed, 1 insertion(+), 9 deletions(-)
>
>diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
>index a969bea1ed07..55f0e48413b0 100644
>--- a/arch/x86/include/asm/processor.h
>+++ b/arch/x86/include/asm/processor.h
>@@ -652,8 +652,6 @@ static __always_inline void prefetchw(const void *x)
> 	.sysenter_cs		= __KERNEL_CS,				  \
> }
> 
>-#define KSTK_ESP(task)		(task_pt_regs(task)->sp)
>-
> #else
> extern unsigned long __top_init_kernel_stack[];
> 
>@@ -661,8 +659,6 @@ extern unsigned long __top_init_kernel_stack[];
> 	.sp	= (unsigned long)&__top_init_kernel_stack,		\
> }
> 
>-extern unsigned long KSTK_ESP(struct task_struct *task);
>-
> #endif /* CONFIG_X86_64 */
> 
> extern void start_thread(struct pt_regs *regs, unsigned long new_ip,
>@@ -676,6 +672,7 @@ extern void start_thread(struct pt_regs *regs, unsigned long new_ip,
> #define TASK_UNMAPPED_BASE		__TASK_UNMAPPED_BASE(TASK_SIZE_LOW)
> 
> #define KSTK_EIP(task)		(task_pt_regs(task)->ip)
>+#define KSTK_ESP(task)		(task_pt_regs(task)->sp)
> 
> /* Get/set a process' ability to use the timestamp counter instruction */
> #define GET_TSC_CTL(adr)	get_tsc_mode((adr))
>diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
>index 4ca73ddfb30b..f983d2a57ac3 100644
>--- a/arch/x86/kernel/process_64.c
>+++ b/arch/x86/kernel/process_64.c
>@@ -979,8 +979,3 @@ long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2)
> 
> 	return ret;
> }
>-
>-unsigned long KSTK_ESP(struct task_struct *task)
>-{
>-	return task_pt_regs(task)->sp;
>-}
>
>base-commit: 693c8502970a533363e9ece482c80bb6db0c12a5

Why using the macro version?