From 2be0a3ed22dc90dfb61bc8549988cef830943d7a Mon Sep 17 00:00:00 2001 From: aliguori Date: Thu, 5 Mar 2009 23:00:02 +0000 Subject: [PATCH] char-mux: Use separate input buffers (Jan Kiszka) Currently, the intermediate input buffer of mux'ed character devices records data across all sub-devices. This has the side effect that we easily leak data recorded over one sub-devices to another once we switch the focus. Avoid data loss and confusion by defining exclusive buffers. Note: In contrast to the original author's claim, the buffering concept still breaks down when the fifo of the currently active sub-device is full. As we cannot accept futher data from this point on without risking to loose it, we will also miss escape sequences, just like without all that buffering. In short: There is no reliable escape sequence handling without infinite buffers or the risk of loosing some data. Signed-off-by: Jan Kiszka Signed-off-by: Anthony Liguori git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6701 c046a42c-6fe2-441c-8c8c-71466251a162 --- qemu-char.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/qemu-char.c b/qemu-char.c index 1332863ed3..1fd3aefe38 100644 --- a/qemu-char.c +++ b/qemu-char.c @@ -225,12 +225,15 @@ typedef struct { IOEventHandler *chr_event[MAX_MUX]; void *ext_opaque[MAX_MUX]; CharDriverState *drv; - unsigned char buffer[MUX_BUFFER_SIZE]; - int prod; - int cons; int mux_cnt; int term_got_escape; int max_size; + /* Intermediate input buffer allows to catch escape sequences even if the + currently active device is not accepting any input - but only until it + is full as well. */ + unsigned char buffer[MAX_MUX][MUX_BUFFER_SIZE]; + int prod[MAX_MUX]; + int cons[MAX_MUX]; } MuxDriver; @@ -360,11 +363,11 @@ static void mux_chr_accept_input(CharDriverState *chr) int m = chr->focus; MuxDriver *d = chr->opaque; - while (d->prod != d->cons && + while (d->prod[m] != d->cons[m] && d->chr_can_read[m] && d->chr_can_read[m](d->ext_opaque[m])) { d->chr_read[m](d->ext_opaque[m], - &d->buffer[d->cons++ & MUX_BUFFER_MASK], 1); + &d->buffer[m][d->cons[m]++ & MUX_BUFFER_MASK], 1); } } @@ -372,11 +375,12 @@ static int mux_chr_can_read(void *opaque) { CharDriverState *chr = opaque; MuxDriver *d = chr->opaque; + int m = chr->focus; - if ((d->prod - d->cons) < MUX_BUFFER_SIZE) + if ((d->prod[m] - d->cons[m]) < MUX_BUFFER_SIZE) return 1; - if (d->chr_can_read[chr->focus]) - return d->chr_can_read[chr->focus](d->ext_opaque[chr->focus]); + if (d->chr_can_read[m]) + return d->chr_can_read[m](d->ext_opaque[m]); return 0; } @@ -391,12 +395,12 @@ static void mux_chr_read(void *opaque, const uint8_t *buf, int size) for(i = 0; i < size; i++) if (mux_proc_byte(chr, d, buf[i])) { - if (d->prod == d->cons && + if (d->prod[m] == d->cons[m] && d->chr_can_read[m] && d->chr_can_read[m](d->ext_opaque[m])) d->chr_read[m](d->ext_opaque[m], &buf[i], 1); else - d->buffer[d->prod++ & MUX_BUFFER_MASK] = buf[i]; + d->buffer[m][d->prod[m]++ & MUX_BUFFER_MASK] = buf[i]; } } -- 2.34.1