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Steven Rostedt 17666f02b1 ftrace: nmi safe code modification 
Impact: fix crashes that can occur in NMI handlers, if their code is modified

Modifying code is something that needs special care. On SMP boxes,
if code that is being modified is also being executed on another CPU,
that CPU will have undefined results.

The dynamic ftrace uses kstop_machine to make the system act like a
uniprocessor system. But this does not address NMIs, that can still
run on other CPUs.

One approach to handle this is to make all code that are used by NMIs
not be traced. But NMIs can call notifiers that spread throughout the
kernel and this will be very hard to maintain, and the chance of missing
a function is very high.

The approach that this patch takes is to have the NMIs modify the code
if the modification is taking place. The way this works is that just
writing to code executing on another CPU is not harmful if what is
written is the same as what exists.

Two buffers are used: an IP buffer and a "code" buffer.

The steps that the patcher takes are:

 1) Put in the instruction pointer into the IP buffer
    and the new code into the "code" buffer.
 2) Set a flag that says we are modifying code
 3) Wait for any running NMIs to finish.
 4) Write the code
 5) clear the flag.
 6) Wait for any running NMIs to finish.

If an NMI is executed, it will also write the pending code.
Multiple writes are OK, because what is being written is the same.
Then the patcher must wait for all running NMIs to finish before
going to the next line that must be patched.

This is basically the RCU approach to code modification.

