From 41dbee81c875300072f6154d6722f6e8e1353cca Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Wed, 18 Apr 2018 15:46:41 +0200 Subject: [PATCH] parisc: Document rules regarding checksum of HPMC handler Signed-off-by: Helge Deller --- arch/parisc/kernel/traps.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c index 68e671a..71d3127 100644 --- a/arch/parisc/kernel/traps.c +++ b/arch/parisc/kernel/traps.c @@ -837,6 +837,17 @@ void __init initialize_ivt(const void *iva) if (pdc_instr(&instr) == PDC_OK) ivap[0] = instr; + /* + * Rules for the checksum of the HPMC handler: + * 1. The IVA does not point to PDC/PDH space (ie: the OS has installed + * its own IVA). + * 2. The word at IVA + 32 is nonzero. + * 3. If Length (IVA + 60) is not zero, then Length (IVA + 60) and + * Address (IVA + 56) are word-aligned. + * 4. The checksum of the 8 words starting at IVA + 32 plus the sum of + * the Length/4 words starting at Address is zero. + */ + /* Compute Checksum for HPMC handler */ length = os_hpmc_size; ivap[7] = length; -- 2.7.4