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fb799447ae
Mark reported that the ORC unwinder incorrectly marks an unwind as
reliable when the unwind terminates prematurely in the dark corners of
return_to_handler() due to lack of information about the next frame.
The problem is UNWIND_HINT_EMPTY is used in two different situations:
1) The end of the kernel stack unwind before hitting user entry, boot
code, or fork entry
2) A blind spot in ORC coverage where the unwinder has to bail due to
lack of information about the next frame
The ORC unwinder has no way to tell the difference between the two.
When it encounters an undefined stack state with 'end=1', it blindly
marks the stack reliable, which can break the livepatch consistency
model.
Fix it by splitting UNWIND_HINT_EMPTY into UNWIND_HINT_UNDEFINED and
UNWIND_HINT_END_OF_STACK.
Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/fd6212c8b450d3564b855e1cb48404d6277b4d9f.1677683419.git.jpoimboe@kernel.org
57 lines
1.8 KiB
C
57 lines
1.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_OBJTOOL_TYPES_H
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#define _LINUX_OBJTOOL_TYPES_H
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#ifndef __ASSEMBLY__
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#include <linux/types.h>
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/*
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* This struct is used by asm and inline asm code to manually annotate the
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* location of registers on the stack.
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*/
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struct unwind_hint {
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u32 ip;
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s16 sp_offset;
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u8 sp_reg;
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u8 type;
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u8 signal;
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};
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#endif /* __ASSEMBLY__ */
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/*
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* UNWIND_HINT_TYPE_UNDEFINED: A blind spot in ORC coverage which can result in
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* a truncated and unreliable stack unwind.
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*
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* UNWIND_HINT_TYPE_END_OF_STACK: The end of the kernel stack unwind before
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* hitting user entry, boot code, or fork entry (when there are no pt_regs
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* available).
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*
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* UNWIND_HINT_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP
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* (the caller's SP right before it made the call). Used for all callable
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* functions, i.e. all C code and all callable asm functions.
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*
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* UNWIND_HINT_TYPE_REGS: Used in entry code to indicate that sp_reg+sp_offset
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* points to a fully populated pt_regs from a syscall, interrupt, or exception.
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*
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* UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
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* sp_reg+sp_offset points to the iret return frame.
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*
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* UNWIND_HINT_TYPE_FUNC: Generate the unwind metadata of a callable function.
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* Useful for code which doesn't have an ELF function annotation.
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*
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* UNWIND_HINT_TYPE_{SAVE,RESTORE}: Save the unwind metadata at a certain
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* location so that it can be restored later.
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*/
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#define UNWIND_HINT_TYPE_UNDEFINED 0
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#define UNWIND_HINT_TYPE_END_OF_STACK 1
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#define UNWIND_HINT_TYPE_CALL 2
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#define UNWIND_HINT_TYPE_REGS 3
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#define UNWIND_HINT_TYPE_REGS_PARTIAL 4
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/* The below hint types don't have corresponding ORC types */
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#define UNWIND_HINT_TYPE_FUNC 5
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#define UNWIND_HINT_TYPE_SAVE 6
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#define UNWIND_HINT_TYPE_RESTORE 7
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#endif /* _LINUX_OBJTOOL_TYPES_H */
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