selftests/x86: Fix error: variably modified 'altstack_data' at file scope

A glibc 2.34 feature adds support for variable MINSIGSTKSZ and SIGSTKSZ.
When _DYNAMIC_STACK_SIZE_SOURCE or _GNU_SOURCE are defined, MINSIGSTKSZ
and SIGSTKSZ are no longer constant on Linux. glibc 2.34 flags code paths
assuming MINSIGSTKSZ or SIGSTKSZ are constant. Fix these error in x86 test.

Feature description and build error:

NEWS for version 2.34
=====================
Major new features:
 * Add _SC_MINSIGSTKSZ and _SC_SIGSTKSZ.  When _DYNAMIC_STACK_SIZE_SOURCE
   or _GNU_SOURCE are defined, MINSIGSTKSZ and SIGSTKSZ are no longer
   constant on Linux.  MINSIGSTKSZ is redefined to sysconf(_SC_MINSIGSTKSZ)
   and SIGSTKSZ is redefined to sysconf (_SC_SIGSTKSZ).  This supports
   dynamic sized register sets for modern architectural features like
   Arm SVE.
=====================

If _SC_SIGSTKSZ_SOURCE or _GNU_SOURCE are defined, MINSIGSTKSZ and SIGSTKSZ
are redefined as:

/* Default stack size for a signal handler: sysconf (SC_SIGSTKSZ).  */
 # undef SIGSTKSZ
 # define SIGSTKSZ sysconf (_SC_SIGSTKSZ)

/* Minimum stack size for a signal handler: SIGSTKSZ.  */
 # undef MINSIGSTKSZ
 # define MINSIGSTKSZ SIGSTKSZ

Compilation will fail if the source assumes constant MINSIGSTKSZ or
SIGSTKSZ.

Build error with the GNU C Library 2.34:
DEBUG:	| sigreturn.c:150:13: error: variably modified 'altstack_data' at file scope
| sigreturn.c:150:13: error: variably modified 'altstack_data' at file scope
DEBUG:	|   150 | static char altstack_data[SIGSTKSZ];
|   150 | static char altstack_data[SIGSTKSZ];
DEBUG:	|       |             ^~~~~~~~~~~~~

DEBUG:  | single_step_syscall.c:60:22: error: variably modified 'altstack_data' at file scope
DEBUG:  |   60 | static unsigned char altstack_data[SIGSTKSZ];
DEBUG:  |      |                      ^~~~~~~~~~~~~

Fixed commit log to improve formatting and clarity:
Shuah Khan <skhan@linuxfoundation.org>

Link: https://sourceware.org/pipermail/libc-alpha/2021-January/121996.html
Link: https://sourceware.org/pipermail/libc-alpha/2021-August/129718.html
Suggested-by: Jianwei Hu <jianwei.hu@windriver.com>
Signed-off-by: Jun Miao <jun.miao@windriver.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

diff --git a/tools/testing/selftests/x86/mov_ss_trap.c b/tools/testing/selftests/x86/mov_ss_trap.c
index 6da0ac3f0135811321c163cf55cf6b3b5aea027b..cc3de6ff9fba1814d068ee2abc57c86efd8a110d 100644 (file)
--- a/tools/testing/selftests/x86/mov_ss_trap.c
+++ b/tools/testing/selftests/x86/mov_ss_trap.c
@@ -47,7 +47,6 @@
 unsigned short ss;
 extern unsigned char breakpoint_insn[];
 sigjmp_buf jmpbuf;
-static unsigned char altstack_data[SIGSTKSZ];
 
 static void enable_watchpoint(void)
 {
@@ -250,13 +249,14 @@ int main()
        if (sigsetjmp(jmpbuf, 1) == 0) {
                printf("[RUN]\tMOV SS; SYSENTER\n");
                stack_t stack = {
-                       .ss_sp = altstack_data,
+                       .ss_sp = malloc(sizeof(char) * SIGSTKSZ),
                        .ss_size = SIGSTKSZ,
                };
                if (sigaltstack(&stack, NULL) != 0)
                        err(1, "sigaltstack");
                sethandler(SIGSEGV, handle_and_longjmp, SA_RESETHAND | SA_ONSTACK);
                nr = SYS_getpid;
+               free(stack.ss_sp);
                /* Clear EBP first to make sure we segfault cleanly. */
                asm volatile ("xorl %%ebp, %%ebp; mov %[ss], %%ss; SYSENTER" : "+a" (nr)
                              : [ss] "m" (ss) : "flags", "rcx"

