arch/powerpc/lib/checksum_32.S

Source file repositories/reference/linux-study-clean/arch/powerpc/lib/checksum_32.S

File Facts

System: Linux kernel
Corpus path: arch/powerpc/lib/checksum_32.S
Extension: .S
Size: 6422 bytes
Lines: 310
Domain: Architecture Layer
Bucket: arch/powerpc
Inferred role: Architecture Layer: exported/initcall integration point
Status: integration implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.
Exports symbols or registers init work; inspect boot/module ordering and who consumes the exported contract.
Defines or uses C structs; map object ownership, embedded links, reference counts, and lock ownership.

Dependency Surface

linux/export.h
linux/sys.h
asm/processor.h
asm/cache.h
asm/errno.h
asm/ppc_asm.h

Detected Declarations

export __csum_partial
export csum_partial_copy_generic
export csum_ipv6_magic

Annotated Snippet

#include <linux/export.h>
#include <linux/sys.h>
#include <asm/processor.h>
#include <asm/cache.h>
#include <asm/errno.h>
#include <asm/ppc_asm.h>

	.text

/*
 * computes the checksum of a memory block at buff, length len,
 * and adds in "sum" (32-bit)
 *
 * __csum_partial(buff, len, sum)
 */
_GLOBAL(__csum_partial)
	subi	r3,r3,4
	srawi.	r6,r4,2		/* Divide len by 4 and also clear carry */
	beq	3f		/* if we're doing < 4 bytes */
	andi.	r0,r3,2		/* Align buffer to longword boundary */
	beq+	1f
	lhz	r0,4(r3)	/* do 2 bytes to get aligned */
	subi	r4,r4,2
	addi	r3,r3,2
	srwi.	r6,r4,2		/* # words to do */
	adde	r5,r5,r0
	beq	3f
1:	andi.	r6,r6,3		/* Prepare to handle words 4 by 4 */
	beq	21f
	mtctr	r6
2:	lwzu	r0,4(r3)
	adde	r5,r5,r0
	bdnz	2b
21:	srwi.	r6,r4,4		/* # blocks of 4 words to do */
	beq	3f
	lwz	r0,4(r3)
	mtctr	r6
	lwz	r6,8(r3)
	adde	r5,r5,r0
	lwz	r7,12(r3)
	adde	r5,r5,r6
	lwzu	r8,16(r3)
	adde	r5,r5,r7
	bdz	23f
22:	lwz	r0,4(r3)
	adde	r5,r5,r8
	lwz	r6,8(r3)
	adde	r5,r5,r0
	lwz	r7,12(r3)
	adde	r5,r5,r6
	lwzu	r8,16(r3)
	adde	r5,r5,r7
	bdnz	22b
23:	adde	r5,r5,r8
3:	andi.	r0,r4,2
	beq+	4f
	lhz	r0,4(r3)
	addi	r3,r3,2
	adde	r5,r5,r0
4:	andi.	r0,r4,1
	beq+	5f
	lbz	r0,4(r3)
	slwi	r0,r0,8		/* Upper byte of word */
	adde	r5,r5,r0
5:	addze	r3,r5		/* add in final carry */
	blr
EXPORT_SYMBOL(__csum_partial)

/*
 * Computes the checksum of a memory block at src, length len,

Annotation

Immediate include surface: `linux/export.h`, `linux/sys.h`, `asm/processor.h`, `asm/cache.h`, `asm/errno.h`, `asm/ppc_asm.h`.
Detected declarations: `export __csum_partial`, `export csum_partial_copy_generic`, `export csum_ipv6_magic`.
Atlas domain: Architecture Layer / arch/powerpc.
Implementation status: integration implementation candidate.

Implementation Notes

This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.