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Various kprobes updates, mostly centered around cleaning up the no-instrumentation 

logic, instead of the current per debug facility blacklist, use the more generic
 .noinstr.text approach, combined with a 'noinstr' marker for functions.
 
 Also add instrumentation_begin()/end() to better manage the exact place in entry
 code where instrumentation may be used.
 
 Also add a kprobes blacklist for modules.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'core-kprobes-2020-06-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull kprobes updates from Ingo Molnar:
 "Various kprobes updates, mostly centered around cleaning up the
  no-instrumentation logic.

  Instead of the current per debug facility blacklist, use the more
  generic .noinstr.text approach, combined with a 'noinstr' marker for
  functions.

  Also add instrumentation_begin()/end() to better manage the exact
  place in entry code where instrumentation may be used.

  And add a kprobes blacklist for modules"

* tag 'core-kprobes-2020-06-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  kprobes: Prevent probes in .noinstr.text section
  vmlinux.lds.h: Create section for protection against instrumentation
  samples/kprobes: Add __kprobes and NOKPROBE_SYMBOL() for handlers.
  kprobes: Support NOKPROBE_SYMBOL() in modules
  kprobes: Support __kprobes blacklist in modules
  kprobes: Lock kprobe_mutex while showing kprobe_blacklist
This commit is contained in:
Linus Torvalds 2020-06-01 12:45:04 -07:00
parent 9bf9511e3d 66e9b07171
commit 0bd957eb11
11 changed files with 180 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/powerpc/kernel/vmlinux.lds.S
View File

@ -90,6 +90,7 @@ SECTIONS
#ifdef CONFIG_PPC64
*(.tramp.ftrace.text);
#endif
NOINSTR_TEXT
SCHED_TEXT
CPUIDLE_TEXT
LOCK_TEXT

3
include/asm-generic/sections.h
View File

@ -53,6 +53,9 @@ extern char __ctors_start[], __ctors_end[];
/* Start and end of .opd section - used for function descriptors. */
extern char __start_opd[], __end_opd[];
/* Start and end of instrumentation protected text section */
extern char __noinstr_text_start[], __noinstr_text_end[];
extern __visible const void __nosave_begin, __nosave_end;
/* Function descriptor handling (if any). Override in asm/sections.h */

10
include/asm-generic/vmlinux.lds.h
View File

@ -540,6 +540,15 @@
. = ALIGN((align)); \
__end_rodata = .;
/*
* Non-instrumentable text section
*/
#define NOINSTR_TEXT \
ALIGN_FUNCTION(); \
__noinstr_text_start = .; \
*(.noinstr.text) \
__noinstr_text_end = .;
/*
* .text section. Map to function alignment to avoid address changes
* during second ld run in second ld pass when generating System.map
@ -551,6 +560,7 @@
#define TEXT_TEXT \
ALIGN_FUNCTION(); \
*(.text.hot TEXT_MAIN .text.fixup .text.unlikely) \
NOINSTR_TEXT \
*(.text..refcount) \
*(.ref.text) \
MEM_KEEP(init.text*) \

53
include/linux/compiler.h
View File

@ -120,12 +120,65 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
/* Annotate a C jump table to allow objtool to follow the code flow */
#define __annotate_jump_table __section(.rodata..c_jump_table)
#ifdef CONFIG_DEBUG_ENTRY
/* Begin/end of an instrumentation safe region */
#define instrumentation_begin() ({ \
asm volatile("%c0:\n\t" \
".pushsection .discard.instr_begin\n\t" \
".long %c0b - .\n\t" \
".popsection\n\t" : : "i" (__COUNTER__)); \
})
/*
* Because instrumentation_{begin,end}() can nest, objtool validation considers
* _begin() a +1 and _end() a -1 and computes a sum over the instructions.
* When the value is greater than 0, we consider instrumentation allowed.
*
* There is a problem with code like:
*
* noinstr void foo()
* {
* instrumentation_begin();
* ...
* if (cond) {
* instrumentation_begin();
* ...
* instrumentation_end();
* }
* bar();
* instrumentation_end();
* }
*
* If instrumentation_end() would be an empty label, like all the other
* annotations, the inner _end(), which is at the end of a conditional block,
* would land on the instruction after the block.
*
* If we then consider the sum of the !cond path, we'll see that the call to
* bar() is with a 0-value, even though, we meant it to happen with a positive
* value.
*
* To avoid this, have _end() be a NOP instruction, this ensures it will be
* part of the condition block and does not escape.
*/
#define instrumentation_end() ({ \
asm volatile("%c0: nop\n\t" \
".pushsection .discard.instr_end\n\t" \
".long %c0b - .\n\t" \
".popsection\n\t" : : "i" (__COUNTER__)); \
})
#endif /* CONFIG_DEBUG_ENTRY */
#else
#define annotate_reachable()
#define annotate_unreachable()
#define __annotate_jump_table
#endif
#ifndef instrumentation_begin
#define instrumentation_begin() do { } while(0)
#define instrumentation_end() do { } while(0)
#endif
#ifndef ASM_UNREACHABLE
# define ASM_UNREACHABLE
#endif

