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Message-ID: <20081127181008.GB23593@localhost> Date: Thu, 27 Nov 2008 21:10:08 +0300 From: Cyrill Gorcunov <gorcunov@...il.com> To: Ingo Molnar <mingo@...e.hu> Cc: Alexander van Heukelum <heukelum@...tmail.fm>, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH 5/5] x86: entry_64.S - trivial: space, comments fixup [Ingo Molnar - Thu, Nov 27, 2008 at 01:02:34PM +0100] | > > From: Cyrill Gorcunov <gorcunov@...il.com> | > > | > > Impact: cleanup | > > | > > Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com> | > | > Acked-by: Alexander van Heukelum <heukelum@...tmail.fm> | | Cyrill, could you please rework the still relevant bits against latest | tip/master? Alexander's wider patch got in the way. | | Thanks, | | Ingo | Here is an updated version --- From: Cyrill Gorcunov <gorcunov@...il.com> Subject: x86: entry_64.S - trivial: space, comments fixup Impact: cleanup Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com> --- arch/x86/kernel/entry_64.S | 94 ++++++++++++++++++++++----------------------- 1 file changed, 48 insertions(+), 46 deletions(-) Index: linux-2.6.git/arch/x86/kernel/entry_64.S =================================================================== --- linux-2.6.git.orig/arch/x86/kernel/entry_64.S +++ linux-2.6.git/arch/x86/kernel/entry_64.S @@ -1027,7 +1027,7 @@ END(\sym) .macro paranoidzeroentry_ist sym do_sym ist ENTRY(\sym) - INTR_FRAME + INTR_FRAME PARAVIRT_ADJUST_EXCEPTION_FRAME pushq $-1 /* ORIG_RAX: no syscall to restart */ CFI_ADJUST_CFA_OFFSET 8 @@ -1095,36 +1095,36 @@ zeroentry coprocessor_error do_coprocess errorentry alignment_check do_alignment_check zeroentry simd_coprocessor_error do_simd_coprocessor_error - /* Reload gs selector with exception handling */ - /* edi: new selector */ + /* Reload gs selector with exception handling */ + /* edi: new selector */ ENTRY(native_load_gs_index) CFI_STARTPROC pushf CFI_ADJUST_CFA_OFFSET 8 DISABLE_INTERRUPTS(CLBR_ANY | ~(CLBR_RDI)) - SWAPGS + SWAPGS gs_change: - movl %edi,%gs + movl %edi,%gs 2: mfence /* workaround */ SWAPGS - popf + popf CFI_ADJUST_CFA_OFFSET -8 - ret + ret CFI_ENDPROC END(native_load_gs_index) - .section __ex_table,"a" - .align 8 - .quad gs_change,bad_gs - .previous - .section .fixup,"ax" + .section __ex_table,"a" + .align 8 + .quad gs_change,bad_gs + .previous + .section .fixup,"ax" /* running with kernelgs */ bad_gs: SWAPGS /* switch back to user gs */ xorl %eax,%eax - movl %eax,%gs - jmp 2b - .previous + movl %eax,%gs + jmp 2b + .previous /* * Create a kernel thread. @@ -1159,7 +1159,7 @@ ENTRY(kernel_thread) * so internally to the x86_64 port you can rely on kernel_thread() * not to reschedule the child before returning, this avoids the need * of hacks for example to fork off the per-CPU idle tasks. - * [Hopefully no generic code relies on the reschedule -AK] + * [Hopefully no generic code relies on the reschedule -AK] */ RESTORE_ALL UNFAKE_STACK_FRAME @@ -1239,22 +1239,24 @@ END(call_softirq) zeroentry xen_hypervisor_callback xen_do_hypervisor_callback /* -# A note on the "critical region" in our callback handler. -# We want to avoid stacking callback handlers due to events occurring -# during handling of the last event. To do this, we keep events disabled -# until we've done all processing. HOWEVER, we must enable events before -# popping the stack frame (can't be done atomically) and so it would still -# be possible to get enough handler activations to overflow the stack. -# Although unlikely, bugs of that kind are hard to track down, so we'd -# like to avoid the possibility. -# So, on entry to the handler we detect whether we interrupted an -# existing activation in its critical region -- if so, we pop the current -# activation and restart the handler using the previous one. -*/ + * A note on the "critical region" in our callback handler. + * We want to avoid stacking callback handlers due to events occurring + * during handling of the last event. To do this, we keep events disabled + * until we've done all processing. HOWEVER, we must enable events before + * popping the stack frame (can't be done atomically) and so it would still + * be possible to get enough handler activations to overflow the stack. + * Although unlikely, bugs of that kind are hard to track down, so we'd + * like to avoid the possibility. + * So, on entry to the handler we detect whether we interrupted an + * existing activation in its critical region -- if so, we pop the current + * activation and restart the handler using the previous one. + */ ENTRY(xen_do_hypervisor_callback) # do_hypervisor_callback(struct *pt_regs) CFI_STARTPROC -/* Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will - see the correct pointer to the pt_regs */ +/* + * Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will + * see the correct pointer to the pt_regs + */ movq %rdi, %rsp # we don't return, adjust the stack frame CFI_ENDPROC DEFAULT_FRAME @@ -1272,18 +1274,18 @@ ENTRY(xen_do_hypervisor_callback) # do END(do_hypervisor_callback) /* -# Hypervisor uses this for application faults while it executes. -# We get here for two reasons: -# 1. Fault while reloading DS, ES, FS or GS -# 2. Fault while executing IRET -# Category 1 we do not need to fix up as Xen has already reloaded all segment -# registers that could be reloaded and zeroed the others. -# Category 2 we fix up by killing the current process. We cannot use the -# normal Linux return path in this case because if we use the IRET hypercall -# to pop the stack frame we end up in an infinite loop of failsafe callbacks. -# We distinguish between categories by comparing each saved segment register -# with its current contents: any discrepancy means we in category 1. -*/ + * Hypervisor uses this for application faults while it executes. + * We get here for two reasons: + * 1. Fault while reloading DS, ES, FS or GS + * 2. Fault while executing IRET + * Category 1 we do not need to fix up as Xen has already reloaded all segment + * registers that could be reloaded and zeroed the others. + * Category 2 we fix up by killing the current process. We cannot use the + * normal Linux return path in this case because if we use the IRET hypercall + * to pop the stack frame we end up in an infinite loop of failsafe callbacks. + * We distinguish between categories by comparing each saved segment register + * with its current contents: any discrepancy means we in category 1. + */ ENTRY(xen_failsafe_callback) INTR_FRAME 1 (6*8) /*CFI_REL_OFFSET gs,GS*/ @@ -1347,8 +1349,8 @@ paranoidzeroentry machine_check do_machi #endif /* - * "Paranoid" exit path from exception stack. - * Paranoid because this is used by NMIs and cannot take + * "Paranoid" exit path from exception stack. + * Paranoid because this is used by NMIs and cannot take * any kernel state for granted. * We don't do kernel preemption checks here, because only * NMI should be common and it does not enable IRQs and @@ -1453,7 +1455,7 @@ error_kernelspace: cmpq %rcx,RIP+8(%rsp) je error_swapgs cmpq $gs_change,RIP+8(%rsp) - je error_swapgs + je error_swapgs jmp error_sti END(error_entry) @@ -1529,7 +1531,7 @@ nmi_schedule: CFI_ENDPROC #else jmp paranoid_exit - CFI_ENDPROC + CFI_ENDPROC #endif END(nmi) -- 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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