[LTP] [PATCH 1/4] modify_ldt: Add lapi/ldt.h
Andrea Cervesato
andrea.cervesato@suse.com
Tue Mar 25 10:58:06 CET 2025
Hi!
The modify_ldt syscall exists for a long time before the minimum kernel
version 4.4 that we support in LTP.
So we can happily ignore any fallback definition and to remove asm/ldt.h
check from configure.ac.
More comments below.
On 3/24/25 21:45, Ricardo B. Marliere via ltp wrote:
> From: Ricardo B. Marlière <rbm@suse.com>
>
> Add a wrapper to modify_ldt and a fallback to the user_desc structure which
> is used in a few tests and should be reused.
>
> Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
> ---
> include/lapi/ldt.h | 53 ++++++++++++++++++++++
> testcases/cve/cve-2015-3290.c | 15 +++---
> testcases/cve/cve-2017-17053.c | 10 ++--
> testcases/kernel/syscalls/fork/fork05.c | 4 +-
> .../syscalls/set_thread_area/set_thread_area.h | 31 -------------
> .../syscalls/set_thread_area/set_thread_area01.c | 14 +++---
> 6 files changed, 74 insertions(+), 53 deletions(-)
>
> diff --git a/include/lapi/ldt.h b/include/lapi/ldt.h
> new file mode 100644
> index 0000000000000000000000000000000000000000..011138a1d22adfd94bcda9b31cafd3746272556b
> --- /dev/null
> +++ b/include/lapi/ldt.h
> @@ -0,0 +1,53 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2025 SUSE LLC Ricardo B. Marlière <rbm@suse.com>
> + */
> +
> +#if !(defined(__i386__) || defined(__x86_64__))
> +#error "ldt.h should only be included on x86"
> +#endif
> +
> +#ifndef LAPI_LDT_H__
> +#define LAPI_LDT_H__
> +
> +#include "config.h"
> +#include "lapi/syscalls.h"
> +
> +#ifdef HAVE_ASM_LDT_H
> +#include <asm/ldt.h>
> +#else
> +struct user_desc {
> + unsigned int entry_number;
> + unsigned int base_addr;
> + unsigned int limit;
> + unsigned int seg_32bit : 1;
> + unsigned int contents : 2;
> + unsigned int read_exec_only : 1;
> + unsigned int limit_in_pages : 1;
> + unsigned int seg_not_present : 1;
> + unsigned int useable : 1;
> +#ifdef __x86_64__
> + unsigned int lm : 1;
> +#endif /* __x86_64__ */
> +};
> +#endif /* HAVE_ASM_LDT_H */
> +
> +#ifdef HAVE_STRUCT_MODIFY_LDT_LDT_S
> +/*
> + * From man 2 modify_ldt:
> + * In Linux 2.4 and earlier, this structure was named modify_ldt_ldt_s.
> + */
> +typedef struct modify_ldt_ldt_s user_desc;
> +#endif /* HAVE_STRUCT_MODIFY_LDT_LDT_S */
> +
> +/*
> + * From man 2 modify_ldt:
> + * Note: glibc provides no wrapper for modify_ldt(), necessitating the use of
> + * syscall(2).
> + */
> +static int modify_ldt(int func, void *ptr, unsigned long bytecount)
> +{
> + return syscall(__NR_modify_ldt, func, ptr, bytecount);
If we want to define any wrapper around a syscall, we need to use
tst_syscall. It's a safer way to handle syscalls errors due to ENOSYS.
We are also checking for modify_ldt(2) syscall in the configure.ac file,
so we can use HAVE_MODIFY_LDT to verify that no wrappers have been
defined before.
Then we can add a SAFE_MODIFY_LDT() macro in order to use syscall is a
safe way.
> +}
> +
> +#endif /* LAPI_LDT_H__ */
> diff --git a/testcases/cve/cve-2015-3290.c b/testcases/cve/cve-2015-3290.c
> index 63e5d92c91b830cd8066a6a6c329461b72731f32..ce90c90942e5780d8f86adc5bd18718a96c1a95e 100644
> --- a/testcases/cve/cve-2015-3290.c
> +++ b/testcases/cve/cve-2015-3290.c
> @@ -118,12 +118,10 @@ perhaps unsurprisingly.)