Thanks to Ingo Molnar for suggesting the idea, and to Arjan van de Ven
for his guidence on what is safe and what is not.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-30 21:30:08 +01:00
..
acpi Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2008-10-23 12:38:39 -07:00
cpu Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2008-10-23 12:38:39 -07:00
.gitignore arch/x86/kernel/.gitignore: Added vmlinux.lds to .gitignore file because it shouldn't be tracked. 2008-07-10 10:13:51 -07:00
alternative.c x86: improve UP kernel when CPU-hotplug and SMP is enabled 2008-10-13 10:33:46 +02:00
amd_iommu.c x86, AMD IOMMU: convert driver to generic iommu_num_pages function 2008-10-16 11:21:33 -07:00
amd_iommu_init.c amd_iommu: fix nasty bug that caused ILLEGAL_DEVICE_TABLE_ENTRY errors 2008-10-18 14:29:30 +01:00
aperture_64.c x86, debug printouts: IOMMU setup failures should not be KERN_ERR 2008-09-30 10:25:28 +02:00
apic.c x86: apic - unify APIC_DIVISOR 2008-10-16 16:53:14 +02:00
apm_32.c Merge branches 'x86/alternatives', 'x86/cleanups', 'x86/commandline', 'x86/crashdump', 'x86/debug', 'x86/defconfig', 'x86/doc', 'x86/exports', 'x86/fpu', 'x86/gart', 'x86/idle', 'x86/mm', 'x86/mtrr', 'x86/nmi-watchdog', 'x86/oprofile', 'x86/paravirt', 'x86/reboot', 'x86/sparse-fixes', 'x86/tsc', 'x86/urgent' and 'x86/vmalloc' into x86-v28-for-linus-phase1 2008-10-06 18:17:07 +02:00
asm-offsets.c
asm-offsets_32.c x86/paravirt: split sysret and sysexit 2008-07-08 13:13:15 +02:00
asm-offsets_64.c x86: Fix ASM_X86__ header guards 2008-10-22 22:55:23 -07:00
audit_64.c
bios_uv.c x86: Add UV partition call v4 2008-10-16 16:53:13 +02:00
bootflag.c
cpuid.c device create: misc: convert device_create_drvdata to device_create 2008-10-16 09:24:43 -07:00
crash.c
crash_dump_32.c kdump: make elfcorehdr_addr independent of CONFIG_PROC_VMCORE 2008-10-20 08:52:39 -07:00
crash_dump_64.c kdump: make elfcorehdr_addr independent of CONFIG_PROC_VMCORE 2008-10-20 08:52:39 -07:00
doublefault_32.c x86: fix virt_addr_valid() with CONFIG_DEBUG_VIRTUAL=y, v2 2008-10-13 10:33:15 +02:00
ds.c x86: ds.c ptrace.c integer as NULL pointer sparse fixes 2008-09-24 09:57:47 +02:00
dumpstack_32.c x86, kexec: fix hang on i386 when panic occurs while console_sem is held 2008-10-22 13:59:44 +02:00
dumpstack_64.c sysfs: crash debugging 2008-10-16 09:24:41 -07:00
e820.c Merge branches 'core/softlockup', 'core/softirq', 'core/resources', 'core/printk' and 'core/misc' into core-v28-for-linus 2008-10-15 12:48:44 +02:00
early-quirks.c x86: SB600: skip IRQ0 override if it is not routed to INT2 of IOAPIC 2008-10-22 12:00:10 +02:00
early_printk.c warnings: fix arch/x86/kernel/early_printk.c 2008-10-12 15:19:36 +02:00
efi.c x86: Add UV EFI table entry v4 2008-10-16 16:53:13 +02:00
efi_32.c x86: fix i486 suspend to disk CR4 oops 2008-08-18 08:50:19 +02:00
efi_64.c x86: add flags parameter to reserve_bootmem_generic() 2008-07-08 11:49:49 +02:00
efi_stub_32.S
efi_stub_64.S
entry_32.S Merge commit 'v2.6.28-rc2' into tracing/urgent 2008-10-27 10:50:54 +01:00
entry_64.S ftrace: rename FTRACE to FUNCTION_TRACER 2008-10-20 18:27:03 +02:00
es7000_32.c x86: check dsdt before find oem table for es7000, v2 2008-10-13 10:21:07 +02:00
ftrace.c ftrace: nmi safe code modification 2008-10-30 21:30:08 +01:00
