Commit f88723a6 authored by Benjamin Gray's avatar Benjamin Gray Committed by Michael Ellerman
Browse files

selftests/powerpc/dexcr: Add chdexcr utility 



Adds a utility to exercise the prctl DEXCR inheritance in the shell.
Supports setting and clearing each aspect.

Signed-off-by: default avatarBenjamin Gray <bgray@linux.ibm.com>
[mpe: Use correct SPDX license, use execvp() for usability, print errors]
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240417112325.728010-9-bgray@linux.ibm.com
parent 9c4866b2

tools/testing/selftests/powerpc/dexcr/.gitignore

+1 −0
Original line number Diff line number Diff line 
dexcr_test

hashchk_test

chdexcr

lsdexcr

tools/testing/selftests/powerpc/dexcr/Makefile

+1 −1
Original line number Diff line number Diff line 
TEST_GEN_PROGS := dexcr_test hashchk_test

TEST_GEN_FILES := lsdexcr

TEST_GEN_FILES := lsdexcr chdexcr



include ../../lib.mk

include ../flags.mk

tools/testing/selftests/powerpc/dexcr/chdexcr.c

0 → 100644
+112 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-or-later



#include <errno.h>

#include <stddef.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <sys/prctl.h>



#include "dexcr.h"

#include "utils.h"



static void die(const char *msg)

{

	printf("%s\n", msg);

	exit(1);

}



static void help(void)

{

	printf("Invoke a provided program with a custom DEXCR on-exec reset value\n"

	       "\n"

	       "usage: chdexcr [CHDEXCR OPTIONS] -- PROGRAM [ARGS...]\n"

	       "\n"

	       "Each configurable DEXCR aspect is exposed as an option.\n"

	       "\n"

	       "The normal option sets the aspect in the DEXCR. The --no- variant\n"

	       "clears that aspect. For example, --ibrtpd sets the IBRTPD aspect bit,\n"

	       "so indirect branch predicition will be disabled in the provided program.\n"

	       "Conversely, --no-ibrtpd clears the aspect bit, so indirect branch\n"

	       "prediction may occur.\n"

	       "\n"

	       "CHDEXCR OPTIONS:\n");



	for (int i = 0; i < ARRAY_SIZE(aspects); i++) {

		const struct dexcr_aspect *aspect = &aspects[i];



		if (aspect->prctl == -1)

			continue;



		printf("  --%-6s / --no-%-6s : %s\n", aspect->opt, aspect->opt, aspect->desc);

	}

}



static const struct dexcr_aspect *opt_to_aspect(const char *opt)

{

	for (int i = 0; i < ARRAY_SIZE(aspects); i++)

		if (aspects[i].prctl != -1 && !strcmp(aspects[i].opt, opt))

			return &aspects[i];



	return NULL;

}



static int apply_option(const char *option)

{

	const struct dexcr_aspect *aspect;

	const char *opt = NULL;

	const char *set_prefix = "--";

	const char *clear_prefix = "--no-";

	unsigned long ctrl = 0;

	int err;



	if (!strcmp(option, "-h") || !strcmp(option, "--help")) {

		help();

		exit(0);

	}



	/* Strip out --(no-) prefix and determine ctrl value */

	if (!strncmp(option, clear_prefix, strlen(clear_prefix))) {

		opt = &option[strlen(clear_prefix)];

		ctrl |= PR_PPC_DEXCR_CTRL_CLEAR_ONEXEC;

	} else if (!strncmp(option, set_prefix, strlen(set_prefix))) {

		opt = &option[strlen(set_prefix)];

		ctrl |= PR_PPC_DEXCR_CTRL_SET_ONEXEC;

	}



	if (!opt || !*opt)

		return 1;



	aspect = opt_to_aspect(opt);

	if (!aspect)

		die("unknown aspect");



	err = pr_set_dexcr(aspect->prctl, ctrl);

	if (err)

		die("failed to apply option");



	return 0;

