android_kernel_xiaomi_sm8350/arch/x86/kernel/vmlinux_32.lds.S
Jeremy Fitzhardinge 93dbda7cbc x86: add brk allocation for very, very early allocations
Impact: new interface

Add a brk()-like allocator which effectively extends the bss in order
to allow very early code to do dynamic allocations.  This is better than
using statically allocated arrays for data in subsystems which may never
get used.

The space for brk allocations is in the bss ELF segment, so that the
space is mapped properly by the code which maps the kernel, and so
that bootloaders keep the space free rather than putting a ramdisk or
something into it.

The bss itself, delimited by __bss_stop, ends before the brk area
(__brk_base to __brk_limit).  The kernel text, data and bss is reserved
up to __bss_stop.

Any brk-allocated data is reserved separately just before the kernel
pagetable is built, as that code allocates from unreserved spaces
in the e820 map, potentially allocating from any unused brk memory.
Ultimately any unused memory in the brk area is used in the general
kernel memory pool.

Initially the brk space is set to 1MB, which is probably much larger
than any user needs (the largest current user is i386 head_32.S's code
to build the pagetables to map the kernel, which can get fairly large
with a big kernel image and no PSE support).  So long as the system
has sufficient memory for the bootloader to reserve the kernel+1MB brk,
there are no bad effects resulting from an over-large brk.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2009-03-14 15:37:14 -07:00

