Xianting Tian 0986d7bc55 tty: hvc: pass DMA capable memory to put_chars() ... As well known, hvc backend can register its opertions to hvc backend. the operations contain put_chars(), get_chars() and so on. Some hvc backend may do dma in its operations. eg, put_chars() of virtio-console. But in the code of hvc framework, it may pass DMA incapable memory to put_chars() under a specific configuration, which is explained in commit c4baad5029(virtio-console: avoid DMA from stack): 1, c[] is on stack, hvc_console_print(): char c[N_OUTBUF] __ALIGNED__; cons_ops[index]->put_chars(vtermnos[index], c, i); 2, ch is on stack, static void hvc_poll_put_char(,,char ch) { struct tty_struct *tty = driver->ttys[0]; struct hvc_struct *hp = tty->driver_data; int n; do { n = hp->ops->put_chars(hp->vtermno, &ch, 1); } while (n <= 0); } Commit c4baad5029 is just the fix to avoid DMA from stack memory, which is passed to virtio-console by hvc framework in above code. But I think the fix is aggressive, it directly uses kmemdup() to alloc new buffer from kmalloc area and do memcpy no matter the memory is in kmalloc area or not. But most importantly, it should better be fixed in the hvc framework, by changing it to never pass stack memory to the put_chars() function in the first place. Otherwise, we still face the same issue if a new hvc backend using dma added in the furture. In this patch, add 'char cons_outbuf[]' as part of 'struct hvc_struct', so hp->cons_outbuf is no longer the stack memory, we can use it in above cases safely. We also add lock to protect cons_outbuf instead of using the global lock of hvc. Introduce another array(cons_hvcs[]) for hvc pointers next to the cons_ops[] and vtermnos[] arrays. With the array, we can easily find hvc's cons_outbuf and its lock. With the patch, we can revert the fix c4baad5029. Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com> Signed-off-by: Shile Zhang <shile.zhang@linux.alibaba.com> Link: https://lore.kernel.org/r/20211015024658.1353987-3-xianting.tian@linux.alibaba.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2021-10-21 10:34:33 +02:00
..
hvc_console.c	tty: hvc: pass DMA capable memory to put_chars()	2021-10-21 10:34:33 +02:00
hvc_console.h	tty: hvc: pass DMA capable memory to put_chars()	2021-10-21 10:34:33 +02:00
hvc_dcc.c	hvc: dcc: Add earlycon support	2019-10-11 08:38:07 +02:00
hvc_irq.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
hvc_iucv.c	TTY / Serial patches for 5.14-rc1	2021-07-05 14:08:24 -07:00
hvc_opal.c	tty: hvc: hvc_opal: Staticify function invoked by reference	2020-11-06 10:54:05 +01:00
hvc_riscv_sbi.c	tty: Don't force RISCV SBI console as preferred console	2019-05-16 20:42:11 -07:00
hvc_rtas.c	tty: hvc: Remove redundant license text	2017-11-08 13:08:12 +01:00
hvc_udbg.c	tty: hvc: make symbol 'hvc_udbg_dev' static	2021-04-10 10:41:40 +02:00
hvc_vio.c	tty: hvc: udbg_hvc: retry putc on -EAGAIN	2021-05-23 20:51:36 +10:00
hvc_xen.c	xen: branch for v5.15-rc5	2021-10-08 12:55:23 -07:00
hvcs.c	tty: drop put_tty_driver	2021-07-27 12:17:21 +02:00
hvsi_lib.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
hvsi.c	tty: stop using alloc_tty_driver	2021-07-27 12:17:20 +02:00
Kconfig	tty: hvc: fix link error with CONFIG_SERIAL_CORE_CONSOLE=n	2020-09-27 14:17:43 +02:00
Makefile	TTY/Serial driver patches for 4.17-rc1	2018-04-04 18:43:49 -07:00