1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
|
# commit 0b2c2ace3601d5d59cf89130b16840e7f132f7a6
# Author: Alan Modra <amodra@gmail.com>
# Date: Sat Aug 17 18:36:45 2013 +0930
#
# PowerPC makecontext
# http://sourceware.org/ml/libc-alpha/2013-08/msg00092.html
#
# Use conditional form of branch and link to avoid destroying the cpu
# link stack used to predict blr return addresses.
#
# * sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S: Use
# conditional form of branch and link when obtaining pc.
# * sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S: Likewise.
#
---
# sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S | 8 ++++++--
# sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S | 6 ++++--
# 2 files changed, 10 insertions(+), 4 deletions(-)
#
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S
@@ -47,7 +47,9 @@
#ifdef PIC
mflr r0
cfi_register(lr,r0)
- bl 1f
+ /* Use this conditional form of branch and link to avoid destroying
+ the cpu link stack used to predict blr return addresses. */
+ bcl 20,31,1f
1: mflr r6
addi r6,r6,L(exitcode)-1b
mtlr r0
@@ -136,7 +138,9 @@
#ifdef PIC
mflr r0
cfi_register(lr,r0)
- bl 1f
+ /* Use this conditional form of branch and link to avoid destroying
+ the cpu link stack used to predict blr return addresses. */
+ bcl 20,31,1f
1: mflr r6
addi r6,r6,L(novec_exitcode)-1b
mtlr r0
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S
@@ -124,8 +124,10 @@
/* If the target function returns we need to do some cleanup. We use a
code trick to get the address of our cleanup function into the link
- register. Do not add any code between here and L(exitcode). */
- bl L(gotexitcodeaddr);
+ register. Do not add any code between here and L(exitcode).
+ Use this conditional form of branch and link to avoid destroying
+ the cpu link stack used to predict blr return addresses. */
+ bcl 20,31,L(gotexitcodeaddr);
/* This is the helper code which gets called if a function which
is registered with 'makecontext' returns. In this case we
|
