From mboxrd@z Thu Jan 1 00:00:00 1970 From: tixy@linaro.org (Jon Medhurst (Tixy)) Date: Fri, 26 Sep 2014 10:57:23 +0100 Subject: Kprobes build failure In-Reply-To: <20140925233720.GG5182@n2100.arm.linux.org.uk> References: <20140925233720.GG5182@n2100.arm.linux.org.uk> Message-ID: <1411725443.1529.10.camel@linaro1.home> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, 2014-09-26 at 00:37 +0100, Russell King - ARM Linux wrote: > So, Olof's kbuild found this while building my rc5 based for-next tree: > > arm.allmodconfig: > /tmp/ccoT403o.s:21439: Error: bad immediate value for offset (4168) > /tmp/ccoT403o.s:21440: Error: bad immediate value for offset (4176) > /tmp/ccoT403o.s:21475: Error: bad immediate value for offset (4260) > /tmp/ccoT403o.s:21476: Error: bad immediate value for offset (4260) > /tmp/ccoT403o.s:23566: Error: bad immediate value for offset (4132) > /tmp/ccoT403o.s:23567: Error: bad immediate value for offset (4148) > /tmp/ccoT403o.s:23606: Error: bad immediate value for offset (4236) > /tmp/ccoT403o.s:23607: Error: bad immediate value for offset (4248) > > which, when looking at the logs, appears to be: > > /tmp/ccoT403o.s:47583: Error: bad immediate value for offset (5464) > make[3]: *** [arch/arm/kernel/kprobes-test-arm.o] Error 1 > make[3]: Target `__build' not remade because of errors. > make[2]: *** [arch/arm/kernel] Error 2 > > Any ideas? Sounds vaguely familiar as a problem I hit before. Google finds someone else hitting similar problem [1] and the symptoms and cause match my memories of the old kprobe issue. Where can I find a clue of to the config and compiler used in Olof's build, so I can have a go at reproducing and debugging? [1] https://lkml.org/lkml/2012/9/24/223 The relevant explanation of the above post copied below... ------------------------------------------------------------------------ The compiler uses a pretty dumb heuristic to guess the size of asms: 4 * (number of ; or \n in the string) Directives that the compiler can't predict the size of are not safe if they output into any segment that the compiler uses. .fill/.skip are obvious candidates, but macro expansions, .rept, .irp etc. can cause these problems too. For example: void g(int); void f(void) { g(0xd00dfeed); asm(".skip 0x1000"); } If you try building this with gcc -marm -Os for example: /tmp/ccXYm1uP.s: Assembler messages: /tmp/ccXYm1uP.s:21: Error: bad immediate value for offset (4100) ...because the assembler assumes that it can dump a literal at the end of the function and reference it from the g() callsite. ------------------------------------------------------------------------ -- Tixy