[Bug gold/20833] x32 kernel build error

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=20833

--- Comment #7 from H.J. Lu <hjl.tools at gmail dot com> ---
X32 uses 32-bit pointers in 64-bit address space.  It can reach
the full 64-bit address space:

address@hidden far-3]$ cat x.c
#include <stdio.h>

extern int foo (long long);

int
main ()
{
  long long addr = 0xffffffffff600000LL;
  int x = foo (addr);
  printf ("0x%llx: %p\n", addr, x);
  return 0;
}
address@hidden far-3]$ cat foo.S
        .text
        .p2align 4,,15
        .globl  foo
        .type   foo, @function
foo:
.LFB0:
        .cfi_startproc
        movl    (%rdi), %eax
        ret
        .cfi_endproc
.LFE0:
        .size   foo, .-foo
        .section        .note.GNU-stack,"",@progbits
address@hidden far-3]$ gcc x.c foo.S -mx32
address@hidden far-3]$ ./a.out 
0xffffffffff600000: 0x60c0c748
address@hidden far-3]$ 

0xffffffffff600000 is mapped to vsyscall page, which is invisible to
normal x32 application.  In this sense, ld isn't wrong not to issue
an error to access below 0 for both LP64 and ILP32.

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