Re: [PATCH v2 4/4] kprobes: Remove core dependency on modules
From: Jarkko Sakkinen
Date: Thu Apr 04 2024 - 11:21:59 EST
On Thu Apr 4, 2024 at 11:15 AM EEST, Jarkko Sakkinen wrote:
> On Wed Apr 3, 2024 at 6:01 PM EEST, Mark Rutland wrote:
> > From: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
> >
> > Tracing with kprobes while running a monolithic kernel is currently
> > impossible because KPROBES depends on MODULES. While this dependency is
> > necessary when HAVE_KPROBES_ALLOC=n and the core kprobes code allocates
> > memory using module_alloc(), all the other module-specific code only
> > exist to handle the case when MODULES=y, and can be hidden behind
> > ifdeffery.
> >
> > Add the necessary ifdeffery, and remove the dependency on MODULES=y when
> > HAVE_KPROBES_ALLOC=y.
> >
> > As of this patch kprobes can be used when MODULES=n on arm64 and
> > riscv. All other architectures still depend on MODULES, either by virtue
> > of the core dependency on MODULES when HAVE_KPROBES_ALLOC=n, or by
> > virtue of an explciit dependency on MODULES in arch code.
> >
> > Other architectures can enable support by implementing their own
> > kprobes_alloc_insn_page() and kprobes_free_insn_page() which do not
> > depend on MODULES.
> >
> > Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
> > Link: https://lore.kernel.org/lkml/20240326134616.7691-1-jarkko@xxxxxxxxxx/
> > [Mark: Remove execmem changes, depend on HAVE_KPROBES_ALLOC]
> > Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
> > Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
> > Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > Cc: David S. Miller <davem@xxxxxxxxxxxxx>
> > Cc: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
> > Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > Cc: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxx>
> > Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
> > Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
> > Cc: Will Deacon <will@xxxxxxxxxx>
> > ---
> > arch/Kconfig | 2 +-
> > kernel/kprobes.c | 46 ++++++++++++++++++++++---------------
> > kernel/trace/trace_kprobe.c | 15 ++++++++++--
> > 3 files changed, 41 insertions(+), 22 deletions(-)
> >
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index 85bb59f7b8c07..0df2c88547b3c 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -52,7 +52,7 @@ config GENERIC_ENTRY
> >
> > config KPROBES
> > bool "Kprobes"
> > - depends on MODULES
> > + depends on MODULES || HAVE_KPROBES_ALLOC
> > depends on HAVE_KPROBES
> > select KALLSYMS
> > select TASKS_RCU if PREEMPTION
> > diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> > index fa2ee4e59eca2..ec4493a41b505 100644
> > --- a/kernel/kprobes.c
> > +++ b/kernel/kprobes.c
> > @@ -1594,6 +1594,7 @@ static int check_kprobe_address_safe(struct kprobe *p,
> > goto out;
> > }
> >
> > +#ifdef CONFIG_MODULES
> > /*
> > * If the module freed '.init.text', we couldn't insert
> > * kprobes in there.
> > @@ -1604,7 +1605,9 @@ static int check_kprobe_address_safe(struct kprobe *p,
> > *probed_mod = NULL;
> > ret = -ENOENT;
> > }
> > +#endif /* CONFIG_MODULES */
> > }
> > +
> > out:
> > preempt_enable();
> > jump_label_unlock();
> > @@ -2484,24 +2487,6 @@ int kprobe_add_area_blacklist(unsigned long start, unsigned long end)
> > return 0;
> > }
> >
> > -/* Remove all symbols in given area from kprobe blacklist */
> > -static void kprobe_remove_area_blacklist(unsigned long start, unsigned long end)
> > -{
> > - struct kprobe_blacklist_entry *ent, *n;
> > -
> > - list_for_each_entry_safe(ent, n, &kprobe_blacklist, list) {
> > - if (ent->start_addr < start || ent->start_addr >= end)
> > - continue;
> > - list_del(&ent->list);
> > - kfree(ent);
> > - }
> > -}
> > -
> > -static void kprobe_remove_ksym_blacklist(unsigned long entry)
> > -{
> > - kprobe_remove_area_blacklist(entry, entry + 1);
> > -}
> > -
> > int __weak arch_kprobe_get_kallsym(unsigned int *symnum, unsigned long *value,
