tools/testing/selftests/x86/thunks.S

Source file repositories/reference/linux-study-clean/tools/testing/selftests/x86/thunks.S

File Facts

System: Linux kernel
Corpus path: tools/testing/selftests/x86/thunks.S
Extension: .S
Size: 916 bytes
Lines: 62
Domain: Support Tooling And Documentation
Bucket: tools
Inferred role: Support Tooling And Documentation: tools
Status: atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

No C-style include directives detected by the generator.

Detected Declarations

No top-level syscall, struct, function, initcall, or export declaration detected by the generator.

Annotated Snippet

.text

	.global call32_from_64
	.type call32_from_64, @function
call32_from_64:
	// rdi: stack to use
	// esi: function to call

	// Save registers
	pushq %rbx
	pushq %rbp
	pushq %r12
	pushq %r13
	pushq %r14
	pushq %r15
	pushfq

	// Switch stacks
	mov %rsp,(%rdi)
	mov %rdi,%rsp

	// Switch to compatibility mode
	pushq $0x23  /* USER32_CS */
	pushq $1f
	lretq

1:
	.code32
	// Call the function
	call *%esi
	// Switch back to long mode
	jmp $0x33,$1f
	.code64

1:
	// Restore the stack
	mov (%rsp),%rsp

	// Restore registers
	popfq
	popq %r15
	popq %r14
	popq %r13
	popq %r12
	popq %rbp
	popq %rbx

	ret

.size call32_from_64, .-call32_from_64

.section .note.GNU-stack,"",%progbits

Annotation

Atlas domain: Support Tooling And Documentation / tools.
Implementation status: atlas-only.

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.