[PATCH 1/2] powerpc: Flush checkpointed gpr state for 32-bit processes in ptrace

[Christophe Leroy]

Le 19/06/2018 à 21:54, Pedro Franco de Carvalho a écrit :
> Would something like this be ok?
> 
> I factored out the calls to flush_fp_to_thread and flush_altivec_to_thread,
> although I don't really understand why these are necessary. The tm_cvsx_get/set
> functions also calls flush_vsx_to_thread (outside of the helper function).
> 
> I also noticed that tm_ppr/dscr/tar_get/set functions don't flush the tm
> state. Should they do it, and if so, should they also flush the fp and altivec
> state?
> 
> Thanks!
> Pedro
> 
> -- >8 --
> Currently ptrace doesn't flush the register state when the
> checkpointed GPRs of a 32-bit thread are accessed. This can cause core
> dumps to have stale data in the checkpointed GPR note.
> 
> This patch adds a helper function to flush the TM, fpu and altivec
> state and calls it from the tm_cgpr32_get/set functions.

This patch is almost 6 yr old and doesn't apply anymore.

If someone thinks it is still relevant, please rebase and resubmit.

Thanks
Christophe

> 
> Signed-off-by: Pedro Franco de Carvalho <pedromfc at linux.vnet.ibm.com>
> ---
>   arch/powerpc/kernel/ptrace.c | 33 +++++++++++++++++++++++++++++++++
>   1 file changed, 33 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
> index 9667666eb18e..0d56857e1e89 100644
> --- a/arch/powerpc/kernel/ptrace.c
> +++ b/arch/powerpc/kernel/ptrace.c
> @@ -778,6 +778,29 @@ static int evr_set(struct task_struct *target, const struct user_regset *regset,
>   
>   #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
>   /**
> + * tm_flush_if_active - flush TM, fpu and altivec state if TM active
> + * @target:	The target task.
> + *
> + * This function flushes the TM, fpu and altivec state to the target
> + * task and returns 0 if TM is available and active in the target, and
> + * returns an error code suitable for ptrace otherwise.
> + */
> +static int tm_flush_if_active (struct task_struct *target)
> +{
> +	if (!cpu_has_feature(CPU_FTR_TM))
> +		return -ENODEV;
> +
> +	if (!MSR_TM_ACTIVE(target->thread.regs->msr))
> +		return -ENODATA;
> +
> +	flush_tmregs_to_thread(target);
> +	flush_fp_to_thread(target);
> +	flush_altivec_to_thread(target);
> +
> +	return 0;
> +}
> +
> +/**
>    * tm_cgpr_active - get active number of registers in CGPR
>    * @target:	The target task.
>    * @regset:	The user regset structure.
> @@ -2124,6 +2147,11 @@ static int tm_cgpr32_get(struct task_struct *target,
>   		     unsigned int pos, unsigned int count,
>   		     void *kbuf, void __user *ubuf)
>   {
> +	int ret = tm_flush_if_active(target);
> +
> +	if (ret)
> +		return ret;
> +
>   	return gpr32_get_common(target, regset, pos, count, kbuf, ubuf,
>   			&target->thread.ckpt_regs.gpr[0]);
>   }
> @@ -2133,6 +2161,11 @@ static int tm_cgpr32_set(struct task_struct *target,
>   		     unsigned int pos, unsigned int count,
>   		     const void *kbuf, const void __user *ubuf)
>   {
> +	int ret = tm_flush_if_active(target);
> +
> +	if (ret)
> +		return ret;
> +
>   	return gpr32_set_common(target, regset, pos, count, kbuf, ubuf,
>   			&target->thread.ckpt_regs.gpr[0]);
>   }