[patch V4 part 3 09/29] x86/entry/32: Provide macro to emit IDT entry stubs

Thomas Gleixner
2020-05-05T14:15:23Z

From: Thomas Gleixner <tglx@linutronix.de>

32 and 64 bit have unnecessary different ways to populate the exception
entry code. Provide a idtentry macro which allows to consolidate all of
that.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
---
V3: Remove the INVD bug asm. Can be done in C (Brian)
---
arch/x86/entry/entry_32.S | 68 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 68 insertions(+)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -44,6 +44,7 @@
#include <asm/asm.h>
#include <asm/smap.h>
#include <asm/frame.h>
+#include <asm/trapnr.h>
#include <asm/nospec-branch.h>

#include "calling.h"
@@ -726,6 +727,31 @@

.Lend_\@:
.endm
+
+/**
+ * idtentry - Macro to generate entry stubs for simple IDT entries
+ * @vector: Vector number
+ * @asmsym: ASM symbol for the entry point
+ * @cfunc: C function to be called
+ * @has_error_code: Hardware pushed error code on stack
+ * @sane: Compatibility flag with 64bit
+ */
+.macro idtentry vector asmsym cfunc has_error_code:req sane=0
+SYM_CODE_START(\asmsym)
+ ASM_CLAC
+ cld
+
+ .if \has_error_code == 0
+ pushl $0 /* Clear the error code */
+ .endif
+
+ /* Push the C-function address into the GS slot */
+ pushl $\cfunc
+ /* Invoke the common exception entry */
+ jmp handle_exception
+SYM_CODE_END(\asmsym)
+.endm
+
/*
* %eax: prev task
* %edx: next task
@@ -1517,6 +1543,48 @@ SYM_CODE_START_LOCAL_NOALIGN(common_exce
jmp ret_from_exception
SYM_CODE_END(common_exception)

+SYM_CODE_START_LOCAL_NOALIGN(handle_exception)
+ /* the function address is in %gs's slot on the stack */
+ SAVE_ALL switch_stacks=1 skip_gs=1 unwind_espfix=1
+ ENCODE_FRAME_POINTER
+
+ /* fixup %gs */
+ GS_TO_REG %ecx
+ movl PT_GS(%esp), %edi # get the function address
+ REG_TO_PTGS %ecx
+ SET_KERNEL_GS %ecx
+
+ /* fixup orig %eax */
+ movl PT_ORIG_EAX(%esp), %edx # get the error code
+ movl $-1, PT_ORIG_EAX(%esp) # no syscall to restart
+
+ movl %esp, %eax # pt_regs pointer
+ CALL_NOSPEC edi
+
+#ifdef CONFIG_VM86
+ movl PT_EFLAGS(%esp), %eax # mix EFLAGS and CS
+ movb PT_CS(%esp), %al
+ andl $(X86_EFLAGS_VM | SEGMENT_RPL_MASK), %eax
+#else
+ /*
+ * We can be coming here from child spawned by kernel_thread().
+ */
+ movl PT_CS(%esp), %eax
+ andl $SEGMENT_RPL_MASK, %eax
+#endif
+ cmpl $USER_RPL, %eax # returning to v8086 or userspace ?
+ jnb ret_to_user
+
+ PARANOID_EXIT_TO_KERNEL_MODE
+ BUG_IF_WRONG_CR3
+ RESTORE_REGS 4
+ jmp .Lirq_return
+
+ret_to_user:
+ movl %esp, %eax
+ jmp restore_all_switch_stack
+SYM_CODE_END(handle_exception)
+
SYM_CODE_START(debug)
/*
* Entry from sysenter is now handled in common_exception