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From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: mhiramat@kernel.org, Peter Zijlstra <peterz@infradead.org>
Cc: ananth@linux.ibm.com, Christoph Hellwig <hch@lst.de>,
	linux-kernel@vger.kernel.org, mingo@kernel.org,
	rostedt@goodmis.org, x86@kernel.org
Subject: [PATCH] kprobes: Do not increment probe miss count in the fault handler
Date: Tue,  1 Jun 2021 17:31:50 +0530	[thread overview]
Message-ID: <20210601120150.672652-1-naveen.n.rao@linux.vnet.ibm.com> (raw)
In-Reply-To: <20210525073213.561116662@infradead.org>

Kprobes has a counter 'nmissed', that is used to count the number of
times a probe handler was not called. This generally happens when we hit
a kprobe while handling another kprobe.

However, if one of the probe handlers causes a fault, we are currently
incrementing 'nmissed'. The comment in fault handler indicates that this
can be used to account faults taken by the probe handlers. But, this has
never been the intention as is evident from the comment above 'nmissed'
in 'struct kprobe':

	/*count the number of times this probe was temporarily disarmed */
	unsigned long nmissed;

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
I'm posting this here so that these can go together, if the patch is ok 
otherwise.

Thanks,
- Naveen


 arch/arc/kernel/kprobes.c          |  6 ------
 arch/arm/probes/kprobes/core.c     | 14 --------------
 arch/arm64/kernel/probes/kprobes.c |  7 -------
 arch/csky/kernel/probes/kprobes.c  |  7 -------
 arch/ia64/kernel/kprobes.c         |  7 -------
 arch/powerpc/kernel/kprobes.c      |  7 -------
 arch/riscv/kernel/probes/kprobes.c |  7 -------
 arch/s390/kernel/kprobes.c         |  7 -------
 arch/sh/kernel/kprobes.c           |  7 -------
 arch/sparc/kernel/kprobes.c        |  7 -------
 arch/x86/kernel/kprobes/core.c     |  8 --------
 11 files changed, 84 deletions(-)

diff --git a/arch/arc/kernel/kprobes.c b/arch/arc/kernel/kprobes.c
index 9f5b39f387362e..5f0415fc73287b 100644
--- a/arch/arc/kernel/kprobes.c
+++ b/arch/arc/kernel/kprobes.c
@@ -317,12 +317,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned long trapnr)
 		 * caused the fault.
 		 */
 
-		/* We increment the nmissed count for accounting,
-		 * we can also use npre/npostfault count for accounting
-		 * these specific fault cases.
-		 */
-		kprobes_inc_nmissed_count(cur);
-
 		/*
 		 * 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 7b9b9a5a409bb8..27e0af78e88b02 100644
--- a/arch/arm/probes/kprobes/core.c
+++ b/arch/arm/probes/kprobes/core.c
@@ -348,20 +348,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 			reset_current_kprobe();
 		}
 		break;
-
-	case KPROBE_HIT_ACTIVE:
-	case KPROBE_HIT_SSDONE:
-		/*
-		 * We increment the nmissed count for accounting,
-		 * we can also use npre/npostfault count for accounting
-		 * these specific fault cases.
-		 */
-		kprobes_inc_nmissed_count(cur);
-
-		break;
-
-	default:
-		break;
 	}
 
