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| author | Matt Redfearn | 2018-05-23 15:39:59 +0200 |
|---|---|---|
| committer | Paul Burton | 2018-07-25 02:02:43 +0200 |
| commit | 6312455a0437a64059bdeee5696b375593a09947 (patch) | |
| tree | e03d927f4eb75d8cf87434fa7fc6d6ed90623545 /arch/mips/lib | |
| parent | MIPS: memset.S: Fix byte_fixup for MIPSr6 (diff) | |
| download | kernel-qcow2-linux-6312455a0437a64059bdeee5696b375593a09947.tar.gz kernel-qcow2-linux-6312455a0437a64059bdeee5696b375593a09947.tar.xz kernel-qcow2-linux-6312455a0437a64059bdeee5696b375593a09947.zip | |
MIPS: memset.S: Add comments to fault fixup handlers
It is not immediately obvious what the expected inputs to these fault
handlers is and how they calculate the number of unset bytes. Having
stared deeply at this in order to fix some corner cases, add some
comments to assist those who follow.
Signed-off-by: Matt Redfearn <matt.redfearn@mips.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/19339/
Cc: James Hogan <jhogan@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: <linux-mips@linux-mips.org>
Cc: <linux-kernel@vger.kernel.org>
Diffstat (limited to 'arch/mips/lib')
| -rw-r--r-- | arch/mips/lib/memset.S | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/arch/mips/lib/memset.S b/arch/mips/lib/memset.S index fac26ce64b2f..3a6f34ef5ffc 100644 --- a/arch/mips/lib/memset.S +++ b/arch/mips/lib/memset.S @@ -232,16 +232,25 @@ #ifdef CONFIG_CPU_MIPSR6 .Lbyte_fixup\@: + /* + * unset_bytes = (#bytes - (#unaligned bytes)) - (-#unaligned bytes remaining + 1) + 1 + * a2 = a2 - t0 + 1 + */ PTR_SUBU a2, t0 jr ra PTR_ADDIU a2, 1 #endif /* CONFIG_CPU_MIPSR6 */ .Lfirst_fixup\@: + /* unset_bytes already in a2 */ jr ra nop .Lfwd_fixup\@: + /* + * unset_bytes = partial_start_addr + #bytes - fault_addr + * a2 = t1 + (a2 & 3f) - $28->task->BUADDR + */ PTR_L t0, TI_TASK($28) andi a2, 0x3f LONG_L t0, THREAD_BUADDR(t0) @@ -250,6 +259,10 @@ LONG_SUBU a2, t0 .Lpartial_fixup\@: + /* + * unset_bytes = partial_end_addr + #bytes - fault_addr + * a2 = a0 + (a2 & STORMASK) - $28->task->BUADDR + */ PTR_L t0, TI_TASK($28) andi a2, STORMASK LONG_L t0, THREAD_BUADDR(t0) @@ -258,10 +271,15 @@ LONG_SUBU a2, t0 .Llast_fixup\@: + /* unset_bytes already in a2 */ jr ra nop .Lsmall_fixup\@: + /* + * unset_bytes = end_addr - current_addr + 1 + * a2 = t1 - a0 + 1 + */ PTR_SUBU a2, t1, a0 jr ra PTR_ADDIU a2, 1 |