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| author | Michael Ellerman <mpe@ellerman.id.au> | 2024-05-29 15:30:29 +0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2024-05-30 15:57:27 +0300 |
| commit | 50934945d54238d2d6d8db4b7c1d4c90d2696c57 (patch) | |
| tree | 4a8fe4c9ac37e543bcb780f04f7455c2e7e05fa6 /arch/powerpc | |
| parent | 2d43cc701b96f910f50915ac4c2a0cae5deb734c (diff) | |
| download | linux-50934945d54238d2d6d8db4b7c1d4c90d2696c57.tar.xz | |
powerpc/uaccess: Use YZ asm constraint for ld
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
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/include/asm/uaccess.h | 11 |
1 files changed, 11 insertions, 0 deletions
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( \ |