On 3/5/19 12:50 PM, matthias....@kernel.org wrote:
> From: Matthias Brugger <mbrug...@suse.com>
>
> Function term_read_reply tries to read from the serial console until
> the end_char was read. This can hang forever if we are, for some reason,
> not be able to read the full response (e.g. serial buffer too small,
> frame error). This patch moves the timeout detection into
> term_read_reply to assure we will make progress.
>
> Fixes: 6bb591f704 ("efi_loader: query serial console size reliably")
> Signed-off-by: Matthias Brugger <mbrug...@suse.com>
>
> ---
>
> Changes in v2:
> - move timeout into term_get_char
>
> lib/efi_loader/efi_console.c | 60 ++++++++++++++++++++----------------
> 1 file changed, 33 insertions(+), 27 deletions(-)
>
> diff --git a/lib/efi_loader/efi_console.c b/lib/efi_loader/efi_console.c
> index 66c33a551d..1133674faf 100644
> --- a/lib/efi_loader/efi_console.c
> +++ b/lib/efi_loader/efi_console.c
> @@ -62,6 +62,21 @@ static struct simple_text_output_mode efi_con_mode = {
> .cursor_visible = 1,
> };
>
> +static int term_get_char(char *c)
> +{
> + u64 timeout;
> +
> + /* Wait up to 100 ms for a character */
> + timeout = timer_get_us() + 100000;
> +
> + while (!tstc())
> + if (timer_get_us() > timeout)
> + return 1;
> +
> + *c = getc();
> + return 0;
> +}
> +
> /*
> * Receive and parse a reply from the terminal.
> *
> @@ -75,31 +90,31 @@ static int term_read_reply(int *n, int num, char end_char)
> char c;
> int i = 0;
>
> - c = getc();
> - if (c != cESC)
> + if (term_get_char(&c) || c != cESC)
> return -1;
> - c = getc();
> - if (c != '[')
> +
> + if (term_get_char(&c) || c != '[')
> return -1;
>
> n[0] = 0;
> while (1) {
> - c = getc();
> - if (c == ';') {
> - i++;
> - if (i >= num)
> + if (!term_get_char(&c)) {
> + if (c == ';') {
> + i++;
> + if (i >= num)
> + return -1;
> + n[i] = 0;
> + continue;
> + } else if (c == end_char) {
> + break;
> + } else if (c > '9' || c < '0') {
> return -1;
> - n[i] = 0;
> - continue;
> - } else if (c == end_char) {
> - break;
> - } else if (c > '9' || c < '0') {
> - return -1;
> - }
> + }
>
> - /* Read one more decimal position */
> - n[i] *= 10;
> - n[i] += c - '0';
> + /* Read one more decimal position */
> + n[i] *= 10;
> + n[i] += c - '0';
> + }
If no character is received we should throw an error:
} else {
return -1;
Best regards
Heinrich
> }
> if (i != num - 1)
> return -1;
> @@ -196,7 +211,6 @@ static int query_console_serial(int *rows, int *cols)
> {
> int ret = 0;
> int n[2];
> - u64 timeout;
>
> /* Empty input buffer */
> while (tstc())
> @@ -216,14 +230,6 @@ static int query_console_serial(int *rows, int *cols)
> ESC "[999;999H" /* Move to bottom right corner */
> ESC "[6n"); /* Query cursor position */
>
> - /* Allow up to one second for a response */
> - timeout = timer_get_us() + 1000000;
> - while (!tstc())
> - if (timer_get_us() > timeout) {
> - ret = -1;
> - goto out;
> - }
> -
> /* Read {rows,cols} */
> if (term_read_reply(n, 2, 'R')) {
> ret = 1;
>
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