From mboxrd@z Thu Jan 1 00:00:00 1970 From: Allen Martin Date: Fri, 6 Jul 2012 13:33:29 -0700 Subject: [U-Boot] [PATCH 2/7] HACK: rearrange link order for thumb In-Reply-To: <4FF737F7.8040008@wwwdotorg.org> References: <1341598142-28873-1-git-send-email-amartin@nvidia.com> <1341598142-28873-3-git-send-email-amartin@nvidia.com> <4FF737F7.8040008@wwwdotorg.org> Message-ID: <20120706203329.GA29103@nvidia.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On Fri, Jul 06, 2012 at 12:09:43PM -0700, Stephen Warren wrote: > On 07/06/2012 12:08 PM, Allen Martin wrote: > > Rearrange the link order of libraries to avoid out of bound > > relocations in thumb mode. I have no idea how to fix this for real. > > Are the relocations branches or something else? It looks like > unconditional jump range is +/-4MB for Thumb1 and +/-16MB for Thumb2, so > I'm surprised we'd be exceeding that, considering the U-boot binary is > on the order of 256KB on Tegra right now. This is the relcation type: arch/arm/lib/libarm.o: In function `__flush_dcache_all': /home/arm/u-boot/arch/arm/lib/cache.c:52: relocation truncated to fit: R_ARM_THM_JUMP11 against symbol `flush_cache' defined in .text section in arch/arm/cpu/armv7/libarmv7.o The instruction is a "b.n" not a "b", which is what is causing the problem. I think because of the weak alias the compiler used a short jump to the local function, but when it got linked it resolved to a function that was too far away for the short jump: void flush_cache(unsigned long start, unsigned long size) __attribute__((weak, alias("__flush_cache"))); 00000002 <__flush_dcache_all>: 2: 2000 movs r0, #0 4: f04f 31ff mov.w r1, #4294967295 ; 0xffffffff 8: e7fe b.n 0 <__flush_cache> It looks like there's a "-fno-optimize-sibling-calls" option to gcc to avoid this problem. Seems a shame to disable all short jumps for this one case though. -Allen -- nvpublic