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87c482bdfa
In the kernel image vmlinux.lds.S linker scripts the .altinstructions and __bug_table sections are 4- or 8-byte aligned because they hold 32- and/or 64-bit values. Most architectures use altinstructions and BUG() or WARN() in modules as well, but in the module linker script (module.lds.S) those sections are currently missing. As consequence the linker will store their content byte-aligned by default, which then can lead to unnecessary unaligned memory accesses by the CPU when those tables are processed at runtime. Usually unaligned memory accesses are unnoticed, because either the hardware (as on x86 CPUs) or in-kernel exception handlers (e.g. on parisc or sparc) emulate and fix them up at runtime. Nevertheless, such unaligned accesses introduce a performance penalty and can even crash the kernel if there is a bug in the unalignment exception handlers (which happened once to me on the parisc architecture and which is why I noticed that issue at all). This patch fixes a non-critical issue and might be backported at any time. It's trivial and shouldn't introduce any regression because it simply tells the linker to use a different (8-byte alignment) for those sections by default. Signed-off-by: Helge Deller <deller@gmx.de> Link: https://lore.kernel.org/all/Yr8%2Fgr8e8I7tVX4d@p100/ Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
69 lines
1.7 KiB
ArmAsm
69 lines
1.7 KiB
ArmAsm
/*
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* Common module linker script, always used when linking a module.
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* Archs are free to supply their own linker scripts. ld will
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* combine them automatically.
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*/
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#ifdef CONFIG_CFI_CLANG
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# include <asm/page.h>
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# define ALIGN_CFI ALIGN(PAGE_SIZE)
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# define SANITIZER_DISCARDS *(.eh_frame)
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#else
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# define ALIGN_CFI
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# define SANITIZER_DISCARDS
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#endif
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SECTIONS {
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/DISCARD/ : {
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*(.discard)
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*(.discard.*)
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SANITIZER_DISCARDS
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}
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__ksymtab 0 : { *(SORT(___ksymtab+*)) }
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__ksymtab_gpl 0 : { *(SORT(___ksymtab_gpl+*)) }
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__kcrctab 0 : { *(SORT(___kcrctab+*)) }
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__kcrctab_gpl 0 : { *(SORT(___kcrctab_gpl+*)) }
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.ctors 0 : ALIGN(8) { *(SORT(.ctors.*)) *(.ctors) }
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.init_array 0 : ALIGN(8) { *(SORT(.init_array.*)) *(.init_array) }
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.altinstructions 0 : ALIGN(8) { KEEP(*(.altinstructions)) }
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__bug_table 0 : ALIGN(8) { KEEP(*(__bug_table)) }
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__jump_table 0 : ALIGN(8) { KEEP(*(__jump_table)) }
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__patchable_function_entries : { *(__patchable_function_entries) }
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#ifdef CONFIG_LTO_CLANG
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/*
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* With CONFIG_LTO_CLANG, LLD always enables -fdata-sections and
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* -ffunction-sections, which increases the size of the final module.
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* Merge the split sections in the final binary.
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*/
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.bss : {
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*(.bss .bss.[0-9a-zA-Z_]*)
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*(.bss..L*)
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}
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.data : {
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*(.data .data.[0-9a-zA-Z_]*)
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*(.data..L*)
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}
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.rodata : {
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*(.rodata .rodata.[0-9a-zA-Z_]*)
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*(.rodata..L*)
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}
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/*
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* With CONFIG_CFI_CLANG, we assume __cfi_check is at the beginning
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* of the .text section, and is aligned to PAGE_SIZE.
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*/
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.text : ALIGN_CFI {
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*(.text.__cfi_check)
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*(.text .text.[0-9a-zA-Z_]* .text..L.cfi*)
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}
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#endif
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}
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/* bring in arch-specific sections */
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#include <asm/module.lds.h>
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