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galileo: Add a bootstrap stack for C runtime

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All we need to provide to C at this point is a region in memory dedicated to
its stack. This is done by allocating a region in .bss and pushing its start
address to esp. Since the multiboot spec says it is not safe to rely on the
initial stack provided by the bootloader, this patch provides our own stack.

Galileo boards have 512Kb of SRAM and 256Mb of DDR3 RAM, so providing 8kb as
a start seems safe. Moreover, stack sizes are very application-oriented
so it may be too early to provide a bigger (or smaller) stack.
This commit is contained in:
Jesus Sanchez-Palencia 2015-03-16 10:39:13 -03:00
parent 7a1898f73e
commit 595088be09
1 changed files with 8 additions and 0 deletions
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8
platform/galileo/loader.S
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@ -28,6 +28,10 @@
* OF THE POSSIBILITY OF SUCH DAMAGE. * OF THE POSSIBILITY OF SUCH DAMAGE.
*/ */
# Kernel
.set STACK_SIZE, 8192
# Multiboot
.set MAGIC_NUMBER, 0x1BADB002 .set MAGIC_NUMBER, 0x1BADB002
.set FLAGS, 0x0 .set FLAGS, 0x0
.set CHECKSUM, -MAGIC_NUMBER .set CHECKSUM, -MAGIC_NUMBER
@ -38,10 +42,14 @@
.long FLAGS .long FLAGS
.long CHECKSUM .long CHECKSUM
# Reserve space for the C stack.
.lcomm c_stack, STACK_SIZE
.section .text .section .text
.global start .global start
start: start:
cli cli
movl $(c_stack + STACK_SIZE), %esp
call main call main
/* We're not expected to return from main(). But if we do we halt */ /* We're not expected to return from main(). But if we do we halt */