Patch "powerpc/uaccess: Use YZ asm constraint for ld" has been added to the 6.9-stable tree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



This is a note to let you know that I've just added the patch titled

    powerpc/uaccess: Use YZ asm constraint for ld

to the 6.9-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-yz-asm-constraint-for-ld.patch
and it can be found in the queue-6.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit d97895b6c6abbeef07703c35fe3a17a323bd1464
Author: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Date:   Wed May 29 22:30:29 2024 +1000

    powerpc/uaccess: Use YZ asm constraint for ld
    
    [ Upstream commit 50934945d54238d2d6d8db4b7c1d4c90d2696c57 ]
    
    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 <mpe@xxxxxxxxxxxxxx>
    Link: https://msgid.link/20240529123029.146953-2-mpe@xxxxxxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index de10437fd2065..ac4f6e4ae5810 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -165,8 +165,19 @@ 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(					\




[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux