[Qemu-devel] [PATCH v7 5/5] PoC: tpm: add ACPI memory clear interface

[Marc-André Lureau]

This allows to pass the last failing test from the Windows HLK TPM 2.0
TCG PPI 1.3 tests.

The interface is described in the "TCG Platform Reset Attack
Mitigation Specification", chapter 6 "ACPI _DSM Function". According
to Laszlo, it's not so easy to implement in OVMF, he suggested to do
it in qemu instead. It is relatively simple to implement in QEMU, but
make this a proof-of-concept PATCH for discussion, since this is not
a conventional approach.

Signed-off-by: Marc-André Lureau <address@hidden>
---
 hw/i386/acpi-build.c | 47 ++++++++++++++++++++++++++++++++++++++++++++
 hw/tpm/tpm_ppi.c     | 25 +++++++++++++++++++++++
 docs/specs/tpm.txt   |  2 ++
 hw/tpm/trace-events  |  3 +++
 4 files changed, 77 insertions(+)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 8cdfcec935..c96ae4bdf9 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -1835,6 +1835,13 @@ build_tpm_ppi(TPMIf *tpm, Aml *dev)
     pprq = aml_name("PPRQ");
     pprm = aml_name("PPRM");
 
+    aml_append(dev,
+               aml_operation_region("TPP3", AML_SYSTEM_MEMORY,
+                                    aml_int(TPM_PPI_ADDR_BASE + 0x200),
+                                    0x1));
+    field = aml_field("TPP3", AML_ANY_ACC, AML_NOLOCK, AML_PRESERVE);
+    aml_append(field, aml_named_field("MOVV", 8));
+    aml_append(dev, field);
     /*
      * A function to return the value of DerefOf (FUNC [N]), by using
      * accessing the fields individually instead. This is a workaround
@@ -2174,7 +2181,47 @@ build_tpm_ppi(TPMIf *tpm, Aml *dev)
             aml_append(ifctx, aml_return(aml_buffer(1, zerobyte)));
         }
         aml_append(method, ifctx);
+
+        ifctx = aml_if(
+            aml_equal(uuid,
+                      aml_touuid("376054ED-CC13-4675-901C-4756D7F2D45D")));
+        {
+            /* standard DSM query function */
+            ifctx2 = aml_if(aml_equal(function, aml_int(0)));
+            {
+                uint8_t byte_list[1] = { 0x03 };
+                aml_append(ifctx2, aml_return(aml_buffer(1, byte_list)));
+            }
+            aml_append(ifctx, ifctx2);
+
+            /*
+             * TCG Platform Reset Attack Mitigation Specification 1.0 Ch.6
+             *
+             * Arg 2 (Integer): Function Index = 1
+             * Arg 3 (Package): Arguments = Package: Type: Integer
+             *                  Operation Value of the Request
+             * Returns: Type: Integer
+             *          0: Success
+             *          1: General Failure
+             */
+            ifctx2 = aml_if(aml_equal(function, aml_int(1)));
+            {
+                op = aml_local(0);
+                aml_append(ifctx2,
+                           aml_store(aml_derefof(aml_index(arguments,
+                                                           aml_int(0))), op));
+                {
+                    aml_append(ifctx2, aml_store(op, aml_name("MOVV")));
+
+                    /* 0: success */
+                    aml_append(ifctx2, aml_return(aml_int(0)));
+                }
+            }
+            aml_append(ifctx, ifctx2);
+        }
+        aml_append(method, ifctx);
     }
+
     aml_append(dev, method);
 }
 
diff --git a/hw/tpm/tpm_ppi.c b/hw/tpm/tpm_ppi.c
index 8b46b9dd4b..64e8d828e8 100644
--- a/hw/tpm/tpm_ppi.c
+++ b/hw/tpm/tpm_ppi.c
@@ -16,8 +16,31 @@
 #include "qapi/error.h"
 #include "cpu.h"
 #include "sysemu/memory_mapping.h"
+#include "sysemu/reset.h"
 #include "migration/vmstate.h"
 #include "tpm_ppi.h"
+#include "trace.h"
+
+static void tpm_ppi_reset(void *opaque)
+{
+    TPMPPI *tpmppi = opaque;
+    char *ptr = memory_region_get_ram_ptr(&tpmppi->ram);
+
+    if (ptr[0x200] & 0x1) {
+        GuestPhysBlockList guest_phys_blocks;
+        GuestPhysBlock *block;
+
+        guest_phys_blocks_init(&guest_phys_blocks);
+        guest_phys_blocks_append(&guest_phys_blocks);
+        QTAILQ_FOREACH(block, &guest_phys_blocks.head, next) {
+            trace_tpm_ppi_memset(block->host_addr,
+                             block->target_end - block->target_start);
+            memset(block->host_addr, 0,
+                   block->target_end - block->target_start);
+        }
+        guest_phys_blocks_free(&guest_phys_blocks);
+    }
+}
 
 bool tpm_ppi_init(TPMPPI *tpmppi, struct MemoryRegion *m,
                   hwaddr addr, Object *obj, Error **errp)
@@ -27,5 +50,7 @@ bool tpm_ppi_init(TPMPPI *tpmppi, struct MemoryRegion *m,
     vmstate_register_ram(&tpmppi->ram, DEVICE(obj));
 
     memory_region_add_subregion(m, addr, &tpmppi->ram);
+    qemu_register_reset(tpm_ppi_reset, tpmppi);
+
     return true;
 }
diff --git a/docs/specs/tpm.txt b/docs/specs/tpm.txt
index 625f48f0c8..f1d3aded1b 100644
--- a/docs/specs/tpm.txt
+++ b/docs/specs/tpm.txt
@@ -121,6 +121,8 @@ layout:
  +----------+--------+--------+-------------------------------------------+
  | next_step|   0x1  |  0x159 | Operation to execute after reboot by      |
  |          |        |        | firmware. Used by firmware.               |
+ +----------+--------+--------+-------------------------------------------+
+ | movv     |   0x1  |  0x200 | Memory overwrite variable                 |
  +----------+--------+--------+-------------------------------------------+
 
    The following values are supported for the 'func' field. They correspond
diff --git a/hw/tpm/trace-events b/hw/tpm/trace-events
index 25bee0cecf..920d32ad55 100644
--- a/hw/tpm/trace-events
+++ b/hw/tpm/trace-events
@@ -51,3 +51,6 @@ tpm_tis_mmio_write_init_abort(void) "Initiating abort"
 tpm_tis_mmio_write_lowering_irq(void) "Lowering IRQ"
 tpm_tis_mmio_write_data2send(uint32_t value, unsigned size) "Data to send to 
TPM: 0x%08x (size=%d)"
 tpm_tis_pre_save(uint8_t locty, uint32_t rw_offset) "locty: %d, rw_offset = %u"
+
+# hw/tpm/tpm_ppi.c
+tpm_ppi_memset(uint8_t *ptr, size_t size) "memset: %p %zu"
-- 
2.18.0.rc1