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TTY: fix crash obtaining kernel messages

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Also fix a case of potential message loss in TTY and LOG.
This commit is contained in:
David van Moolenbroek 2012-11-06 00:11:16 +01:00
parent 7f007284e6
commit 71d5865b10
2 changed files with 17 additions and 16 deletions
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14
drivers/log/diag.c
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@ -21,8 +21,7 @@ void do_new_kmess(void)
/* Notification for a new kernel message. */
static struct kmessages *kmess; /* entire kmess structure */
static char print_buf[_KMESS_BUF_SIZE]; /* copy new message here */
int bytes;
int i, r;
int i, r, next, bytes;
static int prev_next = 0;
assert(_minix_kerninfo);
@ -31,12 +30,13 @@ void do_new_kmess(void)
/* Print only the new part. Determine how many new bytes there are with
* help of the current and previous 'next' index. Note that the kernel
* buffer is circular. This works fine if less than KMESS_BUF_SIZE bytes
* are new data; else we miss % KMESS_BUF_SIZE here.
* are new data; else we miss % KMESS_BUF_SIZE here. Obtain 'next' only
* once, since we are operating on shared memory here.
* Check for size being positive, the buffer might as well be emptied!
*/
if (kmess->km_size > 0) {
bytes = ((kmess->km_next + _KMESS_BUF_SIZE) - prev_next) %
_KMESS_BUF_SIZE;
next = kmess->km_next;
bytes = ((next + _KMESS_BUF_SIZE) - prev_next) % _KMESS_BUF_SIZE;
if (bytes > 0) {
r= prev_next; /* start at previous old */
i=0;
while (bytes > 0) {
@ -53,5 +53,5 @@ void do_new_kmess(void)
/* Almost done, store 'next' so that we can determine what part of the
* kernel messages buffer to print next time a notification arrives.
*/
prev_next = kmess->km_next;
prev_next = next;
}

19
drivers/tty/tty.c
View file

@ -456,9 +456,9 @@ do_new_kmess(void)
{
/* Kernel wants to print a new message */
struct kmessages *kmess_ptr; /* kmessages structure */
char kernel_buf_copy[2*_KMESS_BUF_SIZE];
char kernel_buf_copy[_KMESS_BUF_SIZE];
static int prev_next = 0;
int bytes, copy, restore = 0;
int next, bytes, copy, restore = 0;
tty_t *tp, rtp;
message print_kmsg;
@ -468,14 +468,15 @@ do_new_kmess(void)
/* The kernel buffer is circular; print only the new part. Determine
* how many new bytes there are with the help of current and
* previous 'next' index. This works fine if less than _KMESS_BUF_SIZE
* bytes is new data; else we miss % _KMESS_BUF_SIZE here.
* bytes is new data; else we miss % _KMESS_BUF_SIZE here. Obtain
* 'next' only once, since we are operating on shared memory here.
* Check for size being positive; the buffer might as well be emptied!
*/
if (kmess_ptr->km_size > 0) {
bytes = ((kmess_ptr->km_next + _KMESS_BUF_SIZE) - prev_next) %
_KMESS_BUF_SIZE;
/* Copy from current position to end of buffer */
copy = (prev_next + bytes) % _KMESS_BUF_SIZE;
next = kmess_ptr->km_next;
bytes = ((next + _KMESS_BUF_SIZE) - prev_next) % _KMESS_BUF_SIZE;
if (bytes > 0) {
/* Copy from current position toward end of buffer */
copy = MIN(_KMESS_BUF_SIZE - prev_next, bytes);
memcpy(kernel_buf_copy, &kmess_ptr->km_buf[prev_next], copy);
/* Copy remainder from start of buffer */
@ -510,7 +511,7 @@ do_new_kmess(void)
/* Store 'next' pointer so that we can determine what part of the
* kernel messages buffer to print next time a notification arrives.
*/
prev_next = kmess_ptr->km_next;
prev_next = next;
}
/*===========================================================================*