Commit 57472306 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/32: Remove ksp_limit 



ksp_limit is there to help detect stack overflows.
That is specific to ppc32 as it was removed from ppc64 in
commit cbc9565e ("powerpc: Remove ksp_limit on ppc64").

There are other means for detecting stack overflows.

As ppc64 has proven to not need it, ppc32 should be able to do
without it too.

Lets remove it and simplify exception handling.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/d789c3385b22e07bedc997613c0d26074cb513e7.1615552866.git.christophe.leroy@csgroup.eu
parent e464d92b

arch/powerpc/include/asm/processor.h

+0 −2
Original line number Diff line number Diff line
@@ -144,7 +144,6 @@ struct thread_struct { 
#endif

#ifdef CONFIG_PPC32

	void		*pgdir;		/* root of page-table tree */

	unsigned long	ksp_limit;	/* if ksp <= ksp_limit stack overflow */

#ifdef CONFIG_PPC_RTAS

	unsigned long	rtas_sp;	/* stack pointer for when in RTAS */

#endif
@@ -282,7 +281,6 @@ struct thread_struct { 
#ifdef CONFIG_PPC32

#define INIT_THREAD { \

	.ksp = INIT_SP, \

	.ksp_limit = INIT_SP_LIMIT, \

	.pgdir = swapper_pg_dir, \

	.fpexc_mode = MSR_FE0 | MSR_FE1, \

	SPEFSCR_INIT \

arch/powerpc/kernel/asm-offsets.c

+0 −2
Original line number Diff line number Diff line
@@ -91,7 +91,6 @@ int main(void) 
	DEFINE(SIGSEGV, SIGSEGV);

	DEFINE(NMI_MASK, NMI_MASK);

#else

	OFFSET(KSP_LIMIT, thread_struct, ksp_limit);

#ifdef CONFIG_PPC_RTAS

	OFFSET(RTAS_SP, thread_struct, rtas_sp);

#endif
@@ -381,7 +380,6 @@ int main(void) 
	DEFINE(_CSRR1, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, csrr1));

	DEFINE(_DSRR0, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, dsrr0));

	DEFINE(_DSRR1, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, dsrr1));

	DEFINE(SAVED_KSP_LIMIT, STACK_INT_FRAME_SIZE+offsetof(struct exception_regs, saved_ksp_limit));

#endif

#endif

arch/powerpc/kernel/entry_32.S

+2 −66
Original line number Diff line number Diff line
@@ -94,12 +94,6 @@ crit_transfer_to_handler: 
	mfspr	r0,SPRN_SRR1

	stw	r0,_SRR1(r11)



	/* set the stack limit to the current stack */

	mfspr	r8,SPRN_SPRG_THREAD

	lwz	r0,KSP_LIMIT(r8)

	stw	r0,SAVED_KSP_LIMIT(r11)

	rlwinm	r0,r1,0,0,(31 - THREAD_SHIFT)

	stw	r0,KSP_LIMIT(r8)

	/* fall through */

_ASM_NOKPROBE_SYMBOL(crit_transfer_to_handler)

#endif
@@ -107,12 +101,6 @@ _ASM_NOKPROBE_SYMBOL(crit_transfer_to_handler) 
#ifdef CONFIG_40x

	.globl	crit_transfer_to_handler

crit_transfer_to_handler:

	/* set the stack limit to the current stack */

	mfspr	r8,SPRN_SPRG_THREAD

	lwz	r0,KSP_LIMIT(r8)

	stw	r0,saved_ksp_limit@l(0)

	rlwinm	r0,r1,0,0,(31 - THREAD_SHIFT)

	stw	r0,KSP_LIMIT(r8)

	/* fall through */

_ASM_NOKPROBE_SYMBOL(crit_transfer_to_handler)

#endif
@@ -151,17 +139,10 @@ transfer_to_handler: 
#endif

	b	3f



2:	/* if from kernel, check interrupted DOZE/NAP mode and

         * check for stack overflow

         */

	/* if from kernel, check interrupted DOZE/NAP mode */

2:

	kuap_save_and_lock r11, r12, r9, r2, r6

	addi	r2, r12, -THREAD

#ifndef CONFIG_VMAP_STACK

	lwz	r9,KSP_LIMIT(r12)

	cmplw	r1,r9			/* if r1 <= ksp_limit */

	ble-	stack_ovf		/* then the kernel stack overflowed */

#endif

5:

#if defined(CONFIG_PPC_BOOK3S_32) || defined(CONFIG_E500)

	lwz	r12,TI_LOCAL_FLAGS(r2)

	mtcrf	0x01,r12
@@ -204,37 +185,6 @@ transfer_to_handler_cont: 
_ASM_NOKPROBE_SYMBOL(transfer_to_handler)

_ASM_NOKPROBE_SYMBOL(transfer_to_handler_cont)



#ifndef CONFIG_VMAP_STACK

/*

 * On kernel stack overflow, load up an initial stack pointer

 * and call StackOverflow(regs), which should not return.

