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kdb: Tidy up code to handle escape sequences 

kdb_read_get_key() has extremely complex break/continue control flow
managed by state variables and is very hard to review or modify. In
particular the way the escape sequence handling interacts with the
general control flow is hard to follow. Separate out the escape key
handling, without changing the control flow. This makes the main body of
the code easier to review.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20191025073328.643-2-daniel.thompson@linaro.org
This commit is contained in:
Daniel Thompson 2019-10-25 08:33:24 +01:00
parent d07ce4e32a
commit 53b63136e8
1 changed files with 67 additions and 61 deletions
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122
kernel/debug/kdb/kdb_io.c
View File

@ -49,6 +49,65 @@ static int kgdb_transition_check(char *buffer)
return 0;
}
/**
* kdb_handle_escape() - validity check on an accumulated escape sequence.
* @buf: Accumulated escape characters to be examined. Note that buf
* is not a string, it is an array of characters and need not be
* nil terminated.
* @sz: Number of accumulated escape characters.
*
* Return: -1 if the escape sequence is unwanted, 0 if it is incomplete,
* otherwise it returns a mapped key value to pass to the upper layers.
*/
static int kdb_handle_escape(char *buf, size_t sz)
{
char *lastkey = buf + sz - 1;
switch (sz) {
case 1:
if (*lastkey == '\e')
return 0;
break;
case 2: /* \e<something> */
if (*lastkey == '[')
return 0;
break;
case 3:
switch (*lastkey) {
case 'A': /* \e[A, up arrow */
return 16;
case 'B': /* \e[B, down arrow */
return 14;
case 'C': /* \e[C, right arrow */
return 6;
case 'D': /* \e[D, left arrow */
return 2;
case '1': /* \e[<1,3,4>], may be home, del, end */
case '3':
case '4':
return 0;
}
break;
case 4:
if (*lastkey == '~') {
switch (buf[2]) {
case '1': /* \e[1~, home */
return 1;
case '3': /* \e[3~, del */
return 4;
case '4': /* \e[4~, end */
return 5;
}
}
break;
}
return -1;
}
static int kdb_read_get_key(char *buffer, size_t bufsize)
{
#define ESCAPE_UDELAY 1000
@ -102,69 +161,16 @@ static int kdb_read_get_key(char *buffer, size_t bufsize)
escape_delay = 2;
continue;
}
if (ped - escape_data == 1) {
/* \e */
continue;
} else if (ped - escape_data == 2) {
/* \e<something> */
if (key != '[')
escape_delay = 2;
continue;
} else if (ped - escape_data == 3) {
/* \e[<something> */
int mapkey = 0;
switch (key) {
case 'A': /* \e[A, up arrow */
mapkey = 16;
break;
case 'B': /* \e[B, down arrow */
mapkey = 14;
break;
case 'C': /* \e[C, right arrow */
mapkey = 6;
break;
case 'D': /* \e[D, left arrow */
mapkey = 2;
break;
case '1': /* dropthrough */
case '3': /* dropthrough */
/* \e[<1,3,4>], may be home, del, end */
case '4':
mapkey = -1;
break;
}
if (mapkey != -1) {
if (mapkey > 0) {
escape_data[0] = mapkey;
escape_data[1] = '\0';
}
escape_delay = 2;
}
continue;
} else if (ped - escape_data == 4) {
/* \e[<1,3,4><something> */
int mapkey = 0;
if (key == '~') {
switch (escape_data[2]) {
case '1': /* \e[1~, home */
mapkey = 1;
break;
case '3': /* \e[3~, del */
mapkey = 4;
break;
case '4': /* \e[4~, end */
mapkey = 5;
break;
}
}
if (mapkey > 0) {
escape_data[0] = mapkey;
key = kdb_handle_escape(escape_data, ped - escape_data);
if (key > 0) {
escape_data[0] = key;
escape_data[1] = '\0';
}
if (key)
escape_delay = 2;
continue;
}
}
break; /* A key to process */
}
return key;