[PATCH v5 1/2] x86/tboot: Add support for parsing DTPR table and disabling TPRs

[Michal Camacho Romero <michal.camacho.romero@linux.intel.com>]

From: Michal Camacho Romero <michal.camacho.romero@intel.com>

Add functions to locate and parse the DMA TXT Protection Ranges (DTPR)
table from the TXT heap's SinitMleData extended data elements (requires
SINIT MLE version >= 9).

* tboot_check_txt_heap_section_bounds() - function checks if a given
                                          TXT heap section is within
                                          the bounds of the heap.

* tboot_get_dtpr_table()                - function walks through the
                                          TXT heap to find the DTPR
                                          extended data element (type
                                          HEAP_EXTDATA_TYPE_DTPR) and
                                          returns pointer to the DTPR
                                          table.

* tboot_disable_tprs()                  - function iterates over TPR
                                          instances and disables each
                                          TPR region by setting bit 4
                                          in the TPRn_BASE register via
                                          MMIO.

Using these functions will allow the kernel to deactivate SINIT
ACM-established TPRs prior to the Linux OS launch.

Link: https://uefi.org/sites/default/files/resources/633933_Intel_TXT_DMA_Protection_Ranges_rev_0p73.pdf
Link: https://cdrdv2-public.intel.com/315168/315168_TXT_MLE_DG_rev_017_7.pdf
Signed-off-by: Michal Camacho Romero <michal.camacho.romero@intel.com>
---

Thanks for the careful review. Summary of how each point is handled:

1. There is no need to validate TPR base addresses in the kernel as the SINIT
   ACM performs the whole DTPR table verification against the platform's
   hardware register map (each address == MCHBAR/IMH base + a known per-TPR
   offset, matching TPR/instance counts, full coverage) and aborts the secure
   launch on any mismatch. Each one sits at MCHBAR + a fixed offset, and that
   offset differs per CPU, so there's no single address range the kernel can
   check against.

2. According to the DTPR spec - Intel® Trusted Execution Technology
   (Intel® TXT) DMA Protection Ranges (633933 rev 0.73, Table 3-1/3-2), the
   serialization registers are not a separate object - SrlCnt and the SR address
   array are trailing fields of the same variable-length DTPR table, right after
   the instance array. So, there is no need to treat the serialization
   registers as a separate object.

4. Extended-element walk / forward progress: the size-driven traversal is
   required by the format - the SinitMleData extended-data area is a
   self-describing, variable-length element list with no stored count,
   terminated only by a TYPE_END element, so it must be walked via each
   element's size field.

The rest of your suggestion have been applied in the current patch version

Regards,
Michal Camacho Romero
 arch/x86/kernel/tboot.c | 400 ++++++++++++++++++++++++++++++++++++++--
 include/linux/tboot.h   |  22 +++
 2 files changed, 407 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
index 46b8f1f16676..4455772d8cc3 100644
--- a/arch/x86/kernel/tboot.c
+++ b/arch/x86/kernel/tboot.c
@@ -18,6 +18,7 @@
 #include <linux/mm.h>
 #include <linux/tboot.h>
 #include <linux/debugfs.h>
+#include <acpi/actbl1.h>
 
 #include <asm/realmode.h>
 #include <asm/processor.h>
@@ -223,6 +224,143 @@ static int tboot_setup_sleep(void)
 
