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Commit db6ccbb6 authored by Russell King's avatar Russell King Committed by Russell King
Browse files

[ARM] Fix kernel-mode undefined instruction aborts 



If the kernel attempts to execute a CP1 or CP2 instruction and it
aborts, and a FP emulator is not loaded, we try to return as if to
a user context, instead of the proper kernel context.  Since the
fault came from kernel mode, we must use the kernel return paths.

Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 4ac941d2

arch/arm/kernel/entry-armv.S

+8 −4
Original line number Diff line number Diff line
@@ -436,7 +436,7 @@ __und_usr: 
	usr_entry



	tst	r3, #PSR_T_BIT			@ Thumb mode?

	bne	fpundefinstr			@ ignore FP

	bne	__und_usr_unknown		@ ignore FP

	sub	r4, r2, #4



	@
@@ -448,7 +448,7 @@ __und_usr: 
	@

1:	ldrt	r0, [r4]

	adr	r9, ret_from_exception

	adr	lr, fpundefinstr

	adr	lr, __und_usr_unknown

	@

	@ fallthrough to call_fpe

	@
@@ -476,7 +476,9 @@ __und_usr: 
 * Emulators may wish to make use of the following registers:

 *  r0  = instruction opcode.

 *  r2  = PC+4

 *  r9  = normal "successful" return address

 *  r10 = this threads thread_info structure.

 *  lr  = unrecognised instruction return address

 */

call_fpe:

	tst	r0, #0x08000000			@ only CDP/CPRT/LDC/STC have bit 27
@@ -545,10 +547,12 @@ do_fpe: 


	.data

ENTRY(fp_enter)

	.word	fpundefinstr

	.word	no_fp

	.text



fpundefinstr:

no_fp:	mov	pc, lr



__und_usr_unknown:

	mov	r0, sp

	adr	lr, ret_from_exception

	b	do_undefinstr