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loongarch64: rewrite makecontext in C
ci/woodpecker/push/woodpecker Pipeline was successful Details 

also fix MCONTEXT_PC and MCONTEXT_GREGS so they actually read and write to/from
the correct addresses in the ucontext structure.
master
Ariadne Conill 2024-08-12 13:17:41 -07:00
parent c3d26b7940
commit d64402737b
3 changed files with 69 additions and 110 deletions
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10
arch/loongarch64/defs.h
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@ -45,11 +45,17 @@
/* frame pointer is actually $22 */
#define REG_FP (22)
/* $s0 is $23 */
#define REG_S0 (23)
/* $ra is $1 */
#define REG_RA (1)
/* offset to mc_gregs in ucontext_t */
#define MCONTEXT_GREGS (48)
#define MCONTEXT_GREGS (184)
/* offset to PC in ucontext_t */
#define MCONTEXT_PC (40)
#define MCONTEXT_PC (176)
/* offset to uc_link in ucontext_t */
#define UCONTEXT_UC_LINK (8)

108
arch/loongarch64/makecontext.S
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@ -1,108 +0,0 @@
/*
* Copyright (c) 2021 Peng Fan <fanpeng@loongson.cn>
*
* 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"
#define LOCALSZ (6)
#define A3_OFF (FRAMESZ - (5 * REG_SZ))
#define A4_OFF (FRAMESZ - (4 * REG_SZ))
#define A5_OFF (FRAMESZ - (3 * REG_SZ))
#define A6_OFF (FRAMESZ - (2 * REG_SZ))
#define A7_OFF (FRAMESZ - (1 * REG_SZ))
ALIAS(makecontext, libucontext_makecontext)
FUNC(libucontext_makecontext)
PUSH_FRAME(libucontext_makecontext)
move $t5, $a0
move $t4, $a1
/* store $a3 through $a7 to the stack frame. */
st.d $a3, $sp, A3_OFF
st.d $a4, $sp, A4_OFF
st.d $a5, $sp, A5_OFF
st.d $a6, $sp, A6_OFF
st.d $a7, $sp, A7_OFF
/* set $zero in the mcontext to 1. */
addi.d $a0, $zero, 1
st.d $a0, $t5, REG_OFFSET(0)
/* ensure the stack is aligned on a quad-word boundary. */
ld.d $t0, $t5, UCONTEXT_STACK_PTR
ld.d $t2, $t5, UCONTEXT_STACK_SIZE
/* the third argument(from zero), that's the first argument of func() */
addi.d $t1, $sp, A3_OFF
add.d $t0, $t0, $t2
addi.d $t7, $zero, ALMASK
and $t0, $t0, $t7
/* number of args */
beq $a2, $zero, no_more_arguments
bltu $a2, $zero, no_more_arguments
/* store register arguments. */
addi.d $t2, $t5, MCONTEXT_GREGS + (4 * REG_SZ)
move $t3, $zero
store_register_arg:
addi.d $t3, $t3, 1
ld.d $a1, $t1, 0
addi.d $t1, $t1, REG_SZ
st.d $a1, $t2, 0
addi.d $t2, $t2, REG_SZ
addi.d $t6, $zero, 8
bltu $t3, $t6, store_register_arg
bgeu $t3, $a2, no_more_arguments
/* make room for stack arguments. */
sub.d $t2, $a2, $t3
addi.d $t6, $zero, 3
sll.d $t2, $t2, $t6
sub.d $t0, $t0, $t2
addi.d $t6, $zero, ALMASK
and $t0, $t0, $t6
/* store stack arguments. */
move $t2, $t0
store_stack_arg:
addi.d $t3, $t3, 1
ld.d $a1, $t1, 0
addi.d $t1, $t1, REG_SZ
st.d $a1, $t2, 0
addi.d $t2, $t2, REG_SZ
bltu $t3, $a2, store_stack_arg
no_more_arguments:
/* trampoline setup. */
la.got $t8, libucontext_trampoline
ld.d $a1, $t5, UCONTEXT_UC_LINK
st.d $a1, $t5, REG_OFFSET(23)
st.d $t0, $t5, REG_OFFSET(3)
st.d $t8, $t5, REG_OFFSET(1)
st.d $t4, $t5, MCONTEXT_PC
POP_FRAME(libucontext_makecontext)
jr $ra
END(libucontext_makecontext)

61
arch/loongarch64/makecontext.c Normal file
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@ -0,0 +1,61 @@
/*
* Copyright (c) 2024 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 <stddef.h>
#include <stdarg.h>
#include <string.h>
#include <stdint.h>
#include <stdio.h>
#include "defs.h"
#include <libucontext/libucontext.h>
extern void libucontext_trampoline(void);
void
libucontext_makecontext(libucontext_ucontext_t *ucp, void (*func)(void), int argc, ...)
{
libucontext_greg_t *sp, *regp;
va_list va;
int i;
/* set up and align the stack. */
sp = (libucontext_greg_t *) ((uintptr_t) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
sp -= argc < 8 ? 0 : argc - 8;
sp = (libucontext_greg_t *) (((uintptr_t) sp & -16L));
/* set up the ucontext structure */
ucp->uc_mcontext.__gregs[REG_RA] = (libucontext_greg_t) libucontext_trampoline;
ucp->uc_mcontext.__gregs[REG_S0] = (libucontext_greg_t) ucp->uc_link;
ucp->uc_mcontext.__gregs[REG_SP] = (libucontext_greg_t) sp;
ucp->uc_mcontext.__pc = (libucontext_greg_t) func;
va_start(va, argc);
/* first 8 args go in $a0 through $a7. */
regp = &(ucp->uc_mcontext.__gregs[REG_A0]);
for (i = 0; (i < argc && i < 8); i++)
*regp++ = va_arg (va, libucontext_greg_t);
/* remainder overflows into stack */
for (; i < argc; i++)
*sp++ = va_arg (va, libucontext_greg_t);
va_end(va);
}
#ifdef EXPORT_UNPREFIXED
extern __typeof(libucontext_makecontext) makecontext __attribute__((weak, __alias__("libucontext_makecontext")));
extern __typeof(libucontext_makecontext) __makecontext __attribute__((weak, __alias__("libucontext_makecontext")));
#endif