[thirdparty/glibc.git] / sysdeps / s390 / s390-32 / start.S

/* Startup code compliant to the ELF s390 ABI.
   Copyright (C) 2000-2015 Free Software Foundation, Inc.
   Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).
   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.

   In addition to the permissions in the GNU Lesser General Public
   License, the Free Software Foundation gives you unlimited
   permission to link the compiled version of this file with other
   programs, and to distribute those programs without any restriction
   coming from the use of this file. (The GNU Lesser General Public
   License restrictions do apply in other respects; for example, they
   cover modification of the file, and distribution when not linked
   into another program.)

   Note that people who make modified versions of this file are not
   obligated to grant this special exception for their modified
   versions; it is their choice whether to do so. The GNU Lesser
   General Public License gives permission to release a modified
   version without this exception; this exception also makes it
   possible to release a modified version which carries forward this
   exception.

   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
   <http://www.gnu.org/licenses/>.  */

/*
   This is the canonical entry point, usually the first thing in the text
   segment. Most registers' values are unspecified, except for:

   %r14         Contains a function pointer to be registered with `atexit'.
		This is how the dynamic linker arranges to have DT_FINI
		functions called for shared libraries that have been loaded
		before this code runs.

   %r15		The stack contains the arguments and environment:
		0(%r15)			argc
		4(%r15)			argv[0]
		...
		(4*argc)(%r15)		NULL
		(4*(argc+1))(%r15)	envp[0]
		...
					NULL
*/

	.text
	.globl _start
	.type _start,@function
_start:
	/* Check if the kernel provides highgprs facility if needed by
	   the binary.  */

	lr	%r6,%r15
	la	%r6,4(%r6)     /* Skip the argument counter.  */

.L11:	l	%r5,0(%r6)     /* Skip the argument vector.  */
	la	%r6,4(%r6)
	ltr	%r5,%r5
	jne	.L11

.L12:	l	%r5,0(%r6)     /* Skip the environment vector.  */
	la	%r6,4(%r6)
	ltr	%r5,%r5
	jne	.L12

	/* Usually the auxiliary vector can be expected directly after
	   the environment variables.  But we have to skip extra zeros
	   because the loader might have removed unsecure variables for
	   setuid programs.  */

.L26:	l	%r5,0(%r6)
	la	%r6,4(%r6)
	ltr	%r5,%r5
	jz	.L26

	ahi	%r6,-4

	/* Obtain the needed values from the auxiliary vector.  */

	lhi	%r7,16	       /* AT_HWCAP */
	lhi	%r8,3	       /* AT_PHDR */
	lhi	%r9,5          /* AT_PHNUM */
	lhi	%r2,4          /* AT_PHENT */
.L13:	l	%r5,0(%r6)
	clr	%r5,%r7
	jne	.L15
	l	%r10,4(%r6)    /* r10 = AT_HWCAP value.  */
.L15:	clr	%r5,%r8
	jne	.L16
	l	%r11,4(%r6)    /* r11 = AT_PHDR value.  */
.L16:	clr	%r5,%r9
	jne	.L17
	l	%r12,4(%r6)    /* r12 = AT_PHNUM value.  */
.L17:	clr	%r5,%r2
	jne	.L18
	l	%r0,4(%r6)     /* r0 = AT_PHENT value.  */
.L18:	ltr	%r5,%r5
	la	%r6,8(%r6)
	jnz	.L13

	/* Locate the ELF header by looking for the first PT_LOAD
	   segment with a p_offset of zero.  */

	lr	%r4,%r11       /* Backup AT_PHDR.  */
	lhi	%r7,1          /* PT_LOAD id */
	lhi	%r8,0
.L19:	cl	%r7,0(%r4)     /* p_type == PT_LOAD? */
	jne	.L20
	cl	%r8,4(%r4)     /* p_offset == 0? */
	jne	.L20
	l	%r9,8(%r4)     /* r9 = PT_LOAD.p_vaddr <- ELF header address  */
	j	.L24
.L20:	alr	%r4,%r0        /* r4 += AT_PHENT value */
	brct	%r12,.L19

