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authorH.J. Lu <hjl.tools@gmail.com>2015-07-09 09:30:09 -0700
committerH.J. Lu <hjl.tools@gmail.com>2015-07-09 09:30:20 -0700
commit2eb9ef29b698bb7706833236b4b9041f0c23ceef (patch)
treedcd7f9da582252e2e77abfcae48079047d59a0c5
parent14c5cbabc2d11004ab223ae5eae761ddf83ef99e (diff)
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Improve bndmov encoding with zero displacement
If x86-64 assembler doesn't support MPX, we encode bndmov instruction by
hand.  When displacement is zero, assembler generates shorter encoding.
This patch improves bndmov encoding with zero displacement so that ld.so
is identical when using assemblers with and without MPX support.

	* sysdeps/x86_64/dl-trampoline.S (_dl_runtime_resolve): Improve
	bndmov encoding with zero displacement.
-rw-r--r--ChangeLog5
-rw-r--r--sysdeps/x86_64/dl-trampoline.S8
2 files changed, 13 insertions, 0 deletions
diff --git a/ChangeLog b/ChangeLog
index f8765bb6b7..c48416b0e5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2015-07-09  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* sysdeps/x86_64/dl-trampoline.S (_dl_runtime_resolve): Improve
+	bndmov encoding with zero displacement.
+
 2015-07-09  Igor Zamyatin  <igor.zamyatin@intel.com>
 	    H.J. Lu  <hongjiu.lu@intel.com>
 
diff --git a/sysdeps/x86_64/dl-trampoline.S b/sysdeps/x86_64/dl-trampoline.S
index b151d3566d..678c57fc24 100644
--- a/sysdeps/x86_64/dl-trampoline.S
+++ b/sysdeps/x86_64/dl-trampoline.S
@@ -80,7 +80,11 @@ _dl_runtime_resolve:
 	bndmov %bnd2, REGISTER_SAVE_BND2(%rsp)
 	bndmov %bnd3, REGISTER_SAVE_BND3(%rsp)
 # else
+#  if REGISTER_SAVE_BND0 == 0
+	.byte 0x66,0x0f,0x1b,0x04,0x24
+#  else
 	.byte 0x66,0x0f,0x1b,0x44,0x24,REGISTER_SAVE_BND0
+#  endif
 	.byte 0x66,0x0f,0x1b,0x4c,0x24,REGISTER_SAVE_BND1
 	.byte 0x66,0x0f,0x1b,0x54,0x24,REGISTER_SAVE_BND2
 	.byte 0x66,0x0f,0x1b,0x5c,0x24,REGISTER_SAVE_BND3
@@ -104,7 +108,11 @@ _dl_runtime_resolve:
 	.byte 0x66,0x0f,0x1a,0x5c,0x24,REGISTER_SAVE_BND3
 	.byte 0x66,0x0f,0x1a,0x54,0x24,REGISTER_SAVE_BND2
 	.byte 0x66,0x0f,0x1a,0x4c,0x24,REGISTER_SAVE_BND1
+#  if REGISTER_SAVE_BND0 == 0
+	.byte 0x66,0x0f,0x1a,0x04,0x24
+#  else
 	.byte 0x66,0x0f,0x1a,0x44,0x24,REGISTER_SAVE_BND0
+#  endif
 # endif
 #endif
 	# Get register content back.