> On Mar 4, 2016, at 11:59 PM, Dave Tian <[email protected]> wrote: > > This ‘P’ is used to make gcc happy and work. > Without ‘P’, this inline would be interpreted as: > leal $-512(%esp), %eax > With ‘P’, this inline is the thing we really want: > leal -512(%esp), %eax > > Eventually, my gcc 4.9.2 does not compile with ‘P’ is missing. I am not sure > if this is still the case for newer gcc (5/6). But you get the point. > > -daveti >
Thank you for your detailed answer ! By the way， If someone have the problems alike, I suggest them to write some inline assembly and check the compiler’s assembly output. > >> On Mar 4, 2016, at 7:36 AM, 张云 <[email protected] <mailto:[email protected]>> >> wrote: >> >> Hi >> >> In /arch/x86/boot/main.c >> (http://lxr.free-electrons.com/source/arch/x86/boot/main.c >> <http://lxr.free-electrons.com/source/arch/x86/boot/main.c>) , >> >> In the function init_heap, >> asm("leal %P1(%%esp),%0" >> 122 >> <http://lxr.free-electrons.com/source/arch/x86/boot/source/arch/x86/boot/main.c#L122> >> : "=r" (stack_end) : "i" (-STACK_SIZE >> <http://lxr.free-electrons.com/source/arch/x86/boot/ident?i=STACK_SIZE>)); >> What does the ‘%P1’ mean in the inline assembly above ? >> >> Thanks ! >> _______________________________________________ >> Kernelnewbies mailing list >> [email protected] <mailto:[email protected]> >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > _______________________________________________ > Kernelnewbies mailing list > [email protected] > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
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