> > char *type, char *sym)
> > {
> > @@ -2566,6 +2551,25 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
> > return ret ? : arch_populate_kprobe_blacklist();
> > }
> >
> > +#ifdef CONFIG_MODULES
> > +/* Remove all symbols in given area from kprobe blacklist */
> > +static void kprobe_remove_area_blacklist(unsigned long start, unsigned long end)
> > +{
> > + struct kprobe_blacklist_entry *ent, *n;
> > +
> > + list_for_each_entry_safe(ent, n, &kprobe_blacklist, list) {
> > + if (ent->start_addr < start || ent->start_addr >= end)
> > + continue;
> > + list_del(&ent->list);
> > + kfree(ent);
> > + }
> > +}
> > +
> > +static void kprobe_remove_ksym_blacklist(unsigned long entry)
> > +{
> > + kprobe_remove_area_blacklist(entry, entry + 1);
> > +}
> > +
> > static void add_module_kprobe_blacklist(struct module *mod)
> > {
> > unsigned long start, end;
> > @@ -2662,6 +2666,9 @@ static int kprobes_module_callback(struct notifier_block *nb,
> > mutex_unlock(&kprobe_mutex);
> > return NOTIFY_DONE;
> > }
> > +#else
> > +#define kprobes_module_callback (NULL)
> > +#endif /* CONFIG_MODULES */
> >
> > static struct notifier_block kprobe_module_nb = {
> > .notifier_call = kprobes_module_callback,
> > @@ -2726,7 +2733,8 @@ static int __init init_kprobes(void)
> > err = arch_init_kprobes();
> > if (!err)
> > err = register_die_notifier(&kprobe_exceptions_nb);
> > - if (!err)
> > +
> > + if (!err && IS_ENABLED(CONFIG_MODULES))
> > err = register_module_notifier(&kprobe_module_nb);
> >
> > kprobes_initialized = (err == 0);
> > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> > index 14099cc17fc9e..c509ba776e679 100644
> > --- a/kernel/trace/trace_kprobe.c
> > +++ b/kernel/trace/trace_kprobe.c
> > @@ -111,6 +111,7 @@ static nokprobe_inline bool trace_kprobe_within_module(struct trace_kprobe *tk,
> > return strncmp(module_name(mod), name, len) == 0 && name[len] == ':';
> > }
> >
> > +#ifdef CONFIG_MODULES
> > static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
> > {
> > char *p;
> > @@ -129,6 +130,9 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
> >
> > return ret;
> > }
> > +#else
> > +#define trace_kprobe_module_exist(tk) false /* aka a module never exists */
> > +#endif /* CONFIG_MODULES */
> >
> > static bool trace_kprobe_is_busy(struct dyn_event *ev)
> > {
> > @@ -670,6 +674,7 @@ static int register_trace_kprobe(struct trace_kprobe *tk)
> > return ret;
> > }
> >
> > +#ifdef CONFIG_MODULES
> > /* Module notifier call back, checking event on the module */
> > static int trace_kprobe_module_callback(struct notifier_block *nb,
> > unsigned long val, void *data)
> > @@ -699,6 +704,9 @@ static int trace_kprobe_module_callback(struct notifier_block *nb,
> >
> > return NOTIFY_DONE;
> > }
> > +#else
> > +#define trace_kprobe_module_callback (NULL)
> > +#endif /* CONFIG_MODULES */
> >
> > static struct notifier_block trace_kprobe_module_nb = {
> > .notifier_call = trace_kprobe_module_callback,
> > @@ -1933,8 +1941,11 @@ static __init int init_kprobe_trace_early(void)
> > if (ret)
> > return ret;
> >
> > - if (register_module_notifier(&trace_kprobe_module_nb))
> > - return -EINVAL;
> > + if (IS_ENABLED(CONFIG_MODULES)) {
> > + ret = register_module_notifier(&trace_kprobe_module_nb);
> > + if (ret)
> > + return -EINVAL;
> > + }
> >
> > return 0;
> > }
>
> 2/4, 3/4, 4/4:
>
> Tested-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> # arch/riscv
Hey, I tried the pci_proc_init example:
[ 3.060703] ------------[ ftrace bug ]------------
[ 3.060944] ftrace faulted on writing
[ 3.060987] [<ffffffff8102c0da>] pci_proc_init+0x0/0x80
[ 3.061509] Updating ftrace call site to call a different ftrace function
[ 3.061756] ftrace record flags: 80100001
[ 3.061925] (1)
[ 3.061925] expected tramp: ffffffff8000aa60
[ 3.062527] ------------[ cut here ]------------
[ 3.062652] WARNING: CPU: 0 PID: 18 at kernel/trace/ftrace.c:2180 ftrace_bug+0x282/0x2b8