 #endif
 
+static bool tboot_check_txt_heap_section_bounds(const u64 heap_end,
+                                                void *heap_section,
+                                                u64* heap_section_size,
+                                                const char *section_name)
+{
+	if (!heap_section) {
+		pr_err("%s section is NULL\n", section_name);
+		return false;
+	}
+
+	if (!heap_section_size) {
+		pr_err("%s section size pointer is NULL\n", section_name);
+		return false;
+	}
+
+	*heap_section_size = 0;
+
+	if ((u64)heap_section > heap_end || heap_end - (u64)heap_section < 8) {
+		pr_err("%s size field exceeds heap boundary\n", section_name);
+		return false;
+	}
+
+	/* Read the size of the current TXT Heap section */
+	*heap_section_size = *(u64 __force *)heap_section;
+
+	if (*heap_section_size < 8) {
+		pr_err("%s size is too small\n", section_name);
+		return false;
+	}
+
+	if (*heap_section_size > heap_end - (u64)heap_section) {
+		pr_err("%s exceeds heap boundary\n", section_name);
+		return false;
+	}
+
+	return true;
+}
+
+static bool tboot_check_dtpr_size(const struct heap_ext_data_elt *elt)
+{
+	u64 dtpr_payload_size, dtpr_offset;
+	u32 i, ref_tpr_cnt;
+
+	struct acpi_table_dtpr   *dtpr        = NULL;
+	struct acpi_tpr_instance *tpr_inst    = NULL;
+	struct acpi_tpr_aux_sr   *tpr_aux_srl = NULL;
+
+	if (!elt) {
+		pr_err("DTPR element heap extension data is NULL\n");
+		return false;
+	}
+
+	dtpr              = (struct acpi_table_dtpr *)elt->data;
+	dtpr_payload_size = elt->size - sizeof(*elt);
+
+	if (dtpr_payload_size < sizeof(struct acpi_table_dtpr)) {
+		pr_err("DTPR element payload too small for a DTPR header\n");
+		return false;
+	}
+
+	if (dtpr->header.length != dtpr_payload_size) {
+		pr_err("Mismatch between DTPR table length and payload size\n");
+		return false;
+	}
+
+	dtpr_offset = sizeof(struct acpi_table_dtpr);
+
+	if (dtpr_offset > dtpr_payload_size) {
+		pr_err("TPR header exceeds table's declared size\n");
+		return false;
+	}
+
+	if (dtpr->ins_cnt < 1) {
+		pr_err("DTPR table declares no TPR instances\n");
+		return false;
+	}
+
+	for (i = 0; i < dtpr->ins_cnt; i++) {
+		/* prove this instance's header is in bounds before reading it */
+		if (dtpr_offset + sizeof(struct acpi_tpr_instance) > dtpr_payload_size) {
+			pr_err("TPR instance No.%u header exceeds DTPR table size\n", i);
+			return false;
+		}
+
+		/* iterate to the current TPR instance */
+		tpr_inst = (struct acpi_tpr_instance *)((u8 *)dtpr + dtpr_offset);
+
+		if (tpr_inst->tpr_cnt < 2) {
+			pr_err("TPR Instance %u has less than 2 TPRs, further DTPR "
+			       "processing interrupted.\n", i);
+			return false;
+		}
+
+		/* all instances must carry the same TPR count as the first */
+		if (i == 0)
+			ref_tpr_cnt = tpr_inst->tpr_cnt;
+		else if (tpr_inst->tpr_cnt != ref_tpr_cnt) {
+			pr_err("TPR Instance %u has inconsistent TPR count: expected %u,"
+			       " found %u\n", i, ref_tpr_cnt, tpr_inst->tpr_cnt);
+			return false;
+		}
+
+		/* iterate over each TPR instance */
+		dtpr_offset += sizeof(struct acpi_tpr_instance) +
+		               tpr_inst->tpr_cnt * sizeof(struct acpi_tpr_array);
+
+		/* verify TPR array size for this instance */
+		if (dtpr_offset > dtpr_payload_size) {
+			pr_err("TPR instance No.%d TPR entries exceed DTPR table size\n",
+			       i);
+			return false;
+		}
+	}
+
+	tpr_aux_srl = (struct acpi_tpr_aux_sr *)((u8 *)dtpr + dtpr_offset);
+	dtpr_offset += sizeof(u32);
+
+	if (dtpr_offset > dtpr_payload_size) {
+		pr_err("TPR SRL count field exceeds DTPR table size\n");
+		return false;
+	}
+
+	dtpr_offset += tpr_aux_srl->srl_cnt *
+	               sizeof(struct acpi_tpr_serialize_request);
+	if (dtpr_offset > dtpr_payload_size) {
+		pr_err("TPR SRL entries exceed DTPR table size\n");
+		return false;
+	}
+
+	if (dtpr_offset < dtpr_payload_size) {
+		pr_err("DTPR table is smaller than expected\n");
+		return false;
+	}
+
+	return true;
+}
+
 void tboot_shutdown(u32 shutdown_type)
 {
 	void (*shutdown)(void);
@@ -454,21 +592,23 @@ struct sha1_hash {
 };
 
