On 12/09/2017 21:11, Josh Poimboeuf wrote: > On Wed, Sep 06, 2017 at 02:37:02PM -0700, Andy Lutomirski wrote: >> Signed-off-by: Andy Lutomirski <[email protected]> >> --- >> arch/x86/include/asm/processor.h | 17 +++++++++++++++++ >> arch/x86/include/asm/thread_info.h | 11 ----------- >> arch/x86/kernel/traps.c | 3 +-- >> 3 files changed, 18 insertions(+), 13 deletions(-) >> >> diff --git a/arch/x86/include/asm/processor.h >> b/arch/x86/include/asm/processor.h >> index 4c137472f530..b6f8dc11c222 100644 >> --- a/arch/x86/include/asm/processor.h >> +++ b/arch/x86/include/asm/processor.h >> @@ -534,6 +534,23 @@ static inline unsigned long current_top_of_stack(void) >> #endif >> } >> >> +static inline unsigned long current_stack_pointer(void) >> +{ >> + unsigned long sp; >> +#ifdef CONFIG_X86_64 >> + asm("mov %%rsp,%0" : "=g" (sp)); >> +#else >> + asm("mov %%esp,%0" : "=g" (sp)); >> +#endif >> + return sp; >> +} > I know you're just moving the function, but this function could also be > cleaned up by using _ASM_SP and getting rid of the ifdef. >
For GCC, there is a rather more efficient way of doing this, which allows the compiler much more flexibility than forcing the use of a mov instruction. http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/include/asm-x86/current.h;h=89849929ebf98e9ba04659f59b5521982a718b2d;hb=HEAD#l47 I don't know how much you care in Linux, but in Xen it makes a massive code-volume difference, as that construct is the core of current (because we can't use %fs/%gs). ~Andrew
