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Re: [Qemu-devel] [PATCH for-2.12] chardev/char-fe: Allow NULL chardev in
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH for-2.12] chardev/char-fe: Allow NULL chardev in qemu_chr_fe_init() |
Date: |
Fri, 23 Mar 2018 17:43:19 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 |
On 23/03/2018 16:29, Peter Maydell wrote:
> All the functions in char-fe.c handle the CharBackend
> having a NULL Chardev pointer, which means that the
> backend exists but is not connected to anything. The
> exception is qemu_chr_fe_init(), which will crash if
> passed a NULL Chardev pointer argument. This can happen
> for various boards if they're started with 'nodefaults':
> arm-softmmu/qemu-system-arm -S -nodefaults -M cubieboard
> riscv32-softmmu/qemu-system-riscv32 -nodefaults -M sifive_e
>
> Make qemu_chr_fe_init() accept a NULL chardev. This allows
> UART models to handle NULL chardev properties without
> generally needing to special case them or to manually
> create a NullChardev.
>
> Reported-by: Thomas Huth <address@hidden>
> Signed-off-by: Peter Maydell <address@hidden>
> ---
> This is my proposal for fixing the crashes with -nodefaults.
> I think we should also change hw/char/serial.c to accept
> a NULL Chardev rather than treating it as an error
> ( "Can't create serial device, empty char device"), and
> similarly for any other devices that currently error out
> on NULL chardevs. I'd rather postpone that part til 2.13, though.
>
>
> chardev/char-fe.c | 22 ++++++++++++----------
> 1 file changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/chardev/char-fe.c b/chardev/char-fe.c
> index 392db78b13..b1f228e8b5 100644
> --- a/chardev/char-fe.c
> +++ b/chardev/char-fe.c
> @@ -198,19 +198,21 @@ bool qemu_chr_fe_init(CharBackend *b, Chardev *s, Error
> **errp)
> {
> int tag = 0;
>
> - if (CHARDEV_IS_MUX(s)) {
> - MuxChardev *d = MUX_CHARDEV(s);
> + if (s) {
> + if (CHARDEV_IS_MUX(s)) {
> + MuxChardev *d = MUX_CHARDEV(s);
>
> - if (d->mux_cnt >= MAX_MUX) {
> + if (d->mux_cnt >= MAX_MUX) {
> + goto unavailable;
> + }
> +
> + d->backends[d->mux_cnt] = b;
> + tag = d->mux_cnt++;
> + } else if (s->be) {
> goto unavailable;
> + } else {
> + s->be = b;
> }
> -
> - d->backends[d->mux_cnt] = b;
> - tag = d->mux_cnt++;
> - } else if (s->be) {
> - goto unavailable;
> - } else {
> - s->be = b;
> }
>
> b->fe_open = false;
>
Queued, thanks.
Paolo