From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [patch V2 09/29] x86/exceptions: Add structs for exception stacks
Date: Fri, 5 Apr 2019 13:50:34 -0700 [thread overview]
Message-ID: <20190405205034.GD15808@linux.intel.com> (raw)
In-Reply-To: <20190405204838.GC15808@linux.intel.com>
On Fri, Apr 05, 2019 at 01:48:38PM -0700, Sean Christopherson wrote:
> On Fri, Apr 05, 2019 at 05:07:07PM +0200, Thomas Gleixner wrote:
> > At the moment everything assumes a full linear mapping of the various
> > exception stacks. Adding guard pages to the cpu entry area mapping of the
> > exception stacks will break that assumption.
> >
> > As a preparatory step convert both the real storage and the effective
> > mapping in the cpu entry area from character arrays to structures.
> >
> > To ensure that both arrays have the same ordering and the same size of the
> > individual stacks fill the members with a macro. The guard size is the only
> > difference between the two resulting structures. For now both have guard
> > size 0 until the preparation of all usage sites is done.
> >
> > Provide a couple of helper macros which are used in the following
> > conversions.
> >
> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> > ---
> > arch/x86/include/asm/cpu_entry_area.h | 51 ++++++++++++++++++++++++++++++----
> > arch/x86/kernel/cpu/common.c | 2 -
> > arch/x86/mm/cpu_entry_area.c | 8 ++---
> > 3 files changed, 50 insertions(+), 11 deletions(-)
> >
> > --- a/arch/x86/include/asm/cpu_entry_area.h
> > +++ b/arch/x86/include/asm/cpu_entry_area.h
> > @@ -7,6 +7,50 @@
> > #include <asm/processor.h>
> > #include <asm/intel_ds.h>
> >
> > +#ifdef CONFIG_X86_64
> > +
> > +/* Macro to enforce the same ordering and stack sizes */
> > +#define ESTACKS_MEMBERS(guardsize) \
> > + char DF_stack[EXCEPTION_STKSZ]; \
> > + char DF_stack_guard[guardsize]; \
> > + char NMI_stack[EXCEPTION_STKSZ]; \
> > + char NMI_stack_guard[guardsize]; \
> > + char DB_stack[DEBUG_STKSZ]; \
> > + char DB_stack_guard[guardsize]; \
> > + char MCE_stack[EXCEPTION_STKSZ]; \
> > + char MCE_stack_guard[guardsize]; \
>
> Conceptually, shouldn't the stack guard precede its associated stack
> since the stacks grow down? And don't we want a guard page below the
> DF_stack? There could still be a guard page above MCE_stack,
> e.g. IST_stack_guard or something.
>
> E.g. the example in patch "Speedup in_exception_stack()" also suggests
Gah, the example is from "x86/exceptions: Split debug IST stack".
> that "guard page" is associated with the stack physical above it:
>
> --- top of DB_stack <- Initial stack
> --- end of DB_stack
> guard page
>
> --- top of DB1_stack <- Top of stack after entering first #DB
> --- end of DB1_stack
> guard page
>
> --- top of DB2_stack <- Top of stack after entering second #DB
> --- end of DB2_stack
> guard page
>
> > +
> > +/* The exception stacks linear storage. No guard pages required */
> > +struct exception_stacks {
> > + ESTACKS_MEMBERS(0)
> > +};
> > +
> > +/*
> > + * The effective cpu entry area mapping with guard pages. Guard size is
> > + * zero until the code which makes assumptions about linear mapping is
> > + * cleaned up.
> > + */
> > +struct cea_exception_stacks {
> > + ESTACKS_MEMBERS(0)
> > +};
> > +
> > +#define CEA_ESTACK_TOP(ceastp, st) \
> > + ((unsigned long)&(ceastp)->st## _stack_guard)
>
> IMO, using the stack guard to define the top of stack is unnecessarily
> confusing and fragile, e.g. reordering the names of the stack guards
> would break this macro.
