C/R of termios

Oren,

Any reason we only checkpoint/restore a 'struct termio' instead of a 'struct termios' ?

AFAICT, 'struct termios' seems to supersede 'struct termio' (i.e includes all fields of 'struct termio' plus more). The TCGETS ioctl and tcgetattr() interface return a 'struct termios' to user space.

The man page termio(7) says the 'struct termio' interface is obsolete.

The kernel uses 'struct ktermios' to represent the attributes internally. So shouldn't we checkpoint/restore the 'struct ktermios' object ?

If application uses legacy interface (TCGETA/TCSETA with 'struct termio') the kernel converts the 'struct ktermios' to the 'struct termio' in kernel_termios_to_user_termio(). So we should be fine if we C/R the ktermios object right ?

Here is a quick hack, just for reference. With this hack, I can C/R an app that does tcgetattr() of a pty before/after checkpoint.

Oren,

Any reason we only checkpoint/restore a 'struct termio' instead of a 'struct termios' ?

AFAICT, 'struct termios' seems to supersede 'struct termio' (i.e includes all fields of 'struct termio' plus more). The TCGETS ioctl and tcgetattr() interface return a 'struct termios' to user space.

The man page termio(7) says the 'struct termio' interface is obsolete.

The kernel uses 'struct ktermios' to represent the attributes internally. So shouldn't we checkpoint/restore the 'struct ktermios' object ?

If application uses legacy interface (TCGETA/TCSETA with 'struct termio') the kernel converts the 'struct ktermios' to the 'struct termio' in kernel_termios_to_user_termio(). So we should be fine if we C/R the ktermios object right ?

Here is a quick hack, just for reference. With this hack, I can C/R an app that does tcgetattr() of a pty before/after checkpoint.

---

arch/x86/include/asm/checkpoint_hdr.h +5 -0

index 0505329..2778aed 100644
@@ -55,6 +55,7 @@ enum {
  /* arch dependent constants */
  #define CKPT_ARCH_NSIG  64
  #define CKPT_TTY_NCC  8
+#define CKPT_TTY_NCCS  19
 
  #ifdef __KERNEL__
 

@@ -68,6 +69,10 @@ enum {
  #error CKPT_TTY_NCC size is wrong per asm-generic/termios.h
  #endif
 
+#if CKPT_TTY_NCCS != NCCS
+#error CKPT_TTY_NCCS size is wrong per asm-generic/termbits.h
+#endif
+
  #endif /* __KERNEL__ */
 
 

drivers/char/tty_io.c +2 -2

index 3a2c770..2b3f001 100644
@@ -2882,7 +2882,7 @@ static int checkpoint_tty(struct ckpt_ctx *ctx, void *ptr)
  	h->termios.c_oflag = tty->termios->c_oflag;
  	h->termios.c_cflag = tty->termios->c_cflag;
  	h->termios.c_lflag = tty->termios->c_lflag;
-	memcpy(h->termios.c_cc, tty->termios->c_cc, NCC);
+	memcpy(h->termios.c_cc, tty->termios->c_cc, NCCS);
  	h->winsize.ws_row = tty->winsize.ws_row;
  	h->winsize.ws_col = tty->winsize.ws_col;
  	h->winsize.ws_ypixel = tty->winsize.ws_ypixel;

@@ -3099,7 +3099,7 @@ static struct tty_struct *do_restore_tty(struct ckpt_ctx *ctx)
  	tty->termios->c_oflag = h->termios.c_oflag;
  	tty->termios->c_cflag = h->termios.c_cflag;
  	tty->termios->c_lflag = h->termios.c_lflag;
-	memcpy(tty->termios->c_cc, h->termios.c_cc, NCC);
+	memcpy(tty->termios->c_cc, h->termios.c_cc, NCCS);
  	tty->winsize.ws_row = h->winsize.ws_row;
  	tty->winsize.ws_col = h->winsize.ws_col;
  	tty->winsize.ws_ypixel = h->winsize.ws_ypixel;

include/linux/checkpoint_hdr.h +3 -1

index 4303235..e432b04 100644
@@ -1143,7 +1143,9 @@ struct ckpt_hdr_tty {
  		__u16 c_cflag;
  		__u16 c_lflag;
  		__u8 c_line;
-		__u8 c_cc[CKPT_TTY_NCC];
+		__u8 c_cc[CKPT_TTY_NCCS];
+		__u32 c_ispeed;
+		__u32 c_ospeed;
  	} __attribute__((aligned(8))) termios;
 
  	/* winsize */

Suka,

Yes, I overlooked it, thanks for pointing out. The patch looks fine - queued for inclusion. (I'll remove the now-unneeded define of CKPT_TTY_NCC)

Quoted 5 lines · Oren Laadan [[email protected]] wrote:

Suka,

Yes, I overlooked it, thanks for pointing out. The patch looks fine - queued for inclusion. (I'll remove the now-unneeded define of CKPT_TTY_NCC)

I can post a cleaner patch in a couple of days - one that works for other architectures too.

Thanks,

Sukadev