 struct sinit_mle_data {
-	u32               version;             /* currently 6 */
-	struct sha1_hash  bios_acm_id;
-	u32               edx_senter_flags;
-	u64               mseg_valid;
-	struct sha1_hash  sinit_hash;
-	struct sha1_hash  mle_hash;
-	struct sha1_hash  stm_hash;
-	struct sha1_hash  lcp_policy_hash;
-	u32               lcp_policy_control;
-	u32               rlp_wakeup_addr;
-	u32               reserved;
-	u32               num_mdrs;
-	u32               mdrs_off;
-	u32               num_vtd_dmars;
-	u32               vtd_dmars_off;
+	u32                      version;             /* currently 9 */
+	struct sha1_hash         bios_acm_id;
+	u32                      edx_senter_flags;
+	u64                      mseg_valid;
+	struct sha1_hash         sinit_hash;
+	struct sha1_hash         mle_hash;
+	struct sha1_hash         stm_hash;
+	struct sha1_hash         lcp_policy_hash;
+	u32                      lcp_policy_control;
+	u32                      rlp_wakeup_addr;
+	u32                      reserved;
+	u32                      num_mdrs;
+	u32                      mdrs_off;
+	u32                      num_vtd_dmars;
+	u32                      vtd_dmars_off;
+	u32                      proc_scrtm_status; /* version 8 or later only*/
+	struct heap_ext_data_elt ext_data_elts[];
 } __packed;
 
 struct acpi_table_header *tboot_get_dmar_table(struct acpi_table_header *dmar_tbl)
@@ -514,3 +654,233 @@ struct acpi_table_header *tboot_get_dmar_table(struct acpi_table_header *dmar_tb
 
