Re: arm: kasan: WARNING: CPU: 0 PID: 0 at arch/arm/kernel/insn.c:47 __arm_gen_branch

[Arnd Bergmann]

On Wed, Nov 11, 2020 at 9:15 AM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
>
> On Wed, 11 Nov 2020 at 07:13, Naresh Kamboju <naresh.kamboju@xxxxxxxxxx> wrote:
> >
> > The following kernel warning noticed on arm KASAN enabled config while booting.
> >
> > [    0.000000] Linux version 5.10.0-rc3-next-20201110
> > (tuxmake@e15fe3b4fdc6) (arm-linux-gnueabihf-gcc (Debian 9.3.0-13)
> > 9.3.0, GNU ld (GNU Binutils for Debian) 2.35.1) #2 SMP Tue Nov 10
> > 07:49:47 UTC 2020
> > [    0.000000] CPU: ARMv7 Processor [410fd034] revision 4 (ARMv7), cr=10c5383d
> > <trim>
> > [    0.000000] kasan: Truncating shadow for memory block at
> > 0x40000000-0xffffffff to lowmem region at 0x70000000
> > [    0.000000] kasan: Mapping kernel virtual memory block:
> > c0000000-f0000000 at shadow: b7000000-bd000000
> > [    0.000000] kasan: Mapping kernel virtual memory block:
> > bf000000-c0000000 at shadow: b6e00000-b7000000
> > [    0.000000] kasan: Kernel address sanitizer initialized
> > <trim>
> > [    0.000000] ftrace: allocating 57178 entries in 112 pages
> > [    0.000000] ------------[ cut here ]------------
> > [    0.000000] WARNING: CPU: 0 PID: 0 at arch/arm/kernel/insn.c:47
> > __arm_gen_branch+0x78/0x80
> > [    0.000000] Modules linked in:
> > [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted
> > 5.10.0-rc3-next-20201110 #2
> > [    0.000000] Hardware name: Generic DT based system
> > [    0.000000] Backtrace:
> > [    0.000000] [<c199f710>] (dump_backtrace) from [<c199fb94>]
> > (show_stack+0x20/0x24)
> > [    0.000000]  r9:00000080 r8:c2e00000 r7:c3023060 r6:600000d3
> > r5:00000000 r4:c3023060
> > [    0.000000] [<c199fb74>] (show_stack) from [<c19a7ad0>]
> > (dump_stack+0xe8/0x10c)
> > [    0.000000] [<c19a79e8>] (dump_stack) from [<c0366518>] (__warn+0x140/0x164)
> > [    0.000000]  r10:00000009 r9:00000000 r8:c2e0e000 r7:00000009
> > r6:c031986c r5:0000002f
> > [    0.000000]  r4:c1a0bbe0 r3:c2e06f50
> > [    0.000000] [<c03663d8>] (__warn) from [<c19a13ac>]
> > (warn_slowpath_fmt+0xc0/0x128)
> > [    0.000000]  r9:c031986c r8:0000002f r7:c1a0bbe0 r6:00000000
> > r5:c2e03ec0 r4:b75c07cc
> > [    0.000000] [<c19a12f0>] (warn_slowpath_fmt) from [<c031986c>]
> > (__arm_gen_branch+0x78/0x80)
> > [    0.000000]  r10:0000d247 r9:c4019238 r8:c400c104 r7:c2e070a0
> > r6:c400c108 r5:c0319250
> > [    0.000000]  r4:00000000
> > [    0.000000] [<c03197f4>] (__arm_gen_branch) from [<c0319720>]
> > (ftrace_make_nop+0x30/0x48)
> > [    0.000000]  r5:c0319250 r4:c2b00354
> > [    0.000000] [<c03196f0>] (ftrace_make_nop) from [<c04ac104>]
> > (ftrace_process_locs+0x470/0x5f0)
> > [    0.000000]  r5:00001248 r4:c400c100
> > [    0.000000] [<c04abc94>] (ftrace_process_locs) from [<c2b2d8f4>]
> > (ftrace_init+0xa8/0x158)
> > [    0.000000]  r10:10c5387d r9:c1a87768 r8:c2cb9f98 r7:c2c82230
> > r6:00000001 r5:c2e070a0
> > [    0.000000]  r4:c37f5c40
> > [    0.000000] [<c2b2d84c>] (ftrace_init) from [<c2b010ec>]
> > (start_kernel+0x174/0x3f8)
> > [    0.000000]  r9:00000001 r8:c2e06f00 r7:00000000 r6:c2e06f00
> > r5:c37c0000 r4:ffffffff
> > [    0.000000] [<c2b00f78>] (start_kernel) from [<00000000>] (0x0)
> > [    0.000000]  r9:410fd034 r8:48000000 r7:ffffffff r6:10c0387d
> > r5:00000051 r4:c2b00334
> > [    0.000000] random: get_random_bytes called from
> > print_oops_end_marker+0x30/0xa0 with crng_init=0
> > [    0.000000] ---[ end trace 0000000000000000 ]---
> > [ #
> >    0.000000] ------------[ ftrace bug ]------------
> > [    0.000000] ftrace failed to modify
> > [    0.000000] [<c2b00354>] set_reset_devices+0x10/0x28
> > [    0.000000]  actual:   0a:3d:04:eb
> > [    0.000000] Initializing ftrace call sites
> > [    0.000000] ftrace record flags: 0
> > [    0.000000]  (0)
> > [    0.000000]  expected tramp: c031925c
> > [    0.000000] ------------[ cut here ]------------
> > [    0.000000] WARNING: CPU: 0 PID: 0 at kernel/trace/ftrace.c:2065
> > ftrace_bug+0x218/0x280
> > [    0.000000] Modules linked in:
