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authorLinus Torvalds <torvalds@linux-foundation.org>2012-03-28 15:58:21 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-28 15:58:21 -0700
commit0195c00244dc2e9f522475868fa278c473ba7339 (patch)
treef97ca98ae64ede2c33ad3de05ed7bbfa4f4495ed /arch/x86/include/asm/switch_to.h
parentf21ce8f8447c8be8847dadcfdbcc76b0d7365fa5 (diff)
parent141124c02059eee9dbc5c86ea797b1ca888e77f7 (diff)
Merge tag 'split-asm_system_h-for-linus-20120328' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-asm_system
Pull "Disintegrate and delete asm/system.h" from David Howells: "Here are a bunch of patches to disintegrate asm/system.h into a set of separate bits to relieve the problem of circular inclusion dependencies. I've built all the working defconfigs from all the arches that I can and made sure that they don't break. The reason for these patches is that I recently encountered a circular dependency problem that came about when I produced some patches to optimise get_order() by rewriting it to use ilog2(). This uses bitops - and on the SH arch asm/bitops.h drags in asm-generic/get_order.h by a circuituous route involving asm/system.h. The main difficulty seems to be asm/system.h. It holds a number of low level bits with no/few dependencies that are commonly used (eg. memory barriers) and a number of bits with more dependencies that aren't used in many places (eg. switch_to()). These patches break asm/system.h up into the following core pieces: (1) asm/barrier.h Move memory barriers here. This already done for MIPS and Alpha. (2) asm/switch_to.h Move switch_to() and related stuff here. (3) asm/exec.h Move arch_align_stack() here. Other process execution related bits could perhaps go here from asm/processor.h. (4) asm/cmpxchg.h Move xchg() and cmpxchg() here as they're full word atomic ops and frequently used by atomic_xchg() and atomic_cmpxchg(). (5) asm/bug.h Move die() and related bits. (6) asm/auxvec.h Move AT_VECTOR_SIZE_ARCH here. Other arch headers are created as needed on a per-arch basis." Fixed up some conflicts from other header file cleanups and moving code around that has happened in the meantime, so David's testing is somewhat weakened by that. We'll find out anything that got broken and fix it.. * tag 'split-asm_system_h-for-linus-20120328' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-asm_system: (38 commits) Delete all instances of asm/system.h Remove all #inclusions of asm/system.h Add #includes needed to permit the removal of asm/system.h Move all declarations of free_initmem() to linux/mm.h Disintegrate asm/system.h for OpenRISC Split arch_align_stack() out from asm-generic/system.h Split the switch_to() wrapper out of asm-generic/system.h Move the asm-generic/system.h xchg() implementation to asm-generic/cmpxchg.h Create asm-generic/barrier.h Make asm-generic/cmpxchg.h #include asm-generic/cmpxchg-local.h Disintegrate asm/system.h for Xtensa Disintegrate asm/system.h for Unicore32 [based on ver #3, changed by gxt] Disintegrate asm/system.h for Tile Disintegrate asm/system.h for Sparc Disintegrate asm/system.h for SH Disintegrate asm/system.h for Score Disintegrate asm/system.h for S390 Disintegrate asm/system.h for PowerPC Disintegrate asm/system.h for PA-RISC Disintegrate asm/system.h for MN10300 ...
Diffstat (limited to 'arch/x86/include/asm/switch_to.h')
-rw-r--r--arch/x86/include/asm/switch_to.h129
1 files changed, 129 insertions, 0 deletions
diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
new file mode 100644
index 00000000000..4ec45b3abba
--- /dev/null
+++ b/arch/x86/include/asm/switch_to.h
@@ -0,0 +1,129 @@
+#ifndef _ASM_X86_SWITCH_TO_H
+#define _ASM_X86_SWITCH_TO_H
+
+struct task_struct; /* one of the stranger aspects of C forward declarations */
+struct task_struct *__switch_to(struct task_struct *prev,
+ struct task_struct *next);
+struct tss_struct;
+void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
+ struct tss_struct *tss);
+
+#ifdef CONFIG_X86_32
+
+#ifdef CONFIG_CC_STACKPROTECTOR
+#define __switch_canary \
+ "movl %P[task_canary](%[next]), %%ebx\n\t" \
+ "movl %%ebx, "__percpu_arg([stack_canary])"\n\t"
+#define __switch_canary_oparam \
+ , [stack_canary] "=m" (stack_canary.canary)
+#define __switch_canary_iparam \
+ , [task_canary] "i" (offsetof(struct task_struct, stack_canary))
+#else /* CC_STACKPROTECTOR */
+#define __switch_canary
+#define __switch_canary_oparam
+#define __switch_canary_iparam
+#endif /* CC_STACKPROTECTOR */
+
+/*
+ * Saving eflags is important. It switches not only IOPL between tasks,
+ * it also protects other tasks from NT leaking through sysenter etc.
