[tip: perf/core] kprobes: Remove kprobe::fault_handler
From: tip-bot2 for Peter Zijlstra
Date: Tue Jun 01 2021 - 10:05:03 EST
The following commit has been merged into the perf/core branch of tip:
Commit-ID: ec6aba3d2be1ed75b3f4c894bb64a36d40db1f55
Gitweb: https://git.kernel.org/tip/ec6aba3d2be1ed75b3f4c894bb64a36d40db1f55
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Tue, 25 May 2021 09:25:19 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 01 Jun 2021 16:00:08 +02:00
kprobes: Remove kprobe::fault_handler
The reason for kprobe::fault_handler(), as given by their comment:
* We come here because instructions in the pre/post
* handler caused the page_fault, this could happen
* if handler tries to access user space by
* copy_from_user(), get_user() etc. Let the
* user-specified handler try to fix it first.
Is just plain bad. Those other handlers are ran from non-preemptible
context and had better use _nofault() functions. Also, there is no
upstream usage of this.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210525073213.561116662@xxxxxxxxxxxxx
---
Documentation/trace/kprobes.rst | 24 +++++-------------------
arch/arc/kernel/kprobes.c | 10 ----------
arch/arm/probes/kprobes/core.c | 9 ---------
arch/arm64/kernel/probes/kprobes.c | 10 ----------
arch/csky/kernel/probes/kprobes.c | 10 ----------
arch/ia64/kernel/kprobes.c | 9 ---------
arch/mips/kernel/kprobes.c | 3 ---
arch/powerpc/kernel/kprobes.c | 10 ----------
arch/riscv/kernel/probes/kprobes.c | 10 ----------
arch/s390/kernel/kprobes.c | 10 ----------
arch/sh/kernel/kprobes.c | 10 ----------
arch/sparc/kernel/kprobes.c | 10 ----------
arch/x86/kernel/kprobes/core.c | 10 ----------
include/linux/kprobes.h | 8 --------
kernel/kprobes.c | 19 -------------------
samples/kprobes/kprobe_example.c | 15 ---------------
16 files changed, 5 insertions(+), 172 deletions(-)
diff --git a/Documentation/trace/kprobes.rst b/Documentation/trace/kprobes.rst
index b757b6d..998149c 100644
--- a/Documentation/trace/kprobes.rst
+++ b/Documentation/trace/kprobes.rst
@@ -362,14 +362,11 @@ register_kprobe
#include <linux/kprobes.h>
int register_kprobe(struct kprobe *kp);
-Sets a breakpoint at the address kp->addr. When the breakpoint is
-hit, Kprobes calls kp->pre_handler. After the probed instruction
-is single-stepped, Kprobe calls kp->post_handler. If a fault
-occurs during execution of kp->pre_handler or kp->post_handler,
-or during single-stepping of the probed instruction, Kprobes calls
-kp->fault_handler. Any or all handlers can be NULL. If kp->flags
-is set KPROBE_FLAG_DISABLED, that kp will be registered but disabled,
-so, its handlers aren't hit until calling enable_kprobe(kp).
+Sets a breakpoint at the address kp->addr. When the breakpoint is hit, Kprobes
+calls kp->pre_handler. After the probed instruction is single-stepped, Kprobe
+calls kp->post_handler. Any or all handlers can be NULL. If kp->flags is set
+KPROBE_FLAG_DISABLED, that kp will be registered but disabled, so, its handlers
+aren't hit until calling enable_kprobe(kp).
.. note::
@@ -415,17 +412,6 @@ User's post-handler (kp->post_handler)::
p and regs are as described for the pre_handler. flags always seems
to be zero.
-User's fault-handler (kp->fault_handler)::
-
- #include <linux/kprobes.h>
- #include <linux/ptrace.h>
- int fault_handler(struct kprobe *p, struct pt_regs *regs, int trapnr);
-
-p and regs are as described for the pre_handler. trapnr is the
-architecture-specific trap number associated with the fault (e.g.,
-on i386, 13 for a general protection fault or 14 for a page fault).
-Returns 1 if it successfully handled the exception.
-
register_kretprobe
------------------
diff --git a/arch/arc/kernel/kprobes.c b/arch/arc/kernel/kprobes.c
index cabef45..9f5b39f 100644
--- a/arch/arc/kernel/kprobes.c
+++ b/arch/arc/kernel/kprobes.c
@@ -324,16 +324,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned long trapnr)
kprobes_inc_nmissed_count(cur);
/*
- * We come here because instructions in the pre/post
- * handler caused the page_fault, this could happen
- * if handler tries to access user space by
- * copy_from_user(), get_user() etc. Let the
- * user-specified handler try to fix it first.
