On Thu, May 17, 2018 at 12:08 AM, Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> wrote:
> On Thu, May 17, 2018 at 12:01:34AM -0700, Andrey Smirnov wrote:
>> On Wed, May 16, 2018 at 11:55 PM, Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> wrote:
>> > On Wed, May 16, 2018 at 01:00:17PM -0700, Andrey Smirnov wrote:
>> >> Seeing
>> >>
>> >> create_sections(ttb, 0, PAGE_SIZE, ...);
>> >>
>> >> as the code the creates initial flat 4 GiB mapping is a bit less
>> >> intuitive then
>> >>
>> >> create_sections(ttb, 0, SZ_4G, ...);
>> >>
>> >> so, for the sake of clarification, convert create_sections() to accept
>> >> size in bytes and do bytes -> MiB converstion as a part of the
>> >> function.
>> >>
>> >> NOTE: To keep all of the arguments of create_sections() 32-bit:
>> >>
>> >> - Move all of the real code into a helper function accepting first
>> >> and last addresses of the region (e.g passing 0 and U32_MAX
>> >> means all 4GiB of address space)
>> >>
>> >> - Convert create_section() into a macro that does necessary size
>> >> -> last addres conversion under the hood to preserve original API
>> >>
>> >> Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx>
>> >> ---
>> >> arch/arm/cpu/mmu-early.c | 4 ++--
>> >> arch/arm/cpu/mmu.c | 4 ++--
>> >> arch/arm/cpu/mmu.h | 22 ++++++++++++++++------
>> >> 3 files changed, 20 insertions(+), 10 deletions(-)
>> >>
>> >> diff --git a/arch/arm/cpu/mmu-early.c b/arch/arm/cpu/mmu-early.c
>> >> index 70ece0d2f..136b33c3a 100644
>> >> --- a/arch/arm/cpu/mmu-early.c
>> >> +++ b/arch/arm/cpu/mmu-early.c
>> >> @@ -16,7 +16,7 @@ static void map_cachable(unsigned long start, unsigned long size)
>> >> start = ALIGN_DOWN(start, SZ_1M);
>> >> size = ALIGN(size, SZ_1M);
>> >>
>> >> - create_sections(ttb, start, size >> 20, PMD_SECT_AP_WRITE |
>> >> + create_sections(ttb, start, size, PMD_SECT_AP_WRITE |
>> >> PMD_SECT_AP_READ | PMD_TYPE_SECT | PMD_SECT_WB);
>> >> }
>> >>
>> >> @@ -30,7 +30,7 @@ void mmu_early_enable(unsigned long membase, unsigned long memsize,
>> >> set_ttbr(ttb);
>> >> set_domain(DOMAIN_MANAGER);
>> >>
>> >> - create_sections(ttb, 0, 4096, PMD_SECT_AP_WRITE |
>> >> + create_sections(ttb, 0, SZ_4G, PMD_SECT_AP_WRITE |
>> >> PMD_SECT_AP_READ | PMD_TYPE_SECT);
>> >>
>> >> map_cachable(membase, memsize);
>> >> diff --git a/arch/arm/cpu/mmu.c b/arch/arm/cpu/mmu.c
>> >> index 0c367e47c..f02c99f65 100644
>> >> --- a/arch/arm/cpu/mmu.c
>> >> +++ b/arch/arm/cpu/mmu.c
>> >> @@ -460,7 +460,7 @@ static int mmu_init(void)
>> >> set_domain(DOMAIN_MANAGER);
>> >>
>> >> /* create a flat mapping using 1MiB sections */
>> >> - create_sections(ttb, 0, PAGE_SIZE, PMD_SECT_AP_WRITE | PMD_SECT_AP_READ |
>> >> + create_sections(ttb, 0, SZ_4G, PMD_SECT_AP_WRITE | PMD_SECT_AP_READ |
>> >> PMD_TYPE_SECT);
>> >> __mmu_cache_flush();
>> >>
>> >> @@ -472,7 +472,7 @@ static int mmu_init(void)
>> >> * below
>> >> */
>> >> for_each_memory_bank(bank) {
>> >> - create_sections(ttb, bank->start, bank->size >> 20,
>> >> + create_sections(ttb, bank->start, bank->size,
>> >> PMD_SECT_DEF_CACHED);
>> >> __mmu_cache_flush();
>> >> }
>> >> diff --git a/arch/arm/cpu/mmu.h b/arch/arm/cpu/mmu.h
>> >> index d71cd7e38..52689359a 100644
>> >> --- a/arch/arm/cpu/mmu.h
>> >> +++ b/arch/arm/cpu/mmu.h
>> >> @@ -27,16 +27,26 @@ static inline void set_domain(unsigned val)
>> >> }
>> >>
>> >> static inline void
>> >> -create_sections(uint32_t *ttb, unsigned long addr,
>> >> - int size_m, unsigned int flags)
>> >> +__create_sections(uint32_t *ttb, unsigned long first,
>> >> + unsigned long last, unsigned int flags)
>> >> {
>> >> - unsigned long ttb_start = addr >> 20;
>> >> - unsigned long ttb_end = ttb_start + size_m;
>> >> - unsigned int i;
>> >> + unsigned long ttb_start = first >> 20;
>> >> + unsigned long ttb_end = (last >> 20) + 1;
>> >> + unsigned int i, addr;
>> >>
>> >> - for (i = ttb_start; i < ttb_end; i++, addr += SZ_1M)
>> >> + for (i = ttb_start, addr = first; i < ttb_end; i++, addr += SZ_1M)
>> >> ttb[i] = addr | flags;
>> >> }
>> >>
>> >> +#define create_sections(ttb, addr, size, flags) \
>> >> + ({ \
>> >> + typeof(addr) __addr = addr; \
>> >> + typeof(size) __size = size; \
>> >> + /* Check for overflow */ \
>> >> + BUG_ON(__addr > ULONG_MAX - __size + 1); \
>> >> + __create_sections(ttb, __addr, __addr + (size) - 1, \
>> >> + flags); \
>> >> + })
>> >
>> > Why do you preserve the original API of create_sections()? I would just
>> > change it. We have only a few callers and they are easy to change.
>> >
>>
>> Mostly because it keeps "addr + size - 1" arithmetic in one place
>> instead of spreading it to every caller. If you'd rather have that
>> instead of the macro above, I can change that in v3.
>
> I agree that the end address calculation often is a source for
> off-by-one errors, still I would prefer not using macros to hide that.
>
I can't think of a way to keep arithmetic in one place and not to make
one of the arguments 64-bit at the same time without resorting to a
macro. AFAICT the options are either to drop the macro and change the
API or keep the API/arithmetic in one place and keep the macro.
I am happy with either, so let me know what you'd prefer.
Thanks,
Andrey Smirnov
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