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| author | Breno Leitao <leitao@debian.org> | 2018-09-20 13:45:05 -0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2018-10-03 15:40:04 +1000 |
| commit | 16d7c69c898531210d13dbd1eb2053759ff0946d (patch) | |
| tree | d5a3d6e906bea9b3f4414678833574999ab392c8 /arch/powerpc/kernel/entry_64.S | |
| parent | 06ec27aea9fc84d9c6d879eb64b5bcf28a8a1eb7 (diff) | |
| download | linux-16d7c69c898531210d13dbd1eb2053759ff0946d.tar.gz linux-16d7c69c898531210d13dbd1eb2053759ff0946d.tar.bz2 linux-16d7c69c898531210d13dbd1eb2053759ff0946d.zip | |
powerpc: Redefine TIF_32BITS thread flag
Moving TIF_32BIT to use bit 20 instead of 4 in the task flag field.
This change is making room for an upcoming new task macro
(_TIF_SYSCALL_EMU) which is preferred to set a bit in the lower 16-bits
part of the word.
This upcoming flag macro will take part in a composed macro
(_TIF_SYSCALL_DOTRACE) which will contain other flags as well, and it is
preferred that the whole _TIF_SYSCALL_DOTRACE macro only sets the lower 16
bits of a word, so, it could be handled using immediate operations (as load
immediate, add immediate, ...) where the immediate operand (SI) is limited
to 16-bits.
Another possible solution would be using the LOAD_REG_IMMEDIATE() macro
to load a full 64-bits word immediate, but it takes 5 operations instead of
one.
Having TIF_32BITS being redefined to use an upper bit is not a problem
since there is only one place in the assembly code where TIF_32BIT is being
used, and it could be replaced with an operation with right shift (addis),
since it is used alone, i.e. not being part of a composed macro, which has
different bits set, and would require LOAD_REG_IMMEDIATE().
Tested on a 64 bits Big Endian machine running a 32 bits task.
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel/entry_64.S')
| -rw-r--r-- | arch/powerpc/kernel/entry_64.S | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 573fa879d785..ed6f6c7f4264 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -171,7 +171,7 @@ system_call: /* label this so stack traces look sane */ * based on caller's run-mode / personality. */ ld r11,SYS_CALL_TABLE@toc(2) - andi. r10,r10,_TIF_32BIT + andis. r10,r10,_TIF_32BIT@h beq 15f addi r11,r11,8 /* use 32-bit syscall entries */ clrldi r3,r3,32 |