[PATCH] lib: sbi: Add additional range checks for RV32

[Andrew Jones]

On RV32, M-mode can only access the first 4G of the physical
address space because M-mode does not have an MMU to access the
full 34-bit physical address space. While we already ensure
the "hi" registers of RV32 physical address inputs are zero we
need to also ensure that the low register plus the size does
not cross into 4G address space. The check added to
sbi_domain_check_addr_range() should be enough for both DBCN
and SSE, but DBCN returns a different error code for high
addresses, so we patch that check too.

Signed-off-by: Andrew Jones <ajones at ventanamicro.com>

---

Should the SSE functions return SBI_ERR_FAILED in this case like DBCN
does? We'd need to patch the SSE spec to call out SBI_ERR_FAILED as
"Failed to write due to I/O errors." like DBCN does too.

 lib/sbi/sbi_domain.c     | 3 +++
 lib/sbi/sbi_ecall_dbcn.c | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/sbi/sbi_domain.c b/lib/sbi/sbi_domain.c
index 374ac36b2f3e..5f6efe884952 100644
--- a/lib/sbi/sbi_domain.c
+++ b/lib/sbi/sbi_domain.c
@@ -412,6 +412,9 @@ bool sbi_domain_check_addr_range(const struct sbi_domain *dom,
 	if (!dom)
 		return false;
 
+	if (max < addr)
+		return false;
+
 	while (addr < max) {
 		reg = find_region(dom, addr);
 		if (!reg)
diff --git a/lib/sbi/sbi_ecall_dbcn.c b/lib/sbi/sbi_ecall_dbcn.c
index 49a7713f48bb..a3262ab9a90c 100644
--- a/lib/sbi/sbi_ecall_dbcn.c
+++ b/lib/sbi/sbi_ecall_dbcn.c
@@ -39,7 +39,7 @@ static int sbi_ecall_dbcn_handler(unsigned long extid, unsigned long funcid,
 		 * physical address (i.e. a2 register) is non-zero on
 		 * RV64.
 		 */
-		if (regs->a2)
+		if (regs->a2 || regs->a1 + regs->a0 < regs->a1)
 			return SBI_ERR_FAILED;
 
 		if (!sbi_domain_check_addr_range(sbi_domain_thishart_ptr(),
-- 
2.45.2