[CRIU] Re: [PATCH cr 1/2] parasite: add a function to execute a parasite code in threads

[Cyrill Gorcunov]

On Tue, Feb 21, 2012 at 09:25:16AM +0300, Andrey Vagin wrote:
> 
> Signed-off-by: Andrey Vagin <avagin at openvz.org>
> ---
>  parasite-syscall.c |   37 +++++++++++++++++++++++++++++--------
>  1 files changed, 29 insertions(+), 8 deletions(-)
> 

> diff --git a/parasite-syscall.c b/parasite-syscall.c
> index 02a50fa..0a27b18 100644
> --- a/parasite-syscall.c
> +++ b/parasite-syscall.c
> @@ -77,9 +77,8 @@ static void parasite_setup_regs(unsigned long new_ip, user_regs_struct_t *regs)
>  }
>  
>  /* we run at @regs->ip */
> -static int __parasite_execute(struct parasite_ctl *ctl, user_regs_struct_t *regs)
> +static int __parasite_execute(struct parasite_ctl *ctl, pid_t pid, user_regs_struct_t *regs)
>  {
> -	pid_t pid = ctl->pid;
>  	siginfo_t siginfo;
>  	int status;
>  	int ret = -1;
> @@ -226,19 +225,29 @@ err:
>  	return ret;
>  }
>  
> -static int parasite_execute(unsigned long cmd, struct parasite_ctl *ctl,
> +static int parasite_execute_by_pid(unsigned long cmd, struct parasite_ctl *ctl,
> +			    pid_t pid,
>  			    parasite_status_t *args, int args_size)
>  {
>  	int ret;
> -
> -	user_regs_struct_t regs = ctl->regs_orig;
> +	user_regs_struct_t regs_orig, regs;
> +
> +	if (ctl->pid == pid)
> +		regs = ctl->regs_orig;
> +	else {
> +		if (ptrace(PTRACE_GETREGS, pid, NULL, &regs_orig)) {
> +			pr_err("Can't obtain registers (pid: %d)\n", pid);
> +			return -1;
> +		}
> +		regs = regs_orig;
> +	}
> 

This won't work well. __parasite_execute *updates* current registers
frame so you rather have to update __parasite_execute as well and
add regs as an argument. Then, in case of signal deliery, you're
to update these regs and return them to a caller with already
modifed contents.

	Cyrill