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x86/entry_32: Remove .fixup usage

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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: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20211110101325.245184699@infradead.org
This commit is contained in:
Peter Zijlstra 2021-11-10 11:01:08 +01:00
parent 16e617d05e
commit aa93e2ad74
3 changed files with 24 additions and 20 deletions
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28
arch/x86/entry/entry_32.S
View file

@ -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
2: movl $0, PT_FS(%esp)
jmp 1b
_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

2
arch/x86/include/asm/extable_fixup_types.h
View file

@ -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

14
arch/x86/mm/extable.c
View file

@ -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();
}