[PATCH 1/3] RISC-V: mm: fix mmap behavior in sv48 address space

[Yangyu Chen]

A commit add2cc6b6515 ("RISC-V: mm: Restrict address space for
sv39,sv48,sv57") from patch[1] restricts regular mmap return address in the
sv48 space if the address hint is not above the sv48 userspace address.
However, this commit treats the address wrong which only use sv48 if the
hint address is above sv48 user address space. Actually, it should use sv48
if the address is above sv39 user address space. Moreover, the original
patch code looks very complex in logic, we can simplify it with min marco.

[1]. https://lore.kernel.org/r/20230809232218.849726-2-charlie@rivosinc.com

Signed-off-by: Yangyu Chen <cyy at cyyself.name>
---
 arch/riscv/include/asm/processor.h | 39 ++++++------------------------
 1 file changed, 8 insertions(+), 31 deletions(-)

diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index e1944ff0757a..7ead6a3e1f12 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -9,6 +9,7 @@
 #include <linux/const.h>
 #include <linux/cache.h>
 #include <linux/prctl.h>
+#include <linux/minmax.h>
 
 #include <vdso/processor.h>
 
@@ -18,37 +19,13 @@
 #define DEFAULT_MAP_WINDOW	(UL(1) << (MMAP_VA_BITS - 1))
 #define STACK_TOP_MAX		TASK_SIZE
 
-#define arch_get_mmap_end(addr, len, flags)			\
-({								\
-	unsigned long mmap_end;					\
-	typeof(addr) _addr = (addr);				\
-	if ((_addr) == 0 || (IS_ENABLED(CONFIG_COMPAT) && is_compat_task())) \
-		mmap_end = STACK_TOP_MAX;			\
-	else if ((_addr) >= VA_USER_SV57)			\
-		mmap_end = STACK_TOP_MAX;			\
-	else if ((((_addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) \
-		mmap_end = VA_USER_SV48;			\
-	else							\
-		mmap_end = VA_USER_SV39;			\
-	mmap_end;						\
-})
-
-#define arch_get_mmap_base(addr, base)				\
-({								\
-	unsigned long mmap_base;				\
-	typeof(addr) _addr = (addr);				\
-	typeof(base) _base = (base);				\
-	unsigned long rnd_gap = DEFAULT_MAP_WINDOW - (_base);	\
-	if ((_addr) == 0 || (IS_ENABLED(CONFIG_COMPAT) && is_compat_task())) \
-		mmap_base = (_base);				\
-	else if (((_addr) >= VA_USER_SV57) && (VA_BITS >= VA_BITS_SV57)) \
-		mmap_base = VA_USER_SV57 - rnd_gap;		\
-	else if ((((_addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) \
-		mmap_base = VA_USER_SV48 - rnd_gap;		\
-	else							\
-		mmap_base = VA_USER_SV39 - rnd_gap;		\
-	mmap_base;						\
-})
+#define arch_get_mmap_end(addr, len, flags) \
+	((addr) >= DEFAULT_MAP_WINDOW ? STACK_TOP_MAX :\
+	 min(DEFAULT_MAP_WINDOW, STACK_TOP_MAX))
+
+#define arch_get_mmap_base(addr, base) \
+	((addr) >= DEFAULT_MAP_WINDOW ? base :\
+	 min(base, DEFAULT_MAP_WINDOW))
 
 #else
 #define DEFAULT_MAP_WINDOW	TASK_SIZE
-- 
2.43.0