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Linus Torvalds 9561ddb626 x86: stop playing stack games in profile_pc() 
[ Upstream commit 093d9603b60093a9aaae942db56107f6432a5dca ]

The 'profile_pc()' function is used for timer-based profiling, which
isn't really all that relevant any more to begin with, but it also ends
up making assumptions based on the stack layout that aren't necessarily
valid.

Basically, the code tries to account the time spent in spinlocks to the
caller rather than the spinlock, and while I support that as a concept,
it's not worth the code complexity or the KASAN warnings when no serious
profiling is done using timers anyway these days.

And the code really does depend on stack layout that is only true in the
simplest of cases.  We've lost the comment at some point (I think when
the 32-bit and 64-bit code was unified), but it used to say:

	Assume the lock function has either no stack frame or a copy
	of eflags from PUSHF.

which explains why it just blindly loads a word or two straight off the
stack pointer and then takes a minimal look at the values to just check
if they might be eflags or the return pc:

	Eflags always has bits 22 and up cleared unlike kernel addresses

but that basic stack layout assumption assumes that there isn't any lock
debugging etc going on that would complicate the code and cause a stack
frame.

It causes KASAN unhappiness reported for years by syzkaller [1] and
others [2].

With no real practical reason for this any more, just remove the code.

Just for historical interest, here's some background commits relating to
this code from 2006:

  0cb91a229364 ("i386: Account spinlocks to the caller during profiling for !FP kernels")
  31679f38d886 ("Simplify profile_pc on x86-64")

and a code unification from 2009:

  ef4512882dbe ("x86: time_32/64.c unify profile_pc")

but the basics of this thing actually goes back to before the git tree.

Link: https://syzkaller.appspot.com/bug?extid=84fe685c02cd112a2ac3 [1]
Link: https://lore.kernel.org/all/CAK55_s7Xyq=nh97=K=G1sxueOFrJDAvPOJAL4TPTCAYvmxO9_A@mail.gmail.com/ [2]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-11-19 14:19:33 +01:00
..
acpi x86/i8259: Skip probing when ACPI/MADT advertises PCAT compatibility 2024-11-18 10:58:32 +01:00
apic genirq/cpuhotplug, x86/vector: Prevent vector leak during CPU offline 2024-11-19 12:27:11 +01:00
cpu x86/cpu: Fix x86_match_cpu() to match just X86_VENDOR_INTEL 2024-11-19 14:19:29 +01:00
fpu Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kprobes x86/kprobes: fix incorrect return address calculation in kprobe_emulate_call_indirect 2024-11-18 12:12:08 +01:00
alternative.c x86/alternative: Make custom return thunk unconditional 2024-11-18 22:25:38 +01:00
amd_gart_64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
amd_nb.c x86/amd_nb: Check for invalid SMN reads 2024-11-19 14:19:30 +01:00
apb_timer.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
aperture_64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
apm_32.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
asm-offsets.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
asm-offsets_32.c x86/stackprotector/32: Make the canary into a regular percpu variable 2024-11-19 09:22:37 +01:00
asm-offsets_64.c x86/xen: Drop USERGS_SYSRET64 paravirt call 2024-11-19 12:26:38 +01:00
audit_64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
bootflag.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cc_platform.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
check.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cpuid.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
crash.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
crash_core_32.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
crash_core_64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
crash_dump_32.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
crash_dump_64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
devicetree.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
doublefault_32.c x86/stackprotector/32: Make the canary into a regular percpu variable 2024-11-19 09:22:37 +01:00
dumpstack.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
dumpstack_32.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
dumpstack_64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
e820.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
early-quirks.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
early_printk.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
ebda.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
eisa.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
espfix_64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
ftrace.c x86/returnthunk: Allow different return thunks 2024-11-18 22:25:38 +01:00
ftrace_32.S Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
ftrace_64.S Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
head32.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
head64.c x86/head/64: Re-enable stack protection 2024-11-19 09:23:16 +01:00
head_32.S x86/stackprotector/32: Make the canary into a regular percpu variable 2024-11-19 09:22:37 +01:00
head_64.S x86/head/64: Re-enable stack protection 2024-11-19 09:23:16 +01:00
hpet.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
hw_breakpoint.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
i8237.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
i8253.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
i8259.c x86/i8259: Skip probing when ACPI/MADT advertises PCAT compatibility 2024-11-18 10:58:32 +01:00
idt.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
ima_arch.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
io_delay.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
ioport.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
irq.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
irq_32.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
irq_64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
irq_work.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
irqflags.S Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
irqinit.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
itmt.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
jailhouse.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
jump_label.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kdebugfs.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kexec-bzimage64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kgdb.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
ksysfs.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kvm.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
kvmclock.c x86/kvm: Do not try to disable kvmclock if it was not enabled 2024-11-18 12:12:48 +01:00
ldt.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
machine_kexec_32.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
machine_kexec_64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
Makefile x86/head/64: Re-enable stack protection 2024-11-19 09:23:16 +01:00
mmconf-fam10h_64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
module.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
mpparse.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
msr.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
nmi.c x86/bugs: Use ALTERNATIVE() instead of mds_user_clear static key 2024-11-19 09:22:40 +01:00
nmi_selftest.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
paravirt-spinlocks.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
paravirt.c x86/xen: Drop USERGS_SYSRET64 paravirt call 2024-11-19 12:26:38 +01:00
paravirt_patch.c x86/xen: Drop USERGS_SYSRET64 paravirt call 2024-11-19 12:26:38 +01:00
pci-dma.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
pci-iommu_table.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
pci-swiotlb.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
pcspeaker.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
perf_regs.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
platform-quirks.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
pmem.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
probe_roms.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
process.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
process.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
process_32.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
process_64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
ptrace.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
pvclock.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
quirks.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
reboot.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
reboot_fixups_32.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
relocate_kernel_32.S Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
relocate_kernel_64.S Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
resource.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
rtc.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
setup.c x86/mm: Fix RESERVE_BRK() for older binutils 2024-11-18 10:58:45 +01:00
setup_percpu.c x86/stackprotector/32: Make the canary into a regular percpu variable 2024-11-19 09:22:37 +01:00
sev-es-shared.c x86/sev: Check for user-space IOIO pointing to kernel space 2024-11-08 11:26:09 +01:00
sev-es.c x86/sev: Check IOBM for IOIO exceptions from user-space 2024-11-08 11:26:09 +01:00
sev_verify_cbit.S Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
signal.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
signal_compat.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
smp.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
smpboot.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
stacktrace.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
static_call.c x86/returnthunk: Allow different return thunks 2024-11-18 22:25:38 +01:00
step.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sys_ia32.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sys_x86_64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sysfb.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sysfb_efi.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sysfb_simplefb.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
tboot.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
time.c x86: stop playing stack games in profile_pc() 2024-11-19 14:19:33 +01:00
tls.c x86/stackprotector/32: Make the canary into a regular percpu variable 2024-11-19 09:22:37 +01:00
tls.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
topology.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
trace_clock.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
tracepoint.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
traps.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
tsc.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
tsc_msr.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
tsc_sync.c x86/tsc: Trust initial offset in architectural TSC-adjust MSRs 2024-11-19 12:26:51 +01:00
umip.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
unwind_frame.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
unwind_guess.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
unwind_orc.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
uprobes.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
verify_cpu.S Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
vm86_32.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
vmlinux.lds.S x86: Fix .brk attribute in linker script 2024-11-18 10:58:46 +01:00
vsmp_64.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
x86_init.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00