Commit 0bd957eb authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'core-kprobes-2020-06-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull kprobes updates from Ingo Molnar:
 "Various kprobes updates, mostly centered around cleaning up the
  no-instrumentation logic.

  Instead of the current per debug facility blacklist, use the more
  generic .noinstr.text approach, combined with a 'noinstr' marker for
  functions.

  Also add instrumentation_begin()/end() to better manage the exact
  place in entry code where instrumentation may be used.

  And add a kprobes blacklist for modules"

* tag 'core-kprobes-2020-06-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  kprobes: Prevent probes in .noinstr.text section
  vmlinux.lds.h: Create section for protection against instrumentation
  samples/kprobes: Add __kprobes and NOKPROBE_SYMBOL() for handlers.
  kprobes: Support NOKPROBE_SYMBOL() in modules
  kprobes: Support __kprobes blacklist in modules
  kprobes: Lock kprobe_mutex while showing kprobe_blacklist
parents 9bf9511e 66e9b071

arch/powerpc/kernel/vmlinux.lds.S

+1 −0
Original line number Diff line number Diff line
@@ -90,6 +90,7 @@ SECTIONS 
#ifdef CONFIG_PPC64

		*(.tramp.ftrace.text);

#endif

		NOINSTR_TEXT

		SCHED_TEXT

		CPUIDLE_TEXT

		LOCK_TEXT

include/asm-generic/sections.h

+3 −0
Original line number Diff line number Diff line
@@ -53,6 +53,9 @@ extern char __ctors_start[], __ctors_end[]; 
/* Start and end of .opd section - used for function descriptors. */

extern char __start_opd[], __end_opd[];



/* Start and end of instrumentation protected text section */

extern char __noinstr_text_start[], __noinstr_text_end[];



extern __visible const void __nosave_begin, __nosave_end;



/* Function descriptor handling (if any).  Override in asm/sections.h */

include/asm-generic/vmlinux.lds.h

+10 −0
Original line number Diff line number Diff line
@@ -540,6 +540,15 @@ 
	. = ALIGN((align));						\

	__end_rodata = .;



/*

 * Non-instrumentable text section

 */

#define NOINSTR_TEXT							\

		ALIGN_FUNCTION();					\

		__noinstr_text_start = .;				\

		*(.noinstr.text)					\

		__noinstr_text_end = .;



/*

 * .text section. Map to function alignment to avoid address changes

 * during second ld run in second ld pass when generating System.map
@@ -551,6 +560,7 @@ 
#define TEXT_TEXT							\

		ALIGN_FUNCTION();					\

		*(.text.hot TEXT_MAIN .text.fixup .text.unlikely)	\

		NOINSTR_TEXT						\

		*(.text..refcount)					\

		*(.ref.text)						\

	MEM_KEEP(init.text*)						\

include/linux/compiler.h

+53 −0
Original line number Diff line number Diff line
@@ -120,12 +120,65 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, 
/* Annotate a C jump table to allow objtool to follow the code flow */

#define __annotate_jump_table __section(.rodata..c_jump_table)



#ifdef CONFIG_DEBUG_ENTRY

/* Begin/end of an instrumentation safe region */

#define instrumentation_begin() ({					\

	asm volatile("%c0:\n\t"						\

		     ".pushsection .discard.instr_begin\n\t"		\

		     ".long %c0b - .\n\t"				\

		     ".popsection\n\t" : : "i" (__COUNTER__));		\

})



/*

 * Because instrumentation_{begin,end}() can nest, objtool validation considers

 * _begin() a +1 and _end() a -1 and computes a sum over the instructions.

 * When the value is greater than 0, we consider instrumentation allowed.

 *

 * There is a problem with code like:

 *

 * noinstr void foo()

 * {

 *	instrumentation_begin();

 *	...

 *	if (cond) {

 *		instrumentation_begin();

 *		...

 *		instrumentation_end();

 *	}

 *	bar();

 *	instrumentation_end();

 * }

 *

 * If instrumentation_end() would be an empty label, like all the other

 * annotations, the inner _end(), which is at the end of a conditional block,

 * would land on the instruction after the block.

 *

 * If we then consider the sum of the !cond path, we'll see that the call to

 * bar() is with a 0-value, even though, we meant it to happen with a positive

 * value.

 *

 * To avoid this, have _end() be a NOP instruction, this ensures it will be

 * part of the condition block and does not escape.

 */

#define instrumentation_end() ({					\

	asm volatile("%c0: nop\n\t"					\

		     ".pushsection .discard.instr_end\n\t"		\

		     ".long %c0b - .\n\t"				\

		     ".popsection\n\t" : : "i" (__COUNTER__));		\

})

#endif /* CONFIG_DEBUG_ENTRY */



#else

#define annotate_reachable()

#define annotate_unreachable()

#define __annotate_jump_table

#endif



#ifndef instrumentation_begin

#define instrumentation_begin()		do { } while(0)

#define instrumentation_end()		do { } while(0)

#endif



#ifndef ASM_UNREACHABLE

# define ASM_UNREACHABLE

#endif

include/linux/compiler_types.h

+4 −0
Original line number Diff line number Diff line
@@ -118,6 +118,10 @@ struct ftrace_likely_data { 
#define notrace			__attribute__((__no_instrument_function__))

#endif



/* Section for code which can't be instrumented at all */

#define noinstr								\

	noinline notrace __attribute((__section__(".noinstr.text")))



/*

 * it doesn't make sense on ARM (currently the only user of __naked)

 * to trace naked functions because then mcount is called without

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