"Yann E. MORIN" <yann.morin.1998@xxxxxxx> writes: > Martin, All, > > On 2013-10-28 03:16 +0100, Martin Walch spake thusly: >> this test case leads to a segmentation fault: >> >> config A >> tristate "A" if m >> >> config MODULES >> boolean "MODULES" >> option modules >> >> As you can see, the MODULES symbol with the option modules is declared after >> the first occurrence of an 'm' dependency. (Actually you can drop the MODULES >> section or use a different symbol name. It does not matter.) Internally 'm' gets >> converted into (symbol_mod && modules_sym), which adds a dependency on a >> bad symbol, finally leading to dereferencing a null pointer. > > Indeed, reproduced here. I'll investigate further (although anyone is > free to hack it, too! :-p) Hi Yann, all, I had a look at the problem, Martin reported and found out that menu_check_dep() is causing the problem: ... case E_SYMBOL: /* change 'm' into 'm' && MODULES */ if (e->left.sym == &symbol_mod) return expr_alloc_and(e, expr_alloc_symbol(modules_sym)); break; ... It generates an expression that uses modules_sym which is NULL at that time. The problem seems to be that since commit 6902dccfda005fa modules_sym is NULL until an "option modules" is found or the default is set but part of the code needs a valid pointer at any time. I played with other possible fixes but got the impression that these would add even more complicated code and I decided to propose the patch that I will send in a minute. That patch basically reverts commit 6902dccfda005fa keeping the changes that (as far as I understood) are the important part of that commit. The parser also needs to be regenerated but that should happen in a separate commit if I remember corretly. So, for now and until a review, I left it out. I would be glad if you could have a look at the patch. Dirk >> If you move the declaration of the MODULES symbol to the top, everything >> works fine. >> >> The crash has been introduced last month with >> >> > 6902dccfda005fa4c42410fa064fdd331ab42479 >> > kconfig: do not special-case 'MODULES' symbol >> >> However, things were probably broken before. The problem has only >> become visible. >> >> The reason that configuring a Linux kernel does not crash the >> configuration system is that there is currently no architecture that has a >> symbol with a dependency on 'm' anywhere before the MODULES symbol. > > Regards, > Yann E. MORIN. -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
