linux.git/arch/powerpc/kernel/align.c, branch v6.12.80

powerpc/inst: Define ppc_inst_t

2021-12-09T11:41:21+00:00

In order to stop using 'struct ppc_inst' on PPC32,
define a ppc_inst_t typedef.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/fe5baa2c66fea9db05a8b300b3e8d2880a42596c.1638208156.git.christophe.leroy@csgroup.eu

powerpc: warn on emulation of dcbz instruction in kernel mode

2021-10-22T04:22:05+00:00

dcbz instruction shouldn't be used on non-cached memory. Using
it on non-cached memory can result in alignment exception and
implies a heavy handling.

Instead of silentely emulating the instruction and resulting in high
performance degradation, warn whenever an alignment exception is
taken in kernel mode due to dcbz, so that the user is made aware that
dcbz instruction has been used unexpectedly by the kernel.

Reported-by: Stan Johnson 
Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/2e3acfe63d289c6fba366e16973c9ab8369e8b75.1631803922.git.christophe.leroy@csgroup.eu

powerpc: Rename probe_kernel_read_inst()

2021-04-21T12:52:33+00:00

When probe_kernel_read_inst() was created, it was to mimic
probe_kernel_read() function.

Since then, probe_kernel_read() has been renamed
copy_from_kernel_nofault().

Rename probe_kernel_read_inst() into copy_inst_from_kernel_nofault().

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/b783d1f7cdb8914992384a669a2af57051b6bdcf.1618405715.git.christophe.leroy@csgroup.eu

powerpc: remove partial register save logic

2021-04-14T13:04:44+00:00

All subarchitectures always save all GPRs to pt_regs interrupt frames
now. Remove FULL_REGS and associated bits.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210316104206.407354-11-npiggin@gmail.com

powerpc/align: Don't use __get_user_instr() on kernel addresses

2021-04-03T10:21:49+00:00

In the old days, when we didn't have kernel userspace access
protection and had set_fs(), it was wise to use __get_user()
and friends to read kernel memory.

Nowadays, get_user() is granting userspace access and is exclusively
for userspace access.

In alignment exception handler, use probe_kernel_read_inst()
instead of __get_user_instr() for reading instructions in kernel.

This will allow to remove the is_kernel_addr() check in
__get/put_user() in a following patch.

Signed-off-by: Christophe Leroy 
Reviewed-by: Daniel Axtens 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/d9ecbce00178484e66ca7adec2ff210058037704.1615398265.git.christophe.leroy@csgroup.eu

powerpc/align: Convert emulate_spe() to user_access_begin

2021-04-03T10:21:39+00:00

This patch converts emulate_spe() to using user_access_begin
logic.

Since commit 662bbcb2747c ("mm, sched: Allow uaccess in atomic with
pagefault_disable()"), might_fault() doesn't fire when called from
sections where pagefaults are disabled, which must be the case
when using _inatomic variants of __get_user and __put_user. So
the might_fault() in user_access_begin() is not a problem.

There was a verification of user_mode() together with the access_ok(),
but there is a second verification of user_mode() just after, that
leads to immediate return. The access_ok() is now part of the
user_access_begin which is called after that other user_mode()
verification, so no need to check user_mode() again.

Signed-off-by: Christophe Leroy 
Reviewed-by: Daniel Axtens 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/c95a648fdf75992c9d88f3c73cc23e7537fcf2ad.1615555354.git.christophe.leroy@csgroup.eu

powerpc: Use fallthrough pseudo-keyword

2020-07-29T11:09:37+00:00

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20200727224201.GA10133@embeddedor

powerpc: Define and use get_user_instr() et. al.

2020-05-18T14:10:37+00:00

Define specialised get_user_instr(), __get_user_instr() and
__get_user_instr_inatomic() macros for reading instructions from user
and/or kernel space.

Signed-off-by: Jordan Niethe 
Reviewed-by: Alistair Popple 
[mpe: Squash in addition of get_user_instr() & __user annotations]
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20200506034050.24806-17-jniethe5@gmail.com

powerpc: Use a datatype for instructions

2020-05-18T14:10:37+00:00

Currently unsigned ints are used to represent instructions on powerpc.
This has worked well as instructions have always been 4 byte words.

However, ISA v3.1 introduces some changes to instructions that mean
this scheme will no longer work as well. This change is Prefixed
Instructions. A prefixed instruction is made up of a word prefix
followed by a word suffix to make an 8 byte double word instruction.
No matter the endianness of the system the prefix always comes first.
Prefixed instructions are only planned for powerpc64.

Introduce a ppc_inst type to represent both prefixed and word
instructions on powerpc64 while keeping it possible to exclusively
have word instructions on powerpc32.

Signed-off-by: Jordan Niethe 
[mpe: Fix compile error in emulate_spe()]
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20200506034050.24806-12-jniethe5@gmail.com

powerpc: Use a function for byte swapping instructions

2020-05-18T14:10:37+00:00

Use a function for byte swapping instructions in preparation of a more
complicated instruction type.

Signed-off-by: Jordan Niethe 
Signed-off-by: Michael Ellerman 
Reviewed-by: Balamuruhan S 
Link: https://lore.kernel.org/r/20200506034050.24806-10-jniethe5@gmail.com