[PATCH v2] powerpc/fadump: define MIN_RMA in bytes value to fix overflow

[Sayali Patil]

The MIN_RMA size checks in fadump_setup_param_area() use
(MIN_RMA * 1024 * 1024), which is evaluated in int and can
overflow when MIN_RMA is increased to values such as SZ_2G.
This triggers compiler warnings such as:

warning: integer overflow in expression of type 'int'
results in '0' [-Woverflow]

Define MIN_RMA directly in bytes using SZ_1M and update the
callers accordingly. This avoids repeated unit conversions and
prevents integer overflow.

Also convert MIN_RMA back to MB when populating the firmware
architecture vector, since firmware expects the value in MB.

Fixes: b7bb46062457 ("powerpc/fadump: fix additional param memory reservation 
for HASH MMU")
Suggested-by: Christophe Leroy (CS GROUP) <chle...@kernel.org>
Signed-off-by: Sayali Patil <saya...@linux.ibm.com>
---
 arch/powerpc/include/asm/prom.h | 4 +++-
 arch/powerpc/kernel/fadump.c    | 4 ++--
 arch/powerpc/kernel/prom_init.c | 2 +-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/prom.h b/arch/powerpc/include/asm/prom.h
index f679a11a7e7f..f4991d10d89e 100644
--- a/arch/powerpc/include/asm/prom.h
+++ b/arch/powerpc/include/asm/prom.h
@@ -12,12 +12,14 @@
  * Updates for PPC64 by Peter Bergner & David Engebretsen, IBM Corp.
  */
 #include <linux/types.h>
+#include <linux/sizes.h>
 #include <asm/firmware.h>
 
 struct device_node;
 struct property;
 
-#define MIN_RMA                        768             /* Minimum RMA (in MB) 
for CAS negotiation */
+/* Minimum RMA in bytes for CAS negotiation */
+#define MIN_RMA                        (768ULL * SZ_1M)
 
 #define OF_DT_BEGIN_NODE       0x1             /* Start of node, full name */
 #define OF_DT_END_NODE         0x2             /* End node */
diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index 501d43bf18f3..bb41150b363c 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -1759,10 +1759,10 @@ void __init fadump_setup_param_area(void)
                 * 2. The range should be between MIN_RMA and RMA size 
(ppc64_rma_size)
                 * 3. It must not overlap with the fadump reserved area.
                 */
-               if (ppc64_rma_size < MIN_RMA*1024*1024)
+               if (ppc64_rma_size < MIN_RMA)
                        return;
 
-               range_start = MIN_RMA * 1024 * 1024;
+               range_start = MIN_RMA;
                range_end = min(ppc64_rma_size, fw_dump.boot_mem_top);
        }
 
diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
index f26e80cbc615..53503937de0e 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -1061,7 +1061,7 @@ static const struct ibm_arch_vec 
ibm_architecture_vec_template __initconst = {
                .virt_base = cpu_to_be32(0xffffffff),
                .virt_size = cpu_to_be32(0xffffffff),
                .load_base = cpu_to_be32(0xffffffff),
-               .min_rma = cpu_to_be32(MIN_RMA),
+               .min_rma = cpu_to_be32(MIN_RMA / SZ_1M),
                .min_load = cpu_to_be32(0xffffffff),    /* full client load */
                .min_rma_percent = 0,   /* min RMA percentage of total RAM */
                .max_pft_size = 48,     /* max log_2(hash table size) */
-- 
2.52.0