Commit ddb69f27 authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes/x86: Fold prepare_fixups() into arch_uprobe_analyze_insn() 



No functional changes, preparation.

Shift the code from prepare_fixups() to arch_uprobe_analyze_insn()
with the following modifications:

	- Do not call insn_get_opcode() again, it was already called
	  by validate_insn_bits().

	- Move "case 0xea" up. This way "case 0xff" can fall through
	  to default case.

	- change "case 0xff" to use the nested "switch (MODRM_REG)",
	  this way the code looks a bit simpler.

	- Make the comments look consistent.

While at it, kill the initialization of rip_rela_target_address and
->fixups, we can rely on kzalloc(). We will add the new members into
arch_uprobe, it would be better to assume that everything is zero by
default.

TODO: cleanup/fix the mess in validate_insn_bits() paths:

	- validate_insn_64bits() and validate_insn_32bits() should be
	  unified.

	- "ifdef" is not used consistently; if good_insns_64 depends
	  on CONFIG_X86_64, then probably good_insns_32 should depend
	  on CONFIG_X86_32/EMULATION

	- the usage of mm->context.ia32_compat looks wrong if the task
	  is TIF_X32.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: default avatarJim Keniston <jkenisto@us.ibm.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
parent 8a6b1732

arch/x86/kernel/uprobes.c

+47 −63
Original line number Diff line number Diff line
@@ -53,7 +53,7 @@ 
#define OPCODE1(insn)		((insn)->opcode.bytes[0])

#define OPCODE2(insn)		((insn)->opcode.bytes[1])

#define OPCODE3(insn)		((insn)->opcode.bytes[2])

#define MODRM_REG(insn)		X86_MODRM_REG(insn->modrm.value)

#define MODRM_REG(insn)		X86_MODRM_REG((insn)->modrm.value)



#define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\

	(((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
@@ -229,63 +229,6 @@ static int validate_insn_32bits(struct arch_uprobe *auprobe, struct insn *insn) 
	return -ENOTSUPP;

}



/*

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

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

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

 */

static void prepare_fixups(struct arch_uprobe *auprobe, struct insn *insn)

{

	bool fix_ip = true, fix_call = false;	/* defaults */

	int reg;



	insn_get_opcode(insn);	/* should be a nop */



	switch (OPCODE1(insn)) {

	case 0x9d:

		/* popf */

		auprobe->fixups |= UPROBE_FIX_SETF;

		break;

	case 0xc3:		/* ret/lret */

	case 0xcb:

	case 0xc2:

	case 0xca:

		/* ip is correct */

		fix_ip = false;

		break;

	case 0xe8:		/* call relative - Fix return addr */

		fix_call = true;

		break;

	case 0x9a:		/* call absolute - Fix return addr, not ip */

		fix_call = true;

		fix_ip = false;

		break;

	case 0xff:

		insn_get_modrm(insn);

		reg = MODRM_REG(insn);

		if (reg == 2 || reg == 3) {

			/* call or lcall, indirect */

			/* Fix return addr; ip is correct. */

			fix_call = true;

			fix_ip = false;

		} else if (reg == 4 || reg == 5) {

			/* jmp or ljmp, indirect */

			/* ip is correct. */

			fix_ip = false;

		}

		break;

	case 0xea:		/* jmp absolute -- ip is correct */

		fix_ip = false;

		break;

	default:

		break;

	}

	if (fix_ip)

		auprobe->fixups |= UPROBE_FIX_IP;

	if (fix_call)

		auprobe->fixups |= UPROBE_FIX_CALL;

}



#ifdef CONFIG_X86_64

/*

 * If arch_uprobe->insn doesn't use rip-relative addressing, return
@@ -318,7 +261,6 @@ handle_riprel_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, struct ins 
	if (mm->context.ia32_compat)

		return;



	auprobe->rip_rela_target_address = 0x0;

	if (!insn_rip_relative(insn))

		return;
@@ -421,16 +363,58 @@ static int validate_insn_bits(struct arch_uprobe *auprobe, struct mm_struct *mm, 
 */

int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long addr)

{

	int ret;

	struct insn insn;

	bool fix_ip = true, fix_call = false;

	int ret;



	auprobe->fixups = 0;

	ret = validate_insn_bits(auprobe, mm, &insn);

	if (ret != 0)

	if (ret)

		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.

	 */

	handle_riprel_insn(auprobe, mm, &insn);

	prepare_fixups(auprobe, &insn);



	switch (OPCODE1(&insn)) {

	case 0x9d:		/* popf */

		auprobe->fixups |= UPROBE_FIX_SETF;

		break;

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

	case 0xcb:

	case 0xc2:

	case 0xca:

		fix_ip = false;

		break;

	case 0xe8:		/* call relative - Fix return addr */

		fix_call = true;

		break;

	case 0x9a:		/* call absolute - Fix return addr, not ip */

		fix_call = true;

		fix_ip = false;

		break;

	case 0xea:		/* jmp absolute -- ip is correct */

		fix_ip = false;

		break;

	case 0xff:

		insn_get_modrm(&insn);

		switch (MODRM_REG(&insn)) {

		case 2: case 3:			/* call or lcall, indirect */

			fix_call = true;

		case 4: case 5:			/* jmp or ljmp, indirect */

			fix_ip = false;

		}

		break;

	default:

		break;

	}



	if (fix_ip)

		auprobe->fixups |= UPROBE_FIX_IP;

	if (fix_call)

		auprobe->fixups |= UPROBE_FIX_CALL;



	return 0;

}

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