+ */
+#define switch_to(prev, next, last) \
+do { \
+ /* \
+ * Context-switching clobbers all registers, so we clobber \
+ * them explicitly, via unused output variables. \
+ * (EAX and EBP is not listed because EBP is saved/restored \
+ * explicitly for wchan access and EAX is the return value of \
+ * __switch_to()) \
+ */ \
+ unsigned long ebx, ecx, edx, esi, edi; \
+ \
+ asm volatile("pushfl\n\t" /* save flags */ \
+ "pushl %%ebp\n\t" /* save EBP */ \
+ "movl %%esp,%[prev_sp]\n\t" /* save ESP */ \
+ "movl %[next_sp],%%esp\n\t" /* restore ESP */ \
+ "movl $1f,%[prev_ip]\n\t" /* save EIP */ \
+ "pushl %[next_ip]\n\t" /* restore EIP */ \
+ __switch_canary \
+ "jmp __switch_to\n" /* regparm call */ \
+ "1:\t" \
+ "popl %%ebp\n\t" /* restore EBP */ \
+ "popfl\n" /* restore flags */ \
+ \
+ /* output parameters */ \
+ : [prev_sp] "=m" (prev->thread.sp), \
+ [prev_ip] "=m" (prev->thread.ip), \
+ "=a" (last), \
+ \
+ /* clobbered output registers: */ \
+ "=b" (ebx), "=c" (ecx), "=d" (edx), \
+ "=S" (esi), "=D" (edi) \
+ \
+ __switch_canary_oparam \
+ \
+ /* input parameters: */ \
+ : [next_sp] "m" (next->thread.sp), \
+ [next_ip] "m" (next->thread.ip), \
+ \
+ /* regparm parameters for __switch_to(): */ \
+ [prev] "a" (prev), \
+ [next] "d" (next) \
+ \
+ __switch_canary_iparam \
+ \
+ : /* reloaded segment registers */ \
+ "memory"); \
+} while (0)
+
+#else /* CONFIG_X86_32 */
+
+/* frame pointer must be last for get_wchan */
+#define SAVE_CONTEXT "pushf ; pushq %%rbp ; movq %%rsi,%%rbp\n\t"
+#define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp ; popf\t"
+
+#define __EXTRA_CLOBBER \
+ , "rcx", "rbx", "rdx", "r8", "r9", "r10", "r11", \
+ "r12", "r13", "r14", "r15"
+
+#ifdef CONFIG_CC_STACKPROTECTOR
+#define __switch_canary \
+ "movq %P[task_canary](%%rsi),%%r8\n\t" \
+ "movq %%r8,"__percpu_arg([gs_canary])"\n\t"
+#define __switch_canary_oparam \
+ , [gs_canary] "=m" (irq_stack_union.stack_canary)
+#define __switch_canary_iparam \
+ , [task_canary] "i" (offsetof(struct task_struct, stack_canary))
+#else /* CC_STACKPROTECTOR */
+#define __switch_canary
+#define __switch_canary_oparam
+#define __switch_canary_iparam
+#endif /* CC_STACKPROTECTOR */
+
+/* Save restore flags to clear handle leaking NT */
+#define switch_to(prev, next, last) \
+ asm volatile(SAVE_CONTEXT \
+ "movq %%rsp,%P[threadrsp](%[prev])\n\t" /* save RSP */ \
+ "movq %P[threadrsp](%[next]),%%rsp\n\t" /* restore RSP */ \
+ "call __switch_to\n\t" \
+ "movq "__percpu_arg([current_task])",%%rsi\n\t" \
+ __switch_canary \
+ "movq %P[thread_info](%%rsi),%%r8\n\t" \
+ "movq %%rax,%%rdi\n\t" \
+ "testl %[_tif_fork],%P[ti_flags](%%r8)\n\t" \
+ "jnz ret_from_fork\n\t" \
+ RESTORE_CONTEXT \
+ : "=a" (last) \
+ __switch_canary_oparam \
+ : [next] "S" (next), [prev] "D" (prev), \
+ [threadrsp] "i" (offsetof(struct task_struct, thread.sp)), \
+ [ti_flags] "i" (offsetof(struct thread_info, flags)), \
+ [_tif_fork] "i" (_TIF_FORK), \
+ [thread_info] "i" (offsetof(struct task_struct, stack)), \
+ [current_task] "m" (current_task) \
+ __switch_canary_iparam \
+ : "memory", "cc" __EXTRA_CLOBBER)
+
+#endif /* CONFIG_X86_32 */
+
+#endif /* _ASM_X86_SWITCH_TO_H */