genapic_64.c GRU Driver: export is_uv_system(), zap_page_range() & follow_page() 2008-07-30 09:41:48 -07:00
genapic_flat_64.c x86: fix section mismatch warning - apic_physflat 2008-10-22 17:36:27 +02:00
genx2apic_cluster.c x86: fix section mismatch warning - apic_x2apic_cluster 2008-10-22 17:36:29 +02:00
genx2apic_phys.c x86: fix section mismatch warning - apic_x2apic_phys 2008-10-22 17:36:30 +02:00
genx2apic_uv_x.c x86/uv: memory allocation at initialization 2008-10-27 14:17:16 +01:00
geode_32.c x86, geode: add a VSA2 ID for General Software 2008-06-19 14:19:03 +02:00
head.c x86: print out EBDA/lowmem address 2008-10-13 10:21:10 +02:00
head32.c x86: extract common part of head32.c and head64.c into head.c 2008-06-05 15:10:02 +02:00
head64.c x86_64: be less annoying on boot, v2 2008-09-29 10:04:53 +02:00
head_32.S x86, cpa: rename PTE attribute macros for kernel direct mapping in early boot 2008-10-10 19:29:11 +02:00
head_64.S x86, cpa: rename PTE attribute macros for kernel direct mapping in early boot 2008-10-10 19:29:11 +02:00
hpet.c hpet: clean up warning 2008-10-16 16:53:12 +02:00
i386_ksyms_32.c ftrace: rename FTRACE to FUNCTION_TRACER 2008-10-20 18:27:03 +02:00
i387.c x86: xsave: set FP, SSE bits in the xsave header in the user sigcontext 2008-10-07 14:36:08 -07:00
i8237.c
i8253.c
i8259.c x64, x2apic/intr-remap: 8259 specific mask/unmask routines 2008-07-12 08:44:55 +02:00
init_task.c
io_apic.c io_apic: make irq_mis_count available on 64-bit too 2008-10-16 16:59:20 +02:00
io_delay.c x86: add io delay quirk for Presario F700 2008-09-03 16:42:51 -07:00
ioport.c x86: Introducing asm/syscalls.h 2008-07-22 14:35:57 +02:00
ipi.c X86_SMP: ipi.c declare functions before they get used 2008-07-25 11:57:46 +05:30
irq.c genirq: fix off by one and coding style 2008-10-21 15:54:40 +02:00
irq_32.c x86: move ack_bad_irq() to irq.c 2008-10-16 16:53:30 +02:00
irq_64.c x86: move ack_bad_irq() to irq.c 2008-10-16 16:53:30 +02:00
irqinit_32.c genirq: remove artifacts from sparseirq removal 2008-10-16 16:53:15 +02:00
irqinit_64.c genirq: remove irq_to_desc_alloc 2008-10-16 16:53:15 +02:00
k8.c x86, gart: add detection of AMD family 0x11 northbridges 2008-09-05 19:11:44 +02:00
kdebugfs.c arch/x86/kernel/kdebugfs.c: introduce missing kfree 2008-09-10 14:03:49 +02:00
kgdb.c kgdb, x86: Avoid invoking kgdb_nmicallback twice per NMI 2008-10-06 13:50:59 -05:00
kprobes.c kprobes: improve kretprobe scalability with hashed locking 2008-07-25 10:53:30 -07:00
kvm.c x86, paravirt_ops: use unsigned long instead of u32 for alloc_p*() pfn args 2008-08-22 05:34:44 +02:00
kvmclock.c x86: KVM guest: use paravirt function to calculate cpu khz 2008-10-15 10:15:17 +02:00
ldt.c Merge branch 'linus' into x86/xen 2008-10-12 12:37:32 +02:00
machine_kexec_32.c kexec jump: fix for ftrace 2008-08-15 08:35:43 -07:00
machine_kexec_64.c kexec jump 2008-07-26 12:00:04 -07:00
Makefile ftrace, powerpc, sparc64, x86: remove notrace from arch ftrace file 2008-10-23 16:00:25 +02:00
mca_32.c
mfgpt_32.c x86, geode-mfgpt: check IRQ before using MFGPT as clocksource 2008-08-15 17:12:32 +02:00
microcode_amd.c x86, microcode_amd: cleanup, mark request_microcode_user() as unsupported 2008-09-24 10:32:37 +02:00
microcode_core.c x86/microcode: fix sleeping function called from invalid context at kernel/mutex.c 2008-10-02 17:52:33 +02:00