- */
- if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
- return 1;
-
- /*
* In case the user-specified fault handler returned zero,
* try to fix up.
*/
diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
index a965311..7b9b9a5 100644
--- a/arch/arm/probes/kprobes/core.c
+++ b/arch/arm/probes/kprobes/core.c
@@ -358,15 +358,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
*/
kprobes_inc_nmissed_count(cur);
- /*
- * We come here because instructions in the pre/post
- * handler caused the page_fault, this could happen
- * if handler tries to access user space by
- * copy_from_user(), get_user() etc. Let the
- * user-specified handler try to fix it.
- */
- if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
- return 1;
break;
default:
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index d607c99..f6b088e 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -284,16 +284,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
kprobes_inc_nmissed_count(cur);
/*
- * We come here because instructions in the pre/post
- * handler caused the page_fault, this could happen
- * if handler tries to access user space by
- * copy_from_user(), get_user() etc. Let the
- * user-specified handler try to fix it first.
- */
- if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
- return 1;
-
- /*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
diff --git a/arch/csky/kernel/probes/kprobes.c b/arch/csky/kernel/probes/kprobes.c
index 589f090..e0e973e 100644
--- a/arch/csky/kernel/probes/kprobes.c
+++ b/arch/csky/kernel/probes/kprobes.c
@@ -302,16 +302,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr)
kprobes_inc_nmissed_count(cur);
/*
- * We come here because instructions in the pre/post
- * handler caused the page_fault, this could happen
- * if handler tries to access user space by
- * copy_from_user(), get_user() etc. Let the
- * user-specified handler try to fix it first.
- */
- if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
- return 1;
-
- /*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index fc1ff8a..6efed4e 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -851,15 +851,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
kprobes_inc_nmissed_count(cur);
/*
- * We come here because instructions in the pre/post
- * handler caused the page_fault, this could happen
- * if handler tries to access user space by
- * copy_from_user(), get_user() etc. Let the
- * user-specified handler try to fix it first.
- */
- if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
- return 1;
- /*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
diff --git a/arch/mips/kernel/kprobes.c b/arch/mips/kernel/kprobes.c
index 54dfba8..75bff0f 100644
--- a/arch/mips/kernel/kprobes.c
+++ b/arch/mips/kernel/kprobes.c
@@ -403,9 +403,6 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
struct kprobe *cur = kprobe_running();
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
- if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
- return 1;
-
if (kcb->kprobe_status & KPROBE_HIT_SS) {
resume_execution(cur, regs, kcb);
regs->cp0_status |= kcb->kprobe_old_SR;
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 01ab216..75b4e87 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -509,16 +509,6 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
kprobes_inc_nmissed_count(cur);
/*
- * We come here because instructions in the pre/post
- * handler caused the page_fault, this could happen
- * if handler tries to access user space by
- * copy_from_user(), get_user() etc. Let the
- * user-specified handler try to fix it first.
- */
- if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
- return 1;
-
- /*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c
index 10b965c..923b5ea 100644
--- a/arch/riscv/kernel/probes/kprobes.c
+++ b/arch/riscv/kernel/probes/kprobes.c
@@ -284,16 +284,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr)
kprobes_inc_nmissed_count(cur);
/*
- * We come here because instructions in the pre/post
- * handler caused the page_fault, this could happen
- * if handler tries to access user space by
- * copy_from_user(), get_user() etc. Let the
- * user-specified handler try to fix it first.
- */
- if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
- return 1;
-
- /*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
index aae24dc..ad631e3 100644
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -453,16 +453,6 @@ static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
kprobes_inc_nmissed_count(p);
/*
- * We come here because instructions in the pre/post
- * handler caused the page_fault, this could happen
- * if handler tries to access user space by
- * copy_from_user(), get_user() etc. Let the
- * user-specified handler try to fix it first.
- */
- if (p->fault_handler && p->fault_handler(p, regs, trapnr))
- return 1;
-
- /*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
diff --git a/arch/sh/kernel/kprobes.c b/arch/sh/kernel/kprobes.c
index 756100b..5826342 100644
--- a/arch/sh/kernel/kprobes.c
+++ b/arch/sh/kernel/kprobes.c
@@ -390,16 +390,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
kprobes_inc_nmissed_count(cur);
/*
- * We come here because instructions in the pre/post
- * handler caused the page_fault, this could happen
- * if handler tries to access user space by
- * copy_from_user(), get_user() etc. Let the
- * user-specified handler try to fix it first.
