From: Marc Zyngier <marc.zyngier@arm.com>
To: Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] arm64: Force SSBS on context switch
Date: Fri, 19 Jul 2019 18:16:51 +0100 [thread overview]
Message-ID: <20190719171651.26165-1-marc.zyngier@arm.com> (raw)
On a CPU that doesn't support SSBS, PSTATE[12] is RES0. In a system
where only some of the CPUs implement SSBS, we end-up losing track of
the SSBS bit across task migration.
To address this issue, let's force the SSBS bit on context switch.
Fixes: 8f04e8e6e29c ("arm64: ssbd: Add support for PSTATE.SSBS rather than trapping to EL3")
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm64/include/asm/processor.h | 14 ++++++++++++--
arch/arm64/kernel/process.c | 15 +++++++++++++++
2 files changed, 27 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index fd5b1a4efc70..844e2964b0f5 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -193,6 +193,16 @@ static inline void start_thread_common(struct pt_regs *regs, unsigned long pc)
regs->pmr_save = GIC_PRIO_IRQON;
}
+static inline void set_ssbs_bit(struct pt_regs *regs)
+{
+ regs->pstate |= PSR_SSBS_BIT;
+}
+
+static inline void set_compat_ssbs_bit(struct pt_regs *regs)
+{
+ regs->pstate |= PSR_AA32_SSBS_BIT;
+}
+
static inline void start_thread(struct pt_regs *regs, unsigned long pc,
unsigned long sp)
{
@@ -200,7 +210,7 @@ static inline void start_thread(struct pt_regs *regs, unsigned long pc,
regs->pstate = PSR_MODE_EL0t;
if (arm64_get_ssbd_state() != ARM64_SSBD_FORCE_ENABLE)
- regs->pstate |= PSR_SSBS_BIT;
+ set_ssbs_bit(regs);
regs->sp = sp;
}
@@ -219,7 +229,7 @@ static inline void compat_start_thread(struct pt_regs *regs, unsigned long pc,
#endif
if (arm64_get_ssbd_state() != ARM64_SSBD_FORCE_ENABLE)
- regs->pstate |= PSR_AA32_SSBS_BIT;
+ set_compat_ssbs_bit(regs);
regs->compat_sp = sp;
}
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 9856395ccdb7..2fb91c8728ae 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -442,6 +442,20 @@ void uao_thread_switch(struct task_struct *next)
}
}
+static void ssbs_thread_switch(struct task_struct *next)
+{
+ if (likely(!(next->flags & PF_KTHREAD)) &&
+ arm64_get_ssbd_state() != ARM64_SSBD_FORCE_ENABLE &&
+ !test_tsk_thread_flag(next, TIF_SSBD)) {
+ struct pt_regs *regs = task_pt_regs(next);
+
+ if (compat_user_mode(regs))
+ set_compat_ssbs_bit(regs);
+ else if (user_mode(regs))
+ set_ssbs_bit(regs);
+ }
+}
+
/*
* We store our current task in sp_el0, which is clobbered by userspace. Keep a
* shadow copy so that we can restore this upon entry from userspace.
@@ -471,6 +485,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
entry_task_switch(next);
uao_thread_switch(next);
ptrauth_thread_switch(next);
+ ssbs_thread_switch(next);
/*
* Complete any pending TLB or cache maintenance on this CPU in case
--
2.20.1
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2019-07-19 17:17 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-19 17:16 Marc Zyngier [this message]
2019-07-19 18:16 ` [PATCH] arm64: Force SSBS on context switch Neeraj Upadhyay
2019-07-22 13:42 ` Marc Zyngier
2019-07-22 5:53 ` Anshuman Khandual
2019-07-22 7:05 ` Marc Zyngier
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190719171651.26165-1-marc.zyngier@arm.com \
--to=marc.zyngier@arm.com \
--cc=catalin.marinas@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=mark.rutland@arm.com \
--cc=neeraju@codeaurora.org \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).