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author | Jan Beulich <JBeulich@suse.com> | 2011-11-29 11:17:45 +0000 |
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committer | Ingo Molnar <mingo@elte.hu> | 2011-12-05 17:24:41 +0100 |
commit | 46db09d3fd847f185a7d23a96bc8fe7a4be0cd05 (patch) | |
tree | 1134b3244ebe89208856c35bf86138d2b1ed791e /arch/x86/ia32/ia32entry.S | |
parent | 39e9543344fa3179e346d2b381c6e0cd17b516de (diff) | |
download | linux-46db09d3fd847f185a7d23a96bc8fe7a4be0cd05.tar.gz linux-46db09d3fd847f185a7d23a96bc8fe7a4be0cd05.tar.bz2 linux-46db09d3fd847f185a7d23a96bc8fe7a4be0cd05.zip |
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@suse.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/4ED4CD690200007800064075@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/ia32/ia32entry.S')
-rw-r--r-- | arch/x86/ia32/ia32entry.S | 36 |
1 files changed, 15 insertions, 21 deletions
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index a6253ec1b284..0d5c279f3732 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 |