> > [    0.000000] CPU: 0 PID: 0 Comm: swapper Tainted: G        W
> > 5.10.0-rc3-next-20201110 #2
> > [    0.000000] Hardware name: Generic DT based system
> > [    0.000000] Backtrace:
> > [    0.000000] [<c199f710>] (dump_backtrace) from [<c199fb94>]
> > (show_stack+0x20/0x24)
> > [    0.000000]  r9:00000080 r8:c2e00000 r7:c3023060 r6:600000d3
> > r5:00000000 r4:c3023060
> > [    0.000000] [<c199fb74>] (show_stack) from [<c19a7ad0>]
> > (dump_stack+0xe8/0x10c)
> > [    0.000000] [<c19a79e8>] (dump_stack) from [<c0366518>] (__warn+0x140/0x164)
> > [    0.000000]  r10:00000009 r9:00000000 r8:c2e0e000 r7:00000009
> > r6:c19a3790 r5:00000811
> > [    0.000000]  r4:c1a863c0 r3:c2e06f50
> > [    0.000000] [<c03663d8>] (__warn) from [<c19a13ac>]
> > (warn_slowpath_fmt+0xc0/0x128)
> > [    0.000000]  r9:c19a3790 r8:00000811 r7:c1a863c0 r6:00000000
> > r5:c2e03ee0 r4:b75c07d0
> > [    0.000000] [<c19a12f0>] (warn_slowpath_fmt) from [<c19a3790>]
> > (ftrace_bug+0x218/0x280)
> > [    0.000000]  r10:0000d247 r9:c4019238 r8:c400c104 r7:c37f5c40
> > r6:c1a86960 r5:c401923c
> > [    0.000000]  r4:c4019238
> > [    0.000000] [<c19a3578>] (ftrace_bug) from [<c04abfc0>]
> > (ftrace_process_locs+0x32c/0x5f0)
> > [    0.000000]  r7:c2e070a0 r6:c400c108 r5:00001248 r4:c400c100
> > [    0.000000] [<c04abc94>] (ftrace_process_locs) from [<c2b2d8f4>]
> > (ftrace_init+0xa8/0x158)
> > [    0.000000]  r10:10c5387d r9:c1a87768 r8:c2cb9f98 r7:c2c82230
> > r6:00000001 r5:c2e070a0
> > [    0.000000]  r4:c37f5c40
> > [    0.000000] [<c2b2d84c>] (ftrace_init) from [<c2b010ec>]
> > (start_kernel+0x174/0x3f8)
> > [    0.000000]  r9:00000001 r8:c2e06f00 r7:00000000 r6:c2e06f00
> > r5:c37c0000 r4:ffffffff
> > [    0.000000] [<c2b00f78>] (start_kernel) from [<00000000>] (0x0)
> > [    0.000000]  r9:410fd034 r8:48000000 r7:ffffffff r6:10c0387d
> > r5:00000051 r4:c2b00334
> > [    0.000000] ---[ end trace f68728a0d3053b52 ]---
> > [    0.000000] ftrace: allocated 112 pages with 3 groups
> >
> > metadata:
> >   git branch: master
> >   git repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next
> >   git describe: next-20201110
> >   make_kernelversion: 5.10.0-rc3
> >   build : https://builds.tuxbuild.com/1k5bYasxkHF7omMh7mjtxjRtkMe/
> >
> > The qemu boot command,
> > -----------------------------------
> > /usr/bin/qemu-system-aarch64 -cpu host,aarch64=off -machine
> > virt-2.10,accel=kvm -nographic -net
> > nic,model=virtio,macaddr=BA:DD:AD:CC:09:03 -net tap -m 2048 -monitor
> > none -kernel kernel/zImage --append "console=ttyAMA0 root=/dev/vda rw"
> > -hda rpb-console-image-lkft-am57xx-evm-20201022181203-3085.rootfs.ext4
> > -m 4096 -smp 2 -nographic
> >
> > Full log:
> > https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20201110/testrun/3420437/suite/linux-log-parser/test/check-kernel-warning-1927841/log
> >
>
> The kernel you are building is too big.
>
> An ordinary multi_v7_defconfig+thumb2 has
>
> (10240K kernel code, 2232K rwdata, 5344K rodata, 2048K init, 441K bss,
> 144040K reserved, 65536K cma-reserved, 3340512K highmem)
>
> whereas your kernel has
>
> (23552K kernel code, 9970K rwdata, 16736K rodata, 3072K init, 4849K
> bss, 189072K reserved, 65536K cma-reserved, 2293756K highmem)
>
> and so the kernel text section is too large to resolve relative branches.
>
> Which config are you building?

The config available from the 'build' link above:
https://builds.tuxbuild.com/1k5bYasxkHF7omMh7mjtxjRtkMe/config

This is a diff of that against multi_v7_defconfig: https://pastebin.com/v2uxkrCe
I ran that on v5.10-rc1, so it's missing KASAN.

I don't think any of the individual drivers is going to be a huge difference,
but these are the ones that might add a percentage to the overall build:

CONFIG_NAMESPACES
CONFIG_KALLSYMS_ALL
CONFIG_KPROBES
CONFIG_KSM
CONFIG_VIDEO_V4L2
CONFIG_FUNCTION_TRACER
CONFIG_DYNAMIC_FTRACE
CONFIG_IRQSOFF_TRACER
CONFIG_KPROBE_EVENTS
CONFIG_FTRACE_MCOUNT_RECORD
CONFIG_UNWINDER_FRAME_POINTER
CONFIG_KASAN

My guess is that the combination of a few of the above
doubles the size.

     Arnd