}



int main(int argc, char *const argv[])

{

	int i;



	if (!dexcr_exists())

		die("DEXCR not detected on this hardware");



	for (i = 1; i < argc; i++)

		if (apply_option(argv[i]))

			break;



	if (i < argc && !strcmp(argv[i], "--"))

		i++;



	if (i >= argc)

		die("missing command");



	execvp(argv[i], &argv[i]);

	perror("execve");



	return errno;

}

tools/testing/selftests/powerpc/dexcr/dexcr.h

+47 −0
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 
#define _SELFTESTS_POWERPC_DEXCR_DEXCR_H



#include <stdbool.h>

#include <sys/prctl.h>

#include <sys/types.h>



#include "reg.h"
@@ -26,6 +27,52 @@ 
#define PPC_RAW_HASHCHK(b, i, a) \

	str(.long (0x7C0005E4 | PPC_RAW_HASH_ARGS(b, i, a));)



struct dexcr_aspect {

	const char *name;	/* Short display name */

	const char *opt;	/* Option name for chdexcr */

	const char *desc;	/* Expanded aspect meaning */

	unsigned int index;	/* Aspect bit index in DEXCR */

	unsigned long prctl;	/* 'which' value for get/set prctl */

};



static const struct dexcr_aspect aspects[] = {

	{

		.name = "SBHE",

		.opt = "sbhe",

		.desc = "Speculative branch hint enable",

		.index = 0,

		.prctl = PR_PPC_DEXCR_SBHE,

	},

	{

		.name = "IBRTPD",

		.opt = "ibrtpd",

		.desc = "Indirect branch recurrent target prediction disable",

		.index = 3,

		.prctl = PR_PPC_DEXCR_IBRTPD,

	},

	{

		.name = "SRAPD",

		.opt = "srapd",

		.desc = "Subroutine return address prediction disable",

		.index = 4,

		.prctl = PR_PPC_DEXCR_SRAPD,

	},

	{

		.name = "NPHIE",

		.opt = "nphie",

		.desc = "Non-privileged hash instruction enable",

		.index = 5,

		.prctl = PR_PPC_DEXCR_NPHIE,

	},

	{

		.name = "PHIE",

		.opt = "phie",

		.desc = "Privileged hash instruction enable",

		.index = 6,

		.prctl = -1,

	},

};



bool dexcr_exists(void);



bool pr_dexcr_aspect_supported(unsigned long which);

tools/testing/selftests/powerpc/dexcr/lsdexcr.c

+26 −104
Original line number Diff line number Diff line
@@ -12,52 +12,6 @@ static unsigned int dexcr; 
static unsigned int hdexcr;

static unsigned int effective;



struct dexcr_aspect {

	const char *name;

	const char *desc;

	unsigned int index;

	unsigned long prctl;

	const char *sysctl;

};



static const struct dexcr_aspect aspects[] = {

	{

		.name = "SBHE",

		.desc = "Speculative branch hint enable",

		.index = 0,

		.prctl = PR_PPC_DEXCR_SBHE,

		.sysctl = "speculative_branch_hint_enable",

	},

	{

		.name = "IBRTPD",

		.desc = "Indirect branch recurrent target prediction disable",

		.index = 3,

		.prctl = PR_PPC_DEXCR_IBRTPD,

		.sysctl = "indirect_branch_recurrent_target_prediction_disable",

	},

	{

		.name = "SRAPD",

		.desc = "Subroutine return address prediction disable",

		.index = 4,

		.prctl = PR_PPC_DEXCR_SRAPD,

		.sysctl = "subroutine_return_address_prediction_disable",

	},

	{

		.name = "NPHIE",

		.desc = "Non-privileged hash instruction enable",

		.index = 5,

		.prctl = PR_PPC_DEXCR_NPHIE,

		.sysctl = "nonprivileged_hash_instruction_enable",

	},

	{

		.name = "PHIE",

		.desc = "Privileged hash instruction enable",

		.index = 6,

		.prctl = -1,

		.sysctl = NULL,

	},

};



static void print_list(const char *list[], size_t len)

