Commit 40d2e763 authored by Brian Gerst's avatar Brian Gerst Committed by H. Peter Anvin
Browse files

x86-32: Rework cache flush denied handler 



The cache flush denied error is an erratum on some AMD 486 clones.  If an invd
instruction is executed in userspace, the processor calls exception 19 (13 hex)
instead of #GP (13 decimal).  On cpus where XMM is not supported, redirect
exception 19 to do_general_protection().  Also, remove die_if_kernel(), since
this was the last user.

Signed-off-by: default avatarBrian Gerst <brgerst@gmail.com>
LKML-Reference: <1269176446-2489-2-git-send-email-brgerst@gmail.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent be1066bb

arch/x86/Kconfig.cpu

+4 −0
Original line number Diff line number Diff line
@@ -338,6 +338,10 @@ config X86_F00F_BUG 
	def_bool y

	depends on M586MMX || M586TSC || M586 || M486 || M386



config X86_INVD_BUG

	def_bool y

	depends on M486 || M386



config X86_WP_WORKS_OK

	def_bool y

	depends on !M386

arch/x86/kernel/entry_32.S

+19 −0
Original line number Diff line number Diff line
@@ -53,6 +53,7 @@ 
#include <asm/processor-flags.h>

#include <asm/ftrace.h>

#include <asm/irq_vectors.h>

#include <asm/cpufeature.h>



/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this.  */

#include <linux/elf-em.h>
@@ -905,7 +906,25 @@ ENTRY(simd_coprocessor_error) 
	RING0_INT_FRAME

	pushl $0

	CFI_ADJUST_CFA_OFFSET 4

#ifdef CONFIG_X86_INVD_BUG

	/* AMD 486 bug: invd from userspace calls exception 19 instead of #GP */

661:	pushl $do_general_protection

662:

.section .altinstructions,"a"

	.balign 4

	.long 661b

	.long 663f

	.byte X86_FEATURE_XMM

	.byte 662b-661b

	.byte 664f-663f

.previous

.section .altinstr_replacement,"ax"

663:	pushl $do_simd_coprocessor_error

664:

.previous

#else

	pushl $do_simd_coprocessor_error

#endif

	CFI_ADJUST_CFA_OFFSET 4

	jmp error_code

	CFI_ENDPROC

arch/x86/kernel/traps.c

+3 −28
Original line number Diff line number Diff line
@@ -108,15 +108,6 @@ static inline void preempt_conditional_cli(struct pt_regs *regs) 
	dec_preempt_count();

}



#ifdef CONFIG_X86_32

static inline void

die_if_kernel(const char *str, struct pt_regs *regs, long err)

{

	if (!user_mode_vm(regs))

		die(str, regs, err);

}

#endif



static void __kprobes

do_trap(int trapnr, int signr, char *str, struct pt_regs *regs,

	long error_code, siginfo_t *info)
@@ -729,30 +720,14 @@ do_simd_coprocessor_error(struct pt_regs *regs, long error_code) 
	conditional_sti(regs);



#ifdef CONFIG_X86_32

	if (cpu_has_xmm) {

		/* Handle SIMD FPU exceptions on PIII+ processors. */

	ignore_fpu_irq = 1;

		simd_math_error((void __user *)regs->ip);

		return;

	}

	/*

	 * Handle strange cache flush from user space exception

	 * in all other cases.  This is undocumented behaviour.

	 */

	if (regs->flags & X86_VM_MASK) {

		handle_vm86_fault((struct kernel_vm86_regs *)regs, error_code);

		return;

	}

	current->thread.trap_no = 19;

	current->thread.error_code = error_code;

	die_if_kernel("cache flush denied", regs, error_code);

	force_sig(SIGSEGV, current);

#else

	if (!user_mode(regs) &&

			kernel_math_error(regs, "kernel simd math error", 19))

		return;

	simd_math_error((void __user *)regs->ip);

#endif



	simd_math_error((void __user *)regs->ip);

}



dotraplinkage void

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