On Wednesday, 1 August 2018 16:22:33 MSK Russell King - ARM Linux wrote: > On Wed, Aug 01, 2018 at 03:00:22PM +0300, Dmitry Osipenko wrote: > > Hello Abbott, > > > > I gave a quick whirl to your KASAN patches on top of current linux-next on > > NVIDIA Tegra20 and here are couple notes: > > > > 1) Kernel is booting fine. > > > > 2) Loading test_kasan.ko makes KASAN to trap faulty memory accesses. > > > > 3) Running Tegra GPU 2D/3D tests works without any issue. > > > > 4) I wanted to try Tegra's video decoder driver under KASAN, but > > unfortunately Xorg server and video player processes are getting stuck > > consuming 100% CPU and processes are not KILL'able. > > > > I've tried to disable Opentegra Xorg driver and result is the same, you > > should be able to reproduce the issue by just running some desktop > > environment. > > > > 5) There is a splat during kernels boot-up if CONFIG_FTRACE=y and > > CONFIG_THUMB2_KERNEL=y. > > > > ftrace: allocating 40389 entries in 79 pages > > ------------[ cut here ]------------ > > WARNING: CPU: 0 PID: 0 at arch/arm/kernel/insn.c:15 > > __arm_gen_branch+0x7f/0x84 > That basically means the branch is out of range for the instruction. > It seems to suggest this is a Thumb2 kernel, and relative offset of > the function to the mcount function is beyond the Thumb2 branch-link > instruction range. (See ftrace_code_disable() in kernel/trace/ftrace.c). > > This unfortunately provokes two warnings - one from the instruction > > generation code, and one from the ftrace code: > > WARNING: CPU: 0 PID: 0 at kernel/trace/ftrace.c:2059 > > ftrace_bug+0x1d7/0x28c > > > > > > Initializing ftrace call sites > > ftrace record flags: 0 > > > > (0) > > > > expected tramp: c010f7dd > > This may not be the affected function - it looks like the ftrace > code bails out on the first ftrace_code_disable() that fails... > > Which ever function it is, the compiler would have had to create > code that would allow it to get to the mcount function, so it > suggests that the ftrace code doesn't know about some compiler > trick... Also.. kernel module may fail to load (even with CONFIG_THUMB2_KERNEL=n): test_kasan: section 4 reloc 357 sym 'arm_copy_from_user': relocation 28 out of range (0xbf004f20 -> 0xc106e0c0) Disabling CONFIG_FTRACE=n helped, but that module loading worked once with enabled ftrace and a slightly different kernel config. I think it is not due to enabled KASAN because I've experienced such (or similar) module load failures a lot with a thumb2 kernel in general. That should be some generic trouble with the ARM kernel. Russell, do you have a clue why a such module- load failure happens? -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