	j	.+2            /* Trap, there must be such a phdr.  */

.L24:	lr	%r4,%r11       /* Backup AT_PHDR.  */
	lhi	%r2,6          /* PT_PHDR id */
.L23:	cl	%r2,0(%r4)
	jne	.L22
	l	%r3,8(%r4)     /* r3 = PT_PHDR p_vaddr */
	j	.L25
.L22:	alr	%r4,%r0        /* r4 += AT_PHENT value */
	brct	%r12,.L23

	j	.L14	       /* No PT_PHDR found - skip checking.  */

.L25:	slr	%r11,%r3       /* AT_PHDR - PT_PHDR.p_vaddr (relocation offset)*/
	alr	%r9,%r11       /* PT_LOAD.p_vaddr += relocation offset */

	l	%r5,36(%r9)    /* Load the e_flags field.  */
	tml	%r5,1
	jz	.L14	       /* Binary does not require highgprs facility.  */

	tml	%r10,512       /* Check the AT_HWCAP value.  */
	jz	2              /* Trap if no highgprs facility available.  */
.L14:

	/* Setup pointer to literal pool of _start */
	basr    %r13,0
.L0:    ahi     %r13,.Llit-.L0

	/* load argc and argv from stack */
	la      %r4,4(%r15)             # get argv
	l       %r3,0(%r15)             # get argc

	/* align the stack to a double word boundary */
	lhi     %r0,-8
	nr      %r15,%r0

	/* Setup a stack frame and a parameter area */
	ahi     %r15,-104               # make room on stack
	xc      0(4,%r15),0(%r15)       # clear back-chain

	/* set up arguments for __libc_start_main:
	   main, argc, argv, envp, _init, _fini, rtld_fini, stack_end
	   Note that envp will be determined later in __libc_start_main
	 */
	stm     %r14,%r15,96(%r15)      # store rtld_fini/stack_end to parameter area
	la      %r7,96(%r15)
	l       %r6,.L2-.Llit(%r13)     # load pointer to __libc_csu_fini
	l       %r5,.L1-.Llit(%r13)     # load pointer to __libc_csu_init
	l       %r2,.L3-.Llit(%r13)     # load pointer to main
	l       %r1,.L4-.Llit(%r13)	# load pointer to __libc_start_main
#ifdef PIC
	l       %r12,.L5-.Llit(%r13)    # load .got pointer
	la	%r6,0(%r13,%r6)
	la	%r5,0(%r13,%r5)
	la	%r12,0(%r13,%r12)
	l	%r2,0(%r12,%r2)
	la	%r1,0(%r13,%r1)
#endif

	/* ok, now branch to the libc main routine */
	basr    %r14,%r1

	/* crash if __libc_start_main returns */
	.word   0

.Llit:
#ifndef PIC
.L1:    .long  __libc_csu_init
.L2:    .long  __libc_csu_fini
.L3:    .long  main
.L4:    .long  __libc_start_main
#else
.L1:    .long  __libc_csu_init-.Llit
.L2:    .long  __libc_csu_fini-.Llit
.L3:    .long  main@GOT
.L4:    .long  __libc_start_main@plt-.Llit
.L5:    .long  _GLOBAL_OFFSET_TABLE_-.Llit
#endif

