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 > On Mar 4, 2016, at 7:36 AM, 张云 <[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] > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
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