lib: sbi: Add functions to map/unmap shared memory

When Smepmp is enabled, M-mode will need to map/unmap the
shared memory before it can read/write to it. This patch
adds functions to create dynamic short-lived mappings.

Signed-off-by: Himanshu Chauhan <hchauhan@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

1 files changed, 42 insertions, 0 deletions

diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index 12f9c7e..7b5f380 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -347,6 +347,48 @@ unsigned int sbi_hart_get_smepmp_flags(struct sbi_scratch *scratch,
 	return pmp_flags;
 }
 
+int sbi_hart_map_saddr(unsigned long addr, unsigned long size)
+{
+	/* shared R/W access for M and S/U mode */
+	unsigned int pmp_flags = (PMP_W | PMP_X);
+	unsigned long order, base = 0;
+	struct sbi_scratch *scratch = sbi_scratch_thishart_ptr();
+
+	/* If Smepmp is not supported no special mapping is required */
+	if (!sbi_hart_has_extension(scratch, SBI_HART_EXT_SMEPMP))
+		return SBI_OK;
+
+	if (is_pmp_entry_mapped(SBI_SMEPMP_RESV_ENTRY))
+		return SBI_ENOSPC;
+
+	for (order = log2roundup(size) ; order <= __riscv_xlen; order++) {
+		if (order < __riscv_xlen) {
+			base = addr & ~((1UL << order) - 1UL);
+			if ((base <= addr) &&
+			    (addr < (base + (1UL << order))) &&
+			    (base <= (addr + size - 1UL)) &&
+			    ((addr + size - 1UL) < (base + (1UL << order))))
+				break;
+		} else {
+			return SBI_EFAIL;
+		}
+	}
+
+	pmp_set(SBI_SMEPMP_RESV_ENTRY, pmp_flags, base, order);
+
+	return SBI_OK;
+}
+
+int sbi_hart_unmap_saddr(void)
+{
+	struct sbi_scratch *scratch = sbi_scratch_thishart_ptr();
+
+	if (!sbi_hart_has_extension(scratch, SBI_HART_EXT_SMEPMP))
+		return SBI_OK;
+
+	return pmp_disable(SBI_SMEPMP_RESV_ENTRY);
+}
+
 int sbi_hart_pmp_configure(struct sbi_scratch *scratch)
 {
 	struct sbi_domain_memregion *reg;