diff options
| author | Steven Rostedt (Red Hat) <rostedt@goodmis.org> | 2016-12-08 12:48:26 -0500 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2017-03-16 02:26:33 +0000 |
| commit | 11c7f11f595f8086c254676102f2db75ac8e4cee (patch) | |
| tree | 7790e558a0cb9712d9702aacf67b99d060156280 | |
| parent | 54404765f851e4de9fdd81071786cb62f792f59f (diff) | |
ftrace/x86_32: Set ftrace_stub to weak to prevent gcc from using short jumps to it
commit 847fa1a6d3d00f3bdf68ef5fa4a786f644a0dd67 upstream.
With new binutils, gcc may get smart with its optimization and change a jmp
from a 5 byte jump to a 2 byte one even though it was jumping to a global
function. But that global function existed within a 2 byte radius, and gcc
was able to optimize it. Unfortunately, that jump was also being modified
when function graph tracing begins. Since ftrace expected that jump to be 5
bytes, but it was only two, it overwrote code after the jump, causing a
crash.
This was fixed for x86_64 with commit 8329e818f149, with the same subject as
this commit, but nothing was done for x86_32.
Fixes: d61f82d06672 ("ftrace: use dynamic patching for updating mcount calls")
Reported-by: Colin Ian King <colin.king@canonical.com>
Tested-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | arch/x86/kernel/entry_32.S | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S index 0d0c9d4ab6d5..2c123171944a 100644 --- a/arch/x86/kernel/entry_32.S +++ b/arch/x86/kernel/entry_32.S @@ -1086,8 +1086,8 @@ ftrace_graph_call: jmp ftrace_stub #endif -.globl ftrace_stub -ftrace_stub: +/* This is weak to keep gas from relaxing the jumps */ +WEAK(ftrace_stub) ret END(ftrace_caller) |