[PATCH 3/6] [v2] hexagon: use generic strncpy/strnlen from_user

Arnd Bergmann
2021-05-15T10:19:37Z

Most per-architecture versions of these functions are broken in some form,
and they are almost certainly slower than the generic code as well.

Remove the ones for hexagon and instead use the generic version.
This custom version reads the data twice for strncpy() by doing an extra
strnlen(), and it apparently lacks a check for user_addr_max().

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
arch/hexagon/Kconfig | 2 +
arch/hexagon/include/asm/uaccess.h | 33 +-------
arch/hexagon/kernel/hexagon_ksyms.c | 1 -
arch/hexagon/mm/Makefile | 2 +-
arch/hexagon/mm/strnlen_user.S | 126 ----------------------------
5 files changed, 5 insertions(+), 159 deletions(-)
delete mode 100644 arch/hexagon/mm/strnlen_user.S

diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig
index f18ec6f49c15..d094186188df 100644
--- a/arch/hexagon/Kconfig
+++ b/arch/hexagon/Kconfig
@@ -19,6 +19,8 @@ config HEXAGON
# GENERIC_ALLOCATOR is used by dma_alloc_coherent()
select GENERIC_ALLOCATOR
select GENERIC_IRQ_SHOW
+ select GENERIC_STRNCPY_FROM_USER
+ select GENERIC_STRNLEN_USER
select HAVE_ARCH_KGDB
select HAVE_ARCH_TRACEHOOK
select NEED_SG_DMA_LENGTH
diff --git a/arch/hexagon/include/asm/uaccess.h b/arch/hexagon/include/asm/uaccess.h
index 59aa3a50744f..d950df12d8c5 100644
--- a/arch/hexagon/include/asm/uaccess.h
+++ b/arch/hexagon/include/asm/uaccess.h
@@ -57,42 +57,13 @@ unsigned long raw_copy_to_user(void __user *to, const void *from,
__kernel_size_t __clear_user_hexagon(void __user *dest, unsigned long count);
#define __clear_user(a, s) __clear_user_hexagon((a), (s))

-extern long __strnlen_user(const char __user *src, long n);
-
-static inline strnlen_user(const char __user *src, long n)
-{
- if (!access_ok(src, 1))
- return 0;
-
- return __strnlen_user(src, n);
-}
-/* get around the ifndef in asm-generic/uaccess.h */
+extern long strnlen_user(const char __user *src, long n);
#define strnlen_user strnlen_user

-static inline long strncpy_from_user(char *dst, const char __user *src, long n);
+extern long strncpy_from_user(char *dst, const char __user *src, long n)
#define strncpy_from_user strncpy_from_user

#include <asm-generic/uaccess.h>

-/* Todo: an actual accelerated version of this. */
-static inline long strncpy_from_user(char *dst, const char __user *src, long n)
-{
- long res = strnlen_user(src, n);
-
- if (unlikely(!res))
- return -EFAULT;
-
- if (res > n) {
- long left = raw_copy_from_user(dst, src, n);
- if (unlikely(left))
- memset(dst + (n - left), 0, left);
- return n;
- } else {
- long left = raw_copy_from_user(dst, src, res);
- if (unlikely(left))
- memset(dst + (res - left), 0, left);
- return res-1;
- }
-}

#endif
diff --git a/arch/hexagon/kernel/hexagon_ksyms.c b/arch/hexagon/kernel/hexagon_ksyms.c
index 35545a7386a0..ec56ce2d92a2 100644
--- a/arch/hexagon/kernel/hexagon_ksyms.c
+++ b/arch/hexagon/kernel/hexagon_ksyms.c
@@ -15,7 +15,6 @@ EXPORT_SYMBOL(__clear_user_hexagon);
EXPORT_SYMBOL(raw_copy_from_user);
EXPORT_SYMBOL(raw_copy_to_user);
EXPORT_SYMBOL(iounmap);
-EXPORT_SYMBOL(__strnlen_user);
EXPORT_SYMBOL(__vmgetie);
EXPORT_SYMBOL(__vmsetie);
EXPORT_SYMBOL(__vmyield);
diff --git a/arch/hexagon/mm/Makefile b/arch/hexagon/mm/Makefile
index 893838499591..49911a906fd0 100644
--- a/arch/hexagon/mm/Makefile
+++ b/arch/hexagon/mm/Makefile
@@ -4,4 +4,4 @@
#

obj-y := init.o ioremap.o uaccess.o vm_fault.o cache.o
-obj-y += copy_to_user.o copy_from_user.o strnlen_user.o vm_tlb.o
+obj-y += copy_to_user.o copy_from_user.o vm_tlb.o
diff --git a/arch/hexagon/mm/strnlen_user.S b/arch/hexagon/mm/strnlen_user.S
deleted file mode 100644
index 4b5574a7cc9c..000000000000
--- a/arch/hexagon/mm/strnlen_user.S
+++ /dev/null
@@ -1,126 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- * User string length functions for kernel
- *
- * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
- */
-
-#define isrc r0
-#define max r1 /* Do not change! */
-
-#define end r2
-#define tmp1 r3
-
-#define obo r6 /* off-by-one */
-#define start r7
-#define mod8 r8
-#define dbuf r15:14
-#define dcmp r13:12
-
-/*
- * The vector mask version of this turned out *really* badly.
- * The hardware loop version also turned out *really* badly.
- * Seems straight pointer arithmetic basically wins here.
- */
-
-#define fname __strnlen_user
-
- .text
- .global fname
- .type fname, @function
- .p2align 5 /* why? */
-fname:
- {
- mod8 = and(isrc,#7);
- end = add(isrc,max);
- start = isrc;
- }
- {
- P0 = cmp.eq(mod8,#0);
- mod8 = and(end,#7);
- dcmp = #0;
- if (P0.new) jump:t dw_loop; /* fire up the oven */
- }
-
-alignment_loop:
-fail_1: {
- tmp1 = memb(start++#1);
- }
- {
- P0 = cmp.eq(tmp1,#0);
- if (P0.new) jump:nt exit_found;
- P1 = cmp.gtu(end,start);
- mod8 = and(start,#7);
- }
- {
- if (!P1) jump exit_error; /* hit the end */
- P0 = cmp.eq(mod8,#0);
- }
- {
- if (!P0) jump alignment_loop;
- }
-
-
-
-dw_loop:
-fail_2: {
- dbuf = memd(start);
- obo = add(start,#1);
- }
- {
- P0 = vcmpb.eq(dbuf,dcmp);
- }
- {
- tmp1 = P0;
- P0 = cmp.gtu(end,start);
- }
- {
- tmp1 = ct0(tmp1);
- mod8 = and(end,#7);
- if (!P0) jump end_check;
- }
- {
- P0 = cmp.eq(tmp1,#32);
- if (!P0.new) jump:nt exit_found;
- if (!P0.new) start = add(obo,tmp1);
- }
- {
- start = add(start,#8);
- jump dw_loop;
- } /* might be nice to combine these jumps... */
-
-
-end_check:
- {
- P0 = cmp.gt(tmp1,mod8);
- if (P0.new) jump:nt exit_error; /* neverfound! */
- start = add(obo,tmp1);
- }
-
-exit_found:
- {
- R0 = sub(start,isrc);
- jumpr R31;
- }
-
-exit_error:
- {
- R0 = add(max,#1);
- jumpr R31;
- }
-
- /* Uh, what does the "fixup" return here? */
- .falign
-fix_1:
- {
- R0 = #0;
- jumpr R31;
- }
-
- .size fname,.-fname
-
-
-.section __ex_table,"a"
-.long fail_1,fix_1
-.long fail_2,fix_1
-.previous
--
2.29.2