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objtool: Combine UNWIND_HINT_RET_OFFSET and UNWIND_HINT_FUNC

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commit b735bd3e68824316655252a931a3353a6ebc036f upstream.

The ORC metadata generated for UNWIND_HINT_FUNC isn't actually very
func-like.  With certain usages it can cause stack state mismatches
because it doesn't set the return address (CFI_RA).

Also, users of UNWIND_HINT_RET_OFFSET no longer need to set a custom
return stack offset.  Instead they just need to specify a func-like
situation, so the current ret_offset code is hacky for no good reason.

Solve both problems by simplifying the RET_OFFSET handling and
converting it into a more useful UNWIND_HINT_FUNC.

If we end up needing the old 'ret_offset' functionality again in the
future, we should be able to support it pretty easily with the addition
of a custom 'sp_offset' in UNWIND_HINT_FUNC.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/db9d1f5d79dddfbb3725ef6d8ec3477ad199948d.1611263462.git.jpoimboe@redhat.com
[bwh: Backported to 5.10:
 - Don't use bswap_if_needed() since we don't have any of the other fixes
   for mixed-endian cross-compilation
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Josh Poimboeuf
2021-01-21 15:29:24 -06:00
committed by Greg Kroah-Hartman
parent 53e89bc78e
commit 3116dee270
8 changed files with 29 additions and 40 deletions
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5
tools/include/linux/objtool.h
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@@ -29,11 +29,14 @@ struct unwind_hint {
*
* UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
* sp_reg+sp_offset points to the iret return frame.
*
* UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
* Useful for code which doesn't have an ELF function annotation.
*/
#define UNWIND_HINT_TYPE_CALL 0
#define UNWIND_HINT_TYPE_REGS 1
#define UNWIND_HINT_TYPE_REGS_PARTIAL 2
#define UNWIND_HINT_TYPE_RET_OFFSET 3
#define UNWIND_HINT_TYPE_FUNC 3
#ifdef CONFIG_STACK_VALIDATION