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diff --git a/sys/arm64/arm64/exception.S b/sys/arm64/arm64/exception.S
--- a/sys/arm64/arm64/exception.S
+++ b/sys/arm64/arm64/exception.S
@@ -66,6 +66,13 @@
mrs x18, tpidr_el1
add x29, sp, #(TF_SIZE)
.if \el == 0
+#if defined(PERTHREAD_SSP)
+ /* Load the SSP canary to sp_el0 */
+ ldr x1, [x18, #(PC_CURTHREAD)]
+ add x1, x1, #(TD_MD_CANARY)
+ msr sp_el0, x1
+#endif
+
/* Apply the SSBD (CVE-2018-3639) workaround if needed */
ldr x1, [x18, #PC_SSBD]
cbz x1, 1f
diff --git a/sys/arm64/arm64/genassym.c b/sys/arm64/arm64/genassym.c
--- a/sys/arm64/arm64/genassym.c
+++ b/sys/arm64/arm64/genassym.c
@@ -73,6 +73,7 @@
ASSYM(TD_FLAGS, offsetof(struct thread, td_flags));
ASSYM(TD_FRAME, offsetof(struct thread, td_frame));
ASSYM(TD_LOCK, offsetof(struct thread, td_lock));
+ASSYM(TD_MD_CANARY, offsetof(struct thread, td_md.md_canary));
ASSYM(TF_SIZE, sizeof(struct trapframe));
ASSYM(TF_SP, offsetof(struct trapframe, tf_sp));
diff --git a/sys/arm64/arm64/locore.S b/sys/arm64/arm64/locore.S
--- a/sys/arm64/arm64/locore.S
+++ b/sys/arm64/arm64/locore.S
@@ -116,6 +116,13 @@
cmp x15, x14
b.lo 1b
+#if defined(PERTHREAD_SSP)
+ /* Set sp_el0 to the boot canary for early per-thread SSP to work */
+ adrp x15, boot_canary
+ add x15, x15, :lo12:boot_canary
+ msr sp_el0, x15
+#endif
+
/* Backup the module pointer */
mov x1, x0
@@ -200,6 +207,13 @@
ldr x4, [x4]
mov sp, x4
+#if defined(PERTHREAD_SSP)
+ /* Set sp_el0 to the boot canary for early per-thread SSP to work */
+ adrp x15, boot_canary
+ add x15, x15, :lo12:boot_canary
+ msr sp_el0, x15
+#endif
+
/* Load the kernel ttbr0 pagetable */
msr ttbr0_el1, x27
isb
diff --git a/sys/arm64/arm64/machdep.c b/sys/arm64/arm64/machdep.c
--- a/sys/arm64/arm64/machdep.c
+++ b/sys/arm64/arm64/machdep.c
@@ -109,6 +109,14 @@
*/
struct pcpu pcpu0;
+#if defined(PERTHREAD_SSP)
+/*
+ * The boot SSP canary. Will be replaced with a per-thread canary when
+ * scheduling has started.
+ */
+uintptr_t boot_canary = 0x49a2d892bc05a0b1ul;
+#endif
+
static struct trapframe proc0_tf;
int early_boot = 1;
@@ -136,6 +144,16 @@
int (*apei_nmi)(void);
+#if defined(PERTHREAD_SSP_WARNING)
+static void
+print_ssp_warning(void *data __unused)
+{
+ printf("WARNING: Per-thread SSP is enabled but the compiler is too old to support it\n");
+}
+SYSINIT(ssp_warn, SI_SUB_COPYRIGHT, SI_ORDER_ANY, print_ssp_warning, NULL);
+SYSINIT(ssp_warn2, SI_SUB_LAST, SI_ORDER_ANY, print_ssp_warning, NULL);
+#endif
+
static void
pan_setup(void)
{
@@ -347,6 +365,9 @@
proc_linkup0(&proc0, &thread0);
thread0.td_kstack = kstack;
thread0.td_kstack_pages = KSTACK_PAGES;
+#if defined(PERTHREAD_SSP)
+ thread0.td_md.md_canary = boot_canary;
+#endif
thread0.td_pcb = (struct pcb *)(thread0.td_kstack +
thread0.td_kstack_pages * PAGE_SIZE) - 1;
thread0.td_pcb->pcb_fpflags = 0;
@@ -781,6 +802,7 @@
"mov x18, %0 \n"
"msr tpidr_el1, %0" :: "r"(pcpup));
+ /* locore.S sets sp_el0 to &thread0 so no need to set it here. */
PCPU_SET(curthread, &thread0);
PCPU_SET(midr, get_midr());
diff --git a/sys/arm64/arm64/pmap.c b/sys/arm64/arm64/pmap.c
--- a/sys/arm64/arm64/pmap.c