>
> What about:
>
> #define CEA_ESTACK_TOP(ceastp, st) \
> (CEA_ESTACK_BOT(ceastp, st) + CEA_ESTACK_SIZE(st))
>
> > +#define CEA_ESTACK_BOT(ceastp, st) \
> > + ((unsigned long)&(ceastp)->st## _stack)
> > +
> > +#define CEA_ESTACK_OFFS(st) \
> > + offsetof(struct cea_exception_stacks, st## _stack)
> > +
> > +#define CEA_ESTACK_SIZE(st) \
> > + sizeof(((struct cea_exception_stacks *)0)->st## _stack)
> > +
> > +#define CEA_ESTACK_PAGES \
> > + (sizeof(struct cea_exception_stacks) / PAGE_SIZE)
> > +
> > +#endif
> > +
> > /*
> > * cpu_entry_area is a percpu region that contains things needed by the CPU
> > * and early entry/exit code. Real types aren't used for all fields here
> > @@ -32,12 +76,9 @@ struct cpu_entry_area {
> >
> > #ifdef CONFIG_X86_64
> > /*
> > - * Exception stacks used for IST entries.
> > - *
> > - * In the future, this should have a separate slot for each stack
> > - * with guard pages between them.
> > + * Exception stacks used for IST entries with guard pages.
> > */
> > - char exception_stacks[(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ];
> > + struct cea_exception_stacks estacks;
> > #endif
> > #ifdef CONFIG_CPU_SUP_INTEL
> > /*
> > --- a/arch/x86/kernel/cpu/common.c
> > +++ b/arch/x86/kernel/cpu/common.c
> > @@ -1754,7 +1754,7 @@ void cpu_init(void)
> > * set up and load the per-CPU TSS
> > */
> > if (!oist->ist[0]) {
> > - char *estacks = get_cpu_entry_area(cpu)->exception_stacks;
> > + char *estacks = (char *)&get_cpu_entry_area(cpu)->estacks;
> >
> > for (v = 0; v < N_EXCEPTION_STACKS; v++) {
> > estacks += exception_stack_sizes[v];
> > --- a/arch/x86/mm/cpu_entry_area.c
> > +++ b/arch/x86/mm/cpu_entry_area.c
> > @@ -13,8 +13,7 @@
> > static DEFINE_PER_CPU_PAGE_ALIGNED(struct entry_stack_page, entry_stack_storage);
> >
> > #ifdef CONFIG_X86_64
> > -static DEFINE_PER_CPU_PAGE_ALIGNED(char, exception_stacks
> > - [(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]);
> > +static DEFINE_PER_CPU_PAGE_ALIGNED(struct exception_stacks, exception_stacks);
> > #endif
> >
> > struct cpu_entry_area *get_cpu_entry_area(int cpu)
> > @@ -138,9 +137,8 @@ static void __init setup_cpu_entry_area(
> > #ifdef CONFIG_X86_64
> > BUILD_BUG_ON(sizeof(exception_stacks) % PAGE_SIZE != 0);
> > BUILD_BUG_ON(sizeof(exception_stacks) !=
> > - sizeof(((struct cpu_entry_area *)0)->exception_stacks));
> > - cea_map_percpu_pages(&cea->exception_stacks,
> > - &per_cpu(exception_stacks, cpu),
> > + sizeof(((struct cpu_entry_area *)0)->estacks));
> > + cea_map_percpu_pages(&cea->estacks, &per_cpu(exception_stacks, cpu),
> > sizeof(exception_stacks) / PAGE_SIZE, PAGE_KERNEL);
> > #endif
> > percpu_setup_debug_store(cpu);
> >
> >
next prev parent reply other threads:[~2019-04-05 20:50 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-05 15:06 [patch V2 00/29] x86: Add guard pages to exception and interrupt stacks Thomas Gleixner
2019-04-05 15:06 ` [patch V2 01/29] x86/irq/64: Limit IST stack overflow check to #DB stack Thomas Gleixner
2019-04-05 15:07 ` [patch V2 02/29] x86/dumpstack: Fix off-by-one errors in stack identification Thomas Gleixner
2019-04-05 15:44 ` Sean Christopherson
2019-04-05 15:07 ` [patch V2 03/29] x86/irq/64: Remove a hardcoded irq_stack_union access Thomas Gleixner
2019-04-05 16:37 ` Sean Christopherson
2019-04-05 16:38 ` Sean Christopherson
2019-04-05 17:18 ` Josh Poimboeuf
2019-04-05 17:47 ` Thomas Gleixner
2019-04-05 15:07 ` [patch V2 04/29] x86/irq/64: Sanitize the top/bottom confusion Thomas Gleixner
