On Fri, Mar 19, 2021 at 07:54:15AM +0800, Nicolas Boichat wrote: > From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > commit 6553896666433e7efec589838b400a2a652b3ffa upstream. > > 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@xxxxxxxxxxxxx> > Reviewed-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx> > Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Link: https://lkml.kernel.org/r/20200505134100.075416272@xxxxxxxxxxxxx > > [Nicolas: context conflicts in: > arch/powerpc/kernel/vmlinux.lds.S > include/asm-generic/vmlinux.lds.h > include/linux/compiler.h > include/linux/compiler_types.h] > Signed-off-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx> Did you build this on x86? I get the following build error: ld:./arch/x86/kernel/vmlinux.lds:20: syntax error And that line looks like: . = ALIGN(8); *(.text.hot .text.hot.*) *(.text .text.fixup) *(.text.unlikely .text.unlikely.*) *(.text.unknown .text.unknown.*) . = ALIGN(8); __noinstr_text_start = .; *(.__attribute__((noinline)) __attribute__((no_instrument_function)) __attribute((__section__(".noinstr.text"))).text) __noinstr_text_end = .; *(.text..refcount) *(.ref.text) *(.meminit.text*) *(.memexit.text*) So I'm going to drop both of these patches from the queue. thanks, greg k-h
