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hurd: Simplify init-first.c a bit

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And make it a bit more 64-bit ready. This is in preparation to moving this
file into x86/

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230218203717.373211-6-bugaevc@gmail.com>
This commit is contained in:
Sergey Bugaev 2023-02-18 23:37:13 +03:00 committed by Samuel Thibault
parent ee10f5dfd8
commit 90ab316b02
1 changed files with 7 additions and 16 deletions
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23
sysdeps/mach/hurd/i386/init-first.c
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@ -195,7 +195,7 @@ init (int *data)
/* Call `init1' (above) with the user code as the return address, and the
argument data immediately above that on the stack. */
int usercode;
void *usercode, **ret_address;
void call_init1 (void);
@ -206,10 +206,11 @@ init (int *data)
recognize that this read operation may alias the following write
operation, and thus is free to reorder the two, clobbering the
original return address. */
usercode = *((int *) __builtin_frame_address (0) + 1);
ret_address = (void **) __builtin_frame_address (0) + 1;
usercode = *ret_address;
/* GCC 4.4.6 also wants us to force loading USERCODE already here. */
asm volatile ("# %0" : : "X" (usercode));
*((void **) __builtin_frame_address (0) + 1) = &call_init1;
*ret_address = &call_init1;
/* Force USERCODE into %eax and &init1 into %ecx, which are not
restored by function return. */
asm volatile ("# a %0 c %1" : : "a" (usercode), "c" (&init1));
@ -223,19 +224,9 @@ init (int *data)
/* The return address of `init' above, was redirected to here, so at
this point our stack is unwound and callers' registers restored.
Only %ecx and %eax are call-clobbered and thus still have the
values we set just above. Fetch from there the new stack pointer
we will run on, and jmp to the run-time address of `init1'; when it
returns, it will run the user code with the argument data at the
top of the stack. */
asm ("switch_stacks:\n"
" movl %eax, %esp\n"
" jmp *%ecx");
/* As in the stack-switching case, at this point our stack is unwound
and callers' registers restored, and only %ecx and %eax communicate
values from the lines above. In this case we have stashed in %eax
the user code return address. Push it on the top of the stack so
it acts as init1's return address, and then jump there. */
values we set just above. We have stashed in %eax the user code
return address. Push it on the top of the stack so it acts as
init1's return address, and then jump there. */
asm ("call_init1:\n"
" push %eax\n"
" jmp *%ecx\n");