Messages in this thread | | | Subject | Re: [PATCH v2 13/16] powerpc/watchpoint: Prepare handler to handle more than one watcnhpoint | From | Christophe Leroy <> | Date | Wed, 1 Apr 2020 11:20:10 +0200 |
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Le 01/04/2020 à 11:13, Ravi Bangoria a écrit : > > > On 4/1/20 12:20 PM, Christophe Leroy wrote: >> >> >> Le 01/04/2020 à 08:13, Ravi Bangoria a écrit : >>> Currently we assume that we have only one watchpoint supported by hw. >>> Get rid of that assumption and use dynamic loop instead. This should >>> make supporting more watchpoints very easy. >>> >>> With more than one watchpoint, exception handler need to know which >>> DAWR caused the exception, and hw currently does not provide it. So >>> we need sw logic for the same. To figure out which DAWR caused the >>> exception, check all different combinations of user specified range, >>> dawr address range, actual access range and dawrx constrains. For ex, >>> if user specified range and actual access range overlaps but dawrx is >>> configured for readonly watchpoint and the instruction is store, this >>> DAWR must not have caused exception. >>> >>> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com> >>> --- >>> arch/powerpc/include/asm/processor.h | 2 +- >>> arch/powerpc/include/asm/sstep.h | 2 + >>> arch/powerpc/kernel/hw_breakpoint.c | 396 +++++++++++++++++++++------ >>> arch/powerpc/kernel/process.c | 3 - >>> 4 files changed, 313 insertions(+), 90 deletions(-) >>> >> >> [...] >> >>> -static bool >>> -dar_range_overlaps(unsigned long dar, int size, struct >>> arch_hw_breakpoint *info) >>> +static bool dar_user_range_overlaps(unsigned long dar, int size, >>> + struct arch_hw_breakpoint *info) >>> { >>> return ((dar <= info->address + info->len - 1) && >>> (dar + size - 1 >= info->address)); >>> } >> >> Here and several other places, I think it would be more clear if you >> could avoid the - 1 : >> >> return ((dar < info->address + info->len) && >> (dar + size > info->address)); > > Ok. see below... > >> >> >>> +static bool dar_in_hw_range(unsigned long dar, struct >>> arch_hw_breakpoint *info) >>> +{ >>> + unsigned long hw_start_addr, hw_end_addr; >>> + >>> + hw_start_addr = ALIGN_DOWN(info->address, HW_BREAKPOINT_SIZE); >>> + hw_end_addr = ALIGN(info->address + info->len, >>> HW_BREAKPOINT_SIZE) - 1; >>> + >>> + return ((hw_start_addr <= dar) && (hw_end_addr >= dar)); >>> +} >> >> hw_end_addr = ALIGN(info->address + info->len, HW_BREAKPOINT_SIZE); >> >> return ((hw_start_addr <= dar) && (hw_end_addr > dar)); > > I'm using -1 while calculating end address is to make it > inclusive. If I don't use -1, the end address points to a > location outside of actual range, i.e. it's not really an > end address.
But that's what is done is several places, for instance:
https://elixir.bootlin.com/linux/v5.6/source/arch/powerpc/mm/dma-noncoherent.c#L22
https://elixir.bootlin.com/linux/v5.6/source/arch/powerpc/include/asm/book3s/32/kup.h#L92
In several places like this, end is outside of the range. My feeling is that is helps with readability.
Christophe
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