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Some code pathes, especially the low level entry code, must be protected against instrumentation for various reasons: - Low level entry code can be a fragile beast, especially on x86. - With NO_HZ_FULL RCU state needs to be established before using it. Having a dedicated section for such code allows to validate with tooling that no unsafe functions are invoked. Add the .noinstr.text section and the noinstr attribute to mark functions. noinstr implies notrace. Kprobes will gain a section check later. Provide also a set of markers: instrumentation_begin()/end() These are used to mark code inside a noinstr function which calls into regular instrumentable text section as safe. The instrumentation markers are only active when CONFIG_DEBUG_ENTRY is enabled as the end marker emits a NOP to prevent the compiler from merging the annotation points. This means the objtool verification requires a kernel compiled with this option. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200505134100.075416272@linutronix.de
176 lines
5.9 KiB
C
176 lines
5.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_GENERIC_SECTIONS_H_
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#define _ASM_GENERIC_SECTIONS_H_
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/* References to section boundaries */
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#include <linux/compiler.h>
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#include <linux/types.h>
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/*
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* Usage guidelines:
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* _text, _data: architecture specific, don't use them in arch-independent code
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* [_stext, _etext]: contains .text.* sections, may also contain .rodata.*
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* and/or .init.* sections
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* [_sdata, _edata]: contains .data.* sections, may also contain .rodata.*
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* and/or .init.* sections.
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* [__start_rodata, __end_rodata]: contains .rodata.* sections
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* [__start_ro_after_init, __end_ro_after_init]:
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* contains .data..ro_after_init section
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* [__init_begin, __init_end]: contains .init.* sections, but .init.text.*
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* may be out of this range on some architectures.
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* [_sinittext, _einittext]: contains .init.text.* sections
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* [__bss_start, __bss_stop]: contains BSS sections
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*
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* Following global variables are optional and may be unavailable on some
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* architectures and/or kernel configurations.
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* _text, _data
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* __kprobes_text_start, __kprobes_text_end
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* __entry_text_start, __entry_text_end
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* __ctors_start, __ctors_end
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* __irqentry_text_start, __irqentry_text_end
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* __softirqentry_text_start, __softirqentry_text_end
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* __start_opd, __end_opd
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*/
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extern char _text[], _stext[], _etext[];
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extern char _data[], _sdata[], _edata[];
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extern char __bss_start[], __bss_stop[];
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extern char __init_begin[], __init_end[];
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extern char _sinittext[], _einittext[];
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extern char __start_ro_after_init[], __end_ro_after_init[];
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extern char _end[];
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extern char __per_cpu_load[], __per_cpu_start[], __per_cpu_end[];
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extern char __kprobes_text_start[], __kprobes_text_end[];
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extern char __entry_text_start[], __entry_text_end[];
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extern char __start_rodata[], __end_rodata[];
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extern char __irqentry_text_start[], __irqentry_text_end[];
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extern char __softirqentry_text_start[], __softirqentry_text_end[];
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extern char __start_once[], __end_once[];
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/* Start and end of .ctors section - used for constructor calls. */
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extern char __ctors_start[], __ctors_end[];
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/* Start and end of .opd section - used for function descriptors. */
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extern char __start_opd[], __end_opd[];
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/* Start and end of instrumentation protected text section */
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extern char __noinstr_text_start[], __noinstr_text_end[];
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extern __visible const void __nosave_begin, __nosave_end;
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/* Function descriptor handling (if any). Override in asm/sections.h */
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#ifndef dereference_function_descriptor
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#define dereference_function_descriptor(p) (p)
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#define dereference_kernel_function_descriptor(p) (p)
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#endif
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/* random extra sections (if any). Override
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* in asm/sections.h */
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#ifndef arch_is_kernel_text
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static inline int arch_is_kernel_text(unsigned long addr)
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{
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return 0;
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}
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#endif
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#ifndef arch_is_kernel_data
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static inline int arch_is_kernel_data(unsigned long addr)
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{
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return 0;
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}
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#endif
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/*
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* Check if an address is part of freed initmem. This is needed on architectures
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* with virt == phys kernel mapping, for code that wants to check if an address
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* is part of a static object within [_stext, _end]. After initmem is freed,
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* memory can be allocated from it, and such allocations would then have
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* addresses within the range [_stext, _end].
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*/
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#ifndef arch_is_kernel_initmem_freed
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static inline int arch_is_kernel_initmem_freed(unsigned long addr)
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{
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return 0;
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}
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#endif
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/**
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* memory_contains - checks if an object is contained within a memory region
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* @begin: virtual address of the beginning of the memory region
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* @end: virtual address of the end of the memory region
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* @virt: virtual address of the memory object
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* @size: size of the memory object
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*
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* Returns: true if the object specified by @virt and @size is entirely
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* contained within the memory region defined by @begin and @end, false
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* otherwise.
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*/
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static inline bool memory_contains(void *begin, void *end, void *virt,
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size_t size)
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{
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return virt >= begin && virt + size <= end;
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}
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/**
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* memory_intersects - checks if the region occupied by an object intersects
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* with another memory region
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* @begin: virtual address of the beginning of the memory regien
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* @end: virtual address of the end of the memory region
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* @virt: virtual address of the memory object
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* @size: size of the memory object
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*
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* Returns: true if an object's memory region, specified by @virt and @size,
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* intersects with the region specified by @begin and @end, false otherwise.
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*/
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static inline bool memory_intersects(void *begin, void *end, void *virt,
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size_t size)
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{
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void *vend = virt + size;
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return (virt >= begin && virt < end) || (vend >= begin && vend < end);
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}
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/**
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* init_section_contains - checks if an object is contained within the init
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* section
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* @virt: virtual address of the memory object
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* @size: size of the memory object
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*
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* Returns: true if the object specified by @virt and @size is entirely
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* contained within the init section, false otherwise.
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*/
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static inline bool init_section_contains(void *virt, size_t size)
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{
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return memory_contains(__init_begin, __init_end, virt, size);
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}
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/**
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* init_section_intersects - checks if the region occupied by an object
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* intersects with the init section
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* @virt: virtual address of the memory object
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* @size: size of the memory object
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*
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* Returns: true if an object's memory region, specified by @virt and @size,
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* intersects with the init section, false otherwise.
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*/
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static inline bool init_section_intersects(void *virt, size_t size)
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{
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return memory_intersects(__init_begin, __init_end, virt, size);
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}
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/**
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* is_kernel_rodata - checks if the pointer address is located in the
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* .rodata section
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*
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* @addr: address to check
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*
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* Returns: true if the address is located in .rodata, false otherwise.
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*/
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static inline bool is_kernel_rodata(unsigned long addr)
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{
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return addr >= (unsigned long)__start_rodata &&
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addr < (unsigned long)__end_rodata;
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}
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#endif /* _ASM_GENERIC_SECTIONS_H_ */
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