linux-stable.git/arch/sh/kernel/dwarf.c, branch linux-2.6.33.y

sh: Don't continue unwinding across interrupts

2010-02-08T01:47:04+00:00

Unfortunately, due to poor DWARF info in current toolchains, unwinding
through interrutps cannot be done reliably. The problem is that the
DWARF info for function epilogues is wrong.

Take this standard epilogue sequence,

80003cc4:       e3 6f           mov     r14,r15
80003cc6:       26 4f           lds.l   @r15+,pr
80003cc8:       f6 6e           mov.l   @r15+,r14
						<---- interrupt here
80003cca:       f6 6b           mov.l   @r15+,r11
80003ccc:       f6 6a           mov.l   @r15+,r10
80003cce:       f6 69           mov.l   @r15+,r9
80003cd0:       0b 00           rts

If we take an interrupt at the highlighted point, the DWARF info will
bogusly claim that the return address can be found at some offset from
the frame pointer, even though the frame pointer was just restored. The
worst part is if the unwinder finds a text address at the bogus stack
address - unwinding will continue, for a bit, until it finally comes
across an unexpected address on the stack and blows up.

The only solution is to stop unwinding once we've calculated the
function that was executing when the interrupt occurred. This PC can be
easily calculated from pt_regs->pc.

Signed-off-by: Matt Fleming 
Signed-off-by: Paul Mundt

sh: Fix access to released memory in dwarf_unwinder_cleanup()

2010-02-02T02:32:22+00:00

Signed-off-by: Marek Skuczynski 
Acked-by: Matt Fleming 
Signed-off-by: Paul Mundt

Merge branch 'sh/stable-updates'

2009-11-09T01:55:36+00:00

sh: unwinder: Fix up invalid PC refetch in dwarf unwinder.

2009-11-06T08:23:33+00:00

The dwarf unwinder presently attempts to provide a sane PC value if none
is provided, however the logic is broken and cases where a previous valid
dwarf frame exists along with a bogus PC value can still proceed. This
fixes up the test and prevents the unwinder from blowing up.

Signed-off-by: Paul Mundt

Merge branch 'sh/stable-updates'

2009-10-26T01:48:18+00:00

Conflicts:
	arch/sh/kernel/dwarf.c

sh: Check for return_to_handler when unwinding the stack

2009-10-26T01:04:56+00:00

When CONFIG_FUNCTION_GRAPH_TRACER is enabled the function graph tracer
may patch return addresses on the stack with the address of
return_to_handler(). This really confuses the DWARF unwinder because it
will try find the caller of return_to_handler(), not the caller of the
real return address.

So teach the DWARF unwinder how to find the real return address whenever
it encounters return_to_handler().

This patch does not cope very well when multiple return addresses on the
stack have been patched. To make it work properly it would require state
to track how many return_to_handler()'s have been seen so that we'd know
where to look in current->curr_ret_stack[]. So for now, instead of
trying to handle this, just moan if more than one return address on the
stack has been patched.

Signed-off-by: Matt Fleming 
Signed-off-by: Paul Mundt

sh: Fix up uninitialized variable warning in dwarf unwinder.

2009-10-19T06:51:21+00:00

Signed-off-by: Paul Mundt

sh: Tidy up the dwarf module helpers.

2009-10-13T04:32:19+00:00

This enables us to build the dwarf unwinder both with modules enabled and
disabled in addition to reducing code size in the latter case. The
helpers are also consolidated, and modified to resemble the BUG module
helpers.

Signed-off-by: Paul Mundt

Merge branch 'sh/dwarf-unwinder'

2009-10-11T23:50:07+00:00

Conflicts:
	arch/sh/kernel/dwarf.c

sh: Remove any reference to recursive functions from comments

2009-10-11T16:12:32+00:00

Originally, dwarf_unwind_stack() was a recursive function and it seems
that some of the old comments were never updated.

Signed-off-by: Matt Fleming