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Diffstat (limited to 'kernel/arch/x86/lib/rwsem.S')
| -rw-r--r-- | kernel/arch/x86/lib/rwsem.S | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/kernel/arch/x86/lib/rwsem.S b/kernel/arch/x86/lib/rwsem.S new file mode 100644 index 000000000..2322abe4d --- /dev/null +++ b/kernel/arch/x86/lib/rwsem.S @@ -0,0 +1,132 @@ +/* + * x86 semaphore implementation. + * + * (C) Copyright 1999 Linus Torvalds + * + * Portions Copyright 1999 Red Hat, Inc. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + * + * rw semaphores implemented November 1999 by Benjamin LaHaise <bcrl@kvack.org> + */ + +#include <linux/linkage.h> +#include <asm/alternative-asm.h> +#include <asm/dwarf2.h> + +#define __ASM_HALF_REG(reg) __ASM_SEL(reg, e##reg) +#define __ASM_HALF_SIZE(inst) __ASM_SEL(inst##w, inst##l) + +#ifdef CONFIG_X86_32 + +/* + * The semaphore operations have a special calling sequence that + * allow us to do a simpler in-line version of them. These routines + * need to convert that sequence back into the C sequence when + * there is contention on the semaphore. + * + * %eax contains the semaphore pointer on entry. Save the C-clobbered + * registers (%eax, %edx and %ecx) except %eax whish is either a return + * value or just clobbered.. + */ + +#define save_common_regs \ + pushl_cfi_reg ecx + +#define restore_common_regs \ + popl_cfi_reg ecx + + /* Avoid uglifying the argument copying x86-64 needs to do. */ + .macro movq src, dst + .endm + +#else + +/* + * x86-64 rwsem wrappers + * + * This interfaces the inline asm code to the slow-path + * C routines. We need to save the call-clobbered regs + * that the asm does not mark as clobbered, and move the + * argument from %rax to %rdi. + * + * NOTE! We don't need to save %rax, because the functions + * will always return the semaphore pointer in %rax (which + * is also the input argument to these helpers) + * + * The following can clobber %rdx because the asm clobbers it: + * call_rwsem_down_write_failed + * call_rwsem_wake + * but %rdi, %rsi, %rcx, %r8-r11 always need saving. + */ + +#define save_common_regs \ + pushq_cfi_reg rdi; \ + pushq_cfi_reg rsi; \ + pushq_cfi_reg rcx; \ + pushq_cfi_reg r8; \ + pushq_cfi_reg r9; \ + pushq_cfi_reg r10; \ + pushq_cfi_reg r11 + +#define restore_common_regs \ + popq_cfi_reg r11; \ + popq_cfi_reg r10; \ + popq_cfi_reg r9; \ + popq_cfi_reg r8; \ + popq_cfi_reg rcx; \ + popq_cfi_reg rsi; \ + popq_cfi_reg rdi + +#endif + +/* Fix up special calling conventions */ +ENTRY(call_rwsem_down_read_failed) + CFI_STARTPROC + save_common_regs + __ASM_SIZE(push,_cfi_reg) __ASM_REG(dx) + movq %rax,%rdi + call rwsem_down_read_failed + __ASM_SIZE(pop,_cfi_reg) __ASM_REG(dx) + restore_common_regs + ret + CFI_ENDPROC +ENDPROC(call_rwsem_down_read_failed) + +ENTRY(call_rwsem_down_write_failed) + CFI_STARTPROC + save_common_regs + movq %rax,%rdi + call rwsem_down_write_failed + restore_common_regs + ret + CFI_ENDPROC +ENDPROC(call_rwsem_down_write_failed) + +ENTRY(call_rwsem_wake) + CFI_STARTPROC + /* do nothing if still outstanding active readers */ + __ASM_HALF_SIZE(dec) %__ASM_HALF_REG(dx) + jnz 1f + save_common_regs + movq %rax,%rdi + call rwsem_wake + restore_common_regs +1: ret + CFI_ENDPROC +ENDPROC(call_rwsem_wake) + +ENTRY(call_rwsem_downgrade_wake) + CFI_STARTPROC + save_common_regs + __ASM_SIZE(push,_cfi_reg) __ASM_REG(dx) + movq %rax,%rdi + call rwsem_downgrade_wake + __ASM_SIZE(pop,_cfi_reg) __ASM_REG(dx) + restore_common_regs + ret + CFI_ENDPROC +ENDPROC(call_rwsem_downgrade_wake) |