Naveen N. Rao c179ea2701 powerpc/kprobes: Fix warnings from __this_cpu_read() on preempt kernels ... Kamalesh pointed out that we are getting the below call traces with livepatched functions when we enable CONFIG_PREEMPT: [ 495.470721] BUG: using __this_cpu_read() in preemptible [00000000] code: cat/8394 [ 495.471167] caller is is_current_kprobe_addr+0x30/0x90 [ 495.471171] CPU: 4 PID: 8394 Comm: cat Tainted: G K 4.13.0-rc7-nnr+ #95 [ 495.471173] Call Trace: [ 495.471178] [c00000008fd9b960] [c0000000009f039c] dump_stack+0xec/0x160 (unreliable) [ 495.471184] [c00000008fd9b9a0] [c00000000059169c] check_preemption_disabled+0x15c/0x170 [ 495.471187] [c00000008fd9ba30] [c000000000046460] is_current_kprobe_addr+0x30/0x90 [ 495.471191] [c00000008fd9ba60] [c00000000004e9a0] ftrace_call+0x1c/0xb8 [ 495.471195] [c00000008fd9bc30] [c000000000376fd8] seq_read+0x238/0x5c0 [ 495.471199] [c00000008fd9bcd0] [c0000000003cfd78] proc_reg_read+0x88/0xd0 [ 495.471203] [c00000008fd9bd00] [c00000000033e5d4] __vfs_read+0x44/0x1b0 [ 495.471206] [c00000008fd9bd90] [c0000000003402ec] vfs_read+0xbc/0x1b0 [ 495.471210] [c00000008fd9bde0] [c000000000342138] SyS_read+0x68/0x110 [ 495.471214] [c00000008fd9be30] [c00000000000bc6c] system_call+0x58/0x6c Commit c05b8c4474 ("powerpc/kprobes: Skip livepatch_handler() for jprobes") introduced a helper is_current_kprobe_addr() to help determine if the current function has been livepatched or if it has a jprobe installed, both of which modify the NIP. This was subsequently renamed to __is_active_jprobe(). In the case of a jprobe, kprobe_ftrace_handler() disables pre-emption before calling into setjmp_pre_handler() which returns without disabling pre-emption. This is done to ensure that the jprobe handler won't disappear beneath us if the jprobe is unregistered between the setjmp_pre_handler() and the subsequent longjmp_break_handler() called from the jprobe handler. Due to this, we can use __this_cpu_read() in __is_active_jprobe() with the pre-emption check as we know that pre-emption will be disabled. However, if this function has been livepatched, we are still doing this check and when we do so, pre-emption won't necessarily be disabled. This results in the call trace shown above. Fix this by only invoking __is_active_jprobe() when pre-emption is disabled. And since we now guard this within a pre-emption check, we can instead use raw_cpu_read() to get the current_kprobe value skipping the check done by __this_cpu_read(). Fixes: c05b8c4474 ("powerpc/kprobes: Skip livepatch_handler() for jprobes") Reported-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> Tested-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>		2017-10-04 23:42:20 +11:00
..
boot	powerpc: conditionally compile platform-specific serial drivers	2017-08-31 14:26:48 +10:00
configs	powerpc/configs: Add Skiroot defconfig	2017-10-04 22:26:46 +11:00
crypto	Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6	2017-05-02 15:53:46 -07:00
include	powerpc/kprobes: Clean up jprobe detection in livepatch handler	2017-10-04 23:42:17 +11:00
kernel	powerpc/kprobes: Fix warnings from __this_cpu_read() on preempt kernels	2017-10-04 23:42:20 +11:00
kvm	kvm,powerpc: Serialize wq active checks in ops->vcpu_kick	2017-09-15 16:57:13 +02:00
lib	powerpc/lib/sstep: Fix fixed-point shift instructions that set CA32	2017-10-04 11:28:04 +11:00
math-emu	Replace <asm/uaccess.h> with <linux/uaccess.h> globally	2016-12-24 11:46:01 -08:00
mm	cxl: Enable global TLBIs for cxl contexts	2017-09-28 17:09:16 +10:00
net	powerpc updates for 4.14	2017-09-07 10:15:40 -07:00
oprofile	powerpc/oprofile: Use setup_timer() helper	2017-10-04 11:28:01 +11:00
perf	powerpc/sysrq: Fix oops whem ppmu is not registered	2017-09-20 13:30:09 +10:00
platforms	powerpc/powermac: Use setup_timer() helper	2017-10-04 11:28:02 +11:00
purgatory	powerpc/asm: Convert .llong directives to .8byte	2017-08-31 14:26:47 +10:00
sysdev	treewide: make "nr_cpu_ids" unsigned	2017-09-08 18:26:48 -07:00
tools	powerpc/64: Tool to check head sections location sanity	2017-05-30 14:59:51 +10:00
xmon	powerpc/xmon: Avoid tripping SMP hardlockup watchdog	2017-10-04 11:26:23 +11:00
Kconfig	powerpc updates for 4.14	2017-09-07 10:15:40 -07:00
Kconfig.debug	powerpc/xmon: Enable disassembly files (compilation changes)	2017-02-15 20:02:42 +11:00
Makefile	Merge branch 'fixes' into next	2017-08-23 22:20:10 +10:00
Makefile.postlink	powerpc/64: Tool to check head sections location sanity	2017-05-30 14:59:51 +10:00