[10/17,v6] Add stack_chk_fail_local to libc.so.
Commit Message
From: Nick Alcock <nick.alcock@oracle.com>
This is required by the next commit, which routes all
__stack_chk_fail() calls in libc.so via this function to avoid
the PLT. It has be duplicated in libc.so and libc_nonshared.a
because its entire reason for existence is to be hidden and avoid
the PLT, so the copy in libc.so is not visible from elsewhere.
Also stop all the variants of __stack_chk_fail from being stack-
protected: this makes no sense and risks recursion.
v5: Better explanation. Add no-stack-protection of
__stack_chk_fail_local etc.
v6: Rework as suggested by Andreas: make a shared-only version of
stack_chk_fail_local.c rather than linking libc_nonshared into
libc.
* debug/libc-stack_chk_fail_local.c: New file.
* debug/Makefile (routines): Add it.
(shared-only-routines): Likewise.
(CFLAGS-stack_chk_fail.c): Use $(no-stack-protector).
(CFLAGS-stack_chk_fail_local.c): Likewise.
(CFLAGS-libc-stack_chk_fail_local.c): Likewise.
---
debug/Makefile | 14 +++++++++++++-
debug/libc-stack_chk_fail_local.c | 3 +++
2 files changed, 16 insertions(+), 1 deletion(-)
create mode 100644 debug/libc-stack_chk_fail_local.c
@@ -48,9 +48,21 @@ routines = backtrace backtracesyms backtracesymsfd noophooks \
vdprintf_chk obprintf_chk \
longjmp_chk ____longjmp_chk \
fdelt_chk poll_chk ppoll_chk \
- stack_chk_fail fortify_fail \
+ stack_chk_fail fortify_fail libc-stack_chk_fail_local \
$(static-only-routines)
+
+# stack_chk_fail_local must be non-PIC, thus static-only, but we also
+# want an identical thunk hidden in libc.so to avoid going via the PLT.
+
static-only-routines := warning-nop stack_chk_fail_local
+shared-only-routines += libc-stack_chk_fail_local
+
+# Building the stack-protector failure routines with stack protection
+# makes no sense.
+
+CFLAGS-stack_chk_fail.c = $(no-stack-protector)
+CFLAGS-stack_chk_fail_local.c = $(no-stack-protector)
+CFLAGS-libc-stack_chk_fail_local.c = $(no-stack-protector)
CFLAGS-backtrace.c = -fno-omit-frame-pointer
CFLAGS-sprintf_chk.c = $(libio-mtsafe)
new file mode 100644
@@ -0,0 +1,3 @@
+/* This goes into the shared libc. */
+
+#include <stack_chk_fail_local.c>