linux/arch/powerpc/kernel/misc.S
Christophe Leroy 33e1402435 powerpc: Avoid link stack corruption in misc asm functions
bl;mflr is used at several places to get code position.

Use bcl 20,31,+4 instead of bl in order to preserve link stack.

See commit c974809a26 ("powerpc/vdso: Avoid link stack corruption
in __get_datapage()") for details.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c6eabb4fb6c156f75d56dcbcc6f243e5ac0fba42.1629791763.git.christophe.leroy@csgroup.eu
2021-08-25 13:35:47 +10:00

119 lines
2.3 KiB
ArmAsm

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* This file contains miscellaneous low-level functions.
* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
*
* Largely rewritten by Cort Dougan (cort@cs.nmt.edu)
* and Paul Mackerras.
*
* PPC64 updates by Dave Engebretsen (engebret@us.ibm.com)
*
* setjmp/longjmp code by Paul Mackerras.
*/
#include <asm/ppc_asm.h>
#include <asm/unistd.h>
#include <asm/asm-compat.h>
#include <asm/asm-offsets.h>
#include <asm/export.h>
.text
/*
* Returns (address we are running at) - (address we were linked at)
* for use before the text and data are mapped to KERNELBASE.
* add_reloc_offset(x) returns x + reloc_offset().
*/
_GLOBAL(reloc_offset)
li r3, 0
_GLOBAL(add_reloc_offset)
mflr r0
bcl 20,31,$+4
1: mflr r5
PPC_LL r4,(2f-1b)(r5)
subf r5,r4,r5
add r3,r3,r5
mtlr r0
blr
_ASM_NOKPROBE_SYMBOL(reloc_offset)
_ASM_NOKPROBE_SYMBOL(add_reloc_offset)
.align 3
2: PPC_LONG 1b
_GLOBAL(setjmp)
mflr r0
PPC_STL r0,0(r3)
PPC_STL r1,SZL(r3)
PPC_STL r2,2*SZL(r3)
#ifdef CONFIG_PPC32
mfcr r12
stmw r12, 3*SZL(r3)
#else
mfcr r0
PPC_STL r0,3*SZL(r3)
PPC_STL r13,4*SZL(r3)
PPC_STL r14,5*SZL(r3)
PPC_STL r15,6*SZL(r3)
PPC_STL r16,7*SZL(r3)
PPC_STL r17,8*SZL(r3)
PPC_STL r18,9*SZL(r3)
PPC_STL r19,10*SZL(r3)
PPC_STL r20,11*SZL(r3)
PPC_STL r21,12*SZL(r3)
PPC_STL r22,13*SZL(r3)
PPC_STL r23,14*SZL(r3)
PPC_STL r24,15*SZL(r3)
PPC_STL r25,16*SZL(r3)
PPC_STL r26,17*SZL(r3)
PPC_STL r27,18*SZL(r3)
PPC_STL r28,19*SZL(r3)
PPC_STL r29,20*SZL(r3)
PPC_STL r30,21*SZL(r3)
PPC_STL r31,22*SZL(r3)
#endif
li r3,0
blr
_GLOBAL(longjmp)
#ifdef CONFIG_PPC32
lmw r12, 3*SZL(r3)
mtcrf 0x38, r12
#else
PPC_LL r13,4*SZL(r3)
PPC_LL r14,5*SZL(r3)
PPC_LL r15,6*SZL(r3)
PPC_LL r16,7*SZL(r3)
PPC_LL r17,8*SZL(r3)
PPC_LL r18,9*SZL(r3)
PPC_LL r19,10*SZL(r3)
PPC_LL r20,11*SZL(r3)
PPC_LL r21,12*SZL(r3)
PPC_LL r22,13*SZL(r3)
PPC_LL r23,14*SZL(r3)
PPC_LL r24,15*SZL(r3)
PPC_LL r25,16*SZL(r3)
PPC_LL r26,17*SZL(r3)
PPC_LL r27,18*SZL(r3)
PPC_LL r28,19*SZL(r3)
PPC_LL r29,20*SZL(r3)
PPC_LL r30,21*SZL(r3)
PPC_LL r31,22*SZL(r3)
PPC_LL r0,3*SZL(r3)
mtcrf 0x38,r0
#endif
PPC_LL r0,0(r3)
PPC_LL r1,SZL(r3)
PPC_LL r2,2*SZL(r3)
mtlr r0
mr. r3, r4
bnelr
li r3, 1
blr
_GLOBAL(current_stack_frame)
PPC_LL r3,0(r1)
blr
EXPORT_SYMBOL(current_stack_frame)