6.6-stable review patch. If anyone has any objections, please let me know.
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From: Michael Ellerman mpe@ellerman.id.au
[ 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@ellerman.id.au Link: https://msgid.link/20240529123029.146953-2-mpe@ellerman.id.au Signed-off-by: Sasha Levin sashal@kernel.org --- 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 4c96de9cd1e99..ad8e5f72c59a0 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( \