On Wed, 10 Feb 2016, Geert Uytterhoeven wrote:
> If CONFIG_DEBUG_RODATA=y, the kernel crashes during system suspend:
>
> Freezing user space processes ... (elapsed 0.004 seconds) done.
> Freezing remaining freezable tasks ... (elapsed 0.002 seconds)
> done.
> PM: suspend of devices complete after 111.948 msecs
> PM: late suspend of devices complete after 1.086 msecs
> PM: noirq suspend of devices complete after 11.576 msecs
> Disabling non-boot CPUs ...
> Kernel panic - not syncing: Attempted to kill the idle task!
> 1014ec ---[ end Kernel panic - not syncing: Attempted to kill the idle task!
> CPU0: stopping
>
> This happens because the .text section is marked read-only, while the
> arrays shmobile_smp_mpidr[], shmobile_smp_fn[], and shmobile_smp_arg[]
> are being written to.
>
> Fix this by moving these arrays from the .text to the .data section.
> This requires accessing them through PC-relative offsets.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
You could replace .data with .bss to avoid allocating zero-initialized
space in the kernel binary. Then you may add
Reviewed-by: Nicolas Pitre <nico@xxxxxxxxxx>
> ---
> v2:
> - Add Reviewed-by,
> - Store offsets instead of pointers, as suggested by Nicolas Pitre
> <nicolas.pitre@xxxxxxxxxx>.
> ---
> arch/arm/mach-shmobile/headsmp.S | 20 ++++++++++++++------
> 1 file changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm/mach-shmobile/headsmp.S b/arch/arm/mach-shmobile/headsmp.S
> index 330c1fc63197df89..4cf7f0b016b0b0fe 100644
> --- a/arch/arm/mach-shmobile/headsmp.S
> +++ b/arch/arm/mach-shmobile/headsmp.S
> @@ -50,9 +50,11 @@ ENTRY(shmobile_smp_boot)
> mrc p15, 0, r1, c0, c0, 5 @ r1 = MPIDR
> and r0, r1, r0 @ r0 = cpu_logical_map() value
> mov r1, #0 @ r1 = CPU index
> - adr r5, 1f @ array of per-cpu mpidr values
> - adr r6, 2f @ array of per-cpu functions
> - adr r7, 3f @ array of per-cpu arguments
> + adr r2, 1f
> + ldmia r2, {r5, r6, r7}
> + add r5, r5, r2 @ array of per-cpu mpidr values
> + add r6, r6, r2 @ array of per-cpu functions
> + add r7, r7, r2 @ array of per-cpu arguments
>
> shmobile_smp_boot_find_mpidr:
> ldr r8, [r5, r1, lsl #2]
> @@ -80,12 +82,18 @@ ENTRY(shmobile_smp_sleep)
> b shmobile_smp_boot
> ENDPROC(shmobile_smp_sleep)
>
> + .align 2
> +1: .long shmobile_smp_mpidr - .
> + .long shmobile_smp_fn - 1b
> + .long shmobile_smp_arg - 1b
> +
> + .data
> .globl shmobile_smp_mpidr
> shmobile_smp_mpidr:
> -1: .space NR_CPUS * 4
> + .space NR_CPUS * 4
> .globl shmobile_smp_fn
> shmobile_smp_fn:
> -2: .space NR_CPUS * 4
> + .space NR_CPUS * 4
> .globl shmobile_smp_arg
> shmobile_smp_arg:
> -3: .space NR_CPUS * 4
> + .space NR_CPUS * 4
> --
> 1.9.1
>
>
