diff mbox series

[v2,1/5] arch/arc: unwind.c: replace swap function with built-in one

Message ID 23405591554057090@iva8-b333b7f98ab0.qloud-c.yandex.net
State New
Headers show
Series simple sort swap function improvements | expand

Commit Message

Andrey Abramov March 31, 2019, 6:31 p.m. UTC 
Replace swap_eh_frame_hdr_table_entries with built-in one, because
swap_eh_frame_hdr_table_entries does a simple byte to byte swap.

Since Spectre mitigations have made indirect function calls more
expensive, and the default simple byte copies swap is implemented
without them, an "optimized" custom swap function is now
a waste of time as well as code.

Signed-off-by: Andrey Abramov <st5pub@yandex.ru>
Reviewed by: George Spelvin <lkml@sdf.org>
---
 arch/arc/kernel/unwind.c | 20 ++------------------
 1 file changed, 2 insertions(+), 18 deletions(-)

Comments

Vineet Gupta April 1, 2019, 5:53 p.m. UTC | #1 
On 3/31/19 11:31 AM, Andrey Abramov wrote:
> Replace swap_eh_frame_hdr_table_entries with built-in one, because
> swap_eh_frame_hdr_table_entries does a simple byte to byte swap.
>
> Since Spectre mitigations have made indirect function calls more
> expensive, and the default simple byte copies swap is implemented
> without them, an "optimized" custom swap function is now
> a waste of time as well as code.
>
> Signed-off-by: Andrey Abramov <st5pub@yandex.ru>
> Reviewed by: George Spelvin <lkml@sdf.org>
>

Acked-by: Vineet Gupta <vgupta@synopsys.com>

Thx,
-Vineet
diff mbox series

Patch

diff --git a/arch/arc/kernel/unwind.c b/arch/arc/kernel/unwind.c
index 271e9fafa479..7610fe84afea 100644
--- a/arch/arc/kernel/unwind.c
+++ b/arch/arc/kernel/unwind.c
@@ -248,20 +248,6 @@  static int cmp_eh_frame_hdr_table_entries(const void *p1, const void *p2)
 	return (e1->start > e2->start) - (e1->start < e2->start);
 }
 
-static void swap_eh_frame_hdr_table_entries(void *p1, void *p2, int size)
-{
-	struct eh_frame_hdr_table_entry *e1 = p1;
-	struct eh_frame_hdr_table_entry *e2 = p2;
-	unsigned long v;
-
-	v = e1->start;
-	e1->start = e2->start;
-	e2->start = v;
-	v = e1->fde;
-	e1->fde = e2->fde;
-	e2->fde = v;
-}
-
 static void init_unwind_hdr(struct unwind_table *table,
 			    void *(*alloc) (unsigned long))
 {
@@ -354,10 +340,8 @@  static void init_unwind_hdr(struct unwind_table *table,
 	}
 	WARN_ON(n != header->fde_count);
 
-	sort(header->table,
-	     n,
-	     sizeof(*header->table),
-	     cmp_eh_frame_hdr_table_entries, swap_eh_frame_hdr_table_entries);
+	sort(header->table, n,
+	     sizeof(*header->table), cmp_eh_frame_hdr_table_entries, NULL);
 
 	table->hdrsz = hdrSize;
 	smp_wmb();