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

From: Anand K Mistry
Date: Thu Nov 05 2020 - 21:11:37 EST


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@xxxxxxxxxx>
---

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