 	return dmar_tbl;
 }
+
+struct acpi_table_dtpr *tboot_get_dtpr_table(void __iomem **heap_base)
+{
+	void *heap_ptr, *config, *sinit_mle_end;
+	struct sinit_mle_data *sinit_mle;
+	struct heap_ext_data_elt *elt;
+	u64 heap_end, heap_size, sinit_mle_size, heap_section_size;
+
+	if (!heap_base) {
+		pr_warn("Heap base pointer is NULL.\n");
+		return NULL;
+	}
+
+	if (!tboot_enabled())
+		return NULL;
+	/*
+	 * ACPI tables may not be DMA protected by tboot, so use DMAR copy
+	 * SINIT saved in SinitMleData in TXT heap (which is DMA protected)
+	 */
+
+	/* map config space in order to get heap addr */
+	config = ioremap(TXT_PUB_CONFIG_REGS_BASE, NR_TXT_CONFIG_PAGES *
+			 PAGE_SIZE);
+	if (!config)
+		return NULL;
+
+	/* now map TXT heap */
+	heap_size  = *(u64 __force *)(config + TXTCR_HEAP_SIZE);
+	*heap_base = ioremap(*(u64 __force *)(config + TXTCR_HEAP_BASE), heap_size);
+	iounmap(config);
+
+	if (!(*heap_base))
+		return NULL;
+
+	if (heap_size == 0 || (u64)(*heap_base) + heap_size < (u64)(*heap_base)) {
+		pr_err("TXT heap size invalid or overflows\n");
+		goto err;
+	}
+
+	heap_end   = (u64)(*heap_base) + heap_size;
+
+	/* walk heap to SinitMleData */
+	/* skip BiosData */
+	/* get BiosData section size */
+	if (!tboot_check_txt_heap_section_bounds(heap_end, *heap_base,
+	                                         &heap_section_size, "BiosData")) {
+		goto err;
+	}
+
+	/* skip OsMleData */
+	heap_ptr = *heap_base + heap_section_size;
+	/* get OsMleData section size */
+	if (!tboot_check_txt_heap_section_bounds(heap_end, heap_ptr,
+	                                         &heap_section_size, "OsMleData")) {
+		goto err;
+	}
+
+	/* skip OsSinitData */
+	heap_ptr += heap_section_size;
+	/* get OsSinitData section size */
+	if (!tboot_check_txt_heap_section_bounds(heap_end, heap_ptr,
+	                                         &heap_section_size, "OsSinitData")) {
+		goto err;
+	}
+
+	/* jump to the SinitMleData */
+	heap_ptr += heap_section_size;
+	sinit_mle_size = 0;
+	/* now points to SinitMleDataSize; set to SinitMleData */
+	if (!tboot_check_txt_heap_section_bounds(heap_end, heap_ptr,
+	                                        &sinit_mle_size, "SinitMleData")) {
+		goto err;
+	}
+
+	heap_ptr += sizeof(u64);
+	sinit_mle = (struct sinit_mle_data *)heap_ptr;
+	sinit_mle_end = (void *)sinit_mle + sinit_mle_size;
+	if (sizeof(struct sinit_mle_data) > sinit_mle_size) {
+		pr_err("SinitMleData size is smaller than expected.\n");
+		goto err;
+	}
+
+	if (sinit_mle->version < 9) {
+		pr_err("Unsupported SinitMleData version: %u\n", sinit_mle->version);
+		goto err;
+	}
+
+	heap_ptr += sizeof(struct sinit_mle_data);
+	if (heap_ptr > sinit_mle_end) {
+		pr_err("SinitMleData header out of bounds.\n");
+		goto err;
+	}
+
+	/*
+	 * The SinitMleData extended-data area is a self-describing list of
+	 * variable-length elements with no stored element count; it is
+	 * terminated only by a HEAP_EXTDATA_TYPE_END element. Traversal must
+	 * therefore be driven by each element's own size field. Forward
+	 * progress and termination are guaranteed on every iteration:
+	 *   - the 8-byte header is bounds-checked before type/size are read,
+	 *   - elt->size >= sizeof(*elt) enforces a strictly-positive advance,
+	 *   - the "elt <= sinit_mle_end" cap bounds the number of steps.
+	 */
+	elt = sinit_mle->ext_data_elts;
+	do {
+		if ((u8 *)elt + sizeof(*elt) > (u8 *)sinit_mle_end) {
+			pr_err("SinitMleData element header out of bounds.\n");
+			goto err;
+		}
+
+		if (elt->size < sizeof(*elt)) {
+			pr_err("Invalid SinitMleData element size: %u\n", elt->size);
+			goto err;
+		}
+
+		if (elt->type == HEAP_EXTDATA_TYPE_END ||
+		    elt->type == HEAP_EXTDATA_TYPE_DTPR) {
+		    break;
+		}
+
+		elt = (void *)elt + elt->size;
+	} while ((void *)elt <= sinit_mle_end);
+
+	if ((void *)elt >= sinit_mle_end){
+		pr_err("Reached the end of SinitMleData without finding DTPR nor END"
+		       " element.\n");
+		goto err;
+	}
+
+	if (elt->type == HEAP_EXTDATA_TYPE_END) {
+		pr_err("DTPR element not found in SinitMleData\n");
+		goto err;
+	}
+
+	if ((u8 *)elt + elt->size > (u8 *)sinit_mle_end) {
+		pr_err("DTPR Table exceeds SinitMleData bounds.\n");
+		goto err;
+	}
+
+	if (!tboot_check_dtpr_size(elt)) {
+		pr_err("Invalid DTPR Table size.\n");
+		goto err;
+	}
+
+	return (struct acpi_table_dtpr *)elt->data;
+
+err:
+	iounmap(*heap_base);
+	*heap_base = NULL;
+	return NULL;
+}
+
+static bool tboot_tpr_enabled = false;
+void tboot_disable_tprs(struct acpi_table_dtpr *dtpr, void __iomem **heap_base)
+{
+	struct acpi_tpr_instance *tpr_inst;
+	struct acpi_tpr_array    *tpr_arr;
+	u32 *instance_cnt;
+	void __iomem *base;
+	u32 i, j;
+
+	if (!heap_base) {
+		pr_warn("Heap base pointer is NULL.\n");
+		return;
+	}
+
+	if (!(*heap_base)) {
+		pr_warn("Heap base is NULL.\n");
+		return;
+	}
+
+	if (dtpr == NULL) {
+		pr_warn("DTPR Table is NULL.\n");
+		goto teardown;
+	}
+
+	if (!tboot_enabled()) {
+		pr_warn("TBOOT is not enabled. TPR weren't set by TBOOT and"
+		        " SINIT ACM.\n");
+		goto teardown;
+	}
+
+	instance_cnt = (u32 *)(&dtpr->ins_cnt);
+	tpr_inst = (struct acpi_tpr_instance *)(instance_cnt + 1);
+
+	for (i = 0; i < *instance_cnt; ++i) {
+		for (j = 0; j < tpr_inst->tpr_cnt; ++j) {
+			tpr_arr =  (struct acpi_tpr_array *)((u8 *) tpr_inst +
+			            sizeof(struct acpi_tpr_instance) +
+			            j * sizeof(struct acpi_tpr_array));
+
+			/*
+			 * Each TPR base address has already been verified by the SINIT ACM,
+			 * so it can be treated as trustworthy and used safely for I/O
+			 * mapping.
+			 */
+			base = ioremap(tpr_arr->base, 16);
+			if (!base) {
+				pr_warn("TPR Instance %d, TPR No.%d disabling failure.\n",
+				        i, j);
+				continue;
+			}
+
+			pr_info("TPR instance %d, TPR %d:base %llx limit %llx\n", i, j,
+			        readq(base), readq((u8 __iomem *)base + 8));
+			writeq(readq(base) | TPR_BASE_DISABLE_BIT, base);
+			if (!tboot_tpr_enabled)
+				tboot_tpr_enabled = true;
+			iounmap(base);
+		}
+
+		tpr_inst = (struct acpi_tpr_instance *)((u8 *)tpr_inst +
+		            sizeof(*tpr_inst) + j * sizeof(struct acpi_tpr_array));
+	}
+
+	if (tboot_tpr_enabled)
+		pr_debug("TPR protection detected, PMR will be disabled\n");
+
+	goto teardown;
+
+teardown:
+	iounmap(*heap_base);
+	*heap_base = NULL;
+	return;
+}
+
+bool tboot_is_tpr_enabled(void)
+{
+	return tboot_tpr_enabled;
+}
diff --git a/include/linux/tboot.h b/include/linux/tboot.h
index d2279160ef39..f59c8026eabf 100644
--- a/include/linux/tboot.h
+++ b/include/linux/tboot.h
@@ -24,10 +24,17 @@ enum {
 #include <linux/acpi.h>
 /* used to communicate between tboot and the launched kernel */
 
