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[PATCH] [BZ #18134] x86-64 ld.so doesn't preserve bound registers
- From: "H.J. Lu" <hongjiu dot lu at intel dot com>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Cc: Igor Zamyatin <igor dot zamyatin at intel dot com>
- Date: Mon, 16 Mar 2015 14:37:53 -0700
- Subject: [PATCH] [BZ #18134] x86-64 ld.so doesn't preserve bound registers
- Authentication-results: sourceware.org; auth=none
- Reply-to: "H.J. Lu" <hjl dot tools at gmail dot com>
We need to add a BND prefix before indirect branch at the end of
_dl_runtime_resolve to preserve bound registers.
Tested on x32, x86-64 Haswell and x86-64 Skylake. I will check it into
master shortly and backport it to 2.21 branch.
Igor, this patch doesn't fix _dl_runtime_profile. Can you take care of
_dl_runtime_profile?
Thanks.
H.J.
---
[BZ #18134]
* sysdeps/x86_64/dl-trampoline.S (PRESERVE_BND_REGS_PREFIX): New.
(_dl_runtime_resolve): Add a BND prefix before indirect branch.
---
sysdeps/x86_64/dl-trampoline.S | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/sysdeps/x86_64/dl-trampoline.S b/sysdeps/x86_64/dl-trampoline.S
index 394441d..5f9b35d 100644
--- a/sysdeps/x86_64/dl-trampoline.S
+++ b/sysdeps/x86_64/dl-trampoline.S
@@ -30,6 +30,7 @@
/* X32 saves RCX, RDX, RSI, RDI, R8 and R9 plus RAX. */
# define REGISTER_SAVE_AREA (8 * 7)
# define REGISTER_SAVE_RAX 0
+# define PRESERVE_BND_REGS_PREFIX
#else
/* X86-64 saves RCX, RDX, RSI, RDI, R8 and R9 plus RAX as well as BND0,
BND1, BND2, BND3. */
@@ -40,6 +41,11 @@
# define REGISTER_SAVE_BND2 (REGISTER_SAVE_BND1 + 16)
# define REGISTER_SAVE_BND3 (REGISTER_SAVE_BND2 + 16)
# define REGISTER_SAVE_RAX (REGISTER_SAVE_BND3 + 16)
+# ifdef HAVE_MPX_SUPPORT
+# define PRESERVE_BND_REGS_PREFIX bnd
+# else
+# define PRESERVE_BND_REGS_PREFIX .byte 0xf2
+# endif
#endif
#define REGISTER_SAVE_RCX (REGISTER_SAVE_RAX + 8)
#define REGISTER_SAVE_RDX (REGISTER_SAVE_RCX + 8)
@@ -112,6 +118,8 @@ _dl_runtime_resolve:
# Adjust stack(PLT did 2 pushes)
addq $(REGISTER_SAVE_AREA + 16), %rsp
cfi_adjust_cfa_offset(-(REGISTER_SAVE_AREA + 16))
+ # Preserve bound registers.
+ PRESERVE_BND_REGS_PREFIX
jmp *%r11 # Jump to function address.
cfi_endproc
.size _dl_runtime_resolve, .-_dl_runtime_resolve
--
1.9.3