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/* Create new context.
Copyright (C) 2002-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
#define __ASSEMBLY__
#include <asm/ptrace.h>
#include "ucontext_i.h"
#include <asm/errno.h>
ENTRY (__makecontext)
CALL_MCOUNT 3
/* Save parameters into the parameter save area of callers frame. */
std r3,FRAME_PARM_SAVE+0(r1) /* ucontext_t *ucp */
std r4,FRAME_PARM_SAVE+8(r1) /* void (*func)(void) */
std r5,FRAME_PARM_SAVE+16(r1) /* int argc */
std r6,FRAME_PARM_SAVE+24(r1) /* ... */
std r7,FRAME_PARM_SAVE+32(r1)
std r8,FRAME_PARM_SAVE+40(r1)
std r9,FRAME_PARM_SAVE+48(r1)
std r10,FRAME_PARM_SAVE+56(r1)
mflr r0
/* Get the address of the target functions first parameter. */
addi r6,r1,FRAME_PARM_SAVE+24
std r0,FRAME_LR_SAVE(r1)
cfi_offset (lr, FRAME_LR_SAVE)
stdu r1,-128(r1)
cfi_adjust_cfa_offset (128)
/* Get the ucontexts stack pointer and size. Compute the top of stack
and round down to a quadword boundary. Then stack a dummy frame
with a null back chain. We store the context pointer in the frames
"compiler double word" field so we can recover if is the function
returns. Finally save the callers link register and TOC pointer
into this frame so the debugger can display a backtrace.
*/
ld r7,UCONTEXT_STACK_SP(r3)
ld r0,UCONTEXT_STACK_SIZE(r3)
add r7,r7,r0
clrrdi r7,r7,4
li r0,0
stdu r0,-64(r7)
std r3,FRAME_PARM_SAVE(r7) /* Store context in dummy parm1. */
mflr r0
std r2,FRAME_TOC_SAVE(r7) /* Store the TOC pointer for later. */
std r0,FRAME_LR_SAVE(r7)
/* Now we need to stack another frame to hold the parameter save area
for the function. We need to allocate a frame with the minimum 48
byte header and 8 parameter register. However if there are more
than 8 parameters addition space is need to hold all the parameters.
The total size it rounded up to a quadword multiple then a frame is
stacked. This address is stored in the ucontext as GPR 1. */
cmpdi cr1,r5,8
sldi r8,r5,3
bgt cr1,L(gt8)
li r8,64
L(gt8):
addi r8,r8,FRAME_PARM_SAVE+8 /* Add header plus rounding factor. */
clrrdi r8,r8,4 /* Round down to quadword. */
subf r8,r8,r7
std r7,0(r8) /* Stack the frame. */
std r8,(SIGCONTEXT_GP_REGS+(PT_R1*8))(r3)
/* Now we need to copy the target functions parameters. The functions
parameters are saved in the parameter save area. We skip over the
first three parameters and copy up to 8 double word into the
SIGCONTEXT_GP_REGS starting with R3. If there are more than 8
parameters then doublewords 8-N are copied into the parameter
save area of the context frame. */
cmpdi r5,0
beq L(noparms)
mr r0,r5
ble cr1,L(le8)
li r0,8
L(le8):
mtctr r0
addi r7,r6,-8
addi r9,r3,(SIGCONTEXT_GP_REGS+(PT_R3*8)-8)
L(parmloop2):
ldu r0,8(r7)
stdu r0,8(r9)
bdnz L(parmloop2)
addi r0,r5,-8
ble cr1,L(noparms)
mtctr r0
addi r9,r8,FRAME_PARM_SAVE+64-8
L(parmloop):
ldu r0,8(r7)
stdu r0,8(r9)
bdnz L(parmloop)
L(noparms):
#if _CALL_ELF != 2
/* Load the function address and TOC from the function descriptor
and store them in the ucontext as NIP and r2. Store the 3rd
field of the function descriptor into the ucontext as r11 in case
the calling language needs the "environment pointer". */
ld r0,0(r4)
ld r10,8(r4);
ld r9,16(r4);
std r0,(SIGCONTEXT_GP_REGS+(PT_NIP*8))(r3)
std r10,(SIGCONTEXT_GP_REGS+(PT_R2*8))(r3)
std r9,(SIGCONTEXT_GP_REGS+(PT_R11*8))(r3)
#else
/* In the ELFv2 ABI, the function pointer is already the address.
Store it as NIP and r12 as required by the ABI. */
std r4,(SIGCONTEXT_GP_REGS+(PT_NIP*8))(r3)
std r4,(SIGCONTEXT_GP_REGS+(PT_R12*8))(r3)
#endif
/* If the target function returns we need to do some cleanup. We use a
code trick to get the address of our cleanup function into the link
register. Do not add any code between here and L(exitcode).
Use this conditional form of branch and link to avoid destroying
the cpu link stack used to predict blr return addresses. */
bcl 20,31,L(gotexitcodeaddr);
/* End FDE now, because while executing on the context's stack
the unwind info would be wrong otherwise. */
cfi_endproc
/* This is the helper code which gets called if a function which
is registered with 'makecontext' returns. In this case we
have to install the context listed in the uc_link element of
the context 'makecontext' manipulated at the time of the
'makecontext' call. If the pointer is NULL the process must
terminate. */
L(exitcode):
/* Recover the ucontext and TOC from the dummy frame. */
ld r1,FRAME_BACKCHAIN(r1) /* Unstack the parameter save area frame. */
ld r3,FRAME_PARM_SAVE(r1)
ld r2,FRAME_TOC_SAVE(r1)
ld r3,UCONTEXT_LINK(r3) /* Load the resume context. */
cmpdi r3,0
beq L(do_exit)
bl JUMPTARGET(__setcontext)
nop
/* If setcontext returns (which can happen if the syscall fails) we will
exit the program with error status (-1). */
li r3,-1
L(do_exit):
#ifdef SHARED
b JUMPTARGET (NOTOC (__GI_exit));
#else
b JUMPTARGET(exit);
nop
#endif
b L(do_exit)
/* Re-establish FDE for the rest of the actual makecontext routine. */
cfi_startproc
cfi_offset (lr, FRAME_LR_SAVE)
cfi_adjust_cfa_offset (128)
/* The address of the exit code is in the link register. Store the lr
in the ucontext as LNK so the target function will return to our
exit code. */
L(gotexitcodeaddr):
mflr r0
std r0,(SIGCONTEXT_GP_REGS+(PT_LNK*8))(r3)
ld r0,128+FRAME_LR_SAVE(r1)
addi r1,r1,128
mtlr r0
blr
END(__makecontext)
weak_alias (__makecontext, makecontext)
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