soc/amd/common/psp_verstage: Add PSP_VERSTACK_STACK_IS_MAPPED config

Crypto Engine in PSP prefers the buffer from Static RAM (SRAM). Hence if
a buffer comes from within SRAM address range, then it is passed
directly to Crypto Engine. Otherwise a bounce bufer from the stack is
used. But on SoCs like Picasso where PSP Verstage stack is mapped to a
virtual address space this check fails causing a bounce buffer to be
used and hence a stack overflow. Fix this issue by assuming that the
buffer comes from the SRAM always in such SoCs and pass the buffer
directly to crypto engine.

BUG=b:259649666
TEST=Build and boot to OS in Dalboz with unsigned PSP verstage.

Change-Id: I2161c8f0720c770efa5c05aece9584c3cbe7712a
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78426
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@amd.corp-partner.google.com>

src/soc/amd/common/psp_verstage/Kconfig

@@ -35,3 +35,11 @@ config SEPARATE_SIGNED_PSPFW
 	help
 	  Put signed AMD/PSP firmwares outside FW_MAIN_[AB] so vboot doesn't verify them,
 	  and rely on PSP's verification.
+
+config PSP_VERSTAGE_STACK_IS_MAPPED
+	bool
+	default y if SOC_AMD_PICASSO
+	default n
+	help
+	  This configuration indicates whether the PSP Verstage stack is mapped to a virtual
+	  address space. This has been the case so far only in Picasso SoC.

src/soc/amd/common/psp_verstage/vboot_crypto.c

@@ -90,8 +90,11 @@ vb2_error_t vb2ex_hwcrypto_digest_extend(const uint8_t *buf, uint32_t size)
 	 * mapped address of SPI flash which makes crypto engine to return invalid address.
 	 * Hence if the buffer is from SRAM, pass it to crypto engine. Else copy into a
 	 * temporary buffer before passing it to crypto engine.
+	 *
+	 * Similarly in some SoCs, PSP verstage stack is mapped to a virtual address space.
+	 * In those SoCs, assume that the buffer is from SRAM and pass it to crypto engine.
 	 */
-	if (buf >= _sram && (buf + size) < _esram)
+	if (CONFIG(PSP_VERSTAGE_STACK_IS_MAPPED) || (buf >= _sram && (buf + size) < _esram))
 		return vb2ex_hwcrypto_digest_extend_psp_sram(buf, size);
 
 	while (size) {