[llvm] [llvm-exegesis][AArch64] Check for PAC keys before disabling them (PR #138643)
Abhilash Majumder via llvm-commits
llvm-commits at lists.llvm.org
Tue May 13 09:11:16 PDT 2025
https://github.com/abhilash1910 updated https://github.com/llvm/llvm-project/pull/138643
>From a88910dccb1d13d5945d5d4ca09135c268461205 Mon Sep 17 00:00:00 2001
From: abmajumder <abmajumder at nvidia.com>
Date: Tue, 6 May 2025 10:35:24 +0530
Subject: [PATCH 01/12] fix pac/pag
---
.../llvm-exegesis/lib/AArch64/Target.cpp | 24 +++++++++++++------
1 file changed, 17 insertions(+), 7 deletions(-)
diff --git a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
index a1eb5a46f21fc..d1da6f41461a7 100644
--- a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
@@ -207,16 +207,26 @@ class ExegesisAArch64Target : public ExegesisTarget {
if (isPointerAuth(Opcode)) {
#if defined(__aarch64__) && defined(__linux__)
+
+ // Fix for some systems where PAC/PAG keys are present but is
+ // explicitly getting disabled
+ unsigned long pac_keys = 0;
+ if (prctl(PR_PAC_GET_ENABLED_KEYS, &pac_keys, 0, 0, 0) < 0) {
+ return "Failed to get PAC key status";
+ }
+
// Disable all PAC keys. Note that while we expect the measurements to
// be the same with PAC keys disabled, they could potentially be lower
// since authentication checks are bypassed.
- if (prctl(PR_PAC_SET_ENABLED_KEYS,
- PR_PAC_APIAKEY | PR_PAC_APIBKEY | PR_PAC_APDAKEY |
- PR_PAC_APDBKEY, // all keys
- 0, // disable all
- 0, 0) < 0) {
- return "Failed to disable PAC keys";
- }
+ if (pac_keys != 0) {
+ if (prctl(PR_PAC_SET_ENABLED_KEYS,
+ PR_PAC_APIAKEY | PR_PAC_APIBKEY | PR_PAC_APDAKEY |
+ PR_PAC_APDBKEY, // all keys
+ 0, // disable all
+ 0, 0) < 0) {
+ return "Failed to disable PAC keys";
+ }
+ }
#else
return "Unsupported opcode: isPointerAuth";
#endif
>From 009d3ba11c4e19da9c0bede0a0979d2f7f03611a Mon Sep 17 00:00:00 2001
From: abmajumder <abmajumder at nvidia.com>
Date: Tue, 6 May 2025 16:12:57 +0530
Subject: [PATCH 02/12] review comments
---
llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
index d1da6f41461a7..33082621c11e4 100644
--- a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
@@ -207,14 +207,17 @@ class ExegesisAArch64Target : public ExegesisTarget {
if (isPointerAuth(Opcode)) {
#if defined(__aarch64__) && defined(__linux__)
-
- // Fix for some systems where PAC/PAG keys are present but is
- // explicitly getting disabled
+
+ // For some systems with existing PAC keys set, it is better to
+ // check the existing state of the key before setting it.
+ // For systems without PAC, this is a No-op but with PAC, it is
+ // safer to check the existing key state and then disable/enable them.
+ // Hence the guard placed for switching.
unsigned long pac_keys = 0;
if (prctl(PR_PAC_GET_ENABLED_KEYS, &pac_keys, 0, 0, 0) < 0) {
return "Failed to get PAC key status";
}
-
+
// Disable all PAC keys. Note that while we expect the measurements to
// be the same with PAC keys disabled, they could potentially be lower
// since authentication checks are bypassed.
@@ -226,7 +229,7 @@ class ExegesisAArch64Target : public ExegesisTarget {
0, 0) < 0) {
return "Failed to disable PAC keys";
}
- }
+ }
#else
return "Unsupported opcode: isPointerAuth";
#endif
>From 2c80855603699c6b37bcf6eab1cab98d7ec241e1 Mon Sep 17 00:00:00 2001
From: abmajumder <abmajumder at nvidia.com>
Date: Wed, 7 May 2025 17:12:59 +0530
Subject: [PATCH 03/12] review comments
---
llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
index 33082621c11e4..93c13dca31e5c 100644
--- a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
@@ -213,7 +213,7 @@ class ExegesisAArch64Target : public ExegesisTarget {
// For systems without PAC, this is a No-op but with PAC, it is
// safer to check the existing key state and then disable/enable them.
// Hence the guard placed for switching.