222 lines
5.3 KiB
ArmAsm

/* ld script to make i386 Linux kernel
* Written by Martin Mares <mj@atrey.karlin.mff.cuni.cz>;
*
* Don't define absolute symbols until and unless you know that symbol
* value is should remain constant even if kernel image is relocated
* at run time. Absolute symbols are not relocated. If symbol value should
* change if kernel is relocated, make the symbol section relative and
* put it inside the section definition.
*/
#define LOAD_OFFSET __PAGE_OFFSET
#include <asm-generic/vmlinux.lds.h>
#include <asm/thread_info.h>
#include <asm/page_types.h>
#include <asm/cache.h>
#include <asm/boot.h>
OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386")
OUTPUT_ARCH(i386)
ENTRY(phys_startup_32)
jiffies = jiffies_64;
PHDRS {
text PT_LOAD FLAGS(5); /* R_E */
data PT_LOAD FLAGS(7); /* RWE */
note PT_NOTE FLAGS(0); /* ___ */
}
SECTIONS
{
. = LOAD_OFFSET + LOAD_PHYSICAL_ADDR;
phys_startup_32 = startup_32 - LOAD_OFFSET;
.text.head : AT(ADDR(.text.head) - LOAD_OFFSET) {
_text = .; /* Text and read-only data */
*(.text.head)
} :text = 0x9090
/* read-only */
.text : AT(ADDR(.text) - LOAD_OFFSET) {
. = ALIGN(PAGE_SIZE); /* not really needed, already page aligned */
*(.text.page_aligned)
TEXT_TEXT
SCHED_TEXT
LOCK_TEXT
KPROBES_TEXT
IRQENTRY_TEXT
*(.fixup)
*(.gnu.warning)
_etext = .; /* End of text section */
} :text = 0x9090
NOTES :text :note
. = ALIGN(16); /* Exception table */
__ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {
__start___ex_table = .;
*(__ex_table)
__stop___ex_table = .;
} :text = 0x9090
RODATA
/* writeable */
. = ALIGN(PAGE_SIZE);
.data : AT(ADDR(.data) - LOAD_OFFSET) { /* Data */
DATA_DATA
CONSTRUCTORS
} :data
. = ALIGN(PAGE_SIZE);
.data_nosave : AT(ADDR(.data_nosave) - LOAD_OFFSET) {
__nosave_begin = .;
*(.data.nosave)
. = ALIGN(PAGE_SIZE);
__nosave_end = .;
}
. = ALIGN(PAGE_SIZE);
.data.page_aligned : AT(ADDR(.data.page_aligned) - LOAD_OFFSET) {
*(.data.page_aligned)
*(.data.idt)
}
. = ALIGN(32);
.data.cacheline_aligned : AT(ADDR(.data.cacheline_aligned) - LOAD_OFFSET) {
*(.data.cacheline_aligned)
}
/* rarely changed data like cpu maps */
. = ALIGN(32);
.data.read_mostly : AT(ADDR(.data.read_mostly) - LOAD_OFFSET) {
*(.data.read_mostly)
_edata = .; /* End of data section */
}
. = ALIGN(THREAD_SIZE); /* init_task */
.data.init_task : AT(ADDR(.data.init_task) - LOAD_OFFSET) {
*(.data.init_task)
}
/* might get freed after init */
. = ALIGN(PAGE_SIZE);
.smp_locks : AT(ADDR(.smp_locks) - LOAD_OFFSET) {
__smp_locks = .;
*(.smp_locks)
__smp_locks_end = .;
}
/* will be freed after init
* Following ALIGN() is required to make sure no other data falls on the
* same page where __smp_alt_end is pointing as that page might be freed
* after boot. Always make sure that ALIGN() directive is present after
* the section which contains __smp_alt_end.
*/
. = ALIGN(PAGE_SIZE);
/* will be freed after init */
. = ALIGN(PAGE_SIZE); /* Init code and data */
.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
__init_begin = .;
_sinittext = .;
INIT_TEXT
_einittext = .;
}
.init.data : AT(ADDR(.init.data) - LOAD_OFFSET) {
INIT_DATA
}
. = ALIGN(16);
.init.setup : AT(ADDR(.init.setup) - LOAD_OFFSET) {
__setup_start = .;
*(.init.setup)
__setup_end = .;
}
.initcall.init : AT(ADDR(.initcall.init) - LOAD_OFFSET) {
__initcall_start = .;
INITCALLS
__initcall_end = .;
}
.con_initcall.init : AT(ADDR(.con_initcall.init) - LOAD_OFFSET) {
__con_initcall_start = .;
*(.con_initcall.init)
__con_initcall_end = .;
}
.x86_cpu_dev.init : AT(ADDR(.x86_cpu_dev.init) - LOAD_OFFSET) {
__x86_cpu_dev_start = .;
*(.x86_cpu_dev.init)
__x86_cpu_dev_end = .;
}
SECURITY_INIT
. = ALIGN(4);
.altinstructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) {
__alt_instructions = .;
*(.altinstructions)
__alt_instructions_end = .;
}
.altinstr_replacement : AT(ADDR(.altinstr_replacement) - LOAD_OFFSET) {
*(.altinstr_replacement)
}
. = ALIGN(4);
.parainstructions : AT(ADDR(.parainstructions) - LOAD_OFFSET) {
__parainstructions = .;
*(.parainstructions)
__parainstructions_end = .;
}
/* .exit.text is discard at runtime, not link time, to deal with references
from .altinstructions and .eh_frame */
.exit.text : AT(ADDR(.exit.text) - LOAD_OFFSET) {
EXIT_TEXT
}
.exit.data : AT(ADDR(.exit.data) - LOAD_OFFSET) {
EXIT_DATA
}
#if defined(CONFIG_BLK_DEV_INITRD)
. = ALIGN(PAGE_SIZE);
.init.ramfs : AT(ADDR(.init.ramfs) - LOAD_OFFSET) {
__initramfs_start = .;
*(.init.ramfs)
__initramfs_end = .;
}
#endif
PERCPU(PAGE_SIZE)
. = ALIGN(PAGE_SIZE);
/* freed after init ends here */
.bss : AT(ADDR(.bss) - LOAD_OFFSET) {
__init_end = .;
__bss_start = .; /* BSS */
*(.bss.page_aligned)
*(.bss)
. = ALIGN(4);
__bss_stop = .;
. = ALIGN(PAGE_SIZE);
__brk_base = . ;
. += 1024 * 1024 ;
__brk_limit = . ;
_end = . ;
/* This is where the kernel creates the early boot page tables */
. = ALIGN(PAGE_SIZE);
pg0 = . ;
}
/* Sections to be discarded */
/DISCARD/ : {
*(.exitcall.exit)
}
STABS_DEBUG
DWARF_DEBUG
}
#ifdef CONFIG_KEXEC
/* Link time checks */
#include <asm/kexec.h>
ASSERT(kexec_control_code_size <= KEXEC_CONTROL_CODE_MAX_SIZE,
"kexec control code size is too big")
#endif