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SubjectRe: [PATCH V2 4/6] ARM: Make PID_IN_CONTEXTIDR incompatible with PID_NS
On Fri, Jan 24, 2014 at 04:40:54PM +0000, Adrien Vergé wrote:
> When using namespaces, different processes can have the same PID.
> It makes no sense to store a PID value in the Context ID register
> to track a specific process, when others share the same value.
>
> Consequently, PID_IN_CONTEXTIDR (which is used for tracing and
> debugging processes) should not be compatible with PID_NS.
>
> Signed-off-by: Adrien Vergé <adrienverge@gmail.com>
> ---
> arch/arm/Kconfig.debug | 2 +-
> arch/arm64/Kconfig.debug | 1 +
> 2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
> index 5765abf..ed46748 100644
> --- a/arch/arm/Kconfig.debug
> +++ b/arch/arm/Kconfig.debug
> @@ -1143,7 +1143,7 @@ config ARM_KPROBES_TEST
>
> config PID_IN_CONTEXTIDR
> bool "Write the current PID to the CONTEXTIDR register"
> - depends on CPU_COPY_V6
> + depends on CPU_COPY_V6 && !PID_NS
> help
> Enabling this option causes the kernel to write the current PID to
> the PROCID field of the CONTEXTIDR register, at the expense of some
> diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
> index 835c559..06b2633b 100644
> --- a/arch/arm64/Kconfig.debug
> +++ b/arch/arm64/Kconfig.debug
> @@ -17,6 +17,7 @@ config EARLY_PRINTK
>
> config PID_IN_CONTEXTIDR
> bool "Write the current PID to the CONTEXTIDR register"
> + depends on !PID_NS
> help
> Enabling this option causes the kernel to write the current PID to
> the CONTEXTIDR register, at the expense of some additional

Are you sure about this? The value we write is actually task_pid_nr, which I
believe to be globally unique.

Will
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