Update Linux to v5.10.109
Sourced from [1]
[1] https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.109.tar.xz
Change-Id: I19bca9fc6762d4e63bcf3e4cba88bbe560d9c76c
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/arch/x86/kernel/doublefault_32.c b/arch/x86/kernel/doublefault_32.c
new file mode 100644
index 0000000..759d392
--- /dev/null
+++ b/arch/x86/kernel/doublefault_32.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/sched/debug.h>
+#include <linux/init_task.h>
+#include <linux/fs.h>
+
+#include <linux/uaccess.h>
+#include <asm/processor.h>
+#include <asm/desc.h>
+#include <asm/traps.h>
+
+#define ptr_ok(x) ((x) > PAGE_OFFSET && (x) < PAGE_OFFSET + MAXMEM)
+
+#define TSS(x) this_cpu_read(cpu_tss_rw.x86_tss.x)
+
+static void set_df_gdt_entry(unsigned int cpu);
+
+/*
+ * Called by double_fault with CR0.TS and EFLAGS.NT cleared. The CPU thinks
+ * we're running the doublefault task. Cannot return.
+ */
+asmlinkage noinstr void __noreturn doublefault_shim(void)
+{
+ unsigned long cr2;
+ struct pt_regs regs;
+
+ BUILD_BUG_ON(sizeof(struct doublefault_stack) != PAGE_SIZE);
+
+ cr2 = native_read_cr2();
+
+ /* Reset back to the normal kernel task. */
+ force_reload_TR();
+ set_df_gdt_entry(smp_processor_id());
+
+ trace_hardirqs_off();
+
+ /*
+ * Fill in pt_regs. A downside of doing this in C is that the unwinder
+ * won't see it (no ENCODE_FRAME_POINTER), so a nested stack dump
+ * won't successfully unwind to the source of the double fault.
+ * The main dump from exc_double_fault() is fine, though, since it
+ * uses these regs directly.
+ *
+ * If anyone ever cares, this could be moved to asm.
+ */
+ regs.ss = TSS(ss);
+ regs.__ssh = 0;
+ regs.sp = TSS(sp);
+ regs.flags = TSS(flags);
+ regs.cs = TSS(cs);
+ /* We won't go through the entry asm, so we can leave __csh as 0. */
+ regs.__csh = 0;
+ regs.ip = TSS(ip);
+ regs.orig_ax = 0;
+ regs.gs = TSS(gs);
+ regs.__gsh = 0;
+ regs.fs = TSS(fs);
+ regs.__fsh = 0;
+ regs.es = TSS(es);
+ regs.__esh = 0;
+ regs.ds = TSS(ds);
+ regs.__dsh = 0;
+ regs.ax = TSS(ax);
+ regs.bp = TSS(bp);
+ regs.di = TSS(di);
+ regs.si = TSS(si);
+ regs.dx = TSS(dx);
+ regs.cx = TSS(cx);
+ regs.bx = TSS(bx);
+
+ exc_double_fault(®s, 0, cr2);
+
+ /*
+ * x86_32 does not save the original CR3 anywhere on a task switch.
+ * This means that, even if we wanted to return, we would need to find
+ * some way to reconstruct CR3. We could make a credible guess based
+ * on cpu_tlbstate, but that would be racy and would not account for
+ * PTI.
+ *
+ * Instead, don't bother. We can return through
+ * rewind_stack_do_exit() instead.
+ */
+ panic("cannot return from double fault\n");
+}
+
+DEFINE_PER_CPU_PAGE_ALIGNED(struct doublefault_stack, doublefault_stack) = {
+ .tss = {
+ /*
+ * No sp0 or ss0 -- we never run CPL != 0 with this TSS
+ * active. sp is filled in later.
+ */
+ .ldt = 0,
+ .io_bitmap_base = IO_BITMAP_OFFSET_INVALID,
+
+ .ip = (unsigned long) asm_exc_double_fault,
+ .flags = X86_EFLAGS_FIXED,
+ .es = __USER_DS,
+ .cs = __KERNEL_CS,
+ .ss = __KERNEL_DS,
+ .ds = __USER_DS,
+ .fs = __KERNEL_PERCPU,
+#ifndef CONFIG_X86_32_LAZY_GS
+ .gs = __KERNEL_STACK_CANARY,
+#endif
+
+ .__cr3 = __pa_nodebug(swapper_pg_dir),
+ },
+};
+
+static void set_df_gdt_entry(unsigned int cpu)
+{
+ /* Set up doublefault TSS pointer in the GDT */
+ __set_tss_desc(cpu, GDT_ENTRY_DOUBLEFAULT_TSS,
+ &get_cpu_entry_area(cpu)->doublefault_stack.tss);
+
+}
+
+void doublefault_init_cpu_tss(void)
+{
+ unsigned int cpu = smp_processor_id();
+ struct cpu_entry_area *cea = get_cpu_entry_area(cpu);
+
+ /*
+ * The linker isn't smart enough to initialize percpu variables that
+ * point to other places in percpu space.
+ */
+ this_cpu_write(doublefault_stack.tss.sp,
+ (unsigned long)&cea->doublefault_stack.stack +
+ sizeof(doublefault_stack.stack));
+
+ set_df_gdt_entry(cpu);
+}