Re: [Buildroot] [PATCH v2] arch: Set max/common-page-size for libgcc & libstdc++

[Peter Korsgaard <peter@korsgaard.com>]

>>>>> "Alexey" == Alexey Brodkin via buildroot <buildroot@buildroot.org> writes:

 > With [1], [2] & [3] we made sure Buildroot packages get built with
 > proper MMU page size assumed. This was done nicely through insertion of
 > required flags into the toolchain wrapper so that there's no need to
 > pass these flags to each and every package separately - toolchain
 > wrapper used for real building has all set internally and so proper
 > flags are impleicitly used.

 > But there's yet another corner case which is not handled that way -
 > these are binaries or rather libraries which are being used as a part of
 > GCC compilation: libgcc_s.so.1 and libstdc++.so.

 > And so to make sure both the libraries get built properly we need to set
 > TARGET_CFLAGS (cures libgcc_s.so) & TARGET_LDFLAGS (cures libstdc++.so).

 > In case of ARM by defaut 64 KiB page size seems to be used, as w/o that
 > patch I see the following for BR2_ARM64_PAGE_SIZE_4K=y:
 ---------------------------> 8----------------------------
 > $ ./output/host/bin/aarch64-linux-readelf -l ./output/target/lib/libgcc_s.so.1

 > Elf file type is DYN (Shared object file)
 > Entry point 0x0
 > There are 6 program headers, starting at offset 64

 > Program Headers:
 >   Type           Offset             VirtAddr           PhysAddr
 >                  FileSiz            MemSiz              Flags  Align
 >   LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
 >                  0x0000000000013d1c 0x0000000000013d1c  R E    0x10000
 >   LOAD           0x000000000001fd98 0x000000000002fd98 0x000000000002fd98
 >                  0x0000000000000438 0x00000000000005c8  RW     0x10000
 >   DYNAMIC        0x000000000001fdb8 0x000000000002fdb8 0x000000000002fdb8
 >                  0x0000000000000200 0x0000000000000200  RW     0x8

 > $ ./output/host/bin/aarch64-linux-readelf -l ./output/target/usr/lib/libstdc++.so.6.0.32

 > Elf file type is DYN (Shared object file)
 > Entry point 0x0
 > There are 7 program headers, starting at offset 64

 > Program Headers:
 >   Type           Offset             VirtAddr           PhysAddr
 >                  FileSiz            MemSiz              Flags  Align
 >   LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
 >                  0x00000000001d3462 0x00000000001d3462  R E    0x10000
 >   LOAD           0x00000000001d5760 0x00000000001e5760 0x00000000001e5760
 >                  0x000000000000e528 0x0000000000012de8  RW     0x10000
 >   DYNAMIC        0x00000000001deef0 0x00000000001eeef0 0x00000000001eeef0
 >                  0x0000000000000240 0x0000000000000240  RW     0x8
 ---------------------------> 8----------------------------

 > Note alignment of 0x10000 in sections marked for loading.
 > And with the patch applied we get expected alignment of 0x1000 (4 KiB):
 ---------------------------> 8----------------------------
 > $ ./output/host/bin/aarch64-linux-readelf -l ./output/target/lib/libgcc_s.so.1

 > Elf file type is DYN (Shared object file)
 > Entry point 0x0
 > There are 6 program headers, starting at offset 64

 > Program Headers:
 >   Type           Offset             VirtAddr           PhysAddr
 >                  FileSiz            MemSiz              Flags  Align
 >   LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
 >                  0x0000000000013d1c 0x0000000000013d1c  R E    0x1000
 >   LOAD           0x0000000000013d98 0x0000000000014d98 0x0000000000014d98
 >                  0x0000000000000438 0x00000000000005c8  RW     0x1000
 >   DYNAMIC        0x0000000000013db8 0x0000000000014db8 0x0000000000014db8
 >                  0x0000000000000200 0x0000000000000200  RW     0x8

 > $ ./output/host/bin/aarch64-linux-readelf -l ./output/target/usr/lib/libstdc++.so.6.0.32

 > Elf file type is DYN (Shared object file)
 > Entry point 0x0
 > There are 7 program headers, starting at offset 64

 > Program Headers:
 >   Type           Offset             VirtAddr           PhysAddr
 >                  FileSiz            MemSiz              Flags  Align
 >   LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
 >                  0x00000000001d3462 0x00000000001d3462  R E    0x1000
 >   LOAD           0x00000000001d3760 0x00000000001d4760 0x00000000001d4760
 >                  0x000000000000e528 0x0000000000012de8  RW     0x1000
 >   DYNAMIC        0x00000000001dcef0 0x00000000001ddef0 0x00000000001ddef0
 >                  0x0000000000000240 0x0000000000000240  RW     0x8
 ---------------------------> 8----------------------------

 > What's nice, we're getting rid of a special handling of "-matomic"
 > as it's already a part of ARCH_TOOLCHAIN_WRAPPER_OPTS.

 > [1] https://git.buildroot.net/buildroot/commit/?id=3cc2c6d19ab2e1bb4634f26f9318da9b07df5fff
 > [2] https://git.buildroot.net/buildroot/commit/?id=dcb74db89e74e512e36b32cea6f574a1a1ca84c4
 > [3] https://git.buildroot.net/buildroot/commit/?id=5e52c28397b79f8c4c99552217cbe95202166626

 > Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
 > Signed-off-by: Vladimir Isaev <VVIsaev@gmail.com>
 > Signed-off-by: Pavel Kozlov <kozlov@synopsys.com>
 > Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
 > Cc: Yann E. MORIN <yann.morin.1998@free.fr>
 > Cc: Arnout Vandecappelle <arnout@mind.be>
 > ---

 > Changes in v2:

 >  * Instead of setting TARGET_{C|LD}FLAGS use
 >    ARCH_TOOLCHAIN_WRAPPER_OPTS for configuring GCC.

Committed to 2023.02.x and 2023.11.x, thanks.

-- 
Bye, Peter Korsgaard
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