Re: [PATCH 1/2] riscv: uaccess should be used in nommu mode

From: Palmer Dabbelt
Date: Wed Mar 18 2020 - 21:45:13 EST


On Tue, 03 Mar 2020 01:34:17 PST (-0800), greentime.hu@xxxxxxxxxx wrote:
It might have the unaligned access exception when trying to exchange data
with user space program. In this case, it failed in tty_ioctl(). Therefore
we should enable uaccess.S for NOMMU mode since the generic code doesn't
handle the unaligned access cases.

0x8013a212 <tty_ioctl+462>: ld a5,460(s1)

[ 0.115279] Oops - load address misaligned [#1]
[ 0.115284] CPU: 0 PID: 29 Comm: sh Not tainted 5.4.0-rc5-00020-gb4c27160d562-dirty #36
[ 0.115294] epc: 000000008013a212 ra : 000000008013a212 sp : 000000008f48dd50
[ 0.115303] gp : 00000000801cac28 tp : 000000008fb80000 t0 : 00000000000000e8
[ 0.115312] t1 : 000000008f58f108 t2 : 0000000000000009 s0 : 000000008f48ddf0
[ 0.115321] s1 : 000000008f8c6220 a0 : 0000000000000001 a1 : 000000008f48dd28
[ 0.115330] a2 : 000000008fb80000 a3 : 00000000801a7398 a4 : 0000000000000000
[ 0.115339] a5 : 0000000000000000 a6 : 000000008f58f0c6 a7 : 000000000000001d
[ 0.115348] s2 : 000000008f8c6308 s3 : 000000008f78b7c8 s4 : 000000008fb834c0
[ 0.115357] s5 : 0000000000005413 s6 : 0000000000000000 s7 : 000000008f58f2b0
[ 0.115366] s8 : 000000008f858008 s9 : 000000008f776818 s10: 000000008f776830
[ 0.115375] s11: 000000008fb840a8 t3 : 1999999999999999 t4 : 000000008f78704c
[ 0.115384] t5 : 0000000000000005 t6 : 0000000000000002
[ 0.115391] status: 0000000200001880 badaddr: 000000008f8c63ec cause: 0000000000000004
[ 0.115401] ---[ end trace 00d490c6a8b6c9ac ]---

This failure could be fixed after this patch applied.

[ 0.002282] Run /init as init process
Initializing random number generator... [ 0.005573] random: dd: uninitialized urandom read (512 bytes read)
done.

Welcome to Buildroot
buildroot login: root
Password:
Jan 1 00:00:00 login[62]: root login on 'ttySIF0'
~ #

Signed-off-by: Greentime Hu <greentime.hu@xxxxxxxxxx>
---
arch/riscv/Kconfig | 1 -
arch/riscv/include/asm/uaccess.h | 36 ++++++++++++++++----------------
arch/riscv/lib/Makefile | 2 +-
3 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 73f029eae0cc..92d63a63aec8 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -50,7 +50,6 @@ config RISCV
select PCI_DOMAINS_GENERIC if PCI
select PCI_MSI if PCI
select RISCV_TIMER
- select UACCESS_MEMCPY if !MMU
select GENERIC_IRQ_MULTI_HANDLER
select GENERIC_ARCH_TOPOLOGY if SMP
select ARCH_HAS_PTE_SPECIAL
diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
index f462a183a9c2..8ce9d607b53d 100644
--- a/arch/riscv/include/asm/uaccess.h
+++ b/arch/riscv/include/asm/uaccess.h
@@ -11,6 +11,24 @@
/*
* User space memory access functions
*/
+
+extern unsigned long __must_check __asm_copy_to_user(void __user *to,
+ const void *from, unsigned long n);
+extern unsigned long __must_check __asm_copy_from_user(void *to,
+ const void __user *from, unsigned long n);
+
+static inline unsigned long
+raw_copy_from_user(void *to, const void __user *from, unsigned long n)
+{
+ return __asm_copy_from_user(to, from, n);
+}
+
+static inline unsigned long
+raw_copy_to_user(void __user *to, const void *from, unsigned long n)
+{
+ return __asm_copy_to_user(to, from, n);
+}
+
#ifdef CONFIG_MMU
#include <linux/errno.h>
#include <linux/compiler.h>
@@ -367,24 +385,6 @@ do { \
-EFAULT; \
})

-
-extern unsigned long __must_check __asm_copy_to_user(void __user *to,
- const void *from, unsigned long n);
-extern unsigned long __must_check __asm_copy_from_user(void *to,
- const void __user *from, unsigned long n);
-
-static inline unsigned long
-raw_copy_from_user(void *to, const void __user *from, unsigned long n)
-{
- return __asm_copy_from_user(to, from, n);
-}
-
-static inline unsigned long
-raw_copy_to_user(void __user *to, const void *from, unsigned long n)
-{
- return __asm_copy_to_user(to, from, n);
-}
-
extern long strncpy_from_user(char *dest, const char __user *src, long count);

extern long __must_check strlen_user(const char __user *str);
diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
index 47e7a8204460..0d0db80800c4 100644
--- a/arch/riscv/lib/Makefile
+++ b/arch/riscv/lib/Makefile
@@ -2,5 +2,5 @@
lib-y += delay.o
lib-y += memcpy.o
lib-y += memset.o
-lib-$(CONFIG_MMU) += uaccess.o
+lib-y += uaccess.o
lib-$(CONFIG_64BIT) += tishift.o

Reviewed-by: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx>