This is a note to let you know that I've just added the patch titled
powerpc/uaccess: Use asm goto for get_user when compiler supports it
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-uaccess-use-asm-goto-for-get_user-when-compi.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 4c528bdeb18f788ffe99be5c97c543fe980a5f00
Author: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Date: Wed Mar 10 17:46:54 2021 +0000
powerpc/uaccess: Use asm goto for get_user when compiler supports it
[ Upstream commit 5cd29b1fd3e8f2b45fe6d011588d832417defe31 ]
clang 11 and future GCC are supporting asm goto with outputs.
Use it to implement get_user in order to get better generated code.
Note that clang requires to set x in the default branch of
__get_user_size_goto() otherwise is compliant about x not being
initialised :puzzled:
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/403745b5aaa1b315bb4e8e46c1ba949e77eecec0.1615398265.git.christophe.leroy@xxxxxxxxxx
Stable-dep-of: 50934945d542 ("powerpc/uaccess: Use YZ asm constraint for ld")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 6b808bcdecd52..d4d59f57c42d9 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -243,6 +243,59 @@ extern long __get_user_bad(void);
: "=r" (err) \
: "b" (uaddr), "b" (kaddr), "i" (-EFAULT), "0" (err))
+#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
+
+#define __get_user_asm_goto(x, addr, label, op) \
+ asm_volatile_goto( \
+ "1: "op"%U1%X1 %0, %1 # get_user\n" \
+ EX_TABLE(1b, %l2) \
+ : "=r" (x) \
+ : "m"UPD_CONSTR (*addr) \
+ : \
+ : label)
+
+#ifdef __powerpc64__
+#define __get_user_asm2_goto(x, addr, label) \
+ __get_user_asm_goto(x, addr, label, "ld")
+#else /* __powerpc64__ */
+#define __get_user_asm2_goto(x, addr, label) \
+ asm_volatile_goto( \
+ "1: lwz%X1 %0, %1\n" \
+ "2: lwz%X1 %L0, %L1\n" \
+ EX_TABLE(1b, %l2) \
+ EX_TABLE(2b, %l2) \
+ : "=r" (x) \
+ : "m" (*addr) \
+ : \
+ : label)
+#endif /* __powerpc64__ */
+
+#define __get_user_size_goto(x, ptr, size, label) \
+do { \
+ BUILD_BUG_ON(size > sizeof(x)); \
+ switch (size) { \
+ case 1: __get_user_asm_goto(x, (u8 __user *)ptr, label, "lbz"); break; \
+ case 2: __get_user_asm_goto(x, (u16 __user *)ptr, label, "lhz"); break; \
+ case 4: __get_user_asm_goto(x, (u32 __user *)ptr, label, "lwz"); break; \
+ case 8: __get_user_asm2_goto(x, (u64 __user *)ptr, label); break; \
+ default: x = 0; BUILD_BUG(); \
+ } \
+} while (0)
+
+#define __get_user_size_allowed(x, ptr, size, retval) \
+do { \
+ __label__ __gus_failed; \
+ \
+ __get_user_size_goto(x, ptr, size, __gus_failed); \
+ retval = 0; \
+ break; \
+__gus_failed: \
+ x = 0; \
+ retval = -EFAULT; \
+} while (0)
+
+#else /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
+
#define __get_user_asm(x, addr, err, op) \
__asm__ __volatile__( \
"1: "op"%U2%X2 %1, %2 # get_user\n" \
@@ -299,6 +352,8 @@ do { \
prevent_read_from_user(ptr, size); \
} while (0)
+#endif /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
+
/*
* This is a type: either unsigned long, if the argument fits into
* that type, or otherwise unsigned long long.