- unsigned long pac_keys = 0;
+ unsigned long PacKeys = 0;
if (prctl(PR_PAC_GET_ENABLED_KEYS, &pac_keys, 0, 0, 0) < 0) {
return "Failed to get PAC key status";
}
@@ -221,7 +221,7 @@ class ExegesisAArch64Target : public ExegesisTarget {
// Disable all PAC keys. Note that while we expect the measurements to
// be the same with PAC keys disabled, they could potentially be lower
// since authentication checks are bypassed.
- if (pac_keys != 0) {
+ if (PacKeys != 0) {
if (prctl(PR_PAC_SET_ENABLED_KEYS,
PR_PAC_APIAKEY | PR_PAC_APIBKEY | PR_PAC_APDAKEY |
PR_PAC_APDBKEY, // all keys
>From 2a9af0f62741e43dd3d6f760a47c0a60833a04bd Mon Sep 17 00:00:00 2001
From: abmajumder <abmajumder at nvidia.com>
Date: Wed, 7 May 2025 20:25:25 +0530
Subject: [PATCH 04/12] typo build error
---
llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
index 93c13dca31e5c..7e6382693c3e9 100644
--- a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
@@ -212,9 +212,9 @@ class ExegesisAArch64Target : public ExegesisTarget {
// check the existing state of the key before setting it.
// For systems without PAC, this is a No-op but with PAC, it is
// safer to check the existing key state and then disable/enable them.
- // Hence the guard placed for switching.
+ // Hence the guard for switching.
unsigned long PacKeys = 0;
- if (prctl(PR_PAC_GET_ENABLED_KEYS, &pac_keys, 0, 0, 0) < 0) {
+ if (prctl(PR_PAC_GET_ENABLED_KEYS, &PacKeys, 0, 0, 0) < 0) {
return "Failed to get PAC key status";
}
>From 7dde4a4a1d0f559d093405680587f9652b7e6174 Mon Sep 17 00:00:00 2001
From: abmajumder <debabhi1396 at gmail.com>
Date: Fri, 9 May 2025 14:19:33 +0530
Subject: [PATCH 05/12] add einval condition and reviews
---
.../llvm-exegesis/lib/AArch64/Target.cpp | 32 ++++++++++++++-----
1 file changed, 24 insertions(+), 8 deletions(-)
diff --git a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
index 7e6382693c3e9..a432eb57026d2 100644
--- a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
@@ -10,6 +10,7 @@
#include "AArch64RegisterInfo.h"
#if defined(__aarch64__) && defined(__linux__)
+#include <errno.h>
#include <linux/prctl.h> // For PR_PAC_* constants
#include <sys/prctl.h>
#ifndef PR_PAC_SET_ENABLED_KEYS
@@ -199,6 +200,11 @@ class ExegesisAArch64Target : public ExegesisTarget {
PM.add(createAArch64ExpandPseudoPass());
}
+ static long prctl_wrapper(int op, long arg2 = 0, long arg3 = 0, long arg4 = 0,
+ long arg5 = 0) {
+ return prctl(op, arg2, arg3, arg4, arg5);
+ }
+
const char *getIgnoredOpcodeReasonOrNull(const LLVMState &State,
unsigned Opcode) const override {
if (const char *Reason =
@@ -213,20 +219,30 @@ class ExegesisAArch64Target : public ExegesisTarget {
// For systems without PAC, this is a No-op but with PAC, it is
// safer to check the existing key state and then disable/enable them.
// Hence the guard for switching.
- unsigned long PacKeys = 0;
- if (prctl(PR_PAC_GET_ENABLED_KEYS, &PacKeys, 0, 0, 0) < 0) {
+ errno = 0;
+ unsigned long PacKeys = prctl_wrapper(PR_PAC_GET_ENABLED_KEYS,
+ 0, // unused
+ 0, // unused
+ 0, // unused
+ 0); // unused
+ if ((long)PacKeys < 0) {
+ if (errno == EINVAL) {
+ return "PAuth not supported on this system";
+ }
return "Failed to get PAC key status";
}
// Disable all PAC keys. Note that while we expect the measurements to
// be the same with PAC keys disabled, they could potentially be lower
// since authentication checks are bypassed.