+++ b/sys/arm64/arm64/pmap.c
@@ -6619,6 +6619,10 @@
/* Store the new curthread */
PCPU_SET(curthread, new);
+#if defined(PERTHREAD_SSP)
+ /* Set the new threads SSP canary */
+ __asm("msr sp_el0, %0" :: "r"(&new->td_md.md_canary));
+#endif
/* And the new pcb */
pcb = new->td_pcb;
diff --git a/sys/arm64/arm64/vm_machdep.c b/sys/arm64/arm64/vm_machdep.c
--- a/sys/arm64/arm64/vm_machdep.c
+++ b/sys/arm64/arm64/vm_machdep.c
@@ -113,6 +113,11 @@
/* Setup to release spin count in fork_exit(). */
td2->td_md.md_spinlock_count = 1;
td2->td_md.md_saved_daif = PSR_DAIF_DEFAULT;
+
+#if defined(PERTHREAD_SSP)
+ /* Set the new canary */
+ arc4random_buf(&td2->td_md.md_canary, sizeof(td2->td_md.md_canary));
+#endif
}
void
@@ -187,6 +192,11 @@
/* Setup to release spin count in fork_exit(). */
td->td_md.md_spinlock_count = 1;
td->td_md.md_saved_daif = PSR_DAIF_DEFAULT;
+
+#if defined(PERTHREAD_SSP)
+ /* Set the new canary */
+ arc4random_buf(&td->td_md.md_canary, sizeof(td->td_md.md_canary));
+#endif
}
/*
diff --git a/sys/arm64/conf/std.arm64 b/sys/arm64/conf/std.arm64
--- a/sys/arm64/conf/std.arm64
+++ b/sys/arm64/conf/std.arm64
@@ -67,6 +67,7 @@
options RCTL # Resource limits
options INTRNG
options LINUX_BOOT_ABI # Boot using booti command from U-Boot
+options PERTHREAD_SSP # Per-thread SSP canary
# Debugging support. Always need this:
options KDB # Enable kernel debugger support.
diff --git a/sys/arm64/include/proc.h b/sys/arm64/include/proc.h
--- a/sys/arm64/include/proc.h
+++ b/sys/arm64/include/proc.h
@@ -37,6 +37,7 @@
struct mdthread {
int md_spinlock_count; /* (k) */
register_t md_saved_daif; /* (k) */
+ uintptr_t md_canary;
};
struct mdproc {
diff --git a/sys/conf/Makefile.arm64 b/sys/conf/Makefile.arm64
--- a/sys/conf/Makefile.arm64
+++ b/sys/conf/Makefile.arm64
@@ -30,6 +30,20 @@
LINUX_DTS_VERSION!= awk '/freebsd,dts-version/ { sub(/;$$/,"", $$NF); print $$NF }' $S/dts/freebsd-compatible.dts
CFLAGS += -DLINUX_DTS_VERSION=\"${LINUX_DTS_VERSION}\"
+PERTHREAD_SSP_ENABLED!= grep PERTHREAD_SSP opt_global.h || true ; echo
+.if !empty(PERTHREAD_SSP_ENABLED)
+. if ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} >= 130000
+ARM64_SSP_CFLAGS = -mstack-protector-guard=sysreg
+ARM64_SSP_CFLAGS += -mstack-protector-guard-reg=sp_el0
+ARM64_SSP_CFLAGS += -mstack-protector-guard-offset=0
+. else
+ARM64_SSP_CFLAGS += -DPERTHREAD_SSP_WARNING
+. warning "Compiler is too old to support PERTHREAD_SSP"
+. endif
+CFLAGS += ${ARM64_SSP_CFLAGS}
+ARCH_FLAGS += ${ARM64_SSP_CFLAGS}
+.endif
+
# Use a custom SYSTEM_LD command to generate the elf kernel, so we can
# set the text segment start address, and also strip the "arm mapping
# symbols" which have names like $a.0 and $d.2; see the document
diff --git a/sys/conf/options.arm64 b/sys/conf/options.arm64
--- a/sys/conf/options.arm64
+++ b/sys/conf/options.arm64
@@ -8,6 +8,10 @@
LINUX_BOOT_ABI opt_global.h
LSE_ATOMICS opt_global.h
+# Per-thread stack smashing protection support
+# Needs clang >= 13
+PERTHREAD_SSP opt_global.h
+
# Binary compatibility
COMPAT_FREEBSD32 opt_global.h

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