/* Define a symbol for the first piece of initialized data.  */
	.data
	.globl __data_start
__data_start:
	.long 0
	.weak data_start
	data_start = __data_start
Commit	Line	Data
847b055c	1	/* Startup code compliant to the ELF s390 ABI.
b168057a	2	Copyright (C) 2000-2015 Free Software Foundation, Inc.
847b055c AJ	3	Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).
	4	This file is part of the GNU C Library.
	5
	6	The GNU C Library is free software; you can redistribute it and/or
41bdb6e2 AJ	7	modify it under the terms of the GNU Lesser General Public
	8	License as published by the Free Software Foundation; either
	9	version 2.1 of the License, or (at your option) any later version.
847b055c	10
92c6ccd1 RM	11	In addition to the permissions in the GNU Lesser General Public
	12	License, the Free Software Foundation gives you unlimited
	13	permission to link the compiled version of this file with other
	14	programs, and to distribute those programs without any restriction
	15	coming from the use of this file. (The GNU Lesser General Public
	16	License restrictions do apply in other respects; for example, they
	17	cover modification of the file, and distribution when not linked
	18	into another program.)
	19
	20	Note that people who make modified versions of this file are not
	21	obligated to grant this special exception for their modified
	22	versions; it is their choice whether to do so. The GNU Lesser
	23	General Public License gives permission to release a modified
	24	version without this exception; this exception also makes it
	25	possible to release a modified version which carries forward this
	26	exception.
	27
847b055c AJ	28	The GNU C Library is distributed in the hope that it will be useful,
	29	but WITHOUT ANY WARRANTY; without even the implied warranty of
	30	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
41bdb6e2	31	Lesser General Public License for more details.
847b055c	32
41bdb6e2	33	You should have received a copy of the GNU Lesser General Public
59ba27a6 PE	34	License along with the GNU C Library; if not, see
59ba27a6 PE	35	<http://www.gnu.org/licenses/>. */
847b055c AJ	36
	37	/*
	38	This is the canonical entry point, usually the first thing in the text
	39	segment. Most registers' values are unspecified, except for:
	40
	41	%r14 Contains a function pointer to be registered with `atexit'.
	42	This is how the dynamic linker arranges to have DT_FINI
	43	functions called for shared libraries that have been loaded
	44	before this code runs.
	45
	46	%r15 The stack contains the arguments and environment:
	47	0(%r15) argc
	48	4(%r15) argv[0]
	49	...
	50	(4*argc)(%r15) NULL
	51	(4*(argc+1))(%r15) envp[0]
	52	...
	53	NULL
	54	*/
	55
	56	.text
	57	.globl _start
d1cf3e71	58	.type _start,@function
847b055c	59	_start:
7760ccce AK	60	/* Check if the kernel provides highgprs facility if needed by
	61	the binary. */
	62
	63	lr %r6,%r15
	64	la %r6,4(%r6) /* Skip the argument counter. */
	65
	66	.L11: l %r5,0(%r6) /* Skip the argument vector. */
	67	la %r6,4(%r6)
	68	ltr %r5,%r5
	69	jne .L11
	70
	71	.L12: l %r5,0(%r6) /* Skip the environment vector. */
	72	la %r6,4(%r6)
	73	ltr %r5,%r5
	74	jne .L12
	75
10442705 AK	76	/* Usually the auxiliary vector can be expected directly after
	77	the environment variables. But we have to skip extra zeros
	78	because the loader might have removed unsecure variables for
	79	setuid programs. */
	80
	81	.L26: l %r5,0(%r6)
	82	la %r6,4(%r6)
	83	ltr %r5,%r5
	84	jz .L26
	85
	86	ahi %r6,-4
	87
7760ccce AK	88	/* Obtain the needed values from the auxiliary vector. */
	89
	90	lhi %r7,16 /* AT_HWCAP */
	91	lhi %r8,3 /* AT_PHDR */
	92	lhi %r9,5 /* AT_PHNUM */
	93	lhi %r2,4 /* AT_PHENT */
	94	.L13: l %r5,0(%r6)
	95	clr %r5,%r7
	96	jne .L15
