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@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20210525073213.561116662@infradead.org

12 files changed, 0 insertions, 111 deletions

diff --git a/arch/arc/kernel/kprobes.c b/arch/arc/kernel/kprobes.c
index cabef45f11df..9f5b39f38736 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 a9653117ca0d..7b9b9a5a409b 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 d607c9912025..f6b088e9fa70 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 589f090f48b9..e0e973e49770 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 fc1ff8a4d7de..6efed4ecff9e 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 54dfba8fa77c..75bff0f77319 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 01ab2163659e..75b4e874269d 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 10b965c34536..923b5ea396ea 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 aae24dc75df6..ad631e33df24 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 756100b01e84..58263420ad2a 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 217c21a6986a..db4e341b4b6e 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 d3d65545cb8b..cfcdf4b8a306 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;