Re: kext loading issue with OSX 10.6, sensitive to the number of symbols in the kext
Re: kext loading issue with OSX 10.6, sensitive to the number of symbols in the kext
- Subject: Re: kext loading issue with OSX 10.6, sensitive to the number of symbols in the kext
- From: Nik Gervae <email@hidden>
- Date: Wed, 21 Apr 2010 14:42:18 -0700
Hi there. I'm catching up on various backlogged items, and just found the root cause of this problem today. It is definitely a bug in the kext management code, introduced with support for 64-bit kexts. I'm doing a file overrun calculation for the symtab, and embarassingly got it the wrong way around for 32/64-bit. Most kexts have long enough symbol names that the size of the string table masks the bug, but with your very short function names you are hitting it squarely.
I rebuilt your kext after making the function names longer, and it passes validation now.
Nik Gervae
Kext Management Engineer
Apple, Inc.
On 07 Apr, 2010, at 13:58 , Joe Lowe wrote:
>
> I am having trouble getting one of the two non-hardware kernel extensions
> I maintain to load on OSX 10.6.x. Both of the kexts load on OSX 10.5.x.
> Both kexts are built the same way, similar Info.plist, same dependencies.
>
> After various dead ends, I ended up building a simple test kext using
> Xcode 3.2.2 that exhibits the load problem. The test kext can be compiled
> with or without 100 empty void(void) functions. With the 100 empty
> functions the kext fails validation check by kextutil. Without the 100
> empty functions it passes validation. This behavior is similar to the
> broken production kext, where if I rip out enough seemingly irrelevent
> code it eventually starts to load. The failure with the test does not
> explain why my second working production kext loads fine even though it
> has many more symbols than the test kext.
>
> The test kext source is at the end of the e-mail. I built and tested the
> kext using a boilerplate new generic kext project named "kext" generated
> by xcode 3.2.2 on a 10.6.3 system running the 32 bit kernel. I changed
> none of the project settings, just edited the generated kext.c and
> Info.plist files. Commenting out the "#define F_100" line in kext.c
> should yield a broken kext. Both versions of the kext load on 10.5.8 .
>
> (build project)
> (copy build/Debug/kext.kext to /System/Library/Extensions/kext.kext/ w/ proper permissions)
>
> host-116-122:kext joe$ sudo kextutil -n -v 6 /System/Library/Extensions/kext.kext
> Kext user-space log filter changed from 0xff2 to 0xfff.
> Kext kernel-space log filter changed from 0xff2 to 0xfff.
> Kext library architecture set to i386.
> No kernel file specified; using running kernel for linking.
> Kext library recording diagnostics for: validation authentication dependencies warnings.
> /System/Library/Extensions/kext.kext is invalid; can't resolve dependencies.
> /System/Library/Extensions/kext.kext is invalid; can't resolve dependencies.
> /System/Library/Extensions/kext.kext has problems:
> Validation Failures:
> Executable file doesn't contain kernel extension code (no kmod_info symbol or bad Mach-O layout).
>
> (comment out #define F_100 line in kext.c)
> (build project)
> (copy build/Debug/kext.kext to /System/Library/Extensions/kext.kext/ w/ proper permissions)
>
> host-116-122:kext joe$ sudo kextutil -n -v 6 /System/Library/Extensions/kext.kext
> Kext user-space log filter changed from 0xff2 to 0xfff.
> Kext kernel-space log filter changed from 0xff2 to 0xfff.
> Kext library architecture set to i386.
> No kernel file specified; using running kernel for linking.
> Kext library recording diagnostics for: validation authentication dependencies warnings.
> (kernel) Received 'Get Kernel Link State' request from user space.
> (kernel) Returning kernel link state.
> /System/Library/Extensions/kext.kext appears to be loadable (including linkage for on-disk libraries).
> host-116-122:kext joe$
>
> Be sure and use the debug build so the compiler does not optimize
> away the empty functions.
>
> Any help would be appreciated.
>
> Joe L.
