Commit 17773afd authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

powerpc/64: use 32-bit immediate for STACK_FRAME_REGS_MARKER 



Using a 32-bit constant for this marker allows it to be loaded with
two ALU instructions, like 32-bit. This avoids a TOC entry and a
TOC load that depends on the r2 value that has just been loaded from
the PACA.

This changes the value for 32-bit as well, so both have the same
value in the low 4 bytes and 64-bit has 0 in the top bytes.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220926034057.2360083-2-npiggin@gmail.com
parent 4b2a9315

arch/powerpc/include/asm/ptrace.h

+2 −2
Original line number Diff line number Diff line
@@ -99,6 +99,8 @@ struct pt_regs 


#define STACK_FRAME_WITH_PT_REGS (STACK_FRAME_OVERHEAD + sizeof(struct pt_regs))



#define STACK_FRAME_REGS_MARKER	ASM_CONST(0x72656773)



#ifdef __powerpc64__



/*
@@ -115,7 +117,6 @@ struct pt_regs 


#define STACK_FRAME_OVERHEAD	112	/* size of minimum stack frame */

#define STACK_FRAME_LR_SAVE	2	/* Location of LR in stack frame */

#define STACK_FRAME_REGS_MARKER	ASM_CONST(0x7265677368657265)

#define STACK_INT_FRAME_SIZE	(sizeof(struct pt_regs) + \

				 STACK_FRAME_OVERHEAD + KERNEL_REDZONE_SIZE)

#define STACK_FRAME_MARKER	12
@@ -136,7 +137,6 @@ struct pt_regs 
#define KERNEL_REDZONE_SIZE	0

#define STACK_FRAME_OVERHEAD	16	/* size of minimum stack frame */

#define STACK_FRAME_LR_SAVE	1	/* Location of LR in stack frame */

#define STACK_FRAME_REGS_MARKER	ASM_CONST(0x72656773)

#define STACK_INT_FRAME_SIZE	(sizeof(struct pt_regs) + STACK_FRAME_OVERHEAD)

#define STACK_FRAME_MARKER	2

#define STACK_FRAME_MIN_SIZE	STACK_FRAME_OVERHEAD

arch/powerpc/kernel/entry_32.S

+3 −3
Original line number Diff line number Diff line
@@ -263,7 +263,7 @@ fast_exception_return: 
	mtcr	r10

	lwz	r10,_LINK(r11)

	mtlr	r10

	/* Clear the exception_marker on the stack to avoid confusing stacktrace */

	/* Clear the exception marker on the stack to avoid confusing stacktrace */

	li	r10, 0

	stw	r10, 8(r11)

	REST_GPR(10, r11)
@@ -320,7 +320,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS) 
	li	r0,0



	/*

	 * Leaving a stale exception_marker on the stack can confuse

	 * Leaving a stale exception marker on the stack can confuse

	 * the reliable stack unwinder later on. Clear it.

	 */

	stw	r0,8(r1)
@@ -372,7 +372,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS) 
	mtspr	SPRN_XER,r5



	/*

	 * Leaving a stale exception_marker on the stack can confuse

	 * Leaving a stale exception marker on the stack can confuse

	 * the reliable stack unwinder later on. Clear it.

	 */

	stw	r0,8(r1)

arch/powerpc/kernel/exceptions-64e.S

+1 −7
Original line number Diff line number Diff line
@@ -378,7 +378,7 @@ exc_##n##_common: \ 
	ld	r9,excf+EX_R1(r13);	/* load orig r1 back from PACA */   \

	lwz	r10,excf+EX_CR(r13);	/* load orig CR back from PACA	*/  \

	lbz	r11,PACAIRQSOFTMASK(r13); /* get current IRQ softe */	    \

	ld	r12,exception_marker@toc(r2);				    \

	LOAD_REG_IMMEDIATE(r12, STACK_FRAME_REGS_MARKER);		    \

	ZEROIZE_GPR(0);							    \

	std	r3,GPR10(r1);		/* save r10 to stackframe */	    \

	std	r4,GPR11(r1);		/* save r11 to stackframe */	    \
@@ -459,12 +459,6 @@ exc_##n##_bad_stack: \ 
	bl	hdlr;							\

	b	interrupt_return



/* This value is used to mark exception frames on the stack. */

	.section	".toc","aw"

exception_marker:

	.tc	ID_EXC_MARKER[TC],STACK_FRAME_REGS_MARKER





/*

 * And here we have the exception vectors !

 */

arch/powerpc/kernel/exceptions-64s.S

+1 −1
Original line number Diff line number Diff line
@@ -589,7 +589,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR) 
	li	r9,IVEC

	std	r9,_TRAP(r1)		/* set trap number		*/

	li	r10,0

	ld	r11,exception_marker@toc(r2)

	LOAD_REG_IMMEDIATE(r11, STACK_FRAME_REGS_MARKER)

	std	r10,RESULT(r1)		/* clear regs->result		*/

	std	r11,STACK_FRAME_OVERHEAD-16(r1) /* mark the frame	*/

.endm

arch/powerpc/kernel/head_64.S

+0 −7
Original line number Diff line number Diff line
@@ -192,13 +192,6 @@ __secondary_hold: 
#endif

CLOSE_FIXED_SECTION(first_256B)



/* This value is used to mark exception frames on the stack. */

	.section ".toc","aw"

/* This value is used to mark exception frames on the stack. */

exception_marker:

	.tc	ID_EXC_MARKER[TC],STACK_FRAME_REGS_MARKER

	.previous



/*

 * On server, we include the exception vectors code here as it

 * relies on absolute addressing which is only possible within