> #include "tst_test.h"
> #include "tst_timer.h"
>
> -#if defined(__x86_64__) || defined(__i386__)
> -
> +#if defined(__i386__) || defined(__x86_64__)
> #include <stdlib.h>
> #include <stdio.h>
> #include <inttypes.h>
> -#include <asm/ldt.h>
> #include <unistd.h>
> #include <sys/syscall.h>
> #include <setjmp.h>
> @@ -132,6 +130,7 @@ perhaps unsurprisingly.)
> #include <sys/wait.h>
> #include <linux/perf_event.h>
>
> +#include "lapi/ldt.h"
> #include "lapi/syscalls.h"
> #include "tst_safe_pthread.h"
>
> @@ -199,7 +198,7 @@ static void set_ldt(void)
> .useable = 0
> };
>
> - TEST(tst_syscall(__NR_modify_ldt, 1, &data_desc, sizeof(data_desc)));
> + TEST(modify_ldt(1, &data_desc, sizeof(data_desc)));
This test can use SAFE_MODIF_LDT
>
> /*
> * The kernel intentionally casts modify_ldt() return value
> @@ -528,8 +527,6 @@ static struct tst_test test = {
> }
> };
>
> -#else /* defined(__x86_64__) || defined(__i386__) */
> -
> -TST_TEST_TCONF("not (i386 or x86_64)");
> -
> -#endif
> +#else
> +TST_TEST_TCONF("Test supported only on x86");
> +#endif /* defined(__i386__) || defined(__x86_64__) */
> diff --git a/testcases/cve/cve-2017-17053.c b/testcases/cve/cve-2017-17053.c
> index fe7b6d694d6ffbbce863abc1672e03ae5f419df1..1258548de8f6803f347aa6d19dcbaeacaffec30d 100644
> --- a/testcases/cve/cve-2017-17053.c
> +++ b/testcases/cve/cve-2017-17053.c
> @@ -16,8 +16,7 @@
> #include "config.h"
> #include "tst_test.h"
>
> -#ifdef HAVE_ASM_LDT_H
> -#include <asm/ldt.h>
> +#if defined(__i386__) || defined(__x86_64__)
> #include <pthread.h>
> #include <signal.h>
> #include <stdlib.h>
> @@ -26,6 +25,7 @@
> #include <unistd.h>
> #include <stdio.h>
>
> +#include "lapi/ldt.h"
> #include "lapi/syscalls.h"
>
> #define EXEC_USEC 5000000
> @@ -109,7 +109,7 @@ void run_test(void)
> struct user_desc desc = { .entry_number = 8191 };
>
> install_sighandler();
> - syscall(__NR_modify_ldt, 1, &desc, sizeof(desc));
> + modify_ldt(1, &desc, sizeof(desc));
This test can use SAFE_MODIF_LDT
>
> for (;;) {
> if (shm->do_exit)
> @@ -164,5 +164,5 @@ static struct tst_test test = {
> };
>
> #else
> -TST_TEST_TCONF("no asm/ldt.h header (only for i386 or x86_64)");
> -#endif
> +TST_TEST_TCONF("Test supported only on x86");
> +#endif /* defined(__i386__) || defined(__x86_64__) */
> diff --git a/testcases/kernel/syscalls/fork/fork05.c b/testcases/kernel/syscalls/fork/fork05.c
> index 22edefc3686978fbb9453dffabfcbccb7ea6bb12..1223aaff7d38152d5116b9011a34ff4c762cc987 100644
> --- a/testcases/kernel/syscalls/fork/fork05.c
> +++ b/testcases/kernel/syscalls/fork/fork05.c
> @@ -55,8 +55,8 @@
>
> #if defined(__i386__)
>
> +#include "lapi/ldt.h"
> #include "lapi/syscalls.h"
> -#include <asm/ldt.h>
>
> static void run(void)
> {
> @@ -76,7 +76,7 @@ static void run(void)
> ldt0.seg_not_present = 0;
> ldt0.useable = 1;
>
> - tst_syscall(__NR_modify_ldt, 1, &ldt0, sizeof(ldt0));