microcode_intel.c x86: moved microcode.c to microcode_intel.c 2008-09-23 12:21:42 +02:00
mmconf-fam10h_64.c x86: mmconf: fix section mismatch warning 2008-08-18 07:49:06 +02:00
module_32.c
module_64.c PAGE_ALIGN(): correctly handle 64-bit values on 32-bit architectures 2008-07-24 10:47:21 -07:00
mpparse.c Merge branch 'x86/apic' into x86-v28-for-linus-phase4-B 2008-10-11 20:17:36 +02:00
msr.c device create: misc: convert device_create_drvdata to device_create 2008-10-16 09:24:43 -07:00
nmi.c x86, NMI watchdog: setup before enabling NMI watchdog 2008-09-22 19:48:19 +02:00
numaq_32.c Merge branch 'x86/apic' into x86-v28-for-linus-phase4-B 2008-10-11 20:17:36 +02:00
olpc.c x86, olpc: fix endian bug in openfirmware workaround 2008-09-24 10:29:04 +02:00
paravirt-spinlocks.c x86: export pv_lock_ops non-GPL 2008-08-22 15:43:17 +02:00
paravirt.c Merge branch 'linus' into x86/xen 2008-10-12 12:37:32 +02:00
paravirt_patch_32.c x86: coding style fixes to arch/x86/kernel/paravirt_patch_32.c 2008-08-15 16:53:25 +02:00
paravirt_patch_64.c x86/paravirt: add sysret/sysexit pvops for returning to 32-bit compatibility userspace 2008-07-08 13:15:52 +02:00
pci-calgary_64.c x86: convert Calgary IOMMU driver to generic iommu_num_pages function 2008-10-16 11:21:33 -07:00
pci-dma.c x86/PCI: build failure at x86/kernel/pci-dma.c with !CONFIG_PCI 2008-10-24 11:09:43 -07:00
pci-gart_64.c x86: convert GART driver to generic iommu_num_pages function 2008-10-16 11:21:33 -07:00
pci-nommu.c x86: export pci-nommu's alloc_coherent 2008-09-25 11:02:25 +02:00
pci-swiotlb_64.c x86: restore the old swiotlb alloc_coherent behavior 2008-10-23 21:54:40 +02:00
pcspeaker.c x86: use platform_device_register_simple() 2008-09-22 12:58:36 +02:00
pmtimer_64.c
probe_roms_32.c x86: seperate probe_roms into another file 2008-07-08 12:50:05 +02:00
process.c Merge branch 'x86/unify-cpu-detect' into x86-v28-for-linus-phase4-D 2008-10-11 20:23:20 +02:00
process_32.c x86: __show_registers() and __show_regs() API unification 2008-10-13 10:33:04 +02:00
process_64.c Merge branch 'linus' into test 2008-10-23 00:11:07 -04:00
ptrace.c Merge branches 'x86/xen', 'x86/build', 'x86/microcode', 'x86/mm-debug-v2', 'x86/memory-corruption-check', 'x86/early-printk', 'x86/xsave', 'x86/ptrace-v2', 'x86/quirks', 'x86/setup', 'x86/spinlocks' and 'x86/signal' into x86/core-v2 2008-10-12 15:50:02 +02:00
pvclock.c x86: pvclock: fix shadowed variable warning 2008-10-15 14:25:14 +02:00
quirks.c x86: remove irqbalance in kernel for 32 bit 2008-10-16 16:52:52 +02:00
reboot.c x86: default to reboot via ACPI 2008-08-25 12:31:32 +02:00
reboot_fixups_32.c
relocate_kernel_32.S kexec jump: check code size in control page 2008-08-15 08:35:42 -07:00
relocate_kernel_64.S
rtc.c rtc: use bcd2bin/bin2bcd 2008-10-20 08:52:41 -07:00
scx200_32.c
setup.c Merge branch 'genirq-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2008-10-20 13:23:01 -07:00
setup_percpu.c x86: remove redundant KERN_DEBUG on pr_debug 2008-10-22 16:56:22 +02:00
sigframe.h Merge branch 'x86/unify-cpu-detect' into x86-v28-for-linus-phase4-D 2008-10-11 20:23:20 +02:00
signal_32.c Merge branch 'x86/unify-cpu-detect' into x86-v28-for-linus-phase4-D 2008-10-11 20:23:20 +02:00
signal_64.c Merge branch 'x86/unify-cpu-detect' into x86-v28-for-linus-phase4-D 2008-10-11 20:23:20 +02:00
