x86/entry/64: Fix stack return address retrieval in thunk

With CONFIG_FRAME_POINTER enabled, a thunk can pass a bad return address
value to the called function.  '9*8(%rsp)' actually gets the frame
pointer, not the return address.

The only users of the 'put_ret_addr_in_rdi' option are two functions
which trace the enabling and disabling of interrupts, so this bug can
result in bad debug or tracing information with CONFIG_IRQSOFF_TRACER or
CONFIG_PROVE_LOCKING.

Fix this by implementing the suggestion of Linus: explicitly push
the frame pointer all the time and constify the stack offsets that
way. This is both correct and easier to read.

Reported-by: Matt Fleming <[email protected]>
Signed-off-by: Josh Poimboeuf <[email protected]>
[ Extended the changelog a bit. ]
Acked-by: Linus Torvalds <[email protected]>
Cc: Alex Thorlton <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Fixes: 058fb73274f9 ("x86/asm/entry: Create stack frames in thunk functions")
Link: http://lkml.kernel.org/r/20160517180606.v5o7wcgdni7443ol@treble
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions