efi_loader: utility function to check the variable name is "Boot####"

Some commands need to enumerate the existing UEFI load
option variable("Boot####"). This commit transfers some code
from cmd/efidebug.c to lib/efi_loder/, then exposes
efi_varname_is_load_option() function to check whether
the UEFI variable name is "Boot####".

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
This commit is contained in:
Masahisa Kojima 2022-12-02 13:59:35 +09:00 committed by Heinrich Schuchardt
parent 78b1ccc430
commit 3ac026ae46
3 changed files with 35 additions and 22 deletions

View file

@ -190,3 +190,36 @@ int efi_unlink_dev(efi_handle_t handle)
return 0;
}
static int u16_tohex(u16 c)
{
if (c >= '0' && c <= '9')
return c - '0';
if (c >= 'A' && c <= 'F')
return c - 'A' + 10;
/* not hexadecimal */
return -1;
}
bool efi_varname_is_load_option(u16 *var_name16, int *index)
{
int id, i, digit;
if (memcmp(var_name16, u"Boot", 8))
return false;
for (id = 0, i = 0; i < 4; i++) {
digit = u16_tohex(var_name16[4 + i]);
if (digit < 0)
break;
id = (id << 4) + digit;
}
if (i == 4 && !var_name16[8]) {
if (index)
*index = id;
return true;
}
return false;
}