PythonQ 248-8XX Especificaciones descargar pdf (Pagina 176)

14.3.4. Linux kernel register usage

For the Power Architecture® architecture, the Linux kernel uses the following registers:

R1:

stack pointer

R2:

pointer to task_struct for the current task

R3-R4:

parameter passing and return values

R5-R10:

parameter passing

R13:

small data area pointer

R30:

GOT pointer

R31:

frame pointer

A function can use r0 and r3 - r12 without saving and restoring them. r13 - r31 have to be preserved so

they must be saved and restored when you want to use them. Also, cr2 - cr4 must be preserved, while cr0,

cr1, cr5 - cr7, lr, ctr and xer can be used without saving & restoring them. [ Posted Tue, 15 Jul 2003

by Paul Mackerras to [email protected] ].

See also the (E)ABI specifications for the Power Architecture® architecture, Developing PowerPC Embedded

Application Binary Interface (EABI) Compliant Programs

14.3.5. Linux Kernel Ignores my bootargs

Question:

Why doesn't the kernel use the command-line options I set in the "bootargs" environment variable in

U-Boot when I boot my target system?

Answer:

This problem is typical for ARM systems only. The following discussion is ARM-centric:

First, check to ensure that you have configured your U-Boot build so that CONFIG_CMDLINE_TAG

is enabled. (Other tags like CONFIG_SETUP_MEMORY_TAGS or CONFIG_INITRD_TAG may be

needed, too.) This ensures that u-boot will boot the kernel with a command-line tag that incorporates

the kernel options you set in the "bootargs" environment variable.

If you have the CONFIG_CMDLINE_TAG option configured, the problem is almost certainly with

your kernel build. You have to instruct the kernel to pick up the boot tags at a certain address. This is

done in the machine descriptor macros, which are found in the processor start-up C code for your

architecture. For the Intel DBPXA250 "Lubbock" development board, the machine descriptor

macros are located at the bottom of the file arch/arm/mach-pxa/lubbock.c, and they look

like this:

MACHINE_START(LUBBOCK, "Intel DBPXA250 Development Platform")

MAINTAINER("MontaVista Software Inc.")

BOOT_MEM(0xa0000000, 0x40000000, io_p2v(0x40000000))

FIXUP(fixup_lubbock)

MAPIO(lubbock_map_io)

INITIRQ(lubbock_init_irq)

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