[PATCH] Set max-page-size when linking the kernel to 0x1000.

[Flavio Cruz]

With the exception of linux, x86_64 ld default's max-page-size
is 2MB (default for i386 is 4K) and compiling gnumach with x86_64-pc-gnu-ld
will generate a kernel image where the boot section starts at the file offset
2MB. This makes it unbootable on grub because the file is no longer multiboot.

Here's the objdump -h output before the patch:

Sections:
Idx Name          Size      VMA               LMA               File off  Algn
  0 .boot         0000c000  0000000001000000  0000000001000000  00200000  2**12
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .text         0009078f  000000004100c000  000000000100c000  0020c000  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  2 .rodata       000110fc  000000004109c7a0  000000000109c7a0  0029c7a0  2**5
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  3 .eh_frame     000101f0  00000000410ad8a0  00000000010ad8a0  002ad8a0  2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  4 .data         000070a0  00000000412bdaa0  00000000012bdaa0  002bdaa0  2**5
                  CONTENTS, ALLOC, LOAD, DATA
  5 .bss          00023f10  00000000412c5000  00000000012c5000  002c4b40  2**12
                  ALLOC
  6 .comment      00000012  0000000000000000  0000000000000000  002c4b40  2**0
                  CONTENTS, READONLY

After, when forcing ld's max-page-size to be 4K:

Sections:
Idx Name          Size      VMA               LMA               File off  Algn
  0 .boot         0000c000  0000000001000000  0000000001000000  00001000  2**12
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .text         0009078f  000000004100c000  000000000100c000  0000d000  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  2 .rodata       000110fc  000000004109c7a0  000000000109c7a0  0009d7a0  2**5
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  3 .eh_frame     000101f0  00000000410ad8a0  00000000010ad8a0  000ae8a0  2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  4 .data         000070a0  00000000410beaa0  00000000010beaa0  000beaa0  2**5
                  CONTENTS, ALLOC, LOAD, DATA
  5 .bss          00023f10  00000000410c6000  00000000010c6000  000c5b40  2**12
                  ALLOC
  6 .comment      00000012  0000000000000000  0000000000000000  000c5b40  2**0
                  CONTENTS, READONLY

It is also possible that something is wrong with the linker script but
couldn't find anything concrete so far. After this patch the kernel is
bootable with x86_64-pc-gnu-ld (and far smaller in size).
---
 x86_64/Makefrag.am | 1 +
 1 file changed, 1 insertion(+)

diff --git a/x86_64/Makefrag.am b/x86_64/Makefrag.am
index edf533fd..1ee1092a 100644
--- a/x86_64/Makefrag.am
+++ b/x86_64/Makefrag.am
@@ -262,6 +262,7 @@ gnumach_LINKFLAGS += \
        --defsym _START_MAP=$(_START_MAP) \
        --defsym _START=$(_START_MAP) \
        --defsym KERNEL_MAP_SHIFT=$(KERNEL_MAP_BASE) \
+       -z max-page-size=0x1000 \
        -T '$(srcdir)'/x86_64/ldscript
 
 AM_CCASFLAGS += \
-- 
2.39.0