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Date: Mon, 5 Dec 2011 10:01:46 -0800 From: tip-bot for Jan Beulich <JBeulich@...e.com> To: linux-tip-commits@...r.kernel.org Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com, jbeulich@...e.com, JBeulich@...e.com, ak@...ux.intel.com, tglx@...utronix.de, mingo@...e.hu Subject: [tip:x86/asm] x86-64: Slightly shorten line system call entry and exit paths Commit-ID: 46db09d3fd847f185a7d23a96bc8fe7a4be0cd05 Gitweb: http://git.kernel.org/tip/46db09d3fd847f185a7d23a96bc8fe7a4be0cd05 Author: Jan Beulich <JBeulich@...e.com> AuthorDate: Tue, 29 Nov 2011 11:17:45 +0000 Committer: Ingo Molnar <mingo@...e.hu> CommitDate: Mon, 5 Dec 2011 17:24:41 +0100 x86-64: Slightly shorten line system call entry and exit paths GET_THREAD_INFO() involves a memory read immediately followed by an "sub" on the value read, in turn (in several cases) immediately followed by a use of the calculated value as the base address of a memory access. This combination of instructions has a non-negligible potential for stalls. In the system call entry point code, however, the (fixed) offset of the stack pointer from the end of the stack is generally known, and hence we can instead avoid the memory load and subtract, and instead do the memory reference using %rsp as the base register. To do so in a legible fashion, introduce a THREAD_INFO() macro which, provided a register (generally %rsp) and the known offset from the end of the stack, produces a suitable memory access operand. The patch attempts to only touch the fast paths (no auditing and alike), but manages to do so only in the 64-bit entry point case; the compatibility mode entry points have so many interdependencies between their various branch targets that it was necessary to also adjust the slow paths to eliminate the risk of having missed some register dependency during code analysis. Signed-off-by: Jan Beulich <jbeulich@...e.com> Reviewed-by: Andi Kleen <ak@...ux.intel.com> Link: http://lkml.kernel.org/r/4ED4CD690200007800064075@nat28.tlf.novell.com Signed-off-by: Ingo Molnar <mingo@...e.hu> --- arch/x86/ia32/ia32entry.S | 36 +++++++++++++++--------------------- arch/x86/include/asm/thread_info.h | 6 ++++++ arch/x86/kernel/entry_64.S | 8 +++----- 3 files changed, 24 insertions(+), 26 deletions(-) diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index a6253ec..0d5c279 100644 --- a/arch/x86/ia32/ia32entry.S +++ b/arch/x86/ia32/ia32entry.S @@ -134,7 +134,7 @@ ENTRY(ia32_sysenter_target) CFI_REL_OFFSET rsp,0 pushfq_cfi /*CFI_REL_OFFSET rflags,0*/ - movl 8*3-THREAD_SIZE+TI_sysenter_return(%rsp), %r10d + movl TI_sysenter_return+THREAD_INFO(%rsp,3*8-KERNEL_STACK_OFFSET),%r10d CFI_REGISTER rip,r10 pushq_cfi $__USER32_CS /*CFI_REL_OFFSET cs,0*/ @@ -150,9 +150,8 @@ ENTRY(ia32_sysenter_target) .section __ex_table,"a" .quad 1b,ia32_badarg .previous - GET_THREAD_INFO(%r10) - orl $TS_COMPAT,TI_status(%r10) - testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10) + orl $TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP-ARGOFFSET) + testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) CFI_REMEMBER_STATE jnz sysenter_tracesys cmpq $(IA32_NR_syscalls-1),%rax @@ -162,13 +161,12 @@ sysenter_do_call: sysenter_dispatch: call *ia32_sys_call_table(,%rax,8) movq %rax,RAX-ARGOFFSET(%rsp) - GET_THREAD_INFO(%r10) DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF - testl $_TIF_ALLWORK_MASK,TI_flags(%r10) + testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) jnz sysexit_audit sysexit_from_sys_call: - andl $~TS_COMPAT,TI_status(%r10) + andl $~TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP-ARGOFFSET) /* clear IF, that popfq doesn't enable interrupts early */ andl $~0x200,EFLAGS-R11(%rsp) movl RIP-R11(%rsp),%edx /* User %eip */ @@ -205,7 +203,7 @@ sysexit_from_sys_call: .endm .macro auditsys_exit exit - testl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),TI_flags(%r10) + testl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) jnz ia32_ret_from_sys_call TRACE_IRQS_ON sti @@ -215,12 +213,11 @@ sysexit_from_sys_call: movzbl %al,%edi /* zero-extend that into %edi */ inc %edi /* first arg, 0->1(AUDITSC_SUCCESS), 1->2(AUDITSC_FAILURE) */ call audit_syscall_exit - GET_THREAD_INFO(%r10) movl RAX-ARGOFFSET(%rsp),%eax /* reload syscall return value */ movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),%edi cli TRACE_IRQS_OFF - testl %edi,TI_flags(%r10) + testl %edi,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) jz \exit CLEAR_RREGS -ARGOFFSET jmp int_with_check @@ -238,7 +235,7 @@ sysexit_audit: sysenter_tracesys: #ifdef CONFIG_AUDITSYSCALL - testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags(%r10) + testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) jz sysenter_auditsys #endif SAVE_REST @@ -309,9 +306,8 @@ ENTRY(ia32_cstar_target) .section __ex_table,"a" .quad 1b,ia32_badarg .previous - GET_THREAD_INFO(%r10) - orl $TS_COMPAT,TI_status(%r10) - testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10) + orl $TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP-ARGOFFSET) + testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) CFI_REMEMBER_STATE jnz cstar_tracesys cmpq $IA32_NR_syscalls-1,%rax @@ -321,13 +317,12 @@ cstar_do_call: cstar_dispatch: call *ia32_sys_call_table(,%rax,8) movq %rax,RAX-ARGOFFSET(%rsp) - GET_THREAD_INFO(%r10) DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF - testl $_TIF_ALLWORK_MASK,TI_flags(%r10) + testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) jnz sysretl_audit sysretl_from_sys_call: - andl $~TS_COMPAT,TI_status(%r10) + andl $~TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP-ARGOFFSET) RESTORE_ARGS 0,-ARG_SKIP,0,0,0 movl RIP-ARGOFFSET(%rsp),%ecx CFI_REGISTER rip,rcx @@ -355,7 +350,7 @@ sysretl_audit: cstar_tracesys: #ifdef CONFIG_AUDITSYSCALL - testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags(%r10) + testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) jz cstar_auditsys #endif xchgl %r9d,%ebp @@ -420,9 +415,8 @@ ENTRY(ia32_syscall) /* note the registers are not zero extended to the sf. this could be a problem. */ SAVE_ARGS 0,1,0 - GET_THREAD_INFO(%r10) - orl $TS_COMPAT,TI_status(%r10) - testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10) + orl $TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP-ARGOFFSET) + testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) jnz ia32_tracesys cmpq $(IA32_NR_syscalls-1),%rax ja ia32_badsys diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index 25ebd79..185b719 100644 --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -232,6 +232,12 @@ static inline struct thread_info *current_thread_info(void) movq PER_CPU_VAR(kernel_stack),reg ; \ subq $(THREAD_SIZE-KERNEL_STACK_OFFSET),reg +/* + * Same if PER_CPU_VAR(kernel_stack) is, perhaps with some offset, already in + * a certain register (to be used in assembler memory operands). + */ +#define THREAD_INFO(reg, off) KERNEL_STACK_OFFSET+(off)-THREAD_SIZE(reg) + #endif #endif /* !X86_32 */ diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 1581f19..75f72a5 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -478,8 +478,7 @@ ENTRY(system_call_after_swapgs) movq %rax,ORIG_RAX-ARGOFFSET(%rsp) movq %rcx,RIP-ARGOFFSET(%rsp) CFI_REL_OFFSET rip,RIP-ARGOFFSET - GET_THREAD_INFO(%rcx) - testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%rcx) + testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) jnz tracesys system_call_fastpath: cmpq $__NR_syscall_max,%rax @@ -496,10 +495,9 @@ ret_from_sys_call: /* edi: flagmask */ sysret_check: LOCKDEP_SYS_EXIT - GET_THREAD_INFO(%rcx) DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF - movl TI_flags(%rcx),%edx + movl TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET),%edx andl %edi,%edx jnz sysret_careful CFI_REMEMBER_STATE @@ -583,7 +581,7 @@ sysret_audit: /* Do syscall tracing */ tracesys: #ifdef CONFIG_AUDITSYSCALL - testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags(%rcx) + testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) jz auditsys #endif SAVE_REST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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