- if (PacKeys != 0) {
- if (prctl(PR_PAC_SET_ENABLED_KEYS,
- PR_PAC_APIAKEY | PR_PAC_APIBKEY | PR_PAC_APDAKEY |
- PR_PAC_APDBKEY, // all keys
- 0, // disable all
- 0, 0) < 0) {
+ if ((long)PacKeys != 0) {
+ if (prctl_wrapper(PR_PAC_SET_ENABLED_KEYS,
+ PR_PAC_APIAKEY | PR_PAC_APIBKEY | PR_PAC_APDAKEY |
+ PR_PAC_APDBKEY, // all keys
+ 0, // disable all
+ 0, // unused
+ 0) // unused
+ < 0) {
return "Failed to disable PAC keys";
}
}
>From 079d268eda9d7d6acb000c71812b14f33a1a46f7 Mon Sep 17 00:00:00 2001
From: Abhilash Majumder <30946547+abhilash1910 at users.noreply.github.com>
Date: Mon, 12 May 2025 18:15:47 +0530
Subject: [PATCH 06/12] Update llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
Co-authored-by: Anatoly Trosinenko <anatoly.trosinenko at gmail.com>
---
llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
index a432eb57026d2..a1583d13fe4ac 100644
--- a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
@@ -220,11 +220,7 @@ class ExegesisAArch64Target : public ExegesisTarget {
// safer to check the existing key state and then disable/enable them.
// Hence the guard for switching.
errno = 0;
- unsigned long PacKeys = prctl_wrapper(PR_PAC_GET_ENABLED_KEYS,
- 0, // unused
- 0, // unused
- 0, // unused
- 0); // unused
+ unsigned long PacKeys = prctl_wrapper(PR_PAC_GET_ENABLED_KEYS);
if ((long)PacKeys < 0) {
if (errno == EINVAL) {
return "PAuth not supported on this system";
>From 635c646010aa773c8e9372181d6e6d87838adf7c Mon Sep 17 00:00:00 2001
From: Abhilash Majumder <30946547+abhilash1910 at users.noreply.github.com>
Date: Mon, 12 May 2025 18:15:57 +0530
Subject: [PATCH 07/12] Update llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
Co-authored-by: Anatoly Trosinenko <anatoly.trosinenko at gmail.com>
---
llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
index a1583d13fe4ac..2f4c191c11517 100644
--- a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
@@ -232,13 +232,13 @@ class ExegesisAArch64Target : public ExegesisTarget {
// be the same with PAC keys disabled, they could potentially be lower
// since authentication checks are bypassed.
if ((long)PacKeys != 0) {
- if (prctl_wrapper(PR_PAC_SET_ENABLED_KEYS,
- PR_PAC_APIAKEY | PR_PAC_APIBKEY | PR_PAC_APDAKEY |
- PR_PAC_APDBKEY, // all keys
- 0, // disable all
- 0, // unused
- 0) // unused
- < 0) {
+ // Operate on all keys.
+ const long KeysToControl =
+ PR_PAC_APIAKEY | PR_PAC_APIBKEY | PR_PAC_APDAKEY | PR_PAC_APDBKEY;
+ // Disable all.
+ const long EnabledBitMask = 0;
+ if (prctl_wrapper(PR_PAC_SET_ENABLED_KEYS, KeysToControl,
+ EnabledBitMask) < 0) {
return "Failed to disable PAC keys";
}
}
>From 7ca6ee78aeb00c84c25158062ceb2593631fb1d3 Mon Sep 17 00:00:00 2001
From: Abhilash Majumder <abmajumder at nvidia.com>
Date: Mon, 12 May 2025 18:18:07 +0530
Subject: [PATCH 08/12] review updates
---
llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
index 2f4c191c11517..2fe3ddf12c08a 100644
--- a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
@@ -200,9 +200,10 @@ class ExegesisAArch64Target : public ExegesisTarget {
PM.add(createAArch64ExpandPseudoPass());
}
- static long prctl_wrapper(int op, long arg2 = 0, long arg3 = 0, long arg4 = 0,
- long arg5 = 0) {
- return prctl(op, arg2, arg3, arg4, arg5);
+ // Converts variadic arguments to `long` and passes zeros for the unused
+ // arg2-arg5, as tested by the Linux kernel.
+ static long prctl_wrapper(int op, long arg2 = 0, long arg3 = 0) {
+ return prctl(op, arg2, arg3, /*arg4=*/0L, /*arg5=*/0L);
}
const char *getIgnoredOpcodeReasonOrNull(const LLVMState &State,
>From e1b6523da8d07025c1da1e42069884ac8a703bce Mon Sep 17 00:00:00 2001
From: Abhilash Majumder <abmajumder at nvidia.com>
Date: Mon, 12 May 2025 18:19:58 +0530
Subject: [PATCH 09/12] format fix
---
llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
index 2fe3ddf12c08a..bc4faedd0b806 100644
--- a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
@@ -234,11 +234,11 @@ class ExegesisAArch64Target : public ExegesisTarget {
// since authentication checks are bypassed.
if ((long)PacKeys != 0) {
// Operate on all keys.