>
>
> --- start kext.c ---
> #include <mach/mach_types.h>
>
> // comment/uncomment following line
> #define F_100
>
> #ifdef F_100
>
> static void f00(void) { }
> static void f01(void) { }
> static void f02(void) { }
> static void f03(void) { }
> static void f04(void) { }
> static void f05(void) { }
> static void f06(void) { }
> static void f07(void) { }
> static void f08(void) { }
> static void f09(void) { }
> static void f10(void) { }
> static void f11(void) { }
> static void f12(void) { }
> static void f13(void) { }
> static void f14(void) { }
> static void f15(void) { }
> static void f16(void) { }
> static void f17(void) { }
> static void f18(void) { }
> static void f19(void) { }
> static void f20(void) { }
> static void f21(void) { }
> static void f22(void) { }
> static void f23(void) { }
> static void f24(void) { }
> static void f25(void) { }
> static void f26(void) { }
> static void f27(void) { }
> static void f28(void) { }
> static void f29(void) { }
> static void f30(void) { }
> static void f31(void) { }
> static void f32(void) { }
> static void f33(void) { }
> static void f34(void) { }
> static void f35(void) { }
> static void f36(void) { }
> static void f37(void) { }
> static void f38(void) { }
> static void f39(void) { }
> static void f40(void) { }
> static void f41(void) { }
> static void f42(void) { }
> static void f43(void) { }
> static void f44(void) { }
> static void f45(void) { }
> static void f46(void) { }
> static void f47(void) { }
> static void f48(void) { }
> static void f49(void) { }
> static void f50(void) { }
> static void f51(void) { }
> static void f52(void) { }
> static void f53(void) { }
> static void f54(void) { }
> static void f55(void) { }
> static void f56(void) { }
> static void f57(void) { }
> static void f58(void) { }
> static void f59(void) { }
> static void f60(void) { }
> static void f61(void) { }
> static void f62(void) { }
> static void f63(void) { }
> static void f64(void) { }
> static void f65(void) { }
> static void f66(void) { }
> static void f67(void) { }
> static void f68(void) { }
> static void f69(void) { }
> static void f70(void) { }
> static void f71(void) { }
> static void f72(void) { }
> static void f73(void) { }
> static void f74(void) { }
> static void f75(void) { }
> static void f76(void) { }
> static void f77(void) { }
> static void f78(void) { }
> static void f79(void) { }
> static void f80(void) { }
> static void f81(void) { }
> static void f82(void) { }
> static void f83(void) { }
> static void f84(void) { }
> static void f85(void) { }
> static void f86(void) { }
> static void f87(void) { }
> static void f88(void) { }
> static void f89(void) { }
> static void f90(void) { }
> static void f91(void) { }
> static void f92(void) { }
> static void f93(void) { }
> static void f94(void) { }
> static void f95(void) { }
> static void f96(void) { }
> static void f97(void) { }
> static void f98(void) { }
> static void f99(void) { }
>
> static void f0(void) { f00(); f01(); f02(); f03(); f04(); f05(); f06(); f07(); f08(); f09(); }
> static void f1(void) { f10(); f11(); f12(); f13(); f14(); f15(); f16(); f17(); f18(); f19(); }
> static void f2(void) { f20(); f21(); f22(); f23(); f24(); f25(); f26(); f27(); f28(); f29(); }
> static void f3(void) { f30(); f31(); f32(); f33(); f34(); f35(); f36(); f37(); f38(); f39(); }
> static void f4(void) { f40(); f41(); f42(); f43(); f44(); f45(); f46(); f47(); f48(); f49(); }
> static void f5(void) { f50(); f51(); f52(); f53(); f54(); f55(); f56(); f57(); f58(); f59(); }
> static void f6(void) { f60(); f61(); f62(); f63(); f64(); f65(); f66(); f67(); f68(); f69(); }
> static void f7(void) { f70(); f71(); f72(); f73(); f74(); f75(); f76(); f77(); f78(); f79(); }
> static void f8(void) { f80(); f81(); f82(); f83(); f84(); f85(); f86(); f87(); f88(); f89(); }
> static void f9(void) { f90(); f91(); f92(); f93(); f94(); f95(); f96(); f97(); f98(); f99(); }
>
> #endif
>
> kern_return_t kext_start (kmod_info_t * ki, void * d) {
> #ifdef F_100
> f0(); f1(); f2(); f3(); f4(); f5(); f6(); f7(); f8(); f9();
> #endif
> return KERN_SUCCESS;
> }
>
> kern_return_t kext_stop (kmod_info_t * ki, void * d) {
> return KERN_SUCCESS;
> }
> --- end kext.c ---
>
>
> --- start Info.plist ---
> <?xml version="1.0" encoding="UTF-8"?>
> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd";>
> <plist version="1.0">
> <dict>
> <key>CFBundleDevelopmentRegion</key>
> <string>English</string>
> <key>CFBundleExecutable</key>
> <string>${EXECUTABLE_NAME}</string>
> <key>CFBundleName</key>
> <string>${PRODUCT_NAME}</string>
> <key>CFBundleIconFile</key>
> <string></string>
> <key>CFBundleIdentifier</key>
> <string>com.yourcompany.kext.${PRODUCT_NAME:rfc1034identifier}</string>
> <key>CFBundleInfoDictionaryVersion</key>
> <string>6.0</string>
> <key>CFBundlePackageType</key>
> <string>KEXT</string>
> <key>CFBundleSignature</key>
> <string>????</string>
> <key>CFBundleVersion</key>
> <string>1</string>
> <key>CFBundleShortVersionString</key>
> <string>1.0</string>
> <key>OSBundleLibraries</key>
> <dict>
> <key>com.apple.kpi.bsd</key>
> <string>9.0.0</string>
> <key>com.apple.kpi.libkern</key>
> <string>9.0.0</string>
> </dict>
> </dict>
> </plist>
> --- end Info.plist ---
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