Back in the day we relied on a default value that used to be 8KiB
and it worked perfectly fine for ARC's default 8KiB page as well as
4 KiB ones, but not for 16 KiB, see [1] for more details.
So that we fixed by setting "max-page-size" if 16KiB pages are in use by
commit d024d369b8 ("arch/arc: Accommodate 16 KiB MMU pages").
But as Yann very rightfully mentioned here [2] we should be setting this
thing explicitly for all page sizes because:
1. Defaults might change unexpectedly
2. Explicitly set stuff is better understood
3. We act similarly to all settings but not only addressing some corner cases
[1] https://git.buildroot.org/buildroot/commit/?id=d024d369b82d2d3d9d4d75489c19e9488202bca0
[2] https://patchwork.ozlabs.org/patch/1212544/#2330647
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
ARC processors are known for its configurability and one of those
configurable things is MMU page size which might be set to any
power of two from 4 KiB to 16 MiB, though in the Linux kernel we
only support 4, 8 and 16 KiB due to practical considerations.
And the most used setting is 8 KiB thus GNU LD assumes maximum
page size is 8 KiB by default and while this works for smaller
pages (it's OK to align segments by larger value it will be still
peoperly aligned) this breaks execution of user-space apps on HW
with larger pages because Elf sections might very well span across
allocated pages and thus make executable broken.
Simplest example:
------------------------------------>8-----------------------------------
$ arc-linux-gcc test.c
$ arc-linux-readelf --segments a.out
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
...
LOAD 0x000000 0x00010000 0x00010000 0x003e8 0x003e8 R E 0x2000 <-- See
LOAD 0x001f24 0x00013f24 0x00013f24 0x000f0 0x0010c RW 0x2000
------------------------------------>8-----------------------------------
Fortunately we may override default page size settings with "max-page-size"
linker option this way:
------------------------------------>8-----------------------------------
$ arc-linux-gcc test.c -Wl,-z,max-page-size=16384
$ arc-linux-readelf --segments a.out
Elf file type is EXEC (Executable file)
Entry point 0x102c4
There are 8 program headers, starting at offset 52
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
...
LOAD 0x000000 0x00010000 0x00010000 0x003e8 0x003e8 R E 0x4000 <-- See
LOAD 0x001f24 0x00015f24 0x00015f24 0x000f0 0x0010c RW 0x4000
------------------------------------>8-----------------------------------
Which we implement with that change.
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
[yann.morin.1998@free.fr: fix comment: s/8196/8192/]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
As reported by Alexey in:
https://patchwork.ozlabs.org/patch/1087480/https://patchwork.ozlabs.org/patch/1087471/
when BR2_ARC_ATOMIC_EXT is enabled, -matomic needs to always be passed
to the compiler to allow atomic instructions to be used. So instead of
passing them through the command-line CFLAGS, we enforce them in the
toolchain wrapper directly.
Reported-by: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Acked-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