4
include/linux/compiler_types.h
View File

@ -118,6 +118,10 @@ struct ftrace_likely_data {
#define notrace __attribute__((__no_instrument_function__))
#endif
/* Section for code which can't be instrumented at all */
#define noinstr \
noinline notrace __attribute((__section__(".noinstr.text")))
/*
* it doesn't make sense on ARM (currently the only user of __naked)
* to trace naked functions because then mcount is called without

8
include/linux/module.h
View File

@ -458,6 +458,8 @@ struct module {
void __percpu *percpu;
unsigned int percpu_size;
#endif
void *noinstr_text_start;
unsigned int noinstr_text_size;
#ifdef CONFIG_TRACEPOINTS
unsigned int num_tracepoints;
@ -489,6 +491,12 @@ struct module {
unsigned int num_ftrace_callsites;
unsigned long *ftrace_callsites;
#endif
#ifdef CONFIG_KPROBES
void *kprobes_text_start;
unsigned int kprobes_text_size;
unsigned long *kprobe_blacklist;
unsigned int num_kprobe_blacklist;
#endif
#ifdef CONFIG_LIVEPATCH
bool klp; /* Is this a livepatch module? */

85
kernel/kprobes.c
View File

@ -2179,6 +2179,24 @@ 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 __init __weak arch_populate_kprobe_blacklist(void)
{
return 0;
@ -2211,10 +2229,62 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
/* Symbols in __kprobes_text are blacklisted */
ret = kprobe_add_area_blacklist((unsigned long)__kprobes_text_start,
(unsigned long)__kprobes_text_end);
if (ret)
return ret;
/* Symbols in noinstr section are blacklisted */
ret = kprobe_add_area_blacklist((unsigned long)__noinstr_text_start,
(unsigned long)__noinstr_text_end);
return ret ? : arch_populate_kprobe_blacklist();
}
static void add_module_kprobe_blacklist(struct module *mod)
{
unsigned long start, end;
int i;
if (mod->kprobe_blacklist) {
for (i = 0; i < mod->num_kprobe_blacklist; i++)
kprobe_add_ksym_blacklist(mod->kprobe_blacklist[i]);
}
start = (unsigned long)mod->kprobes_text_start;
if (start) {
end = start + mod->kprobes_text_size;
kprobe_add_area_blacklist(start, end);
}
start = (unsigned long)mod->noinstr_text_start;
if (start) {
end = start + mod->noinstr_text_size;
kprobe_add_area_blacklist(start, end);
}
}
static void remove_module_kprobe_blacklist(struct module *mod)
{
unsigned long start, end;
int i;
if (mod->kprobe_blacklist) {
for (i = 0; i < mod->num_kprobe_blacklist; i++)
kprobe_remove_ksym_blacklist(mod->kprobe_blacklist[i]);
}
start = (unsigned long)mod->kprobes_text_start;
if (start) {
end = start + mod->kprobes_text_size;
kprobe_remove_area_blacklist(start, end);
}
start = (unsigned long)mod->noinstr_text_start;
if (start) {
end = start + mod->noinstr_text_size;
kprobe_remove_area_blacklist(start, end);
}
}
/* Module notifier call back, checking kprobes on the module */
static int kprobes_module_callback(struct notifier_block *nb,
unsigned long val, void *data)
@ -2225,6 +2295,11 @@ static int kprobes_module_callback(struct notifier_block *nb,
unsigned int i;
int checkcore = (val == MODULE_STATE_GOING);
if (val == MODULE_STATE_COMING) {
mutex_lock(&kprobe_mutex);
add_module_kprobe_blacklist(mod);
mutex_unlock(&kprobe_mutex);
}
if (val != MODULE_STATE_GOING && val != MODULE_STATE_LIVE)
return NOTIFY_DONE;
@ -2255,6 +2330,8 @@ static int kprobes_module_callback(struct notifier_block *nb,
kill_kprobe(p);
}
}
if (val == MODULE_STATE_GOING)
remove_module_kprobe_blacklist(mod);
mutex_unlock(&kprobe_mutex);
return NOTIFY_DONE;
}
@ -2420,6 +2497,7 @@ static const struct file_operations debugfs_kprobes_operations = {
/* kprobes/blacklist -- shows which functions can not be probed */
static void *kprobe_blacklist_seq_start(struct seq_file *m, loff_t *pos)
{
mutex_lock(&kprobe_mutex);
return seq_list_start(&kprobe_blacklist, *pos);
}
@ -2446,10 +2524,15 @@ static int kprobe_blacklist_seq_show(struct seq_file *m, void *v)
return 0;
}
static void kprobe_blacklist_seq_stop(struct seq_file *f, void *v)
{
mutex_unlock(&kprobe_mutex);
}
static const struct seq_operations kprobe_blacklist_seq_ops = {
.start = kprobe_blacklist_seq_start,
.next = kprobe_blacklist_seq_next,
.stop = kprobe_seq_stop, /* Reuse void function */
.stop = kprobe_blacklist_seq_stop,
.show = kprobe_blacklist_seq_show,
};