- */
- if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
- return 1;
-
- /*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
diff --git a/arch/sparc/kernel/kprobes.c b/arch/sparc/kernel/kprobes.c
index 217c21a..db4e341 100644
--- a/arch/sparc/kernel/kprobes.c
+++ b/arch/sparc/kernel/kprobes.c
@@ -353,16 +353,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
kprobes_inc_nmissed_count(cur);
/*
- * We come here because instructions in the pre/post
- * handler caused the page_fault, this could happen
- * if handler tries to access user space by
- * copy_from_user(), get_user() etc. Let the
- * user-specified handler try to fix it first.
- */
- if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
- return 1;
-
- /*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index d3d6554..cfcdf4b 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -1110,16 +1110,6 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
* these specific fault cases.
*/
kprobes_inc_nmissed_count(cur);
-
- /*
- * We come here because instructions in the pre/post
- * handler caused the page_fault, this could happen
- * if handler tries to access user space by
- * copy_from_user(), get_user() etc. Let the
- * user-specified handler try to fix it first.
- */
- if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
- return 1;
}
return 0;
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 1883a4a..523ffc7 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -54,8 +54,6 @@ struct kretprobe_instance;
typedef int (*kprobe_pre_handler_t) (struct kprobe *, struct pt_regs *);
typedef void (*kprobe_post_handler_t) (struct kprobe *, struct pt_regs *,
unsigned long flags);
-typedef int (*kprobe_fault_handler_t) (struct kprobe *, struct pt_regs *,
- int trapnr);
typedef int (*kretprobe_handler_t) (struct kretprobe_instance *,
struct pt_regs *);
@@ -83,12 +81,6 @@ struct kprobe {
/* Called after addr is executed, unless... */
kprobe_post_handler_t post_handler;
- /*
- * ... called if executing addr causes a fault (eg. page fault).
- * Return 1 if it handled fault, otherwise kernel will see it.
- */
- kprobe_fault_handler_t fault_handler;
-
/* Saved opcode (which has been replaced with breakpoint) */
kprobe_opcode_t opcode;
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 745f08f..e41385a 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1183,23 +1183,6 @@ static void aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
}
NOKPROBE_SYMBOL(aggr_post_handler);
-static int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
- int trapnr)
-{
- struct kprobe *cur = __this_cpu_read(kprobe_instance);
-
- /*
- * if we faulted "during" the execution of a user specified
- * probe handler, invoke just that probe's fault handler
- */
- if (cur && cur->fault_handler) {
- if (cur->fault_handler(cur, regs, trapnr))
- return 1;
- }
- return 0;
-}
-NOKPROBE_SYMBOL(aggr_fault_handler);
-
/* Walks the list and increments nmissed count for multiprobe case */
void kprobes_inc_nmissed_count(struct kprobe *p)
{
@@ -1330,7 +1313,6 @@ static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
ap->addr = p->addr;
ap->flags = p->flags & ~KPROBE_FLAG_OPTIMIZED;
ap->pre_handler = aggr_pre_handler;
- ap->fault_handler = aggr_fault_handler;
/* We don't care the kprobe which has gone. */
if (p->post_handler && !kprobe_gone(p))
ap->post_handler = aggr_post_handler;
@@ -2014,7 +1996,6 @@ int register_kretprobe(struct kretprobe *rp)
rp->kp.pre_handler = pre_handler_kretprobe;
rp->kp.post_handler = NULL;
- rp->kp.fault_handler = NULL;
/* Pre-allocate memory for max kretprobe instances */
if (rp->maxactive <= 0) {
diff --git a/samples/kprobes/kprobe_example.c b/samples/kprobes/kprobe_example.c
index c495664..4b2f318 100644
--- a/samples/kprobes/kprobe_example.c
+++ b/samples/kprobes/kprobe_example.c
@@ -94,26 +94,11 @@ static void __kprobes handler_post(struct kprobe *p, struct pt_regs *regs,
#endif
}
-/*
- * fault_handler: this is called if an exception is generated for any
- * instruction within the pre- or post-handler, or when Kprobes
- * single-steps the probed instruction.
- */
-static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
-{
- pr_info("fault_handler: p->addr = 0x%p, trap #%dn", p->addr, 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)
{
int ret;
kp.pre_handler = handler_pre;
kp.post_handler = handler_post;
- kp.fault_handler = handler_fault;
ret = register_kprobe(&kp);
if (ret < 0) {