2024-04-12 08:47:59

by Steven Price

Subject: [PATCH v2 13/14] arm64: rsi: Interfaces to query attestation token

From: Sami Mujawar <[email protected]>

Add interfaces to query the attestation token using
the RSI calls.

Signed-off-by: Sami Mujawar <[email protected]>
Signed-off-by: Suzuki K Poulose <[email protected]>
Signed-off-by: Steven Price <[email protected]>
---
arch/arm64/include/asm/rsi_cmds.h | 74 +++++++++++++++++++++++++++++++
1 file changed, 74 insertions(+)

diff --git a/arch/arm64/include/asm/rsi_cmds.h b/arch/arm64/include/asm/rsi_cmds.h
index b4cbeafa2f41..c1850aefe54e 100644
--- a/arch/arm64/include/asm/rsi_cmds.h
+++ b/arch/arm64/include/asm/rsi_cmds.h
@@ -10,6 +10,9 @@

#include <asm/rsi_smc.h>

+#define GRANULE_SHIFT 12
+#define GRANULE_SIZE (_AC(1, UL) << GRANULE_SHIFT)
+
enum ripas {
RSI_RIPAS_EMPTY,
RSI_RIPAS_RAM,
@@ -66,4 +69,75 @@ static inline unsigned long rsi_set_addr_range_state(phys_addr_t start,
return res.a0;
}

+/**
+ * rsi_attestation_token_init - Initialise the operation to retrieve an
+ * attestation token.
+ *
+ * @challenge: The challenge data to be used in the attestation token
+ * generation.
+ * @size: Size of the challenge data in bytes.
+ *
+ * Initialises the attestation token generation and returns an upper bound
+ * on the attestation token size that can be used to allocate an adequate
+ * buffer. The caller is expected to subsequently call
+ * rsi_attestation_token_continue() to retrieve the attestation token data on
+ * the same CPU.
+ *
+ * Returns:
+ * On success, returns the upper limit of the attestation report size.
+ * Otherwise, -EINVAL
+ */
+static inline unsigned long
+rsi_attestation_token_init(const u8 *challenge, unsigned long size)
+{
+ struct arm_smccc_1_2_regs regs = { 0 };
+
+ /* The challenge must be at least 32bytes and at most 64bytes */
+ if (!challenge || size < 32 || size > 64)
+ return -EINVAL;
+
+ regs.a0 = SMC_RSI_ATTESTATION_TOKEN_INIT;
+ memcpy(&regs.a1, challenge, size);
+ arm_smccc_1_2_smc(&regs, &regs);
+
+ if (regs.a0 == RSI_SUCCESS)
+ return regs.a1;
+
+ return -EINVAL;
+}
+
+/**
+ * rsi_attestation_token_continue - Continue the operation to retrieve an
+ * attestation token.
+ *
+ * @granule: {I}PA of the Granule to which the token will be written.
+ * @offset: Offset within Granule to start of buffer in bytes.
+ * @size: The size of the buffer.
+ * @len: The number of bytes written to the buffer.
+ *
+ * Retrieves up to a GRANULE_SIZE worth of token data per call. The caller is
+ * expected to call rsi_attestation_token_init() before calling this function
+ * to retrieve the attestation token.
+ *
+ * Return:
+ * * %RSI_SUCCESS - Attestation token retrieved successfully.
+ * * %RSI_INCOMPLETE - Token generation is not complete.
+ * * %RSI_ERROR_INPUT - A parameter was not valid.
+ * * %RSI_ERROR_STATE - Attestation not in progress.
+ */
+static inline int rsi_attestation_token_continue(phys_addr_t granule,
+ unsigned long offset,
+ unsigned long size,
+ unsigned long *len)
+{
+ struct arm_smccc_res res;
+
+ arm_smccc_1_1_invoke(SMC_RSI_ATTESTATION_TOKEN_CONTINUE,
+ granule, offset, size, 0, &res);
+
+ if (len)
+ *len = res.a1;
+ return res.a0;
+}
+
#endif
--
2.34.1