{

	for (size_t i = 0; i < len; i++) {
@@ -117,89 +71,57 @@ static void print_aspect(const struct dexcr_aspect *aspect) 


static void print_aspect_config(const struct dexcr_aspect *aspect)

{

	char sysctl_path[128] = "/proc/sys/kernel/dexcr/";

	const char *reason = "unknown";

	const char *reason = NULL;

	const char *reason_hyp = NULL;

	const char *reason_sysctl = "no sysctl";

	const char *reason_prctl = "no prctl";

	bool actual = effective & DEXCR_PR_BIT(aspect->index);

	bool expected = false;



	long sysctl_ctrl = 0;

	int prctl_ctrl = 0;

	int err;



	if (aspect->prctl >= 0) {

		prctl_ctrl = pr_get_dexcr(aspect->prctl);

		if (prctl_ctrl < 0)

			reason_prctl = "(failed to read prctl)";

		else {

			if (prctl_ctrl & PR_PPC_DEXCR_CTRL_SET) {

	bool expected = actual;  /* Assume it's fine if we don't expect a specific set/clear value */



	if (actual)

		reason = "set by unknown";

	else

		reason = "cleared by unknown";



	if (aspect->prctl != -1) {

		int ctrl = pr_get_dexcr(aspect->prctl);



		if (ctrl < 0) {

			reason_prctl = "failed to read prctl";

		} else {

			if (ctrl & PR_PPC_DEXCR_CTRL_SET) {

				reason_prctl = "set by prctl";

				expected = true;

			} else if (prctl_ctrl & PR_PPC_DEXCR_CTRL_CLEAR) {

			} else if (ctrl & PR_PPC_DEXCR_CTRL_CLEAR) {

				reason_prctl = "cleared by prctl";

				expected = false;

			} else

			} else {

				reason_prctl = "unknown prctl";



			reason = reason_prctl;

		}

			}



	if (aspect->sysctl) {

		strcat(sysctl_path, aspect->sysctl);

		err = read_long(sysctl_path, &sysctl_ctrl, 10);

		if (err)

			reason_sysctl = "(failed to read sysctl)";

		else {

			switch (sysctl_ctrl) {

			case 0:

				reason_sysctl = "cleared by sysctl";

				reason = reason_sysctl;

				expected = false;

				break;

			case 1:

				reason_sysctl = "set by sysctl";

				reason = reason_sysctl;

				expected = true;

				break;

			case 2:

				reason_sysctl = "not modified by sysctl";

				break;

			case 3:

				reason_sysctl = "cleared by sysctl (permanent)";

				reason = reason_sysctl;

				expected = false;

				break;

			case 4:

				reason_sysctl = "set by sysctl (permanent)";

				reason = reason_sysctl;

				expected = true;

				break;

			default:

				reason_sysctl = "unknown sysctl";

				break;

			}

			reason = reason_prctl;

		}

	}





	if (hdexcr & DEXCR_PR_BIT(aspect->index)) {

		reason_hyp = "set by hypervisor";

		reason = reason_hyp;

		expected = true;

	} else

	} else {

		reason_hyp = "not modified by hypervisor";

	}



	printf("%12s (%d): %-28s (%s, %s, %s)\n",

	printf("%12s (%d): %-28s (%s, %s)\n",

	       aspect->name,

	       aspect->index,

	       reason,

	       reason_hyp,

	       reason_sysctl,

	       reason_prctl);



	/*

	 * The checks are not atomic, so this can technically trigger if the

	 * hypervisor makes a change while we are checking each source. It's

	 * far more likely to be a bug if we see this though.

	 */

	if (actual != expected)

		printf("                : ! actual %s does not match config\n", aspect->name);

}