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[acpi] Generalise DSDT/SSDT data extraction logic

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Allow for the DSDT/SSDT signature-scanning and value extraction code
to be reused for extracting a pass-through MAC address.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2021-09-08 12:53:12 +01:00
parent e09e1142a3
commit 02ec659b73
3 changed files with 98 additions and 68 deletions
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92
src/core/acpi.c
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@@ -169,33 +169,22 @@ userptr_t acpi_find_via_rsdt ( uint32_t signature, unsigned int index ) {
}
/**
* Extract \_Sx value from DSDT/SSDT
* Extract value from DSDT/SSDT
*
* @v zsdt DSDT or SSDT
* @v signature Signature (e.g. "_S5_")
* @ret sx \_Sx value, or negative error
*
* In theory, extracting the \_Sx value from the DSDT/SSDT requires a
* full ACPI parser plus some heuristics to work around the various
* broken encodings encountered in real ACPI implementations.
*
* In practice, we can get the same result by scanning through the
* DSDT/SSDT for the signature (e.g. "_S5_"), extracting the first
* four bytes, removing any bytes with bit 3 set, and treating
* whatever is left as a little-endian value. This is one of the
* uglier hacks I have ever implemented, but it's still prettier than
* the ACPI specification itself.
* @v data Data buffer
* @v extract Extraction method
* @ret rc Return status code
*/
static int acpi_sx_zsdt ( userptr_t zsdt, uint32_t signature ) {
static int acpi_zsdt ( userptr_t zsdt, uint32_t signature, void *data,
int ( * extract ) ( userptr_t zsdt, size_t len,
size_t offset, void *data ) ) {
struct acpi_header acpi;
union {
uint32_t dword;
uint8_t byte[4];
} buf;
uint32_t buf;
size_t offset;
size_t len;
unsigned int sx;
uint8_t *byte;
int rc;
/* Read table header */
copy_from_user ( &acpi, zsdt, 0, sizeof ( acpi ) );
@@ -203,75 +192,51 @@ static int acpi_sx_zsdt ( userptr_t zsdt, uint32_t signature ) {
/* Locate signature */
for ( offset = sizeof ( acpi ) ;
( ( offset + sizeof ( buf ) /* signature */ + 3 /* pkg header */
+ sizeof ( buf ) /* value */ ) < len ) ;
( ( offset + sizeof ( buf ) /* signature */ ) < len ) ;
offset++ ) {
/* Check signature */
copy_from_user ( &buf, zsdt, offset, sizeof ( buf ) );
if ( buf.dword != cpu_to_le32 ( signature ) )
if ( buf != cpu_to_le32 ( signature ) )
continue;
DBGC ( zsdt, "DSDT/SSDT %#08lx found %s at offset %#zx\n",
user_to_phys ( zsdt, 0 ), acpi_name ( signature ),
offset );
offset += sizeof ( buf );
/* Read first four bytes of value */
copy_from_user ( &buf, zsdt, ( offset + 3 /* pkg header */ ),
sizeof ( buf ) );
DBGC ( zsdt, "DSDT/SSDT %#08lx found %s containing "
"%02x:%02x:%02x:%02x\n", user_to_phys ( zsdt, 0 ),
acpi_name ( signature ), buf.byte[0], buf.byte[1],
buf.byte[2], buf.byte[3] );
/* Extract \Sx value. There are three potential
* encodings that we might encounter:
*
* - SLP_TYPa, SLP_TYPb, rsvd, rsvd
*
* - <byteprefix>, SLP_TYPa, <byteprefix>, SLP_TYPb, ...
*
* - <dwordprefix>, SLP_TYPa, SLP_TYPb, 0, 0
*
* Since <byteprefix> and <dwordprefix> both have bit
* 3 set, and valid SLP_TYPx must have bit 3 clear
* (since SLP_TYPx is a 3-bit field), we can just skip
* any bytes with bit 3 set.
*/
byte = &buf.byte[0];
if ( *byte & 0x08 )
byte++;
sx = *(byte++);
if ( *byte & 0x08 )
byte++;
sx |= ( *byte << 8 );
return sx;
/* Attempt to extract data */
if ( ( rc = extract ( zsdt, len, offset, data ) ) == 0 )
return 0;
}
return -ENOENT;
}
/**
* Extract \_Sx value from DSDT/SSDT
* Extract value from DSDT/SSDT
*
* @v signature Signature (e.g. "_S5_")
* @ret sx \_Sx value, or negative error
* @v data Data buffer
* @v extract Extraction method
* @ret rc Return status code
*/
int acpi_sx ( uint32_t signature ) {
int acpi_extract ( uint32_t signature, void *data,
int ( * extract ) ( userptr_t zsdt, size_t len,
size_t offset, void *data ) ) {
struct acpi_fadt fadtab;
userptr_t fadt;
userptr_t dsdt;
userptr_t ssdt;
unsigned int i;
int sx;
int rc;
/* Try DSDT first */
fadt = acpi_find ( FADT_SIGNATURE, 0 );
if ( fadt ) {
copy_from_user ( &fadtab, fadt, 0, sizeof ( fadtab ) );
dsdt = phys_to_user ( fadtab.dsdt );
if ( ( sx = acpi_sx_zsdt ( dsdt, signature ) ) >= 0 )
return sx;
if ( ( rc = acpi_zsdt ( dsdt, signature, data,
extract ) ) == 0 )
return 0;
}
/* Try all SSDTs */
@@ -279,11 +244,12 @@ int acpi_sx ( uint32_t signature ) {
ssdt = acpi_find ( SSDT_SIGNATURE, i );
if ( ! ssdt )
break;
if ( ( sx = acpi_sx_zsdt ( ssdt, signature ) ) >= 0 )
return sx;
if ( ( rc = acpi_zsdt ( ssdt, signature, data,
extract ) ) == 0 )
return 0;
}
DBGC ( colour, "ACPI could not find \\_Sx \"%s\"\n",
DBGC ( colour, "ACPI could not find \"%s\"\n",
acpi_name ( signature ) );
return -ENOENT;
}