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Commit 3cdfcbfd authored by Paul Mackerras's avatar Paul Mackerras Committed by Michael Ellerman
Browse files

powerpc: Change analyse_instr so it doesn't modify *regs 



The analyse_instr function currently doesn't just work out what an
instruction does, it also executes those instructions whose effect
is only to update CPU registers that are stored in struct pt_regs.
This is undesirable because optprobes uses analyse_instr to work out
if an instruction could be successfully emulated in future.

This changes analyse_instr so it doesn't modify *regs; instead it
stores information in the instruction_op structure to indicate what
registers (GPRs, CR, XER, LR) would be set and what value they would
be set to.  A companion function called emulate_update_regs() can
then use that information to update a pt_regs struct appropriately.

As a minor cleanup, this replaces inline asm using the cntlzw and
cntlzd instructions with calls to __builtin_clz() and __builtin_clzl().

Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 93b2d3cf

arch/powerpc/include/asm/sstep.h

+48 −4
Original line number Diff line number Diff line
@@ -23,9 +23,6 @@ struct pt_regs; 
#define IS_RFID(instr)		(((instr) & 0xfc0007fe) == 0x4c000024)

#define IS_RFI(instr)		(((instr) & 0xfc0007fe) == 0x4c000064)



/* Emulate instructions that cause a transfer of control. */

extern int emulate_step(struct pt_regs *regs, unsigned int instr);



enum instruction_type {

	COMPUTE,		/* arith/logical/CR op, etc. */

	LOAD,
@@ -55,11 +52,29 @@ enum instruction_type { 


#define INSTR_TYPE_MASK	0x1f



/* Compute flags, ORed in with type */

#define SETREG		0x20

#define SETCC		0x40

#define SETXER		0x80



/* Branch flags, ORed in with type */

#define SETLK		0x20

#define BRTAKEN		0x40

#define DECCTR		0x80



/* Load/store flags, ORed in with type */

#define SIGNEXT		0x20

#define UPDATE		0x40	/* matches bit in opcode 31 instructions */

#define BYTEREV		0x80



/* Barrier type field, ORed in with type */

#define BARRIER_MASK	0xe0

#define BARRIER_SYNC	0x00

#define BARRIER_ISYNC	0x20

#define BARRIER_EIEIO	0x40

#define BARRIER_LWSYNC	0x60

#define BARRIER_PTESYNC	0x80



/* Cacheop values, ORed in with type */

#define CACHEOP_MASK	0x700

#define DCBST		0
@@ -83,7 +98,36 @@ struct instruction_op { 
	int update_reg;

	/* For MFSPR */

	int spr;

	u32 ccval;

	u32 xerval;

};



extern int analyse_instr(struct instruction_op *op, struct pt_regs *regs,

/*

 * Decode an instruction, and return information about it in *op

 * without changing *regs.

 *

 * Return value is 1 if the instruction can be emulated just by

 * updating *regs with the information in *op, -1 if we need the

 * GPRs but *regs doesn't contain the full register set, or 0

 * otherwise.

 */

extern int analyse_instr(struct instruction_op *op, const struct pt_regs *regs,

			 unsigned int instr);



/*

 * Emulate an instruction that can be executed just by updating

 * fields in *regs.

 */

void emulate_update_regs(struct pt_regs *reg, struct instruction_op *op);



/*

 * Emulate instructions that cause a transfer of control,

 * arithmetic/logical instructions, loads and stores,

 * cache operations and barriers.

 *

 * Returns 1 if the instruction was emulated successfully,

 * 0 if it could not be emulated, or -1 for an instruction that

 * should not be emulated (rfid, mtmsrd clearing MSR_RI, etc.).

 */

extern int emulate_step(struct pt_regs *regs, unsigned int instr);

arch/powerpc/lib/sstep.c

+348 −253

File changed.

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