10
kernel/module.c
View File

@ -3150,6 +3150,9 @@ static int find_module_sections(struct module *mod, struct load_info *info)
}
#endif
mod->noinstr_text_start = section_objs(info, ".noinstr.text", 1,
&mod->noinstr_text_size);
#ifdef CONFIG_TRACEPOINTS
mod->tracepoints_ptrs = section_objs(info, "__tracepoints_ptrs",
sizeof(*mod->tracepoints_ptrs),
@ -3193,6 +3196,13 @@ static int find_module_sections(struct module *mod, struct load_info *info)
mod->ei_funcs = section_objs(info, "_error_injection_whitelist",
sizeof(*mod->ei_funcs),
&mod->num_ei_funcs);
#endif
#ifdef CONFIG_KPROBES
mod->kprobes_text_start = section_objs(info, ".kprobes.text", 1,
&mod->kprobes_text_size);
mod->kprobe_blacklist = section_objs(info, "_kprobe_blacklist",
sizeof(unsigned long),
&mod->num_kprobe_blacklist);
#endif
mod->extable = section_objs(info, "__ex_table",
sizeof(*mod->extable), &mod->num_exentries);

6
samples/kprobes/kprobe_example.c
View File

@ -25,7 +25,7 @@ static struct kprobe kp = {
};
/* kprobe pre_handler: called just before the probed instruction is executed */
static int handler_pre(struct kprobe *p, struct pt_regs *regs)
static int __kprobes handler_pre(struct kprobe *p, struct pt_regs *regs)
{
#ifdef CONFIG_X86
pr_info("<%s> pre_handler: p->addr = 0x%p, ip = %lx, flags = 0x%lx\n",
@ -54,7 +54,7 @@ static int handler_pre(struct kprobe *p, struct pt_regs *regs)
}
/* kprobe post_handler: called after the probed instruction is executed */
static void handler_post(struct kprobe *p, struct pt_regs *regs,
static void __kprobes handler_post(struct kprobe *p, struct pt_regs *regs,
unsigned long flags)
{
#ifdef CONFIG_X86
@ -90,6 +90,8 @@ static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
/* Return 0 because we don't handle the fault. */
return 0;
}
/* NOKPROBE_SYMBOL() is also available */
NOKPROBE_SYMBOL(handler_fault);
static int __init kprobe_init(void)
{

2
samples/kprobes/kretprobe_example.c
View File

@ -48,6 +48,7 @@ static int entry_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
data->entry_stamp = ktime_get();
return 0;
}
NOKPROBE_SYMBOL(entry_handler);
/*
* Return-probe handler: Log the return value and duration. Duration may turn
@ -67,6 +68,7 @@ static int ret_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
func_name, retval, (long long)delta);
return 0;
}
NOKPROBE_SYMBOL(ret_handler);
static struct kretprobe my_kretprobe = {
.handler = ret_handler,

2
scripts/mod/modpost.c
View File

@ -948,7 +948,7 @@ static void check_section(const char *modname, struct elf_info *elf,
#define DATA_SECTIONS ".data", ".data.rel"
#define TEXT_SECTIONS ".text", ".text.unlikely", ".sched.text", \
".kprobes.text", ".cpuidle.text"
".kprobes.text", ".cpuidle.text", ".noinstr.text"
#define OTHER_TEXT_SECTIONS ".ref.text", ".head.text", ".spinlock.text", \
".fixup", ".entry.text", ".exception.text", ".text.*", \
".coldtext"