ftrace/x86_32: Set ftrace_stub to weak to prevent gcc from using short jumps to it

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commit 847fa1a6d3 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 8329e818f1, with the same subject as
this commit, but nothing was done for x86_32.

Fixes: d61f82d066 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Steven Rostedt (Red Hat) 2016-12-08 12:48:26 -05:00 • committed by Greg Kroah-Hartman

parent e80ceb2da5

commit 21be088c36

1 changed files with 2 additions and 2 deletions

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arch/x86/entry/entry_32.S

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