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bootstd: Add a function to update a command line
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The Linux command line consists of a number of words with optional values.
At present U-Boot allows this to be changed using the bootargs environment
variable.

But this is quite painful, since the command line can be very long.

Add a function which can adjust a single field in the command line, so
that it is easier to make changes before booting.

Signed-off-by: Simon Glass <[email protected]>
Reviewed-by: Bin Meng <[email protected]>
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@sjg20 @lbmeng
sjg20 authored and lbmeng committed Jul 17, 2023
1 parent 347a845 commit d07861c
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191 changes: 191 additions & 0 deletions boot/bootflow.c
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Original file line number Diff line number Diff line change
Expand Up @@ -610,3 +610,194 @@ static int on_bootargs(const char *name, const char *value, enum env_op op,
}
U_BOOT_ENV_CALLBACK(bootargs, on_bootargs);
#endif

/**
* copy_in() - Copy a string into a cmdline buffer
*
* @buf: Buffer to copy into
* @end: End of buffer (pointer to char after the end)
* @arg: String to copy from
* @len: Number of chars to copy from @arg (note that this is not usually the
* sane as strlen(arg) since the string may contain following arguments)
* @new_val: Value to put after arg, or BOOTFLOWCL_EMPTY to use an empty value
* with no '=' sign
* Returns: Number of chars written to @buf
*/
static int copy_in(char *buf, char *end, const char *arg, int len,
const char *new_val)
{
char *to = buf;

/* copy the arg name */
if (to + len >= end)
return -E2BIG;
memcpy(to, arg, len);
to += len;

if (new_val == BOOTFLOWCL_EMPTY) {
/* no value */
} else {
bool need_quote = strchr(new_val, ' ');
len = strlen(new_val);

/* need space for value, equals sign and maybe two quotes */
if (to + 1 + (need_quote ? 2 : 0) + len >= end)
return -E2BIG;
*to++ = '=';
if (need_quote)
*to++ = '"';
memcpy(to, new_val, len);
to += len;
if (need_quote)
*to++ = '"';
}

return to - buf;
}

int cmdline_set_arg(char *buf, int maxlen, const char *cmdline,
const char *set_arg, const char *new_val, int *posp)
{
bool found_arg = false;
const char *from;
char *to, *end;
int set_arg_len;
char empty = '\0';
int ret;

from = cmdline ?: &empty;

/* check if the value has quotes inside */
if (new_val && new_val != BOOTFLOWCL_EMPTY && strchr(new_val, '"'))
return -EBADF;

set_arg_len = strlen(set_arg);
for (to = buf, end = buf + maxlen; *from;) {
const char *val, *arg_end, *val_end, *p;
bool in_quote;

if (to >= end)
return -E2BIG;
while (*from == ' ')
from++;
if (!*from)
break;

/* find the end of this arg */
val = NULL;
arg_end = NULL;
val_end = NULL;
in_quote = false;
for (p = from;; p++) {
if (in_quote) {
if (!*p)
return -EINVAL;
if (*p == '"')
in_quote = false;
continue;
}
if (*p == '=') {
arg_end = p;
val = p + 1;
} else if (*p == '"') {
in_quote = true;
} else if (!*p || *p == ' ') {
val_end = p;
if (!arg_end)
arg_end = p;
break;
}
}
/*
* At this point val_end points to the end of the value, or the
* last char after the arg name, if there is no label.
* arg_end is the char after the arg name
* val points to the value, or NULL if there is none
* char after the value.
*
* fred=1234
* ^ ^^ ^
* from || |
* / \ \
* arg_end val val_end
*/
log_debug("from %s arg_end %ld val %ld val_end %ld\n", from,
(long)(arg_end - from), (long)(val - from),
(long)(val_end - from));

if (to != buf) {
if (to >= end)
return -E2BIG;
*to++ = ' ';
}

/* if this is the target arg, update it */
if (!strncmp(from, set_arg, arg_end - from)) {
if (!buf) {
bool has_quote = val_end[-1] == '"';

/*
* exclude any start/end quotes from
* calculations
*/
if (!val)
val = val_end;
*posp = val - cmdline + has_quote;
return val_end - val - 2 * has_quote;
}
found_arg = true;
if (!new_val) {
/* delete this arg */
from = val_end + (*val_end == ' ');
log_debug("delete from: %s\n", from);
if (to != buf)
to--; /* drop the space we added */
continue;
}

ret = copy_in(to, end, from, arg_end - from, new_val);
if (ret < 0)
return ret;
to += ret;

/* if not the target arg, copy it unchanged */
} else if (to) {
int len;

len = val_end - from;
if (to + len >= end)
return -E2BIG;
memcpy(to, from, len);
to += len;
}
from = val_end;
}

/* If we didn't find the arg, add it */
if (!found_arg) {
/* trying to delete something that is not there */
if (!new_val || !buf)
return -ENOENT;
if (to >= end)
return -E2BIG;

/* add a space to separate it from the previous arg */
if (to != buf && to[-1] != ' ')
*to++ = ' ';
ret = copy_in(to, end, set_arg, set_arg_len, new_val);
log_debug("ret=%d, to: %s buf: %s\n", ret, to, buf);
if (ret < 0)
return ret;
to += ret;
}

/* delete any trailing space */
if (to > buf && to[-1] == ' ')
to--;

if (to >= end)
return -E2BIG;
*to++ = '\0';

return to - buf;
}
40 changes: 40 additions & 0 deletions include/bootflow.h
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Original file line number Diff line number Diff line change
Expand Up @@ -444,4 +444,44 @@ int bootflow_menu_apply_theme(struct expo *exp, ofnode node);
int bootflow_menu_run(struct bootstd_priv *std, bool text_mode,
struct bootflow **bflowp);

#define BOOTFLOWCL_EMPTY ((void *)1)

/**
* cmdline_set_arg() - Update or read an argument in a cmdline string
*
* Handles updating a single arg in a cmdline string, returning it in a supplied
* buffer; also reading an arg from a cmdline string
*
* When updating, consecutive spaces are squashed as are spaces at the start and
* end.
*
* @buf: Working buffer to use (initial contents are ignored). Use NULL when
* reading
* @maxlen: Length of working buffer. Use 0 when reading
* @cmdline: Command line to update, in the form:
*
* fred mary= jane=123 john="has spaces"
*
* @set_arg: Argument to set or read (may or may not exist)
* @new_val: Value for the new argument. May not include quotes (") but may
* include embedded spaces, in which case it will be quoted when added to the
* command line. Use NULL to delete the argument from @cmdline, BOOTFLOWCL_EMPTY
* to set it to an empty value (no '=' sign after arg), "" to add an '=' sign
* but with an empty value. Use NULL when reading.
* @posp: Ignored when setting an argument; when getting an argument, returns
* the start position of its value in @cmdline, after the first quote, if any
*
* Return:
* For updating:
* length of new buffer (including \0 terminator) on success, -ENOENT if
* @new_val is NULL and @set_arg does not exist in @from, -EINVAL if a
* quoted arg-value in @from is not terminated with a quote, -EBADF if
* @new_val has spaces but does not start and end with quotes (or it has
* quotes in the middle of the string), -E2BIG if @maxlen is too small
* For reading:
* length of arg value (excluding quotes), -ENOENT if not found
*/
int cmdline_set_arg(char *buf, int maxlen, const char *cmdline,
const char *set_arg, const char *new_val, int *posp);

#endif
154 changes: 154 additions & 0 deletions test/boot/bootflow.c
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Original file line number Diff line number Diff line change
Expand Up @@ -683,3 +683,157 @@ static int bootflow_menu_theme(struct unit_test_state *uts)
return 0;
}
BOOTSTD_TEST(bootflow_menu_theme, UT_TESTF_DM | UT_TESTF_SCAN_FDT);

/**
* check_arg() - Check both the normal case and the buffer-overflow case
*
* @uts: Unit-test state
* @expect_ret: Expected return value (i.e. buffer length)
* @expect_str: String expected to be returned
* @buf: Buffer to use
* @from: Original cmdline to update
* @arg: Argument to update (e.g. "console")
* @val: Value to set (e.g. "ttyS2") or NULL to delete the argument if present,
* "" to set it to an empty value (e.g. "console=") and BOOTFLOWCL_EMPTY to add
* it without any value ("initrd")
*/
static int check_arg(struct unit_test_state *uts, int expect_ret,
const char *expect_str, char *buf, const char *from,
const char *arg, const char *val)
{
/* check for writing outside the reported bounds */
buf[expect_ret] = '[';
ut_asserteq(expect_ret,
cmdline_set_arg(buf, expect_ret, from, arg, val, NULL));
ut_asserteq_str(expect_str, buf);
ut_asserteq('[', buf[expect_ret]);

/* do the test again but with one less byte in the buffer */
ut_asserteq(-E2BIG, cmdline_set_arg(buf, expect_ret - 1, from, arg,
val, NULL));

return 0;
}

/* Test of bootflow_cmdline_set_arg() */
static int test_bootflow_cmdline_set(struct unit_test_state *uts)
{
char buf[50];
const int size = sizeof(buf);

/*
* note that buffer-overflow tests are immediately each test case, just
* top keep the code together
*/

/* add an arg that doesn't already exist, starting from empty */
ut_asserteq(-ENOENT, cmdline_set_arg(buf, size, NULL, "me", NULL,
NULL));

ut_assertok(check_arg(uts, 3, "me", buf, NULL, "me", BOOTFLOWCL_EMPTY));
ut_assertok(check_arg(uts, 4, "me=", buf, NULL, "me", ""));
ut_assertok(check_arg(uts, 8, "me=fred", buf, NULL, "me", "fred"));

/* add an arg that doesn't already exist, starting from non-empty */
ut_assertok(check_arg(uts, 11, "arg=123 me", buf, "arg=123", "me",
BOOTFLOWCL_EMPTY));
ut_assertok(check_arg(uts, 12, "arg=123 me=", buf, "arg=123", "me",
""));
ut_assertok(check_arg(uts, 16, "arg=123 me=fred", buf, "arg=123", "me",
"fred"));