	97	l %r10,4(%r6) /* r10 = AT_HWCAP value. */
	98	.L15: clr %r5,%r8
	99	jne .L16
	100	l %r11,4(%r6) /* r11 = AT_PHDR value. */
	101	.L16: clr %r5,%r9
	102	jne .L17
	103	l %r12,4(%r6) /* r12 = AT_PHNUM value. */
	104	.L17: clr %r5,%r2
	105	jne .L18
	106	l %r0,4(%r6) /* r0 = AT_PHENT value. */
	107	.L18: ltr %r5,%r5
	108	la %r6,8(%r6)
	109	jnz .L13
	110
	111	/* Locate the ELF header by looking for the first PT_LOAD
	112	segment with a p_offset of zero. */
	113
	114	lr %r4,%r11 /* Backup AT_PHDR. */
	115	lhi %r7,1 /* PT_LOAD id */
	116	lhi %r8,0
	117	.L19: cl %r7,0(%r4) /* p_type == PT_LOAD? */
	118	jne .L20
	119	cl %r8,4(%r4) /* p_offset == 0? */
	120	jne .L20
87a97932	121	l %r9,8(%r4) /* r9 = PT_LOAD.p_vaddr <- ELF header address */
7760ccce AK	122	j .L24
	123	.L20: alr %r4,%r0 /* r4 += AT_PHENT value */
	124	brct %r12,.L19
	125
	126	j .+2 /* Trap, there must be such a phdr. */
	127
	128	.L24: lr %r4,%r11 /* Backup AT_PHDR. */
	129	lhi %r2,6 /* PT_PHDR id */
	130	.L23: cl %r2,0(%r4)
	131	jne .L22
	132	l %r3,8(%r4) /* r3 = PT_PHDR p_vaddr */
	133	j .L25
	134	.L22: alr %r4,%r0 /* r4 += AT_PHENT value */
	135	brct %r12,.L23
	136
87a97932	137	j .L14 /* No PT_PHDR found - skip checking. */
7760ccce	138
87a97932 AK	139	.L25: slr %r11,%r3 /* AT_PHDR - PT_PHDR.p_vaddr (relocation offset)*/
87a97932 AK	140	alr %r9,%r11 /* PT_LOAD.p_vaddr += relocation offset */
7760ccce	141
87a97932	142	l %r5,36(%r9) /* Load the e_flags field. */
7760ccce AK	143	tml %r5,1
	144	jz .L14 /* Binary does not require highgprs facility. */
	145
	146	tml %r10,512 /* Check the AT_HWCAP value. */
	147	jz 2 /* Trap if no highgprs facility available. */
	148	.L14:
	149
847b055c AJ	150	/* Setup pointer to literal pool of _start */
	151	basr %r13,0
	152	.L0: ahi %r13,.Llit-.L0
	153
	154	/* load argc and argv from stack */
	155	la %r4,4(%r15) # get argv
	156	l %r3,0(%r15) # get argc
	157
	158	/* align the stack to a double word boundary */
	159	lhi %r0,-8
	160	nr %r15,%r0
	161
	162	/* Setup a stack frame and a parameter area */
	163	ahi %r15,-104 # make room on stack
	164	xc 0(4,%r15),0(%r15) # clear back-chain
	165
	166	/* set up arguments for __libc_start_main:
	167	main, argc, argv, envp, _init, _fini, rtld_fini, stack_end
	168	Note that envp will be determined later in __libc_start_main
	169	*/
	170	stm %r14,%r15,96(%r15) # store rtld_fini/stack_end to parameter area
	171	la %r7,96(%r15)
06b31ad3 RM	172	l %r6,.L2-.Llit(%r13) # load pointer to __libc_csu_fini
06b31ad3 RM	173	l %r5,.L1-.Llit(%r13) # load pointer to __libc_csu_init
847b055c	174	l %r2,.L3-.Llit(%r13) # load pointer to main
57a5ea02 UD	175	l %r1,.L4-.Llit(%r13) # load pointer to __libc_start_main
	176	#ifdef PIC
	177	l %r12,.L5-.Llit(%r13) # load .got pointer
	178	la %r6,0(%r13,%r6)
	179	la %r5,0(%r13,%r5)
a334319f	180	la %r12,0(%r13,%r12)
308bb2d5 UD	181	l %r2,0(%r12,%r2)
308bb2d5 UD	182	la %r1,0(%r13,%r1)
57a5ea02	183	#endif
847b055c AJ	184
847b055c AJ	185	/* ok, now branch to the libc main routine */
847b055c AJ	186	basr %r14,%r1
	187
	188	/* crash if __libc_start_main returns */
	189	.word 0
	190
	191	.Llit:
57a5ea02	192	#ifndef PIC
06b31ad3 RM	193	.L1: .long __libc_csu_init
06b31ad3 RM	194	.L2: .long __libc_csu_fini
847b055c AJ	195	.L3: .long main
847b055c AJ	196	.L4: .long __libc_start_main
57a5ea02 UD	197	#else
	198	.L1: .long __libc_csu_init-.Llit
	199	.L2: .long __libc_csu_fini-.Llit
308bb2d5	200	.L3: .long main@GOT
57a5ea02 UD	201	.L4: .long __libc_start_main@plt-.Llit
	202	.L5: .long _GLOBAL_OFFSET_TABLE_-.Llit
	203	#endif
847b055c	204
847b055c AJ	205	/* Define a symbol for the first piece of initialized data. */
	206	.data
	207	.globl __data_start
	208	__data_start:
	209	.long 0
	210	.weak data_start
	211	data_start = __data_start