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arch: set ld's common-page-size explicitly

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On some CPU architecures it's possible to use MMU pages of different
sizes, for example on ARC or ARM. And while for user-space
applications the page size is supposed to be transparent, there's
still some use of that extra information. In particular it's possible
to align data structures or code/data sections on page boundary, etc.

For these tricks to become possible tools which pack data (think of
the linker, like GNU "ld") need to be informed of the page size to
be considered.

Obviously, there're some sane defaults which are being used most of
the time, so we even think about that peculiarity, but when non-default
value needs to be used, GNU "ld" accepts 2 properties related to page
size:

 -z common-page-size=XXX
 -z max-page-size=YYY

And while in thery those might be different (but always "common" <= "max"),
and that might make sense if we build for some unknown platfrom,
in case of Buildroot when we build entire target's filesystem and so
know exactly the configuration we're targeting to, we may safely assume
"common-page-size"="max-page-size".

See a lengthy discussion in this thread [1].

Fixes:

  http://autobuild.buildroot.net/results/c8b2f331c98453670cd982558144c4fd84674a3d/ (uclibc)
  http://autobuild.buildroot.net/results/3a22f7aac38145b26c549254b819f87329e7a77e/ (glibc)

And while at it, recover use of "XX-page-size" for ARC, as with [2]
moving page size selection in the generic code we've got unexpected
override for ARC (note "=", but not "+="):
--------------------->8--------------------
ARCH_TOOLCHAIN_WRAPPER_OPTS = -matomic
--------------------->8--------------------

[1] https://lists.buildroot.org/pipermail/buildroot/2022-July/646176.html
[2] https://git.buildroot.net/buildroot/commit/?id=dcb74db89e74e512e36b32cea6f574a1a1ca84c4

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
This commit is contained in:
Alexey Brodkin 2022-08-15 10:17:44 -07:00 committed by Thomas Petazzoni
parent 81aa9e7b8b
commit 5e52c28397
2 changed files with 5 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
arch/arch.mk
View File

@ -20,13 +20,13 @@ GCC_TARGET_MODE := $(call qstrip,$(BR2_GCC_TARGET_MODE))
# Explicitly set LD's "max-page-size" instead of relying on some defaults
ifeq ($(BR2_ARC_PAGE_SIZE_4K)$(BR2_ARM64_PAGE_SIZE_4K),y)
ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=4096
ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096
else ifeq ($(BR2_ARC_PAGE_SIZE_8K),y)
ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=8192
ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=8192 -Wl,-z,common-page-size=8192
else ifeq ($(BR2_ARC_PAGE_SIZE_16K),y)
ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=16384
ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=16384 -Wl,-z,common-page-size=16384
else ifeq ($(BR2_ARM64_PAGE_SIZE_64K),y)
ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=65536
ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=65536 -Wl,-z,common-page-size=65536
endif
# Include any architecture specific makefiles.

2
arch/arch.mk.arc
View File

@ -2,7 +2,7 @@ ifeq ($(BR2_arc),y)
# -matomic is always required when the ARC core has the atomic extensions
ifeq ($(BR2_ARC_ATOMIC_EXT),y)
ARCH_TOOLCHAIN_WRAPPER_OPTS = -matomic
ARCH_TOOLCHAIN_WRAPPER_OPTS += -matomic
endif
endif