/* update an arg at the start */
ut_assertok(check_arg(uts, 1, "", buf, "arg=123", "arg", NULL));
ut_assertok(check_arg(uts, 4, "arg", buf, "arg=123", "arg",
BOOTFLOWCL_EMPTY));
ut_assertok(check_arg(uts, 5, "arg=", buf, "arg=123", "arg", ""));
ut_assertok(check_arg(uts, 6, "arg=1", buf, "arg=123", "arg", "1"));
ut_assertok(check_arg(uts, 9, "arg=1234", buf, "arg=123", "arg",
"1234"));

/* update an arg at the end */
ut_assertok(check_arg(uts, 5, "mary", buf, "mary arg=123", "arg",
NULL));
ut_assertok(check_arg(uts, 9, "mary arg", buf, "mary arg=123", "arg",
BOOTFLOWCL_EMPTY));
ut_assertok(check_arg(uts, 10, "mary arg=", buf, "mary arg=123", "arg",
""));
ut_assertok(check_arg(uts, 11, "mary arg=1", buf, "mary arg=123", "arg",
"1"));
ut_assertok(check_arg(uts, 14, "mary arg=1234", buf, "mary arg=123",
"arg", "1234"));

/* update an arg in the middle */
ut_assertok(check_arg(uts, 16, "mary=abc john=2", buf,
"mary=abc arg=123 john=2", "arg", NULL));
ut_assertok(check_arg(uts, 20, "mary=abc arg john=2", buf,
"mary=abc arg=123 john=2", "arg",
BOOTFLOWCL_EMPTY));
ut_assertok(check_arg(uts, 21, "mary=abc arg= john=2", buf,
"mary=abc arg=123 john=2", "arg", ""));
ut_assertok(check_arg(uts, 22, "mary=abc arg=1 john=2", buf,
"mary=abc arg=123 john=2", "arg", "1"));
ut_assertok(check_arg(uts, 25, "mary=abc arg=1234 john=2", buf,
"mary=abc arg=123 john=2", "arg", "1234"));

/* handle existing args with quotes */
ut_assertok(check_arg(uts, 16, "mary=\"abc\" john", buf,
"mary=\"abc\" arg=123 john", "arg", NULL));

/* handle existing args with quoted spaces */
ut_assertok(check_arg(uts, 20, "mary=\"abc def\" john", buf,
"mary=\"abc def\" arg=123 john", "arg", NULL));

ut_assertok(check_arg(uts, 34, "mary=\"abc def\" arg=123 john def=4",
buf, "mary=\"abc def\" arg=123 john", "def",
"4"));

/* quote at the start */
ut_asserteq(-EBADF, cmdline_set_arg(buf, size,
"mary=\"abc def\" arg=\"123 456\"",
"arg", "\"4 5 6", NULL));

/* quote at the end */
ut_asserteq(-EBADF, cmdline_set_arg(buf, size,
"mary=\"abc def\" arg=\"123 456\"",
"arg", "4 5 6\"", NULL));

/* quote in the middle */
ut_asserteq(-EBADF, cmdline_set_arg(buf, size,
"mary=\"abc def\" arg=\"123 456\"",
"arg", "\"4 \"5 6\"", NULL));

/* handle updating a quoted arg */
ut_assertok(check_arg(uts, 27, "mary=\"abc def\" arg=\"4 5 6\"", buf,
"mary=\"abc def\" arg=\"123 456\"", "arg",
"4 5 6"));

/* changing a quoted arg to a non-quoted arg */
ut_assertok(check_arg(uts, 23, "mary=\"abc def\" arg=789", buf,
"mary=\"abc def\" arg=\"123 456\"", "arg",
"789"));

/* changing a non-quoted arg to a quoted arg */
ut_assertok(check_arg(uts, 29, "mary=\"abc def\" arg=\"456 789\"", buf,
"mary=\"abc def\" arg=123", "arg", "456 789"));

/* handling of spaces */
ut_assertok(check_arg(uts, 8, "arg=123", buf, " ", "arg", "123"));
ut_assertok(check_arg(uts, 8, "arg=123", buf, " ", "arg", "123"));
ut_assertok(check_arg(uts, 13, "john arg=123", buf, " john ", "arg",
"123"));
ut_assertok(check_arg(uts, 13, "john arg=123", buf, " john arg=123 ",
"arg", "123"));
ut_assertok(check_arg(uts, 18, "john arg=123 mary", buf,
" john arg=123 mary ", "arg", "123"));

/* unchanged arg */
ut_assertok(check_arg(uts, 3, "me", buf, "me", "me", BOOTFLOWCL_EMPTY));

/* arg which starts with the same name */
ut_assertok(check_arg(uts, 28, "mary=abc johnathon=2 john=3", buf,
"mary=abc johnathon=2 john=1", "john", "3"));

return 0;
}
BOOTSTD_TEST(test_bootflow_cmdline_set, 0);

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