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131484c8da
So the dwarf2 annotations in low level assembly code have become an increasing hindrance: unreadable, messy macros mixed into some of the most security sensitive code paths of the Linux kernel. These debug info annotations don't even buy the upstream kernel anything: dwarf driven stack unwinding has caused problems in the past so it's out of tree, and the upstream kernel only uses the much more robust framepointers based stack unwinding method. In addition to that there's a steady, slow bitrot going on with these annotations, requiring frequent fixups. There's no tooling and no functionality upstream that keeps it correct. So burn down the sick forest, allowing new, healthier growth: 27 files changed, 350 insertions(+), 1101 deletions(-) Someone who has the willingness and time to do this properly can attempt to reintroduce dwarf debuginfo in x86 assembly code plus dwarf unwinding from first principles, with the following conditions: - it should be maximally readable, and maximally low-key to 'ordinary' code reading and maintenance. - find a build time method to insert dwarf annotations automatically in the most common cases, for pop/push instructions that manipulate the stack pointer. This could be done for example via a preprocessing step that just looks for common patterns - plus special annotations for the few cases where we want to depart from the default. We have hundreds of CFI annotations, so automating most of that makes sense. - it should come with build tooling checks that ensure that CFI annotations are sensible. We've seen such efforts from the framepointer side, and there's no reason it couldn't be done on the dwarf side. Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frédéric Weisbecker <fweisbec@gmail.com Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jan Beulich <JBeulich@suse.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
69 lines
1.5 KiB
ArmAsm
69 lines
1.5 KiB
ArmAsm
/*
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* Save registers before calling assembly functions. This avoids
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* disturbance of register allocation in some inline assembly constructs.
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* Copyright 2001,2002 by Andi Kleen, SuSE Labs.
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* Added trace_hardirqs callers - Copyright 2007 Steven Rostedt, Red Hat, Inc.
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* Subject to the GNU public license, v.2. No warranty of any kind.
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*/
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#include <linux/linkage.h>
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#include <asm/calling.h>
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#include <asm/asm.h>
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/* rdi: arg1 ... normal C conventions. rax is saved/restored. */
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.macro THUNK name, func, put_ret_addr_in_rdi=0
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.globl \name
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\name:
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/* this one pushes 9 elems, the next one would be %rIP */
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pushq %rdi
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pushq %rsi
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pushq %rdx
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pushq %rcx
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pushq %rax
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pushq %r8
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pushq %r9
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pushq %r10
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pushq %r11
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.if \put_ret_addr_in_rdi
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/* 9*8(%rsp) is return addr on stack */
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movq 9*8(%rsp), %rdi
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.endif
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call \func
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jmp restore
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_ASM_NOKPROBE(\name)
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.endm
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#ifdef CONFIG_TRACE_IRQFLAGS
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THUNK trace_hardirqs_on_thunk,trace_hardirqs_on_caller,1
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THUNK trace_hardirqs_off_thunk,trace_hardirqs_off_caller,1
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#endif
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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THUNK lockdep_sys_exit_thunk,lockdep_sys_exit
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#endif
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#ifdef CONFIG_PREEMPT
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THUNK ___preempt_schedule, preempt_schedule
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#ifdef CONFIG_CONTEXT_TRACKING
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THUNK ___preempt_schedule_context, preempt_schedule_context
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#endif
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#endif
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#if defined(CONFIG_TRACE_IRQFLAGS) \
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|| defined(CONFIG_DEBUG_LOCK_ALLOC) \
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|| defined(CONFIG_PREEMPT)
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restore:
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popq %r11
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popq %r10
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popq %r9
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popq %r8
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popq %rax
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popq %rcx
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popq %rdx
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popq %rsi
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popq %rdi
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ret
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_ASM_NOKPROBE(restore)
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#endif
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