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Date: Thu, 27 Nov 2008 11:39:01 +0100 From: "Alexander van Heukelum" <heukelum@...tmail.fm> To: "Cyrill Gorcunov" <gorcunov@...il.com>, "Ingo Molnar" <mingo@...e.hu>, "Thomas Gleixner" <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com> Cc: linux-kernel@...r.kernel.org, "Cyrill Gorcunov" <gorcunov@...il.com> Subject: Re: [PATCH 5/5] x86: entry_64.S - trivial: space, comments fixup On Wed, 26 Nov 2008 22:17:04 +0300, gorcunov@...il.com said: > From: Cyrill Gorcunov <gorcunov@...il.com> > > Impact: cleanup > > Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com> Acked-by: Alexander van Heukelum <heukelum@...tmail.fm> > arch/x86/kernel/entry_64.S | 92 > ++++++++++++++++++++++--------------------- > 1 files changed, 47 insertions(+), 45 deletions(-) > > diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S > index a21be86..5ccf410 100644 > --- a/arch/x86/kernel/entry_64.S > +++ b/arch/x86/kernel/entry_64.S > @@ -1119,8 +1119,8 @@ paranoidzeroentry machine_check do_machine_check > zeroentry simd_coprocessor_error do_simd_coprocessor_error > > /* > - * "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 > @@ -1225,7 +1225,7 @@ 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 > KPROBE_END(error_entry) > > @@ -1249,36 +1249,36 @@ KPROBE_ENTRY(error_exit) > CFI_ENDPROC > KPROBE_END(error_exit) > > - /* 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. > @@ -1313,7 +1313,7 @@ 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 > @@ -1420,7 +1420,7 @@ nmi_schedule: > CFI_ENDPROC > #else > jmp paranoid_exit > - CFI_ENDPROC > + CFI_ENDPROC > #endif > KPROBE_END(nmi) > > @@ -1455,22 +1455,24 @@ KPROBE_END(ignore_sysret) > 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 > @@ -1488,18 +1490,18 @@ ENTRY(xen_do_hypervisor_callback) # > do_hypervisor_callback(struct *pt_regs) > 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*/ > -- > 1.6.0.4.603.gbc9c0 > -- Alexander van Heukelum heukelum@...tmail.fm -- http://www.fastmail.fm - The way an email service should be -- 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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