2019-04-05 16:54 ` Sean Christopherson
2019-04-05 15:07 ` [patch V2 05/29] x86/idt: Remove unused macro SISTG Thomas Gleixner
2019-04-05 15:07 ` [patch V2 06/29] x86/exceptions: Remove unused stack defines on 32bit Thomas Gleixner
2019-04-05 15:07 ` [patch V2 07/29] x86/exceptions: Make IST index zero based Thomas Gleixner
2019-04-05 18:59 ` Sean Christopherson
2019-04-05 15:07 ` [patch V2 08/29] x86/cpu_entry_area: Cleanup setup functions Thomas Gleixner
2019-04-05 19:25 ` Sean Christopherson
2019-04-05 15:07 ` [patch V2 09/29] x86/exceptions: Add structs for exception stacks Thomas Gleixner
2019-04-05 20:48 ` Sean Christopherson
2019-04-05 20:50 ` Sean Christopherson [this message]
2019-04-05 21:00 ` Thomas Gleixner
2019-04-05 15:07 ` [patch V2 10/29] x86/cpu_entry_area: Prepare for IST guard pages Thomas Gleixner
2019-04-05 15:07 ` [patch V2 11/29] x86/cpu_entry_area: Provide exception stack accessor Thomas Gleixner
2019-04-05 15:07 ` [patch V2 12/29] x86/traps: Use cpu_entry_area instead of orig_ist Thomas Gleixner
2019-04-05 15:07 ` [patch V2 13/29] x86/irq/64: Use cpu entry area " Thomas Gleixner
2019-04-05 15:07 ` [patch V2 14/29] x86/dumpstack/64: Use cpu_entry_area " Thomas Gleixner
2019-04-05 15:07 ` [patch V2 15/29] x86/cpu: Prepare TSS.IST setup for guard pages Thomas Gleixner
2019-04-05 15:07 ` [patch V2 16/29] x86/cpu: Remove orig_ist array Thomas Gleixner
2019-04-05 15:07 ` [patch V2 17/29] x86/exceptions: Disconnect IST index and stack order Thomas Gleixner
2019-04-05 21:57 ` Josh Poimboeuf
2019-04-05 22:00 ` Thomas Gleixner
2019-04-05 15:07 ` [patch V2 18/29] x86/exceptions: Enable IST guard pages Thomas Gleixner
2019-04-05 15:07 ` [patch V2 19/29] x86/exceptions: Split debug IST stack Thomas Gleixner
2019-04-05 20:55 ` Sean Christopherson
2019-04-05 21:01 ` Thomas Gleixner
2019-04-05 15:07 ` [patch V2 20/29] x86/dumpstack/64: Speedup in_exception_stack() Thomas Gleixner
2019-04-05 21:55 ` Josh Poimboeuf
2019-04-05 21:56 ` Thomas Gleixner
2019-04-05 15:07 ` [patch V2 21/29] x86/irq/32: Define IRQ_STACK_SIZE Thomas Gleixner
2019-04-05 15:07 ` [patch V2 22/29] x86/irq/32: Make irq stack a character array Thomas Gleixner
2019-04-05 15:07 ` [patch V2 23/29] x86/irq/32: Rename hard/softirq_stack to hard/softirq_stack_ptr Thomas Gleixner
2019-04-05 15:07 ` [patch V2 24/29] x86/irq/64: Rename irq_stack_ptr to hardirq_stack_ptr Thomas Gleixner
2019-04-05 15:07 ` [patch V2 25/29] x86/irq/32: Invoke irq_ctx_init() from init_IRQ() Thomas Gleixner
2019-04-05 15:27 ` Juergen Gross
2019-04-05 15:07 ` [patch V2 26/29] x86/irq/32: Handle irq stack allocation failure proper Thomas Gleixner
2019-04-05 15:07 ` [patch V2 27/29] x86/irq/64: Split the IRQ stack into its own pages Thomas Gleixner
2019-04-05 15:07 ` [patch V2 28/29] x86/irq/64: Remap the IRQ stack with guard pages Thomas Gleixner
2019-04-07 4:56 ` Andy Lutomirski
2019-04-07 6:08 ` Thomas Gleixner
2019-04-07 9:28 ` Andy Lutomirski
2019-04-07 9:34 ` Thomas Gleixner
2019-04-07 14:03 ` Andy Lutomirski
2019-04-07 22:44 ` Thomas Gleixner
2019-04-08 2:23 ` Andy Lutomirski
2019-04-08 6:46 ` Thomas Gleixner
2019-04-08 16:18 ` Andy Lutomirski
2019-04-08 16:36 ` Josh Poimboeuf
2019-04-08 16:44 ` Thomas Gleixner
2019-04-08 18:19 ` Thomas Gleixner
2019-04-05 15:07 ` [patch V2 29/29] x86/irq/64: Remove stack overflow debug code Thomas Gleixner
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