On Wed, May 10, 2017 at 4:57 PM, Michael Ellerman <m...@ellerman.id.au> wrote: > On powerpc we can build the kernel with two different ABIs for mcount(), which > is used by ftrace. Kernels built with one ABI do not know how to load modules > built with the other ABI. The new style ABI is called "mprofile-kernel", for > want of a better name. > > Currently if we build a module using the old style ABI, and the kernel with > mprofile-kernel, when we load the module we'll oops something like: > > # insmod autofs4-no-mprofile-kernel.ko > ftrace-powerpc: Unexpected instruction f8810028 around bl _mcount > ------------[ cut here ]------------ > WARNING: CPU: 6 PID: 3759 at ../kernel/trace/ftrace.c:2024 > ftrace_bug+0x2b8/0x3c0 > CPU: 6 PID: 3759 Comm: insmod Not tainted > 4.11.0-rc3-gcc-5.4.1-00017-g5a61ef74f269 #11 > ... > NIP [c0000000001eaa48] ftrace_bug+0x2b8/0x3c0 > LR [c0000000001eaff8] ftrace_process_locs+0x4a8/0x590 > Call Trace: > alloc_pages_current+0xc4/0x1d0 (unreliable) > ftrace_process_locs+0x4a8/0x590 > load_module+0x1c8c/0x28f0 > SyS_finit_module+0x110/0x140 > system_call+0x38/0xfc > ... > ftrace failed to modify > [<d000000002a31024>] 0xd000000002a31024 > actual: 35:65:00:48 > > We can avoid this by including in the vermagic whether the kernel/module was > built with mprofile-kernel. Which results in: > > # insmod autofs4-pg.ko > autofs4: version magic > '4.11.0-rc3-gcc-5.4.1-00017-g5a61ef74f269 SMP mod_unload modversions ' > should be > '4.11.0-rc3-gcc-5.4.1-00017-g5a61ef74f269-dirty SMP mod_unload modversions > mprofile-kernel' > insmod: ERROR: could not insert module autofs4-pg.ko: Invalid module format > > Signed-off-by: Michael Ellerman <m...@ellerman.id.au> > --- > arch/powerpc/include/asm/module.h | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/powerpc/include/asm/module.h > b/arch/powerpc/include/asm/module.h > index 53885512b8d3..6c0132c7212f 100644 > --- a/arch/powerpc/include/asm/module.h > +++ b/arch/powerpc/include/asm/module.h > @@ -14,6 +14,10 @@ > #include <asm-generic/module.h> > > > +#ifdef CC_USING_MPROFILE_KERNEL > +#define MODULE_ARCH_VERMAGIC "mprofile-kernel" > +#endif > + > #ifndef __powerpc64__ > /* > * Thanks to Paul M for explaining this. > --
Makes sense Acked-by: Balbir Singh <bsinghar...@gmail.com>
