On Tue, Feb 1, 2011 at 23:26, Dmitry Torokhov <dtor@xxxxxxxxxx> wrote: > On Tue, Feb 01, 2011 at 02:03:23PM -0800, Geert Uytterhoeven wrote: >> On Tue, Feb 1, 2011 at 22:09, Dmitry Torokhov <dtor@xxxxxxxxxx> wrote: >> > On Tue, Feb 01, 2011 at 12:33:29PM -0800, Geert Uytterhoeven wrote: >> >> On Mon, Jan 24, 2011 at 11:59, Linux Kernel Mailing List >> >> <linux-kernel@xxxxxxxxxxxxxxx> wrote: >> >> > Gitweb: Â Â http://git.kernel.org/linus/e94965ed5beb23c6fabf7ed31f625e66d7ff28de >> >> >> >> > Â Âmodule: show version information for built-in modules in sysfs >> >> > >> >> > Â ÂCurrently only drivers that are built as modules have their versions >> >> > Â Âshown in /sys/module/<module_name>/version, but this information might >> >> > Â Âalso be useful for built-in drivers as well. This especially important >> >> > Â Âfor drivers that do not define any parameters - such drivers, if >> >> > Â Âbuilt-in, are completely invisible from userspace. >> >> > >> >> > Â ÂThis patch changes MODULE_VERSION() macro so that in case when we are >> >> > Â Âcompiling built-in module, version information is stored in a separate >> >> > Â Âsection. Kernel then uses this data to create 'version' sysfs attribute >> >> > Â Âin the same fashion it creates attributes for module parameters. >> >> >> >> This commit causes the crash below on m68k (ARAnyM). >> >> Reverting this commit and its dependency >> >> 3b90a5b292321b2acac3921f77046ae195aef53f >> >> ("module: fix linker error for MODULE_VERSION when !MODULE and CONFIG_SYSFS=n") >> >> makes it boot again. >> >> >> > >> > Hi Geert, >> > >> > Does the follwing help by any chance? >> > >> > From d6fd4a6e0fc2d3f0a74962d4a6f663a46d230ecd Mon Sep 17 00:00:00 2001 >> > diff --git a/arch/m68knommu/kernel/vmlinux.lds.S b/arch/m68knommu/kernel/vmlinux.lds.S >> > index ef33213..47e15eb 100644 >> > --- a/arch/m68knommu/kernel/vmlinux.lds.S >> > +++ b/arch/m68knommu/kernel/vmlinux.lds.S >> >> The crash happened on m68k with MMU, not m68knommu. >> > > Hmm, OK then. Could you please see if the crash happens if you return > early in kernel/params.c::version_sysfs_builtin() ? Also, do you see It does not crash if version_sysfs_builtin() returns early. > anything in __modev section of your build? "objdump -h" says: | Sections: | Idx Name Size VMA LMA File off Algn | 7 __modver 0000007c 002e0f84 002e0f84 002e0f84 2**2 | CONTENTS, ALLOC, LOAD, DATA "nm vmlinux | grep __modver" says: | 002e0f84 d __modver_version_attr | 002e0fa8 d __modver_version_attr | 00039026 T __modver_version_show | 002e0f84 D __start___modver | 002e0fca D __stop___modver The section size (0x7c) is larger than __stop___modver - __start___modver (0x46)? Adding some debugging code (which increases the section size even more?) shows: vattr = 002e1004 vattr->module_name = xz_dec mk = 00c2ee50 err = 0 kobject_uevent done kobject_put done vattr = 002e1026 vattr->module_name = (null) Unable to handle kernel NULL pointer dereference at virtual address 0000002c So the second module in the list has no name. Why? Aha, it's not NULL, but just < PAGE_SIZE (0x2c). sizeof(struct module_version_attribute) = 34, which you can see from the 2 consecutive vattr pointers above. But the "aligned(sizeof(void *))" in the definition of MODULE_VERSION() puts the next module_version_attribute struct in the array at offset 36, not offset 34! On m68k, the alignment of 32-bit integrals is 2 bytes, not 4. Removing the alignment, cfr. this (gmail-pasted hence whitespace-corrupted) patch fixes it: --- a/include/linux/module.h +++ b/include/linux/module.h @@ -176,7 +176,7 @@ extern struct module __this_module; struct module *, char *); \ static struct module_version_attribute __modver_version_attr \ __used \ - __attribute__ ((__section__ ("__modver"),aligned(sizeof(void *)))) \ + __attribute__ ((__section__ ("__modver"))) \ = { \ .mattr = { \ .attr = { \ Why is the explicit alignment there? Can it be removed? If not, you can move the alignment into the definition of struct module_version_attribute, so it will be honoured everywhere. Gr{oetje,eeting}s, Â Â Â Â Â Â Â Â Â Â Â Â Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. Â Â Â Â Â Â Â Â Â Â Â Â Â ÂÂ ÂÂ -- Linus Torvalds -- 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