 	return 0;
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index f6b088e9fa70e6..004b86eff9c2d9 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -276,13 +276,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 		break;
 	case KPROBE_HIT_ACTIVE:
 	case KPROBE_HIT_SSDONE:
-		/*
-		 * We increment the nmissed count for accounting,
-		 * we can also use npre/npostfault count for accounting
-		 * these specific fault cases.
-		 */
-		kprobes_inc_nmissed_count(cur);
-
 		/*
 		 * 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 e0e973e4977037..68b22b499aebf7 100644
--- a/arch/csky/kernel/probes/kprobes.c
+++ b/arch/csky/kernel/probes/kprobes.c
@@ -294,13 +294,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr)
 		break;
 	case KPROBE_HIT_ACTIVE:
 	case KPROBE_HIT_SSDONE:
-		/*
-		 * We increment the nmissed count for accounting,
-		 * we can also use npre/npostfault count for accounting
-		 * these specific fault cases.
-		 */
-		kprobes_inc_nmissed_count(cur);
-
 		/*
 		 * 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 6efed4ecff9e92..441ed04b103785 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -843,13 +843,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 		break;
 	case KPROBE_HIT_ACTIVE:
 	case KPROBE_HIT_SSDONE:
-		/*
-		 * We increment the nmissed count for accounting,
-		 * we can also use npre/npostfault count for accounting
-		 * these specific fault cases.
-		 */
-		kprobes_inc_nmissed_count(cur);
-
 		/*
 		 * In case the user-specified fault handler returned
 		 * zero, try to fix up.
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 75b4e874269d48..3f700830169fad 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -501,13 +501,6 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 		break;
 	case KPROBE_HIT_ACTIVE:
 	case KPROBE_HIT_SSDONE:
-		/*
-		 * We increment the nmissed count for accounting,
-		 * we can also use npre/npostfault count for accounting
-		 * these specific fault cases.
-		 */
-		kprobes_inc_nmissed_count(cur);
-
 		/*
 		 * 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 39eaa2091efd5d..247e33fa5bc75f 100644
--- a/arch/riscv/kernel/probes/kprobes.c
+++ b/arch/riscv/kernel/probes/kprobes.c
@@ -278,13 +278,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr)
 		break;
 	case KPROBE_HIT_ACTIVE:
 	case KPROBE_HIT_SSDONE:
-		/*
-		 * We increment the nmissed count for accounting,
-		 * we can also use npre/npostfault count for accounting
-		 * these specific fault cases.
-		 */
-		kprobes_inc_nmissed_count(cur);
-
 		/*
 		 * 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 ad631e33df24f3..74b0bd2c24d4c1 100644
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -445,13 +445,6 @@ static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
 		break;
 	case KPROBE_HIT_ACTIVE:
 	case KPROBE_HIT_SSDONE:
-		/*
-		 * We increment the nmissed count for accounting,
-		 * we can also use npre/npostfault count for accounting
-		 * these specific fault cases.
-		 */
-		kprobes_inc_nmissed_count(p);
-
 		/*
 		 * 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 58263420ad2a58..1c7f358ef0be1c 100644
--- a/arch/sh/kernel/kprobes.c
+++ b/arch/sh/kernel/kprobes.c
@@ -382,13 +382,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 		break;
 	case KPROBE_HIT_ACTIVE:
 	case KPROBE_HIT_SSDONE:
-		/*
-		 * We increment the nmissed count for accounting,
-		 * we can also use npre/npostfault count for accounting
-		 * these specific fault cases.
-		 */
-		kprobes_inc_nmissed_count(cur);
-
 		/*
 		 * 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 db4e341b4b6ea8..4c05a4ee6a0e71 100644
--- a/arch/sparc/kernel/kprobes.c
+++ b/arch/sparc/kernel/kprobes.c
@@ -345,13 +345,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 		break;
 	case KPROBE_HIT_ACTIVE:
 	case KPROBE_HIT_SSDONE:
-		/*
-		 * We increment the nmissed count for accounting,
-		 * we can also use npre/npostfault count for accounting
-		 * these specific fault cases.
-		 */
-		kprobes_inc_nmissed_count(cur);
-
 		/*
 		 * 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 cfcdf4b8a306f3..1b3fe0edd3299f 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -1102,14 +1102,6 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 			restore_previous_kprobe(kcb);
 		else
 			reset_current_kprobe();
-	} else if (kcb->kprobe_status == KPROBE_HIT_ACTIVE ||
-		   kcb->kprobe_status == KPROBE_HIT_SSDONE) {
-		/*
-		 * We increment the nmissed count for accounting,
-		 * we can also use npre/npostfault count for accounting
-		 * these specific fault cases.
-		 */
-		kprobes_inc_nmissed_count(cur);
 	}
 
 	return 0;

base-commit: c2131f7e73c9e9365613e323d65c7b9e5b910f56
prerequisite-patch-id: 78c74d348e7072bc263e19753ca25e04dda45981
-- 
2.31.1


  parent reply	other threads:[~2021-06-01 12:02 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-25  7:25 [PATCH 0/2] kprobes: Remove kprobe::fault_handler Peter Zijlstra
2021-05-25  7:25 ` [PATCH 1/2] " Peter Zijlstra
2021-05-25 14:06   ` Masami Hiramatsu
2021-05-26 10:50   ` Naveen N. Rao
2021-05-26 13:51     ` Masami Hiramatsu
2021-06-01 12:01   ` Naveen N. Rao [this message]
2021-06-01 13:20     ` [PATCH] kprobes: Do not increment probe miss count in the fault handler Peter Zijlstra
2021-06-01 23:48       ` Masami Hiramatsu
2021-06-04 13:38     ` [tip: perf/core] " tip-bot2 for Naveen N. Rao
2021-06-01 14:04   ` [tip: perf/core] kprobes: Remove kprobe::fault_handler tip-bot2 for Peter Zijlstra
2021-05-25  7:25 ` [PATCH 2/2] x86,kprobes: WARN if kprobes tries to handle a fault Peter Zijlstra
2021-05-25 14:21   ` Masami Hiramatsu
2021-06-01 14:04   ` [tip: perf/core] " tip-bot2 for Peter Zijlstra

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