[ 3.062747] CPU: 0 PID: 18 Comm: migration/0 Not tainted 6.9.0-rc1 #2
[ 3.062807] Hardware name: riscv-virtio,qemu (DT)
[ 3.062868] Stopper: multi_cpu_stop+0x0/0x1a0 <- stop_machine_cpuslocked+0x140/0x18c
[ 3.062925] epc : ftrace_bug+0x282/0x2b8
[ 3.062957] ra : ftrace_bug+0x282/0x2b8
[ 3.062989] epc : ffffffff80fc31f4 ra : ffffffff80fc31f4 sp : ff20000000093c70
[ 3.063014] gp : ffffffff824b7780 tp : ff60000002a85940 t0 : ffffffff800923a6
[ 3.063037] t1 : 0000000000000020 t2 : 6465746365707865 s0 : ff20000000093cb0
[ 3.063061] s1 : ffffffff8102c0da a0 : 0000000000000022 a1 : ffffffff8229b7f0
[ 3.063084] a2 : 0000000000000010 a3 : fffffffffffffffe a4 : 0000000000000000
[ 3.063108] a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000000000001
[ 3.063131] s2 : ff60000002850ab0 s3 : ffffffffffffffff s4 : 0000000000000002
[ 3.063154] s5 : 0000000002000000 s6 : 0000000082000000 s7 : 0000000000000000
[ 3.063178] s8 : 0000000000000001 s9 : ffffffff824bca18 s10: ff60000002845140
[ 3.063202] s11: 00000000000000ab t3 : ffffffff824ce9ef t4 : ffffffff824ce9ef
[ 3.063225] t5 : ffffffff824ce9f0 t6 : ff20000000093aa8
[ 3.063248] status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000003
[ 3.063331] [<ffffffff80fc31f4>] ftrace_bug+0x282/0x2b8
[ 3.063398] [<ffffffff80108b1a>] ftrace_replace_code+0xfe/0x168
[ 3.063430] [<ffffffff80108c82>] ftrace_modify_all_code+0x5c/0x16a
[ 3.063460] [<ffffffff80108da2>] __ftrace_modify_code+0x12/0x1c
[ 3.063490] [<ffffffff800f299c>] multi_cpu_stop+0x118/0x1a0
[ 3.063519] [<ffffffff800f242e>] cpu_stopper_thread+0xb2/0x12a
[ 3.063548] [<ffffffff8005dece>] smpboot_thread_fn+0x1aa/0x1d2
[ 3.063577] [<ffffffff80057fec>] kthread+0xfe/0x106
[ 3.063606] [<ffffffff80fe3d76>] ret_from_fork+0xe/0x20
[ 3.063676] ---[ end trace 0000000000000000 ]---
[ 3.069730] ------------[ cut here ]------------
[ 3.069861] Failed to disarm kprobe-ftrace at pci_proc_init+0x0/0x80 (error -19)
[ 3.070078] WARNING: CPU: 0 PID: 1 at kernel/kprobes.c:1128 __disarm_kprobe_ftrace+0x9a/0xae
[ 3.070124] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 69.0-rc1 #2
[ 3.070133] Hardware name: riscv-virtio,qemu (DT)
[ 3.070141] epc : __disarm_kprobe_ftrace+0x9a/0xae
[ 3.070150] ra : __disarm_kprobe_ftrace+0x9a/0xae
[ 3.070157] epc : ffffffff800ffcda ra : ffffffff800ffcda sp : ff2000000000be30
[ 3.070162] gp : ffffffff824b7780 tp : ff60000002a70000 t0 : ffffffff800923a6
[ 3.070167] t1 : 0000000000000046 t2 : 6f742064656c6961 s0 : ff2000000000be60
[ 3.070173] s1 : ffffffffffffffed a0 : 0000000000000044 a1 : ffffffff8229b7f0
[ 3.070178] a2 : 0000000000000010 a3 : fffffffffffffffe a4 : 0000000000000000
[ 3.070182] a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000000000001
[ 3.070187] s2 : ffffffff824bc940 s3 : ffffffff822ac158 s4 : ff60000002b53c80
[ 3.070192] s5 : ffffffff824bc940 s6 : ffffffff822ac158 s7 : ffffffff81000000
[ 3.070197] s8 : ffffffff814775f8 s9 : ffffffff824f23d8 s10: 0000000000000000
[ 3.070202] s11: 0000000000000000 t3 : ffffffff824ce9d7 t4 : ffffffff824ce9d7
[ 3.070206] t5 : ffffffff824ce9d8 t6 : ff2000000000bc48
[ 3.070211] status: 0000000200000120 badaddr: 0000000000000000 cause: 0000000000000003
[ 3.070218] [<ffffffff800ffcda>] __disarm_kprobe_ftrace+0x9a/0xae
[ 3.070228] [<ffffffff80101b16>] kprobe_free_init_mem+0xc2/0x130
[ 3.070236] [<ffffffff80fd9b38>] kernel_init+0x46/0x14e
[ 3.070245] [<ffffffff80fe3d76>] ret_from_fork+0xe/0x20
[ 3.070254] ---[ end trace 0000000000000000 ]---
[
This is with riscv64 defconfig, tracing shenanigans and the following
bootconfig and the bug was realized in QEMU:
ftrace {
tracing_on = 0
tracer = "function_graph"
event {
kprobes.pci_proc_init_begin {
probes = "pci_proc_init"
actions = "traceon"
}
kprobes.pci_proc_init_end {
probes = "pci_proc_init%return"
actions = "traceoff"
}
}
}
kernel {
console = hvc0
dyndbg = "file arch/riscv/kernel/* +p"
earlycon = sbi
memblock = debug
memtest = 1
tp_printk
frace_dump_on_oops
}
BR, Jarkko