 */

stack_ovf:

	/* sometimes we use a statically-allocated stack, which is OK. */

	lis	r12,_end@h

	ori	r12,r12,_end@l

	cmplw	r1,r12

	ble	5b			/* r1 <= &_end is OK */

	SAVE_NVGPRS(r11)

	addi	r3,r1,STACK_FRAME_OVERHEAD

	lis	r1,init_thread_union@ha

	addi	r1,r1,init_thread_union@l

	addi	r1,r1,THREAD_SIZE-STACK_FRAME_OVERHEAD

	lis	r9,StackOverflow@ha

	addi	r9,r9,StackOverflow@l

	LOAD_REG_IMMEDIATE(r10,MSR_KERNEL)

#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PERF_EVENTS)

	mtspr	SPRN_NRI, r0

#endif

	mtspr	SPRN_SRR0,r9

	mtspr	SPRN_SRR1,r10

	rfi

#ifdef CONFIG_40x

	b .	/* Prevent prefetch past rfi */

#endif

_ASM_NOKPROBE_SYMBOL(stack_ovf)

#endif



	.globl	transfer_to_syscall

transfer_to_syscall:

	SAVE_NVGPRS(r1)
@@ -815,11 +765,6 @@ _ASM_NOKPROBE_SYMBOL(exc_exit_restart) 
#ifdef CONFIG_40x

	.globl	ret_from_crit_exc

ret_from_crit_exc:

	mfspr	r9,SPRN_SPRG_THREAD

	lis	r10,saved_ksp_limit@ha;

	lwz	r10,saved_ksp_limit@l(r10);

	tovirt(r9,r9);

	stw	r10,KSP_LIMIT(r9)

	lis	r9,crit_srr0@ha;

	lwz	r9,crit_srr0@l(r9);

	lis	r10,crit_srr1@ha;
@@ -833,9 +778,6 @@ _ASM_NOKPROBE_SYMBOL(ret_from_crit_exc) 
#ifdef CONFIG_BOOKE

	.globl	ret_from_crit_exc

ret_from_crit_exc:

	mfspr	r9,SPRN_SPRG_THREAD

	lwz	r10,SAVED_KSP_LIMIT(r1)

	stw	r10,KSP_LIMIT(r9)

	RESTORE_xSRR(SRR0,SRR1);

	RESTORE_MMU_REGS;

	RET_FROM_EXC_LEVEL(SPRN_CSRR0, SPRN_CSRR1, PPC_RFCI)
@@ -843,9 +785,6 @@ _ASM_NOKPROBE_SYMBOL(ret_from_crit_exc) 


	.globl	ret_from_debug_exc

ret_from_debug_exc:

	mfspr	r9,SPRN_SPRG_THREAD

	lwz	r10,SAVED_KSP_LIMIT(r1)

	stw	r10,KSP_LIMIT(r9)

	RESTORE_xSRR(SRR0,SRR1);

	RESTORE_xSRR(CSRR0,CSRR1);

	RESTORE_MMU_REGS;
@@ -854,9 +793,6 @@ _ASM_NOKPROBE_SYMBOL(ret_from_debug_exc) 


	.globl	ret_from_mcheck_exc

ret_from_mcheck_exc:

	mfspr	r9,SPRN_SPRG_THREAD

	lwz	r10,SAVED_KSP_LIMIT(r1)

	stw	r10,KSP_LIMIT(r9)

	RESTORE_xSRR(SRR0,SRR1);

	RESTORE_xSRR(CSRR0,CSRR1);

	RESTORE_xSRR(DSRR0,DSRR1);

arch/powerpc/kernel/head_40x.S

+0 −2
Original line number Diff line number Diff line
@@ -95,8 +95,6 @@ _ENTRY(crit_dear) 
	.space	4

_ENTRY(crit_esr)

	.space	4

_ENTRY(saved_ksp_limit)

	.space	4



/*

 * Exception prolog for critical exceptions.  This is a little different

arch/powerpc/kernel/head_booke.h

+0 −1
Original line number Diff line number Diff line
@@ -481,7 +481,6 @@ struct exception_regs { 
	unsigned long csrr1;

	unsigned long dsrr0;

	unsigned long dsrr1;

	unsigned long saved_ksp_limit;

};



/* ensure this structure is always sized to a multiple of the stack alignment */