diff options
| -rw-r--r-- | src/acpi/acpigen.c | 53 |
1 files changed, 47 insertions, 6 deletions
diff --git a/src/acpi/acpigen.c b/src/acpi/acpigen.c index 57f0d10488..e5d76ba58e 100644 --- a/src/acpi/acpigen.c +++ b/src/acpi/acpigen.c @@ -38,16 +38,57 @@ void acpigen_write_len_f(void) void acpigen_pop_len(void) { - int len; + size_t len; ASSERT(ltop > 0) char *p = len_stack[--ltop]; len = gencurrent - p; ASSERT(len <= ACPIGEN_MAXLEN) - /* generate store length for 0xfffff max */ - p[0] = (0x80 | (len & 0xf)); - p[1] = (len >> 4 & 0xff); - p[2] = (len >> 12 & 0xff); - + const size_t payload_len = len - 3; + + if (len <= 0x3f + 2) { + /* PkgLength of up to 0x3f can be encoded in one PkgLength byte instead of the + reserved 3 bytes. Since only 1 PkgLength byte will be written, the payload + data needs to be moved by 2 bytes */ + memmove(&p[1], &p[3], payload_len); + /* Adjust the PkgLength to take into account that we only use 1 of the 3 + reserved bytes */ + len -= 2; + /* The two most significant bits of PkgLength get the value of 0 to indicate + there are no additional PkgLength bytes. In this case the single PkgLength + byte encodes the length in its lower 6 bits */ + p[0] = len; + /* Adjust pointer for next ACPI bytecode byte */ + acpigen_set_current(p + len); + } else if (len <= 0xfff + 1) { + /* PkgLength of up to 0xfff can be encoded in 2 PkgLength bytes instead of the + reserved 3 bytes. Since only 2 PkgLength bytes will be written, the payload + data needs to be moved by 1 byte */ + memmove(&p[2], &p[3], payload_len); + /* Adjust the PkgLength to take into account that we only use 2 of the 3 + reserved bytes */ + len -= 1; + /* The two most significant bits of PkgLength get the value of 1 to indicate + there's a second PkgLength byte. The lower 4 bits of the first PkgLength + byte and the second PkgLength byte encode the length */ + p[0] = (0x1 << 6 | (len & 0xf)); + p[1] = (len >> 4 & 0xff); + /* Adjust pointer for next ACPI bytecode byte */ + acpigen_set_current(p + len); + } else if (len <= 0xfffff) { + /* PkgLength of up to 0xfffff can be encoded in 3 PkgLength bytes. Since this + is the amount of reserved bytes, no need to move the payload in this case */ + /* The two most significant bits of PkgLength get the value of 2 to indicate + there are two more PkgLength bytes following the first one. The lower 4 bits + of the first PkgLength byte and the two following PkgLength bytes encode the + length */ + p[0] = (0x2 << 6 | (len & 0xf)); + p[1] = (len >> 4 & 0xff); + p[2] = (len >> 12 & 0xff); + /* No need to adjust pointer for next ACPI bytecode byte */ + } else { + /* The case of PkgLength up to 0xfffffff isn't supported at the moment */ + printk(BIOS_ERR, "%s: package length exceeds maximum of 0xfffff.\n", __func__); + } } void acpigen_set_current(char *curr) |