get_segment_base() will be used by the unwind_user code, so make it
global and rename it so it doesn't conflict with a KVM function of the
same name.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/events/core.c            | 10 +++++-----
 arch/x86/include/asm/perf_event.h |  2 ++
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index c75c482d4c52..23ac6343cf86 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2790,7 +2790,7 @@ valid_user_frame(const void __user *fp, unsigned long size)
 	return __access_ok(fp, size);
 }
 
-static unsigned long get_segment_base(unsigned int segment)
+unsigned long segment_base_address(unsigned int segment)
 {
 	struct desc_struct *desc;
 	unsigned int idx = segment >> 3;
@@ -2874,8 +2874,8 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry_ctx *ent
 	if (user_64bit_mode(regs))
 		return 0;
 
-	cs_base = get_segment_base(regs->cs);
-	ss_base = get_segment_base(regs->ss);
+	cs_base = segment_base_address(regs->cs);
+	ss_base = segment_base_address(regs->ss);
 
 	fp = compat_ptr(ss_base + regs->bp);
 	pagefault_disable();
@@ -2994,11 +2994,11 @@ static unsigned long code_segment_base(struct pt_regs *regs)
 		return 0x10 * regs->cs;
 
 	if (user_mode(regs) && regs->cs != __USER_CS)
-		return get_segment_base(regs->cs);
+		return segment_base_address(regs->cs);
 #else
 	if (user_mode(regs) && !user_64bit_mode(regs) &&
 	    regs->cs != __USER32_CS)
-		return get_segment_base(regs->cs);
+		return segment_base_address(regs->cs);
 #endif
 	return 0;
 }
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index d95f902acc52..75956c68356f 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -639,4 +639,6 @@ static __always_inline void perf_lopwr_cb(bool lopwr_in)
 
 #define arch_perf_out_copy_user copy_from_user_nmi
 
+unsigned long segment_base_address(unsigned int segment);
+
 #endif /* _ASM_X86_PERF_EVENT_H */
-- 
2.48.1

On Tue, 21 Jan 2025 18:31:06 -0800
Josh Poimboeuf <jpoimboe@kernel.org> wrote:

> diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
> index c75c482d4c52..23ac6343cf86 100644
> --- a/arch/x86/events/core.c
> +++ b/arch/x86/events/core.c
> @@ -2790,7 +2790,7 @@ valid_user_frame(const void __user *fp, unsigned long size)
>  	return __access_ok(fp, size);
>  }
>  
> -static unsigned long get_segment_base(unsigned int segment)
> +unsigned long segment_base_address(unsigned int segment)
>  {
>  	struct desc_struct *desc;
>  	unsigned int idx = segment >> 3;

As this requires interrupts disabled, and if you do move this out of this
file, you probably should add:

	lockdep_assert_irqs_disabled();

-- Steve

On Fri, Jan 24, 2025 at 03:09:27PM -0500, Steven Rostedt wrote:
> On Tue, 21 Jan 2025 18:31:06 -0800
> Josh Poimboeuf <jpoimboe@kernel.org> wrote:
> 
> > diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
> > index c75c482d4c52..23ac6343cf86 100644
> > --- a/arch/x86/events/core.c
> > +++ b/arch/x86/events/core.c
> > @@ -2790,7 +2790,7 @@ valid_user_frame(const void __user *fp, unsigned long size)
> >  	return __access_ok(fp, size);
> >  }
> >  
> > -static unsigned long get_segment_base(unsigned int segment)
> > +unsigned long segment_base_address(unsigned int segment)
> >  {
> >  	struct desc_struct *desc;
> >  	unsigned int idx = segment >> 3;
> 
> As this requires interrupts disabled, and if you do move this out of this
> file, you probably should add:
> 
> 	lockdep_assert_irqs_disabled();

Indeed...

-- 
Josh

On Tue, Jan 21, 2025 at 06:31:06PM -0800, Josh Poimboeuf wrote:
> get_segment_base() will be used by the unwind_user code, so make it
> global and rename it so it doesn't conflict with a KVM function of the
> same name.

Should it not also get moved out of the perf code in this case?

On Wed, Jan 22, 2025 at 01:51:54PM +0100, Peter Zijlstra wrote:
> On Tue, Jan 21, 2025 at 06:31:06PM -0800, Josh Poimboeuf wrote:
> > get_segment_base() will be used by the unwind_user code, so make it
> > global and rename it so it doesn't conflict with a KVM function of the
> > same name.
> 
> Should it not also get moved out of the perf code in this case?

True, I'll try to find it a better home.

-- 
Josh