Commit 3fa3db32 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/align: Convert emulate_spe() to user_access_begin 



This patch converts emulate_spe() to using user_access_begin
logic.

Since commit 662bbcb2 ("mm, sched: Allow uaccess in atomic with
pagefault_disable()"), might_fault() doesn't fire when called from
sections where pagefaults are disabled, which must be the case
when using _inatomic variants of __get_user and __put_user. So
the might_fault() in user_access_begin() is not a problem.

There was a verification of user_mode() together with the access_ok(),
but there is a second verification of user_mode() just after, that
leads to immediate return. The access_ok() is now part of the
user_access_begin which is called after that other user_mode()
verification, so no need to check user_mode() again.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: default avatarDaniel Axtens <dja@axtens.net>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c95a648fdf75992c9d88f3c73cc23e7537fcf2ad.1615555354.git.christophe.leroy@csgroup.eu
parent 9bd68dc5

arch/powerpc/kernel/align.c

+33 −28
Original line number Original line Diff line number Diff line
@@ -107,7 +107,6 @@ static struct aligninfo spe_aligninfo[32] = { 
static int emulate_spe(struct pt_regs *regs, unsigned int reg,

static int emulate_spe(struct pt_regs *regs, unsigned int reg,

		       struct ppc_inst ppc_instr)

		       struct ppc_inst ppc_instr)

{

{

	int ret;

	union {

	union {

		u64 ll;

		u64 ll;

		u32 w[2];

		u32 w[2];
@@ -127,11 +126,6 @@ static int emulate_spe(struct pt_regs *regs, unsigned int reg, 
	nb = spe_aligninfo[instr].len;

	nb = spe_aligninfo[instr].len;

	flags = spe_aligninfo[instr].flags;

	flags = spe_aligninfo[instr].flags;





	/* Verify the address of the operand */

	if (unlikely(user_mode(regs) &&

		     !access_ok(addr, nb)))

		return -EFAULT;



	/* userland only */

	/* userland only */

	if (unlikely(!user_mode(regs)))

	if (unlikely(!user_mode(regs)))

		return 0;

		return 0;
@@ -169,26 +163,27 @@ static int emulate_spe(struct pt_regs *regs, unsigned int reg, 
		}

		}

	} else {

	} else {

		temp.ll = data.ll = 0;

		temp.ll = data.ll = 0;

		ret = 0;

		p = addr;

		p = addr;





		if (!user_read_access_begin(addr, nb))

			return -EFAULT;



		switch (nb) {

		switch (nb) {

		case 8:

		case 8:

			ret |= __get_user_inatomic(temp.v[0], p++);

			unsafe_get_user(temp.v[0], p++, Efault_read);

			ret |= __get_user_inatomic(temp.v[1], p++);

			unsafe_get_user(temp.v[1], p++, Efault_read);

			ret |= __get_user_inatomic(temp.v[2], p++);

			unsafe_get_user(temp.v[2], p++, Efault_read);

			ret |= __get_user_inatomic(temp.v[3], p++);

			unsafe_get_user(temp.v[3], p++, Efault_read);

			fallthrough;

			fallthrough;

		case 4:

		case 4:

			ret |= __get_user_inatomic(temp.v[4], p++);

			unsafe_get_user(temp.v[4], p++, Efault_read);

			ret |= __get_user_inatomic(temp.v[5], p++);

			unsafe_get_user(temp.v[5], p++, Efault_read);

			fallthrough;

			fallthrough;

		case 2:

		case 2:

			ret |= __get_user_inatomic(temp.v[6], p++);

			unsafe_get_user(temp.v[6], p++, Efault_read);

			ret |= __get_user_inatomic(temp.v[7], p++);

			unsafe_get_user(temp.v[7], p++, Efault_read);

			if (unlikely(ret))

				return -EFAULT;

		}

		}

		user_read_access_end();





		switch (instr) {

		switch (instr) {

		case EVLDD:

		case EVLDD:
@@ -255,31 +250,41 @@ static int emulate_spe(struct pt_regs *regs, unsigned int reg, 




	/* Store result to memory or update registers */

	/* Store result to memory or update registers */

	if (flags & ST) {

	if (flags & ST) {

		ret = 0;

		p = addr;

		p = addr;



		if (!user_write_access_begin(addr, nb))

			return -EFAULT;



		switch (nb) {

		switch (nb) {

		case 8:

		case 8:

			ret |= __put_user_inatomic(data.v[0], p++);

			unsafe_put_user(data.v[0], p++, Efault_write);

			ret |= __put_user_inatomic(data.v[1], p++);

			unsafe_put_user(data.v[1], p++, Efault_write);

			ret |= __put_user_inatomic(data.v[2], p++);

			unsafe_put_user(data.v[2], p++, Efault_write);

			ret |= __put_user_inatomic(data.v[3], p++);

			unsafe_put_user(data.v[3], p++, Efault_write);

			fallthrough;

			fallthrough;

		case 4:

		case 4:

			ret |= __put_user_inatomic(data.v[4], p++);

			unsafe_put_user(data.v[4], p++, Efault_write);

			ret |= __put_user_inatomic(data.v[5], p++);

			unsafe_put_user(data.v[5], p++, Efault_write);

			fallthrough;

			fallthrough;

		case 2:

		case 2:

			ret |= __put_user_inatomic(data.v[6], p++);

			unsafe_put_user(data.v[6], p++, Efault_write);

			ret |= __put_user_inatomic(data.v[7], p++);

			unsafe_put_user(data.v[7], p++, Efault_write);

		}

		}

		if (unlikely(ret))

		user_write_access_end();

			return -EFAULT;

	} else {

	} else {

		*evr = data.w[0];

		*evr = data.w[0];

		regs->gpr[reg] = data.w[1];

		regs->gpr[reg] = data.w[1];

	}

	}





	return 1;

	return 1;



Efault_read:

	user_read_access_end();

	return -EFAULT;



Efault_write:

	user_write_access_end();

	return -EFAULT;

}

}

#endif /* CONFIG_SPE */

#endif /* CONFIG_SPE */