54a0151041
The prevent_tail_call() macro works around the problem of the compiler clobbering argument words on the stack, which for asmlinkage functions is the caller's (user's) struct pt_regs. The tail/sibling-call optimization is not the only way that the compiler can decide to use stack argument words as scratch space, which we have to prevent. Other optimizations can do it too. Until we have new compiler support to make "asmlinkage" binding on the compiler's own use of the stack argument frame, we have work around all the manifestations of this issue that crop up. More cases seem to be prevented by also keeping the incoming argument variables live at the end of the function. This makes their original stack slots attractive places to leave those variables, so the compiler tends not clobber them for something else. It's still no guarantee, but it handles some observed cases that prevent_tail_call() did not. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
77 lines
1.3 KiB
C
77 lines
1.3 KiB
C
#ifndef _LINUX_LINKAGE_H
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#define _LINUX_LINKAGE_H
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#include <asm/linkage.h>
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#ifdef __cplusplus
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#define CPP_ASMLINKAGE extern "C"
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#else
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#define CPP_ASMLINKAGE
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#endif
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#ifndef asmlinkage
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#define asmlinkage CPP_ASMLINKAGE
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#endif
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#ifndef asmregparm
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# define asmregparm
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#endif
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#ifndef asmlinkage_protect
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# define asmlinkage_protect(n, ret, args...) do { } while (0)
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#endif
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#ifndef __ALIGN
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#define __ALIGN .align 4,0x90
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#define __ALIGN_STR ".align 4,0x90"
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#endif
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#ifdef __ASSEMBLY__
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#define ALIGN __ALIGN
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#define ALIGN_STR __ALIGN_STR
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#ifndef ENTRY
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#define ENTRY(name) \
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.globl name; \
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ALIGN; \
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name:
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#endif
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#ifndef WEAK
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#define WEAK(name) \
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.weak name; \
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name:
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#endif
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#define KPROBE_ENTRY(name) \
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.pushsection .kprobes.text, "ax"; \
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ENTRY(name)
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#define KPROBE_END(name) \
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END(name); \
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.popsection
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#ifndef END
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#define END(name) \
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.size name, .-name
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#endif
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/* If symbol 'name' is treated as a subroutine (gets called, and returns)
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* then please use ENDPROC to mark 'name' as STT_FUNC for the benefit of
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* static analysis tools such as stack depth analyzer.
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*/
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#ifndef ENDPROC
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#define ENDPROC(name) \
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.type name, @function; \
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END(name)
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#endif
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#endif
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#define NORET_TYPE /**/
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#define ATTRIB_NORET __attribute__((noreturn))
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#define NORET_AND noreturn,
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#endif
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