From: Nicholas Piggin <npiggin@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail.com>
Subject: [PATCH 6/7] powerpc/security: Allow for processors that flush the link stack using the special bcctr
Date: Tue, 9 Jun 2020 17:06:09 +1000 [thread overview]
Message-ID: <20200609070610.846703-7-npiggin@gmail.com> (raw)
In-Reply-To: <20200609070610.846703-1-npiggin@gmail.com>
If both count cache and link stack are to be flushed, and can be flushed
with the special bcctr, patch that in directly to the flush/branch nop
site.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/powerpc/include/asm/security_features.h | 2 ++
arch/powerpc/kernel/security.c | 27 ++++++++++++++------
2 files changed, 21 insertions(+), 8 deletions(-)
diff --git a/arch/powerpc/include/asm/security_features.h b/arch/powerpc/include/asm/security_features.h
index 7c05e95a5c44..fbb8fa32150f 100644
--- a/arch/powerpc/include/asm/security_features.h
+++ b/arch/powerpc/include/asm/security_features.h
@@ -63,6 +63,8 @@ static inline bool security_ftr_enabled(u64 feature)
// bcctr 2,0,0 triggers a hardware assisted count cache flush
#define SEC_FTR_BCCTR_FLUSH_ASSIST 0x0000000000000800ull
+// bcctr 2,0,0 triggers a hardware assisted link stack flush
+#define SEC_FTR_BCCTR_LINK_FLUSH_ASSIST 0x0000000000002000ull
// Features indicating need for Spectre/Meltdown mitigations
diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
index 2a413af21124..6ad5c753d47c 100644
--- a/arch/powerpc/kernel/security.c
+++ b/arch/powerpc/kernel/security.c
@@ -219,24 +219,25 @@ ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, c
if (ccd)
seq_buf_printf(&s, "Indirect branch cache disabled");
- if (link_stack_flush_type == BRANCH_CACHE_FLUSH_SW)
- seq_buf_printf(&s, ", Software link stack flush");
-
} else if (count_cache_flush_type != BRANCH_CACHE_FLUSH_NONE) {
seq_buf_printf(&s, "Mitigation: Software count cache flush");
if (count_cache_flush_type == BRANCH_CACHE_FLUSH_HW)
seq_buf_printf(&s, " (hardware accelerated)");
- if (link_stack_flush_type == BRANCH_CACHE_FLUSH_SW)
- seq_buf_printf(&s, ", Software link stack flush");
-
} else if (btb_flush_enabled) {
seq_buf_printf(&s, "Mitigation: Branch predictor state flush");
} else {
seq_buf_printf(&s, "Vulnerable");
}
+ if (bcs || ccd || count_cache_flush_type != BRANCH_CACHE_FLUSH_NONE) {
+ if (link_stack_flush_type != BRANCH_CACHE_FLUSH_NONE)
+ seq_buf_printf(&s, ", Software link stack flush");
+ if (link_stack_flush_type == BRANCH_CACHE_FLUSH_HW)
+ seq_buf_printf(&s, " (hardware accelerated)");
+ }
+
seq_buf_printf(&s, "\n");
return s.len;
@@ -435,6 +436,7 @@ static void update_branch_cache_flush(void)
patch_instruction_site(&patch__call_kvm_flush_link_stack,
ppc_inst(PPC_INST_NOP));
} else {
+ // Could use HW flush, but that could also flush count cache
patch_branch_site(&patch__call_kvm_flush_link_stack,
(u64)&kvm_flush_link_stack, BRANCH_SET_LINK);
}
@@ -445,6 +447,10 @@ static void update_branch_cache_flush(void)
link_stack_flush_type == BRANCH_CACHE_FLUSH_NONE) {
patch_instruction_site(&patch__call_flush_branch_caches,
ppc_inst(PPC_INST_NOP));
+ } else if (count_cache_flush_type == BRANCH_CACHE_FLUSH_HW &&
+ link_stack_flush_type == BRANCH_CACHE_FLUSH_HW) {
+ patch_instruction_site(&patch__call_flush_branch_caches,
+ ppc_inst(PPC_INST_BCCTR_FLUSH));
} else {
patch_branch_site(&patch__call_flush_branch_caches,
(u64)&flush_branch_caches, BRANCH_SET_LINK);
@@ -485,8 +491,13 @@ static void toggle_branch_cache_flush(bool enable)
pr_info("link-stack-flush: flush disabled.\n");
}
} else {
- link_stack_flush_type = BRANCH_CACHE_FLUSH_SW;
- pr_info("link-stack-flush: software flush enabled.\n");
+ if (security_ftr_enabled(SEC_FTR_BCCTR_LINK_FLUSH_ASSIST)) {
+ link_stack_flush_type = BRANCH_CACHE_FLUSH_HW;
+ pr_info("link-stack-flush: hardware flush enabled.\n");
+ } else {
+ link_stack_flush_type = BRANCH_CACHE_FLUSH_SW;
+ pr_info("link-stack-flush: software flush enabled.\n");
+ }
}
update_branch_cache_flush();
--
2.23.0
next prev parent reply other threads:[~2020-06-09 7:39 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-09 7:06 [PATCH 0/7] powerpc: branch cache flush changes Nicholas Piggin
2020-06-09 7:06 ` [PATCH 1/7] powerpc/security: re-name count cache flush to branch cache flush Nicholas Piggin
2020-06-09 7:06 ` [PATCH 2/7] powerpc/security: change link stack flush state to the flush type enum Nicholas Piggin
2020-06-09 7:06 ` [PATCH 3/7] powerpc/security: make display of branch cache flush more consistent Nicholas Piggin
2020-06-09 7:06 ` [PATCH 4/7] powerpc/security: split branch cache flush toggle from code patching Nicholas Piggin
2020-06-09 7:06 ` [PATCH 5/7] powerpc/64s: Move branch cache flushing bcctr variant to ppc-ops.h Nicholas Piggin
2020-06-09 7:06 ` Nicholas Piggin [this message]
2020-06-09 7:06 ` [PATCH 7/7] powerpc/64s: advertise hardware link stack flush Nicholas Piggin
2020-07-16 12:56 ` [PATCH 0/7] powerpc: branch cache flush changes Michael Ellerman
-- strict thread matches above, loose matches on Subject: below --
2020-06-09 6:16 Nicholas Piggin
2020-06-09 6:16 ` [PATCH 6/7] powerpc/security: Allow for processors that flush the link stack using the special bcctr Nicholas Piggin
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