smp.c x86: add cpu hotplug hooks into smp_ops 2008-08-25 10:59:18 +02:00
smpboot.c x86: do_boot_cpu - check if we have ESR register 2008-10-22 16:56:16 +02:00
smpcommon.c x86: change init_gdt to update the gdt via write_gdt, rather than a direct write. 2008-08-15 19:16:05 +02:00
stacktrace.c stacktrace: fix modular build, export print_stack_trace and save_stack_trace 2008-06-30 09:20:55 +02:00
step.c x86 ptrace: user-sets-TF nits 2008-07-16 12:15:17 -07:00
summit_32.c x86: mach_summit to summit 2008-07-26 16:31:35 +02:00
sys_i386_32.c x86: Introducing asm/syscalls.h 2008-07-22 14:35:57 +02:00
sys_x86_64.c Merge branches 'x86/alternatives', 'x86/cleanups', 'x86/commandline', 'x86/crashdump', 'x86/debug', 'x86/defconfig', 'x86/doc', 'x86/exports', 'x86/fpu', 'x86/gart', 'x86/idle', 'x86/mm', 'x86/mtrr', 'x86/nmi-watchdog', 'x86/oprofile', 'x86/paravirt', 'x86/reboot', 'x86/sparse-fixes', 'x86/tsc', 'x86/urgent' and 'x86/vmalloc' into x86-v28-for-linus-phase1 2008-10-06 18:17:07 +02:00
syscall_64.c x86: Fix ASM_X86__ header guards 2008-10-22 22:55:23 -07:00
syscall_table_32.S flag parameters add-on: remove epoll_create size param 2008-07-24 10:47:29 -07:00
tce_64.c
test_nx.c
test_rodata.c
time_32.c x86: wrap MCA_bus test around an ifdef 2008-10-13 10:21:47 +02:00
time_64.c x86: move vgetcpu mode probing to cpu detection 2008-10-13 10:21:49 +02:00
tlb_32.c x86: build fix for !CONFIG_SMP 2008-09-05 17:44:08 +02:00
tlb_64.c Merge branch 'generic-ipi' into generic-ipi-for-linus 2008-07-15 21:55:59 +02:00
tlb_uv.c x86/tlb_uv: remove strange mc146818rtc include 2008-10-22 16:56:23 +02:00
tls.c x86: Introducing asm/syscalls.h 2008-07-22 14:35:57 +02:00
tls.h
topology.c
trampoline.c
trampoline_32.S
trampoline_64.S
traps.c MCE: Don't run 32bit machine checks with interrupts on 2008-10-22 13:19:01 +02:00
tsc.c Merge branches 'x86/alternatives', 'x86/cleanups', 'x86/commandline', 'x86/crashdump', 'x86/debug', 'x86/defconfig', 'x86/doc', 'x86/exports', 'x86/fpu', 'x86/gart', 'x86/idle', 'x86/mm', 'x86/mtrr', 'x86/nmi-watchdog', 'x86/oprofile', 'x86/paravirt', 'x86/reboot', 'x86/sparse-fixes', 'x86/tsc', 'x86/urgent' and 'x86/vmalloc' into x86-v28-for-linus-phase1 2008-10-06 18:17:07 +02:00
tsc_sync.c x86: use WARN() in arch/x86/kernel 2008-08-21 10:01:52 +02:00
uv_irq.c x86, UV: add uv_setup_irq() and uv_teardown_irq() functions, v3, fix 2008-10-16 16:53:13 +02:00
uv_sysfs.c x86: Add sysfs entries for UV v4 2008-10-16 16:53:13 +02:00
verify_cpu_64.S
visws_quirks.c genirq: revert dynarray 2008-10-16 16:53:15 +02:00
vm86_32.c x86: Introducing asm/syscalls.h 2008-07-22 14:35:57 +02:00
vmi_32.c Merge branch 'x86/apic' into x86-v28-for-linus-phase4-B 2008-10-11 20:17:36 +02:00
vmiclock_32.c x86: VMI, initialize IRQ vector 2008-10-16 16:52:59 +02:00
vmlinux.lds.S
vmlinux_32.lds.S genirq: revert dynarray 2008-10-16 16:53:15 +02:00
vmlinux_64.lds.S genirq: remove artifacts from sparseirq removal 2008-10-16 16:53:15 +02:00
vsmp_64.c x86: fix 27-rc crash on vsmp due to paravirt during module load 2008-09-23 10:31:26 +02:00
vsyscall_64.c Merge branch 'generic-ipi' into generic-ipi-for-linus 2008-07-15 21:55:59 +02:00
x8664_ksyms_64.c ftrace: rename FTRACE to FUNCTION_TRACER 2008-10-20 18:27:03 +02:00
xsave.c x86: make variables static 2008-10-22 07:31:28 +02:00