Commit aa93e2ad authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

x86/entry_32: Remove .fixup usage 



Where possible, push the .fixup into code, at the tail of functions.

This is hard for macros since they're used in multiple functions,
therefore introduce a new extable handler to pop zeros.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20211110101325.245184699@infradead.org
parent 16e617d0

arch/x86/entry/entry_32.S

+8 −20
Original line number Diff line number Diff line
@@ -270,17 +270,9 @@ 
3:	popl	%fs

	addl	$(4 + \pop), %esp	/* pop the unused "gs" slot */

	IRET_FRAME

.pushsection .fixup, "ax"

4:	movl	$0, (%esp)

	jmp	1b

5:	movl	$0, (%esp)

	jmp	2b

6:	movl	$0, (%esp)

	jmp	3b

.popsection

	_ASM_EXTABLE(1b, 4b)

	_ASM_EXTABLE(2b, 5b)

	_ASM_EXTABLE(3b, 6b)

	_ASM_EXTABLE_TYPE(1b, 1b, EX_TYPE_POP_ZERO)

	_ASM_EXTABLE_TYPE(2b, 2b, EX_TYPE_POP_ZERO)

	_ASM_EXTABLE_TYPE(3b, 3b, EX_TYPE_POP_ZERO)

.endm



.macro RESTORE_ALL_NMI cr3_reg:req pop=0
@@ -925,10 +917,8 @@ SYM_FUNC_START(entry_SYSENTER_32) 
	sti

	sysexit



.pushsection .fixup, "ax"

2:	movl    $0, PT_FS(%esp)

	jmp     1b

.popsection

	_ASM_EXTABLE(1b, 2b)



.Lsysenter_fix_flags:
@@ -996,8 +986,7 @@ restore_all_switch_stack: 
	 */

	iret



.section .fixup, "ax"

SYM_CODE_START(asm_iret_error)

.Lasm_iret_error:

	pushl	$0				# no error code

	pushl	$iret_error
@@ -1014,9 +1003,8 @@ SYM_CODE_START(asm_iret_error) 
#endif



	jmp	handle_exception

SYM_CODE_END(asm_iret_error)

.previous

	_ASM_EXTABLE(.Lirq_return, asm_iret_error)



	_ASM_EXTABLE(.Lirq_return, .Lasm_iret_error)

SYM_FUNC_END(entry_INT80_32)



.macro FIXUP_ESPFIX_STACK

arch/x86/include/asm/extable_fixup_types.h

+2 −0
Original line number Diff line number Diff line
@@ -19,4 +19,6 @@ 
#define	EX_TYPE_DEFAULT_MCE_SAFE	12

#define	EX_TYPE_FAULT_MCE_SAFE		13



#define	EX_TYPE_POP_ZERO		14



#endif

arch/x86/mm/extable.c

+14 −0
Original line number Diff line number Diff line
@@ -99,6 +99,18 @@ static bool ex_handler_clear_fs(const struct exception_table_entry *fixup, 
	return ex_handler_default(fixup, regs);

}



static bool ex_handler_pop_zero(const struct exception_table_entry *fixup,

				struct pt_regs *regs)

{

	/*

	 * Typically used for when "pop %seg" traps, in which case we'll clear

	 * the stack slot and re-try the instruction, which will then succeed

	 * to pop zero.

	 */

	*((unsigned long *)regs->sp) = 0;

	return ex_handler_default(fixup, regs);

}



int ex_get_fixup_type(unsigned long ip)

{

	const struct exception_table_entry *e = search_exception_tables(ip);
@@ -156,6 +168,8 @@ int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code, 
	case EX_TYPE_WRMSR_IN_MCE:

		ex_handler_msr_mce(regs, true);

		break;

	case EX_TYPE_POP_ZERO:

		return ex_handler_pop_zero(e, regs);

	}

	BUG();

}