x86: switch back to using x86-specific trampoline
ci/woodpecker/push/woodpecker Pipeline was successful Details

Jumping into the generic trampoline causes the stack pointer to get
clobbered.

Fixes #61
master
Ariadne Conill 2024-08-07 18:34:45 -07:00
parent 5445f70157
commit c1ecb0ea59
3 changed files with 41 additions and 6 deletions

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@ -57,9 +57,6 @@
#define MCONTEXT_GREGS (20) #define MCONTEXT_GREGS (20)
#define FETCH_LINKPTR(dest) \
asm("movl (%%esp, %%ebx, 4), %0" : "=r" ((dest)));
#include "common-defs.h" #include "common-defs.h"
#endif #endif

41
arch/x86/startcontext.S Normal file
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@ -0,0 +1,41 @@
/*
* Copyright (c) 2018, 2020 Ariadne Conill <ariadne@dereferenced.org>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* This software is provided 'as is' and without any warranty, express or
* implied. In no event shall the authors be liable for any damages arising
* from the use of this software.
*/
#include "defs.h"
FUNC(libucontext_trampoline)
/* get the proper context into position and test for NULL */
leal (%esp,%ebx,4), %esp
cmpl $0, (%esp)
/* restore global offset table, exit@plt and libucontext_setcontext@plt need this */
call __i686_get_pc_thunk_bx
addl $_GLOBAL_OFFSET_TABLE_, %ebx
/* if we have no linked context, lets get out of here */
je no_linked_context
/* call setcontext to switch to the linked context */
call libucontext_setcontext@plt
movl %eax, (%esp)
no_linked_context:
/* we are returning into a null context, it seems, so maybe we should exit */
call exit@plt
/* something is really hosed, call hlt to force termination */
hlt
__i686_get_pc_thunk_bx:
mov (%esp), %ebx
ret
END(libucontext_trampoline)

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@ -1,3 +0,0 @@
#include "defs.h"
#include <libucontext/libucontext.h>
#include "common-trampoline.c"