[tip: x86/mm] mm: Expose untagging mask in /proc/$PID/status

[tip-bot2 for Kirill A. Shutemov]

The following commit has been merged into the x86/mm branch of tip:

Commit-ID:     f7d304343b9d2456ffba23b99d2345408251ea45
Gitweb:        https://git.kernel.org/tip/f7d304343b9d2456ffba23b99d2345408251ea45
Author:        Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
AuthorDate:    Sun, 12 Mar 2023 14:26:04 +03:00
Committer:     Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Thu, 16 Mar 2023 13:08:40 -07:00

mm: Expose untagging mask in /proc/$PID/status

Add a line in /proc/$PID/status to report untag_mask. It can be
used to find out LAM status of the process from the outside. It is
useful for debuggers.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: Alexander Potapenko <glider@xxxxxxxxxx>
Link: https://lore.kernel.org/all/20230312112612.31869-10-kirill.shutemov%40linux.intel.com
---
 arch/arm64/include/asm/mmu_context.h    | 6 ++++++
 arch/sparc/include/asm/mmu_context_64.h | 6 ++++++
 arch/x86/include/asm/mmu_context.h      | 6 ++++++
 fs/proc/array.c                         | 7 +++++++
 include/linux/mmu_context.h             | 7 +++++++
 5 files changed, 32 insertions(+)

diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index 72dbd64..5691169 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -288,6 +288,12 @@ void post_ttbr_update_workaround(void);
 unsigned long arm64_mm_context_get(struct mm_struct *mm);
 void arm64_mm_context_put(struct mm_struct *mm);
 
+#define mm_untag_mask mm_untag_mask
+static inline unsigned long mm_untag_mask(struct mm_struct *mm)
+{
+	return -1UL >> 8;
+}
+
 #include <asm-generic/mmu_context.h>
 
 #endif /* !__ASSEMBLY__ */
diff --git a/arch/sparc/include/asm/mmu_context_64.h b/arch/sparc/include/asm/mmu_context_64.h
index 7a8380c..799e797 100644
--- a/arch/sparc/include/asm/mmu_context_64.h
+++ b/arch/sparc/include/asm/mmu_context_64.h
@@ -185,6 +185,12 @@ static inline void finish_arch_post_lock_switch(void)
 	}
 }
 
+#define mm_untag_mask mm_untag_mask
+static inline unsigned long mm_untag_mask(struct mm_struct *mm)
+{
+       return -1UL >> adi_nbits();
+}
+
 #include <asm-generic/mmu_context.h>
 
 #endif /* !(__ASSEMBLY__) */
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index eb1387a..06eaaf7 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -104,6 +104,12 @@ static inline void dup_lam(struct mm_struct *oldmm, struct mm_struct *mm)
 	mm->context.untag_mask = oldmm->context.untag_mask;
 }
 
+#define mm_untag_mask mm_untag_mask
+static inline unsigned long mm_untag_mask(struct mm_struct *mm)
+{
+	return mm->context.untag_mask;
+}
+
 static inline void mm_reset_untag_mask(struct mm_struct *mm)
 {
 	mm->context.untag_mask = -1UL;
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 9b0315d..6daea62 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -91,6 +91,7 @@
 #include <linux/user_namespace.h>
 #include <linux/fs_struct.h>
 #include <linux/kthread.h>
+#include <linux/mmu_context.h>
 
 #include <asm/processor.h>
 #include "internal.h"
@@ -423,6 +424,11 @@ static inline void task_thp_status(struct seq_file *m, struct mm_struct *mm)
 	seq_printf(m, "THP_enabled:\t%d\n", thp_enabled);
 }
 
+static inline void task_untag_mask(struct seq_file *m, struct mm_struct *mm)
+{
+	seq_printf(m, "untag_mask:\t%#lx\n", mm_untag_mask(mm));
+}
+
 int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
 			struct pid *pid, struct task_struct *task)
 {
@@ -438,6 +444,7 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
 		task_mem(m, mm);
 		task_core_dumping(m, task);
 		task_thp_status(m, mm);
+		task_untag_mask(m, mm);
 		mmput(mm);
 	}
 	task_sig(m, task);
diff --git a/include/linux/mmu_context.h b/include/linux/mmu_context.h
index b9b970f..14b9c1f 100644
--- a/include/linux/mmu_context.h
+++ b/include/linux/mmu_context.h
@@ -28,4 +28,11 @@ static inline void leave_mm(int cpu) { }
 # define task_cpu_possible(cpu, p)	cpumask_test_cpu((cpu), task_cpu_possible_mask(p))
 #endif
 
+#ifndef mm_untag_mask
+static inline unsigned long mm_untag_mask(struct mm_struct *mm)
+{
+	return -1UL;
+}
+#endif
+
 #endif