lkml.org 
[lkml]   [2021]   [Feb]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v19 3/7] x86/cet/ibt: Handle signals for Indirect Branch Tracking
Date
When an indirect CALL/JMP instruction is executed and before it reaches
the target, it is in 'WAIT_ENDBR' status, which can be read from
MSR_IA32_U_CET. The status is part of a task's status before a signal is
raised and preserved in the signal frame. It is restored for sigreturn.

IBT state machine is described in Intel SDM Vol. 1, Sec. 18.3.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
arch/x86/kernel/cet.c | 27 +++++++++++++++++++++++++--
arch/x86/kernel/fpu/signal.c | 8 +++++---
2 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c
index fff0b35ed0d9..68d602aecb1c 100644
--- a/arch/x86/kernel/cet.c
+++ b/arch/x86/kernel/cet.c
@@ -295,6 +295,13 @@ void cet_restore_signal(struct sc_ext *sc_ext)
msr_val |= CET_SHSTK_EN;
}

+ if (cet->ibt_enabled) {
+ msr_val |= (CET_ENDBR_EN | CET_NO_TRACK_EN);
+
+ if (sc_ext->wait_endbr)
+ msr_val |= CET_WAIT_ENDBR;
+ }
+
if (test_thread_flag(TIF_NEED_FPU_LOAD))
cet_user_state->user_cet = msr_val;
else
@@ -335,9 +342,25 @@ int cet_setup_signal(bool ia32, unsigned long rstor_addr, struct sc_ext *sc_ext)
sc_ext->ssp = new_ssp;
}

- if (ssp) {
+ if (ssp || cet->ibt_enabled) {
+
start_update_msrs();
- wrmsrl(MSR_IA32_PL3_SSP, ssp);
+
+ if (ssp)
+ wrmsrl(MSR_IA32_PL3_SSP, ssp);
+
+ if (cet->ibt_enabled) {
+ u64 r;
+
+ rdmsrl(MSR_IA32_U_CET, r);
+
+ if (r & CET_WAIT_ENDBR) {
+ sc_ext->wait_endbr = 1;
+ r &= ~CET_WAIT_ENDBR;
+ wrmsrl(MSR_IA32_U_CET, r);
+ }
+ }
+
end_update_msrs();
}

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 270e4649f435..b914d74c8ba6 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -57,7 +57,8 @@ int save_cet_to_sigframe(int ia32, void __user *fp, unsigned long restorer)
{
int err = 0;

- if (!current->thread.cet.shstk_size)
+ if (!current->thread.cet.shstk_size &&
+ !current->thread.cet.ibt_enabled)
return 0;

if (fp) {
@@ -89,7 +90,8 @@ static int get_cet_from_sigframe(int ia32, void __user *fp, struct sc_ext *ext)

memset(ext, 0, sizeof(*ext));

- if (!current->thread.cet.shstk_size)
+ if (!current->thread.cet.shstk_size &&
+ !current->thread.cet.ibt_enabled)
return 0;

if (fp) {
@@ -577,7 +579,7 @@ static unsigned long fpu__alloc_sigcontext_ext(unsigned long sp)
* sigcontext_ext is at: fpu + fpu_user_xstate_size +
* FP_XSTATE_MAGIC2_SIZE, then aligned to 8.
*/
- if (cet->shstk_size)
+ if (cet->shstk_size || cet->ibt_enabled)
sp -= (sizeof(struct sc_ext) + 8);

return sp;
--
2.21.0
\
 
 \ /
  Last update: 2021-02-04 00:13    [W:0.061 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site