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Merge tag 'noinstr-lds-2020-05-19' into core/kprobes
Get the noinstr section and markers to base the kprobe changes on.
This commit is contained in:
commit
4e321b7746
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@ -90,6 +90,7 @@ SECTIONS
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#ifdef CONFIG_PPC64
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*(.tramp.ftrace.text);
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#endif
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NOINSTR_TEXT
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SCHED_TEXT
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CPUIDLE_TEXT
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LOCK_TEXT
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@ -53,6 +53,9 @@ 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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@ -540,6 +540,15 @@
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. = ALIGN((align)); \
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__end_rodata = .;
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/*
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* Non-instrumentable text section
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*/
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#define NOINSTR_TEXT \
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ALIGN_FUNCTION(); \
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__noinstr_text_start = .; \
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*(.noinstr.text) \
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__noinstr_text_end = .;
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/*
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* .text section. Map to function alignment to avoid address changes
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* during second ld run in second ld pass when generating System.map
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@ -551,6 +560,7 @@
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#define TEXT_TEXT \
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ALIGN_FUNCTION(); \
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*(.text.hot TEXT_MAIN .text.fixup .text.unlikely) \
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NOINSTR_TEXT \
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*(.text..refcount) \
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*(.ref.text) \
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MEM_KEEP(init.text*) \
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@ -120,12 +120,65 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
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/* Annotate a C jump table to allow objtool to follow the code flow */
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#define __annotate_jump_table __section(.rodata..c_jump_table)
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#ifdef CONFIG_DEBUG_ENTRY
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/* Begin/end of an instrumentation safe region */
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#define instrumentation_begin() ({ \
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asm volatile("%c0:\n\t" \
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".pushsection .discard.instr_begin\n\t" \
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".long %c0b - .\n\t" \
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".popsection\n\t" : : "i" (__COUNTER__)); \
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})
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/*
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* Because instrumentation_{begin,end}() can nest, objtool validation considers
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* _begin() a +1 and _end() a -1 and computes a sum over the instructions.
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* When the value is greater than 0, we consider instrumentation allowed.
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*
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* There is a problem with code like:
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*
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* noinstr void foo()
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* {
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* instrumentation_begin();
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* ...
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* if (cond) {
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* instrumentation_begin();
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* ...
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* instrumentation_end();
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* }
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* bar();
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* instrumentation_end();
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* }
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*
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* If instrumentation_end() would be an empty label, like all the other
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* annotations, the inner _end(), which is at the end of a conditional block,
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* would land on the instruction after the block.
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*
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* If we then consider the sum of the !cond path, we'll see that the call to
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* bar() is with a 0-value, even though, we meant it to happen with a positive
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* value.
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*
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* To avoid this, have _end() be a NOP instruction, this ensures it will be
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* part of the condition block and does not escape.
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*/
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#define instrumentation_end() ({ \
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asm volatile("%c0: nop\n\t" \
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".pushsection .discard.instr_end\n\t" \
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".long %c0b - .\n\t" \
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".popsection\n\t" : : "i" (__COUNTER__)); \
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})
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#endif /* CONFIG_DEBUG_ENTRY */
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#else
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#define annotate_reachable()
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#define annotate_unreachable()
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#define __annotate_jump_table
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#endif
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#ifndef instrumentation_begin
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#define instrumentation_begin() do { } while(0)
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#define instrumentation_end() do { } while(0)
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#endif
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#ifndef ASM_UNREACHABLE
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# define ASM_UNREACHABLE
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#endif
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@ -118,6 +118,10 @@ struct ftrace_likely_data {
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#define notrace __attribute__((__no_instrument_function__))
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#endif
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/* Section for code which can't be instrumented at all */
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#define noinstr \
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noinline notrace __attribute((__section__(".noinstr.text")))
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/*
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* it doesn't make sense on ARM (currently the only user of __naked)
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* to trace naked functions because then mcount is called without
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@ -948,7 +948,7 @@ static void check_section(const char *modname, struct elf_info *elf,
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#define DATA_SECTIONS ".data", ".data.rel"
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#define TEXT_SECTIONS ".text", ".text.unlikely", ".sched.text", \
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".kprobes.text", ".cpuidle.text"
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".kprobes.text", ".cpuidle.text", ".noinstr.text"
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#define OTHER_TEXT_SECTIONS ".ref.text", ".head.text", ".spinlock.text", \
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".fixup", ".entry.text", ".exception.text", ".text.*", \
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".coldtext"
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