- const long KeysToControl =
+ const long KeysToControl =
PR_PAC_APIAKEY | PR_PAC_APIBKEY | PR_PAC_APDAKEY | PR_PAC_APDBKEY;
// Disable all.
const long EnabledBitMask = 0;
- if (prctl_wrapper(PR_PAC_SET_ENABLED_KEYS, KeysToControl,
+ if (prctl_wrapper(PR_PAC_SET_ENABLED_KEYS, KeysToControl,
EnabledBitMask) < 0) {
return "Failed to disable PAC keys";
}
>From fd254b057fb34686d1f425592d57fe70a894fb44 Mon Sep 17 00:00:00 2001
From: Abhilash Majumder <abmajumder at nvidia.com>
Date: Mon, 12 May 2025 18:22:20 +0530
Subject: [PATCH 10/12] format fix
---
llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp | 1 -
1 file changed, 1 deletion(-)
diff --git a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
index bc4faedd0b806..feb798c8ea8d8 100644
--- a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
@@ -214,7 +214,6 @@ class ExegesisAArch64Target : public ExegesisTarget {
if (isPointerAuth(Opcode)) {
#if defined(__aarch64__) && defined(__linux__)
-
// For some systems with existing PAC keys set, it is better to
// check the existing state of the key before setting it.
// For systems without PAC, this is a No-op but with PAC, it is
>From 42075c69605df3aaff814ce1f9ee7c3894e1c1ac Mon Sep 17 00:00:00 2001
From: Abhilash Majumder <abmajumder at nvidia.com>
Date: Tue, 13 May 2025 21:07:24 +0530
Subject: [PATCH 11/12] use nullptr as silentcondition
---
llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
index feb798c8ea8d8..f9396cfdaaca7 100644
--- a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
@@ -200,11 +200,13 @@ class ExegesisAArch64Target : public ExegesisTarget {
PM.add(createAArch64ExpandPseudoPass());
}
+#if defined(__aarch64__) && defined(__linux__)
// Converts variadic arguments to `long` and passes zeros for the unused
// arg2-arg5, as tested by the Linux kernel.
static long prctl_wrapper(int op, long arg2 = 0, long arg3 = 0) {
return prctl(op, arg2, arg3, /*arg4=*/0L, /*arg5=*/0L);
}
+#endif
const char *getIgnoredOpcodeReasonOrNull(const LLVMState &State,
unsigned Opcode) const override {
@@ -222,9 +224,8 @@ class ExegesisAArch64Target : public ExegesisTarget {
errno = 0;
unsigned long PacKeys = prctl_wrapper(PR_PAC_GET_ENABLED_KEYS);
if ((long)PacKeys < 0) {
- if (errno == EINVAL) {
- return "PAuth not supported on this system";
- }
+ if (errno == EINVAL)
+ return nullptr;
return "Failed to get PAC key status";
}
@@ -241,9 +242,12 @@ class ExegesisAArch64Target : public ExegesisTarget {
EnabledBitMask) < 0) {
return "Failed to disable PAC keys";
}
+ llvm::errs() << "llvm-exegesis: PAC keys were disabled at runtime for "
+ "benchmarking.\n";
}
#else
- return "Unsupported opcode: isPointerAuth";
+ // Silently return nullptr to ensure forward progress
+ return nullptr;
#endif
}
>From 2b5c69ae09679bf0c7dc17f7876ead21a5a224da Mon Sep 17 00:00:00 2001
From: Abhilash Majumder <abmajumder at nvidia.com>
Date: Tue, 13 May 2025 21:40:41 +0530
Subject: [PATCH 12/12] use nullptr as silentcondition
---
llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
index f9396cfdaaca7..96e0c9ec23a9d 100644
--- a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
@@ -223,11 +223,8 @@ class ExegesisAArch64Target : public ExegesisTarget {
// Hence the guard for switching.
errno = 0;
unsigned long PacKeys = prctl_wrapper(PR_PAC_GET_ENABLED_KEYS);
- if ((long)PacKeys < 0) {
- if (errno == EINVAL)
- return nullptr;
- return "Failed to get PAC key status";
- }
+ if ((long)PacKeys < 0 || errno == EINVAL)
+ return nullptr;
// Disable all PAC keys. Note that while we expect the measurements to
// be the same with PAC keys disabled, they could potentially be lower
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