The 'ld' instruction requires a 4-byte aligned displacement because it
is a DS-form instruction. But the "m" asm constraint doesn't enforce
that.
Add a special case of __get_user_asm2_goto() so that the "YZ" constraint
can be used for "ld".
The "Z" constraint is documented in the GCC manual PowerPC machine
constraints, and specifies a "memory operand accessed with indexed or
indirect addressing". "Y" is not documented in the manual but specifies
a "memory operand for a DS-form instruction". Using both allows the
compiler to generate a DS-form "ld" or X-form "ldx" as appropriate.
The change has to be conditional on CONFIG_PPC_KERNEL_PREFIXED because
the "Y" constraint does not guarantee 4-byte alignment when prefixed
instructions are enabled.
No build errors have been reported due to this, but the possibility is
there depending on compiler code generation decisions.
Fixes: c20beffeec3c ("powerpc/uaccess: Use flexible addressing with
__put_user()/__get_user()")
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
---
arch/powerpc/include/asm/uaccess.h | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/arch/powerpc/include/asm/uaccess.h
b/arch/powerpc/include/asm/uaccess.h
index 4cba724c8899..fd594bf6c6a9 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -181,8 +181,19 @@ do {
\
#endif
#ifdef __powerpc64__
+#ifdef CONFIG_PPC_KERNEL_PREFIXED
#define __get_user_asm2_goto(x, addr, label) \
__get_user_asm_goto(x, addr, label, "ld")
+#else
+#define __get_user_asm2_goto(x, addr, label) \
+ asm_goto_output( \
+ "1: ld%U1%X1 %0, %1 # get_user\n" \
+ EX_TABLE(1b, %l2) \
+ : "=r" (x) \
+ : DS_FORM_CONSTRAINT (*addr) \
+ : \
+ : label)
+#endif // CONFIG_PPC_KERNEL_PREFIXED
#else /* __powerpc64__ */
#define __get_user_asm2_goto(x, addr, label) \
asm_goto_output( \
--
2.45.1