+/*TXT Extended Data Element Types*/
+#define HEAP_EXTDATA_TYPE_END   0
+#define HEAP_EXTDATA_TYPE_DTPR 14
+
 #define TB_KEY_SIZE             64   /* 512 bits */
 
 #define MAX_TB_MAC_REGIONS      32
 
+/*TPR Base Disable BIT*/
+#define TPR_BASE_DISABLE_BIT  BIT(4)
+
 struct tboot_mac_region {
 	u64  start;         /* must be 64 byte -aligned */
 	u32  size;          /* must be 64 byte -granular */
@@ -58,6 +65,15 @@ struct tboot_acpi_sleep_info {
 	u64 kernel_s3_resume_vector;
 } __packed;
 
+/*
+ * structure for tboot extended data elements
+ */
+struct heap_ext_data_elt {
+	u32 type;
+	u32 size;
+	u8  data[];
+} __packed;
+
 /*
  * shared memory page used for communication between tboot and kernel
  */
@@ -122,10 +138,13 @@ struct tboot {
 			 0xaa, 0x19, 0xea, 0x4d, 0x5, 0x7a, 0x8}
 
 bool tboot_enabled(void);
+extern void tboot_disable_tprs(struct acpi_table_dtpr *, void __iomem **);
 extern void tboot_probe(void);
 extern void tboot_shutdown(u32 shutdown_type);
 extern struct acpi_table_header *tboot_get_dmar_table(
 				      struct acpi_table_header *dmar_tbl);
+extern struct acpi_table_dtpr *tboot_get_dtpr_table(void __iomem **);
+extern bool tboot_is_tpr_enabled(void);
 
 #else
 
@@ -135,6 +154,9 @@ extern struct acpi_table_header *tboot_get_dmar_table(
 #define tboot_sleep(sleep_state, pm1a_control, pm1b_control)	\
 					do { } while (0)
 #define tboot_get_dmar_table(dmar_tbl)	(dmar_tbl)
+#define tboot_get_dtpr_table(heap_base) NULL
+#define tboot_disable_tprs(dtpr, heap_base) do { } while (0)
+#define tboot_is_tpr_enabled() 0
 
 #endif /* !CONFIG_INTEL_TXT */
 
-- 
2.55.0