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Commit 97aa5cdd authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes/x86: Move default_xol_ops's data into arch_uprobe->def 



Finally we can move arch_uprobe->fixups/rip_rela_target_address
into the new "def" struct and place this struct in the union, they
are only used by default_xol_ops paths.

The patch also renames rip_rela_target_address to riprel_target just
to make this name shorter.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarJim Keniston <jkenisto@us.ibm.com>
parent 220ef8dc

arch/x86/include/asm/uprobes.h

+7 −5
Original line number Diff line number Diff line
@@ -41,18 +41,20 @@ struct arch_uprobe { 
		u8			ixol[MAX_UINSN_BYTES];

	};



	u16				fixups;

	const struct uprobe_xol_ops	*ops;



	union {

#ifdef CONFIG_X86_64

		unsigned long			rip_rela_target_address;

#endif

		struct {

			s32	offs;

			u8	ilen;

			u8	opc1;

		}			branch;

		struct {

#ifdef CONFIG_X86_64

			long	riprel_target;

#endif

			u16	fixups;

		} 			def;

	};

};

arch/x86/kernel/uprobes.c

+21 −22
Original line number Diff line number Diff line
@@ -251,10 +251,9 @@ static inline bool is_64bit_mm(struct mm_struct *mm) 
 * If arch_uprobe->insn doesn't use rip-relative addressing, return

 * immediately.  Otherwise, rewrite the instruction so that it accesses

 * its memory operand indirectly through a scratch register.  Set

 * arch_uprobe->fixups and arch_uprobe->rip_rela_target_address

 * accordingly.  (The contents of the scratch register will be saved

 * before we single-step the modified instruction, and restored

 * afterward.)

 * def->fixups and def->riprel_target accordingly. (The contents of the

 * scratch register will be saved before we single-step the modified

 * instruction, and restored afterward).

 *

 * We do this because a rip-relative instruction can access only a

 * relatively small area (+/- 2 GB from the instruction), and the XOL
@@ -308,18 +307,18 @@ handle_riprel_insn(struct arch_uprobe *auprobe, struct insn *insn) 
		 * is NOT the register operand, so we use %rcx (register

		 * #1) for the scratch register.

		 */

		auprobe->fixups = UPROBE_FIX_RIP_CX;

		auprobe->def.fixups = UPROBE_FIX_RIP_CX;

		/* Change modrm from 00 000 101 to 00 000 001. */

		*cursor = 0x1;

	} else {

		/* Use %rax (register #0) for the scratch register. */

		auprobe->fixups = UPROBE_FIX_RIP_AX;

		auprobe->def.fixups = UPROBE_FIX_RIP_AX;

		/* Change modrm from 00 xxx 101 to 00 xxx 000 */

		*cursor = (reg << 3);

	}



	/* Target address = address of next instruction + (signed) offset */

	auprobe->rip_rela_target_address = (long)insn->length + insn->displacement.value;

	auprobe->def.riprel_target = (long)insn->length + insn->displacement.value;



	/* Displacement field is gone; slide immediate field (if any) over. */

	if (insn->immediate.nbytes) {
@@ -336,25 +335,25 @@ static void 
pre_xol_rip_insn(struct arch_uprobe *auprobe, struct pt_regs *regs,

				struct arch_uprobe_task *autask)

{

	if (auprobe->fixups & UPROBE_FIX_RIP_AX) {

	if (auprobe->def.fixups & UPROBE_FIX_RIP_AX) {

		autask->saved_scratch_register = regs->ax;

		regs->ax = current->utask->vaddr;

		regs->ax += auprobe->rip_rela_target_address;

	} else if (auprobe->fixups & UPROBE_FIX_RIP_CX) {

		regs->ax += auprobe->def.riprel_target;

	} else if (auprobe->def.fixups & UPROBE_FIX_RIP_CX) {

		autask->saved_scratch_register = regs->cx;

		regs->cx = current->utask->vaddr;

		regs->cx += auprobe->rip_rela_target_address;

		regs->cx += auprobe->def.riprel_target;

	}

}



static void

handle_riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs, long *correction)

{

	if (auprobe->fixups & (UPROBE_FIX_RIP_AX | UPROBE_FIX_RIP_CX)) {

	if (auprobe->def.fixups & (UPROBE_FIX_RIP_AX | UPROBE_FIX_RIP_CX)) {

		struct arch_uprobe_task *autask;



		autask = &current->utask->autask;

		if (auprobe->fixups & UPROBE_FIX_RIP_AX)

		if (auprobe->def.fixups & UPROBE_FIX_RIP_AX)

			regs->ax = autask->saved_scratch_register;

		else

			regs->cx = autask->saved_scratch_register;
@@ -432,17 +431,17 @@ static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs 
	long correction = (long)(utask->vaddr - utask->xol_vaddr);



	handle_riprel_post_xol(auprobe, regs, &correction);

	if (auprobe->fixups & UPROBE_FIX_IP)

	if (auprobe->def.fixups & UPROBE_FIX_IP)

		regs->ip += correction;



	if (auprobe->fixups & UPROBE_FIX_CALL) {

	if (auprobe->def.fixups & UPROBE_FIX_CALL) {

		if (adjust_ret_addr(regs->sp, correction)) {

			regs->sp += sizeof_long();

			return -ERESTART;

		}

	}

	/* popf; tell the caller to not touch TF */

	if (auprobe->fixups & UPROBE_FIX_SETF)

	if (auprobe->def.fixups & UPROBE_FIX_SETF)

		utask->autask.saved_tf = true;



	return 0;
@@ -646,13 +645,13 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, 
		return ret;



	/*

	 * Figure out which fixups arch_uprobe_post_xol() will need to perform,

	 * and annotate arch_uprobe->fixups accordingly. To start with, ->fixups

	 * is either zero or it reflects rip-related fixups.

	 * Figure out which fixups default_post_xol_op() will need to perform,

	 * and annotate def->fixups accordingly. To start with, ->fixups is

	 * either zero or it reflects rip-related fixups.

	 */

	switch (OPCODE1(&insn)) {

	case 0x9d:		/* popf */

		auprobe->fixups |= UPROBE_FIX_SETF;

		auprobe->def.fixups |= UPROBE_FIX_SETF;

		break;

	case 0xc3:		/* ret or lret -- ip is correct */

	case 0xcb:
@@ -680,9 +679,9 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, 
	}



	if (fix_ip)

		auprobe->fixups |= UPROBE_FIX_IP;

		auprobe->def.fixups |= UPROBE_FIX_IP;

	if (fix_call)

		auprobe->fixups |= UPROBE_FIX_CALL;

		auprobe->def.fixups |= UPROBE_FIX_CALL;



	auprobe->ops = &default_xol_ops;

	return 0;