diff --git a/tools/testing/selftests/x86/sigreturn.c b/tools/testing/selftests/x86/sigreturn.c
index 57c4f67f16ef2930b85ad6d4701756085bb7b312..5d7961a5f7f6ef05abd81c8d341f9caefcf0311b 100644 (file)
--- a/tools/testing/selftests/x86/sigreturn.c
+++ b/tools/testing/selftests/x86/sigreturn.c
@@ -138,9 +138,6 @@ static unsigned short LDT3(int idx)
        return (idx << 3) | 7;
 }
 
-/* Our sigaltstack scratch space. */
-static char altstack_data[SIGSTKSZ];
-
 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
                       int flags)
 {
@@ -771,7 +768,8 @@ int main()
        setup_ldt();
 
        stack_t stack = {
-               .ss_sp = altstack_data,
+               /* Our sigaltstack scratch space. */
+               .ss_sp = malloc(sizeof(char) * SIGSTKSZ),
                .ss_size = SIGSTKSZ,
        };
        if (sigaltstack(&stack, NULL) != 0)
@@ -872,5 +870,6 @@ int main()
        total_nerrs += test_nonstrict_ss();
 #endif
 
+       free(stack.ss_sp);
        return total_nerrs ? 1 : 0;
 }

diff --git a/tools/testing/selftests/x86/single_step_syscall.c b/tools/testing/selftests/x86/single_step_syscall.c
index 120ac741fe4405a9fe049672c52d88be6c79f7c6..9a30f443e92862631040c321dda42b0de87c0988 100644 (file)
--- a/tools/testing/selftests/x86/single_step_syscall.c
+++ b/tools/testing/selftests/x86/single_step_syscall.c
@@ -57,7 +57,6 @@ static void clearhandler(int sig)
 
 static volatile sig_atomic_t sig_traps, sig_eflags;
 sigjmp_buf jmpbuf;
-static unsigned char altstack_data[SIGSTKSZ];
 
 #ifdef __x86_64__
 # define REG_IP REG_RIP
@@ -210,7 +209,7 @@ int main()
                unsigned long nr = SYS_getpid;
                printf("[RUN]\tSet TF and check SYSENTER\n");
                stack_t stack = {
-                       .ss_sp = altstack_data,
+                       .ss_sp = malloc(sizeof(char) * SIGSTKSZ),
                        .ss_size = SIGSTKSZ,
                };
                if (sigaltstack(&stack, NULL) != 0)
@@ -219,6 +218,7 @@ int main()
                           SA_RESETHAND | SA_ONSTACK);
                sethandler(SIGILL, print_and_longjmp, SA_RESETHAND);
                set_eflags(get_eflags() | X86_EFLAGS_TF);
+               free(stack.ss_sp);
                /* Clear EBP first to make sure we segfault cleanly. */
                asm volatile ("xorl %%ebp, %%ebp; SYSENTER" : "+a" (nr) :: "flags", "rcx"
 #ifdef __x86_64__

diff --git a/tools/testing/selftests/x86/syscall_arg_fault.c b/tools/testing/selftests/x86/syscall_arg_fault.c
index bff474b5efc6e884d6fba87ba3e4ef1230e85a84..461fa41a4d02aad8c579d9f1287bec16fc155475 100644 (file)
--- a/tools/testing/selftests/x86/syscall_arg_fault.c
+++ b/tools/testing/selftests/x86/syscall_arg_fault.c
@@ -17,9 +17,6 @@
 
 #include "helpers.h"
 
-/* Our sigaltstack scratch space. */
-static unsigned char altstack_data[SIGSTKSZ];
-
 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
                       int flags)
 {
@@ -104,7 +101,8 @@ static void sigill(int sig, siginfo_t *info, void *ctx_void)
 int main()
 {
        stack_t stack = {
-               .ss_sp = altstack_data,
+               /* Our sigaltstack scratch space. */
+               .ss_sp = malloc(sizeof(char) * SIGSTKSZ),
                .ss_size = SIGSTKSZ,
        };
        if (sigaltstack(&stack, NULL) != 0)
@@ -233,5 +231,6 @@ int main()
        set_eflags(get_eflags() & ~X86_EFLAGS_TF);
 #endif
 
+       free(stack.ss_sp);
        return 0;
 }