On Thu, 21 Jan 2016 18:19:43 +0100 Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: > Similar to how relative extables are implemented, it is possible to emit > the kallsyms table in such a way that it contains offsets relative to some > anchor point in the kernel image rather than absolute addresses. The benefit > is that such table entries are no longer subject to dynamic relocation when > the build time and runtime offsets of the kernel image are different. Also, > on 64-bit architectures, it essentially cuts the size of the address table > in half since offsets can typically be expressed in 32 bits. > > Since it is useful for some architectures (like x86) to retain the ability > to emit absolute values as well, this patch adds support for both, by > emitting absolute addresses as positive 32-bit values, and addresses > relative to the lowest encountered relative symbol as negative values, which > are subtracted from the runtime address of this base symbol to produce the > actual address. > > Support for the above is enabled by default for all architectures except > IA-64, whose symbols are too far apart to capture in this manner. scripts/kallsyms.c: In function 'record_relative_base': scripts/kallsyms.c:744: error: 'ULLONG_MAX' undeclared (first use in this function) scripts/kallsyms.c:744: error: (Each undeclared identifier is reported only once scripts/kallsyms.c:744: error: for each function it appears in.) That's with (ancient) glibc-headers-2.5-3. It appears that limits.h's ULLONG_MAX requires "#ifdef __USE_ISOC99". I'm not sure what's the correct way of turning this on. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
