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-rw-r--r--arch/x86/mm/extable.c78
1 files changed, 78 insertions, 0 deletions
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 271dcb2dea..b522933bfa 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -6,6 +6,7 @@
#include <xen/xen.h>
#include <asm/fpu/api.h>
+#include <asm/fred.h>
#include <asm/sev.h>
#include <asm/traps.h>
#include <asm/kdebug.h>
@@ -223,6 +224,79 @@ static bool ex_handler_ucopy_len(const struct exception_table_entry *fixup,
return ex_handler_uaccess(fixup, regs, trapnr, fault_address);
}
+#ifdef CONFIG_X86_FRED
+static bool ex_handler_eretu(const struct exception_table_entry *fixup,
+ struct pt_regs *regs, unsigned long error_code)
+{
+ struct pt_regs *uregs = (struct pt_regs *)(regs->sp - offsetof(struct pt_regs, orig_ax));
+ unsigned short ss = uregs->ss;
+ unsigned short cs = uregs->cs;
+
+ /*
+ * Move the NMI bit from the invalid stack frame, which caused ERETU
+ * to fault, to the fault handler's stack frame, thus to unblock NMI
+ * with the fault handler's ERETS instruction ASAP if NMI is blocked.
+ */
+ regs->fred_ss.nmi = uregs->fred_ss.nmi;
+
+ /*
+ * Sync event information to uregs, i.e., the ERETU return frame, but
+ * is it safe to write to the ERETU return frame which is just above
+ * current event stack frame?
+ *
+ * The RSP used by FRED to push a stack frame is not the value in %rsp,
+ * it is calculated from %rsp with the following 2 steps:
+ * 1) RSP = %rsp - (IA32_FRED_CONFIG & 0x1c0) // Reserve N*64 bytes
+ * 2) RSP = RSP & ~0x3f // Align to a 64-byte cache line
+ * when an event delivery doesn't trigger a stack level change.
+ *
+ * Here is an example with N*64 (N=1) bytes reserved:
+ *
+ * 64-byte cache line ==> ______________
+ * |___Reserved___|
+ * |__Event_data__|
+ * |_____SS_______|
+ * |_____RSP______|
+ * |_____FLAGS____|
+ * |_____CS_______|
+ * |_____IP_______|
+ * 64-byte cache line ==> |__Error_code__| <== ERETU return frame
+ * |______________|
+ * |______________|
+ * |______________|
+ * |______________|
+ * |______________|
+ * |______________|
+ * |______________|
+ * 64-byte cache line ==> |______________| <== RSP after step 1) and 2)
+ * |___Reserved___|
+ * |__Event_data__|
+ * |_____SS_______|
+ * |_____RSP______|
+ * |_____FLAGS____|
+ * |_____CS_______|
+ * |_____IP_______|
+ * 64-byte cache line ==> |__Error_code__| <== ERETS return frame
+ *
+ * Thus a new FRED stack frame will always be pushed below a previous
+ * FRED stack frame ((N*64) bytes may be reserved between), and it is
+ * safe to write to a previous FRED stack frame as they never overlap.
+ */
+ fred_info(uregs)->edata = fred_event_data(regs);
+ uregs->ssx = regs->ssx;
+ uregs->fred_ss.ss = ss;
+ /* The NMI bit was moved away above */
+ uregs->fred_ss.nmi = 0;
+ uregs->csx = regs->csx;
+ uregs->fred_cs.sl = 0;
+ uregs->fred_cs.wfe = 0;
+ uregs->cs = cs;
+ uregs->orig_ax = error_code;
+
+ return ex_handler_default(fixup, regs);
+}
+#endif
+
int ex_get_fixup_type(unsigned long ip)
{
const struct exception_table_entry *e = search_exception_tables(ip);
@@ -300,6 +374,10 @@ int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code,
return ex_handler_ucopy_len(e, regs, trapnr, fault_addr, reg, imm);
case EX_TYPE_ZEROPAD:
return ex_handler_zeropad(e, regs, fault_addr);
+#ifdef CONFIG_X86_FRED
+ case EX_TYPE_ERETU:
+ return ex_handler_eretu(e, regs, error_code);
+#endif
}
BUG();
}