linux-kernel - [PATCH v2] proc: Provide details on indirect branch speculation

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Message-Id: <20201106131015.v2.1.I7782b0cedb705384a634cfd8898eb7523562da99@changeid>
Date:   Fri,  6 Nov 2020 13:10:43 +1100
From:   Anand K Mistry <amistry@...gle.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     asteinhauser@...gle.com, sfr@...b.auug.org.au, rppt@...nel.org,
        joelaf@...gle.com, tglx@...utronix.de,
        Anand K Mistry <amistry@...gle.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Alexey Gladkov <gladkov.alexey@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] proc: Provide details on indirect branch speculation

Similar to speculation store bypass, show information about the indirect
branch speculation mode of a task in /proc/$pid/status.

Signed-off-by: Anand K Mistry <amistry@...gle.com>
---

Changes in v2:
- Remove underscores from field name to workaround documentation issue

 Documentation/filesystems/proc.rst |  2 ++
 fs/proc/array.c                    | 28 ++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 533c79e8d2cd..531edaf07924 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -210,6 +210,7 @@ read the file /proc/PID/status::
   NoNewPrivs:     0
   Seccomp:        0
   Speculation_Store_Bypass:       thread vulnerable
+  SpeculationIndirectBranch:      conditional enabled
   voluntary_ctxt_switches:        0
   nonvoluntary_ctxt_switches:     1
 
@@ -292,6 +293,7 @@ It's slow but very precise.
  NoNewPrivs                  no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
  Seccomp                     seccomp mode, like prctl(PR_GET_SECCOMP, ...)
  Speculation_Store_Bypass    speculative store bypass mitigation status
+ SpeculationIndirectBranch   indirect branch speculation mode
  Cpus_allowed                mask of CPUs on which this process may run
  Cpus_allowed_list           Same as previous, but in "list format"
  Mems_allowed                mask of memory nodes allowed to this process
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 65ec2029fa80..014c1859554d 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -368,6 +368,34 @@ static inline void task_seccomp(struct seq_file *m, struct task_struct *p)
 		seq_puts(m, "vulnerable");
 		break;
 	}
+
+	seq_puts(m, "\nSpeculationIndirectBranch:\t");
+	switch (arch_prctl_spec_ctrl_get(p, PR_SPEC_INDIRECT_BRANCH)) {
+	case -EINVAL:
+		seq_puts(m, "unsupported");
+		break;
+	case PR_SPEC_NOT_AFFECTED:
+		seq_puts(m, "not affected");
+		break;
+	case PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE:
+		seq_puts(m, "conditional force disabled");
+		break;
+	case PR_SPEC_PRCTL | PR_SPEC_DISABLE:
+		seq_puts(m, "conditional disabled");
+		break;
+	case PR_SPEC_PRCTL | PR_SPEC_ENABLE:
+		seq_puts(m, "conditional enabled");
+		break;
+	case PR_SPEC_ENABLE:
+		seq_puts(m, "always enabled");
+		break;
+	case PR_SPEC_DISABLE:
+		seq_puts(m, "always disabled");
+		break;
+	default:
+		seq_puts(m, "unknown");
+		break;
+	}
 	seq_putc(m, '\n');
 }
 
-- 
2.29.1.341.ge80a0c044ae-goog