kernel/arch/x86/include/asm/unwind_hints.h, branch linux-5.14.y

objtool: Combine UNWIND_HINT_RET_OFFSET and UNWIND_HINT_FUNC

2021-01-26T17:12:00Z

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 Link: https://lore.kernel.org/r/db9d1f5d79dddfbb3725ef6d8ec3477ad199948d.1611263462.git.jpoimboe@redhat.com

objtool: Make unwind hint definitions available to other architectures

2020-09-10T15:43:13Z

Unwind hints are useful to provide objtool with information about stack states in non-standard functions/code. While the type of information being provided might be very arch specific, the mechanism to provide the information can be useful for other architectures. Move the relevant unwint hint definitions for all architectures to see. [ jpoimboe: REGS_IRET -> REGS_PARTIAL ] Signed-off-by: Julien Thierry Signed-off-by: Josh Poimboeuf

objtool: Remove SAVE/RESTORE hints

2020-04-22T08:53:50Z

The SAVE/RESTORE hints are now unused; remove them. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Miroslav Benes Reviewed-by: Alexandre Chartre Acked-by: Josh Poimboeuf Link: https://lkml.kernel.org/r/20200416115118.926738768@infradead.org Signed-off-by: Ingo Molnar

objtool: Introduce HINT_RET_OFFSET

2020-04-22T08:53:50Z

Normally objtool ensures a function keeps the stack layout invariant. But there is a useful exception, it is possible to stuff the return stack in order to 'inject' a 'call': push $fun ret In this case the invariant mentioned above is violated. Add an objtool HINT to annotate this and allow a function exit with a modified stack frame. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Miroslav Benes Reviewed-by: Alexandre Chartre Acked-by: Josh Poimboeuf Link: https://lkml.kernel.org/r/20200416115118.690601403@infradead.org Signed-off-by: Ingo Molnar

ftrace/x86: Tell objtool to ignore nondeterministic ftrace stack layout

2019-11-13T14:36:50Z

Objtool complains about the new ftrace direct trampoline code: arch/x86/kernel/ftrace_64.o: warning: objtool: ftrace_regs_caller()+0x190: stack state mismatch: cfa1=7+16 cfa2=7+24 Typically, code has a deterministic stack layout, such that at a given instruction address, the stack frame size is always the same. That's not the case for the new ftrace_regs_caller() code after it adjusts the stack for the direct case. Just plead ignorance and assume it's always the non-direct path. Note this creates a tiny window for ORC to get confused. Link: http://lkml.kernel.org/r/20191108225100.ea3bhsbdf6oerj6g@treble Reported-by: Steven Rostedt Signed-off-by: Josh Poimboeuf Signed-off-by: Steven Rostedt (VMware)

x86/unwind/orc: Detect the end of the stack

2018-06-21T14:34:56Z

The existing UNWIND_HINT_EMPTY annotations happen to be good indicators of where entry code calls into C code for the first time. So also use them to mark the end of the stack for the ORC unwinder. Use that information to set unwind->error if the ORC unwinder doesn't unwind all the way to the end. This will be needed for enabling HAVE_RELIABLE_STACKTRACE for the ORC unwinder so we can use it with the livepatch consistency model. Thanks to Jiri Slaby for teaching the ORCs about the unwind hints. Signed-off-by: Josh Poimboeuf Signed-off-by: Jiri Slaby Acked-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: https://lkml.kernel.org/lkml/20180518064713.26440-5-jslaby@suse.cz Signed-off-by: Ingo Molnar

x86/asm: Fix UNWIND_HINT_REGS macro for older binutils

2017-08-10T12:16:19Z

Apparently the binutils 2.20 assembler can't handle the '&&' operator in the UNWIND_HINT_REGS macro. Rearrange the macro to do without it. This fixes the following error: arch/x86/entry/entry_64.S: Assembler messages: arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement Reported-by: Andrew Morton Signed-off-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: 39358a033b2e ("objtool, x86: Add facility for asm code to provide unwind hints") Link: http://lkml.kernel.org/r/e2ad97c1ae49a484644b4aaa4dd3faa4d6d969b2.1502116651.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar

objtool, x86: Add facility for asm code to provide unwind hints

2017-07-18T08:57:44Z

Some asm (and inline asm) code does special things to the stack which objtool can't understand. (Nor can GCC or GNU assembler, for that matter.) In such cases we need a facility for the code to provide annotations, so the unwinder can unwind through it. This provides such a facility, in the form of unwind hints. They're similar to the GNU assembler .cfi* directives, but they give more information, and are needed in far fewer places, because objtool can fill in the blanks by following branches and adjusting the stack pointer for pushes and pops. Signed-off-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Jiri Slaby Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/0f5f3c9104fca559ff4088bece1d14ae3bca52d5.1499786555.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar