[patch V4 part 3 29/29] x86/entry/32: Convert IRET exception to IDTENTRY_SW

Thomas Gleixner
2020-05-05T14:16:02Z

From: Thomas Gleixner <tglx@linutronix.de>

Convert the IRET exception handler to IDTENTRY_SW. This is slightly
different than the conversions of hardware exceptions as the IRET exception
is invoked via an exception table when IRET faults. So it just uses the
IDTENTRY_SW mechanism for consistency. It does not emit ASM code as it does
not fit the other idtentry exceptions.

- Implement the C entry point with DEFINE_IDTENTRY_SW() which maps to
DEFINE_IDTENTRY()
- Fixup the XEN/PV code
- Remove the old prototyoes
- Remove the RCU warning as the new entry macro ensures correctness

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
arch/x86/entry/entry_32.S | 14 +++++++-------
arch/x86/include/asm/idtentry.h | 10 ++++++++++
arch/x86/include/asm/traps.h | 3 ---
arch/x86/kernel/traps.c | 8 +++-----
arch/x86/xen/xen-asm_32.S | 2 +-
5 files changed, 21 insertions(+), 16 deletions(-)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1147,9 +1147,9 @@ SYM_FUNC_START(entry_INT80_32)
jmp .Lirq_return

.section .fixup, "ax"
-SYM_CODE_START(iret_exc)
+SYM_CODE_START(asm_exc_iret_error)
pushl $0 # no error code
- pushl $do_iret_error
+ pushl $exc_iret_error

#ifdef CONFIG_DEBUG_ENTRY
/*
@@ -1163,10 +1163,10 @@ SYM_CODE_START(iret_exc)
popl %eax
#endif

- jmp common_exception
-SYM_CODE_END(iret_exc)
+ jmp handle_exception
+SYM_CODE_END(asm_exc_iret_error)
.previous
- _ASM_EXTABLE(.Lirq_return, iret_exc)
+ _ASM_EXTABLE(.Lirq_return, asm_exc_iret_error)
SYM_FUNC_END(entry_INT80_32)

.macro FIXUP_ESPFIX_STACK
@@ -1293,7 +1293,7 @@ SYM_FUNC_END(name)
#ifdef CONFIG_PARAVIRT
SYM_CODE_START(native_iret)
iret
- _ASM_EXTABLE(native_iret, iret_exc)
+ _ASM_EXTABLE(native_iret, asm_exc_iret_error)
SYM_CODE_END(native_iret)
#endif

@@ -1358,7 +1358,7 @@ SYM_FUNC_START(xen_failsafe_callback)
popl %eax
lea 16(%esp), %esp
jz 5f
- jmp iret_exc
+ jmp asm_exc_iret_error
5: pushl $-1 /* orig_ax = -1 => not a system call */
SAVE_ALL
ENCODE_FRAME_POINTER
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -57,6 +57,10 @@ static __always_inline void __##func(str
\
static __always_inline void __##func(struct pt_regs *regs)

+/* Special case for 32bit IRET 'trap' */
+#define DECLARE_IDTENTRY_SW DECLARE_IDTENTRY
+#define DEFINE_IDTENTRY_SW DEFINE_IDTENTRY
+
/**
* DECLARE_IDTENTRY_ERRORCODE - Declare functions for simple IDT entry points
* Error code pushed by hardware
@@ -111,6 +115,9 @@ static __always_inline void __##func(str
#define DECLARE_IDTENTRY_ERRORCODE(vector, func) \
idtentry vector asm_##func func has_error_code=1 sane=1

+/* Special case for 32bit IRET 'trap'. Do not emit ASM code */
+#define DECLARE_IDTENTRY_SW(vector, func)
+
#endif /* __ASSEMBLY__ */

/*
@@ -133,6 +140,9 @@ DECLARE_IDTENTRY(X86_TRAP_SPURIOUS, exc_
DECLARE_IDTENTRY(X86_TRAP_MF, exc_coprocessor_error);
DECLARE_IDTENTRY(X86_TRAP_XF, exc_simd_coprocessor_error);

+/* 32bit software IRET trap. Do not emit ASM code */
+DECLARE_IDTENTRY_SW(X86_TRAP_IRET, exc_iret_error);
+
/* Simple exception entries with error code pushed by hardware */
DECLARE_IDTENTRY_ERRORCODE(X86_TRAP_TS, exc_invalid_tss);
DECLARE_IDTENTRY_ERRORCODE(X86_TRAP_NP, exc_segment_not_present);
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -41,9 +41,6 @@ dotraplinkage void do_int3(struct pt_reg
dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsigned long cr2);
#endif
dotraplinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address);
-#ifdef CONFIG_X86_32
-dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code);
-#endif
dotraplinkage void do_mce(struct pt_regs *regs, long error_code);

#ifdef CONFIG_X86_64
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -917,14 +917,12 @@ DEFINE_IDTENTRY(exc_device_not_available
}

#ifdef CONFIG_X86_32
-dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code)
+DEFINE_IDTENTRY_SW(exc_iret_error)
{
- RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
local_irq_enable();
-
- if (notify_die(DIE_TRAP, "iret exception", regs, error_code,
+ if (notify_die(DIE_TRAP, "iret exception", regs, 0,
X86_TRAP_IRET, SIGILL) != NOTIFY_STOP) {
- do_trap(X86_TRAP_IRET, SIGILL, "iret exception", regs, error_code,
+ do_trap(X86_TRAP_IRET, SIGILL, "iret exception", regs, 0,
ILL_BADSTK, (void __user *)NULL);
}
local_irq_disable();
--- a/arch/x86/xen/xen-asm_32.S
+++ b/arch/x86/xen/xen-asm_32.S
@@ -117,7 +117,7 @@ SYM_CODE_START(xen_iret)

1: iret
xen_iret_end_crit:
- _ASM_EXTABLE(1b, iret_exc)
+ _ASM_EXTABLE(1b, asm_exc_iret_error)

hyper_iret:
/* put this out of line since its very rarely used */