> + modify_ldt(1, &ldt0, sizeof(ldt0));
>
This test can use SAFE_MODIF_LDT
> asm volatile ("movw %w0, %%fs"::"q" (7));
> asm volatile ("movl %%fs:0, %0":"=r" (lo));
> diff --git a/testcases/kernel/syscalls/set_thread_area/set_thread_area.h b/testcases/kernel/syscalls/set_thread_area/set_thread_area.h
> deleted file mode 100644
> index 2bd2469d549ecf8c5c589a0a9485f886d043f7ed..0000000000000000000000000000000000000000
> --- a/testcases/kernel/syscalls/set_thread_area/set_thread_area.h
> +++ /dev/null
> @@ -1,31 +0,0 @@
> -#include <stdio.h>
> -#include <errno.h>
> -
> -/* Harness Specific Include Files. */
> -#include "test.h"
> -#include "lapi/syscalls.h"
> -#include "config.h"
> -
> -#if defined HAVE_ASM_LDT_H
> -#include <linux/unistd.h>
> -#include <asm/ldt.h>
> -
> -#if defined HAVE_STRUCT_USER_DESC
> -typedef struct user_desc thread_area_s;
> -#elif defined HAVE_STRUCT_MODIFY_LDT_LDT_S
> -typedef struct modify_ldt_ldt_s thread_area_s;
> -#else
> -typedef struct user_desc {
> - unsigned int entry_number;
> - unsigned long int base_addr;
> - unsigned int limit;
> - unsigned int seg_32bit:1;
> - unsigned int contents:2;
> - unsigned int read_exec_only:1;
> - unsigned int limit_in_pages:1;
> - unsigned int seg_not_present:1;
> - unsigned int useable:1;
> - unsigned int empty:25;
> -} thread_area_s;
> -#endif /* HAVE_STRUCT_USER_DESC */
> -#endif /* HAVE_ASM_LDT_H */
> diff --git a/testcases/kernel/syscalls/set_thread_area/set_thread_area01.c b/testcases/kernel/syscalls/set_thread_area/set_thread_area01.c
> index 30626d5e90ebf8e20624c370cc4474cb51a6b102..6c6fd522cb153acc3693718097a0c33a656ad747 100644
> --- a/testcases/kernel/syscalls/set_thread_area/set_thread_area01.c
> +++ b/testcases/kernel/syscalls/set_thread_area/set_thread_area01.c
> @@ -19,13 +19,16 @@
> *
> ************************************************************************/
>
> -#include "set_thread_area.h"
> +#include "config.h"
> +#include "test.h"
> +
> +#if defined(__i386__) || defined(__x86_64__)
> +#include "lapi/syscalls.h"
> +#include "lapi/ldt.h"
>
> char *TCID = "set_thread_area_01";
> int TST_TOTAL = 6;
>
> -#if defined(HAVE_ASM_LDT_H) && defined(HAVE_STRUCT_USER_DESC)
> -
> static void cleanup(void)
> {
> }
> @@ -38,7 +41,7 @@ static void setup(void)
> struct test {
> int syscall;
> const char *const syscall_name;
> - thread_area_s *u_info;
> + struct user_desc *u_info;
In general we don't both too much with old tests, unless there's a big
issue. I wouldn't to touch it at the moment, unless we want to refactor it.
> int exp_ret;
> int exp_errno;
> };
> @@ -105,7 +108,6 @@ int main(int argc, char *argv[])
> #else
> int main(void)
> {
> - tst_brkm(TCONF, NULL,
> - "set_thread_area isn't available for this architecture");
> + tst_brkm(TCONF, NULL, "Test supported only in x86");
> }
> #endif
Kind regards,
Andrea Cervesato
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