From: Ammar Faizi ammarfaizi2@gnuweeb.org

This commit adds the initial implementation of nolibc `sigaction()` function. Currently, this implementation is only available on the x86-64 arch.

`sigaction()` needs an architecture-dependent "signal trampoline" function that invokes the __rt_sigreturn syscall to resume the process after a signal gets handled.

On Linux x86-64, the "signal trampoline" function has to be written in inline Assembly to prevent the compiler from controlling the `%rsp` (e.g., with `-fno-omit-frame-pointer`, every function has a `pushq %rbp` that makes the `%rsp` no longer point to `struct rt_sigframe`).

The "signal trampoline" function is called `__arch_restore_rt` in this implementation.

Signed-off-by: Ammar Faizi ammarfaizi2@gnuweeb.org --- tools/include/nolibc/arch-x86_64.h | 12 +++++ tools/include/nolibc/sys.h | 80 ++++++++++++++++++++++++++++++ 2 files changed, 92 insertions(+)

diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch-x86_64.h index 0e1e9eb8545d..b6470943e836 100644 --- a/tools/include/nolibc/arch-x86_64.h +++ b/tools/include/nolibc/arch-x86_64.h @@ -212,4 +212,16 @@ __asm__ (".section .text\n" "hlt\n" // ensure it does not return "");

+void __arch_restore_rt(void); + +__asm__ ( +".section .text\n" +"__arch_restore_rt:\n\t" + "movl $0xf, %eax\n\t" // __NR_rt_sigreturn == 0xf + "syscall\n\t" // %rsp must point to a valid struct rt_sigframe. + "int3" +); + +#define __HAVE_ARCH_RESTORE_RT + #endif // _NOLIBC_ARCH_X86_64_H diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h index 3db1dd8c74ee..91532a2fbe2c 100644 --- a/tools/include/nolibc/sys.h +++ b/tools/include/nolibc/sys.h @@ -1026,6 +1026,86 @@ pid_t setsid(void) return ret; }

+typedef void (*sighandler_t)(int sig); + +/* + * int sigaction(int signum, const struct sigaction *act, struct sigaction *oldact); + */ + +static __attribute__((unused)) +int sys_sigaction(int signum, const struct sigaction *act, + struct sigaction *oldact) +{ + return my_syscall4(__NR_rt_sigaction, signum, act, oldact, + sizeof(sigset_t)); +} + +static __attribute__((unused)) +int sigaction(int signum, const struct sigaction *act, struct sigaction *oldact) +{ +#ifdef __HAVE_ARCH_RESTORE_RT + struct sigaction act2 = *act; + int ret; + + /* + * On Linux x86-64, libc's sigaction() always sets the + * @act->sa_restorer when the caller passes a NULL. + * + * @act->sa_restorer is an arch-specific function used + * as a "signal trampoline". + * + * @act->sa_handler is a signal handler provided by the + * user. + * + * When the handled signal is caught, the %rip jumps to + * @act->sa_handler with user stack already set by the + * kernel as below: + * + * |--------------------| + * %rsp -> | act->sa_restorer | (return address) + * |--------------------| + * | struct rt_sigframe | (process context info) + * | | + * | | + * .................... + * + * Once this signal handler executes the "ret" instruction, + * the %rip jumps to @act->sa_restorer. The sa_restorer + * function has to invoke the __rt_sigreturn syscall with + * %rsp pointing to the `struct rt_sigframe` that the kernel + * constructed previously to resume the process. + * + * The "signal trampoline" function has to be written in + * inline Assembly to prevent the compiler from controlling + * the %rsp (e.g., with -fno-omit-frame-pointer, every + * function has a `pushq %rbp` that makes the %rsp no longer + * point to `struct rt_sigframe`). + * + * `struct rt_sigframe` contains the registers' value before + * the signal is caught. + * + */ + if (!act2.sa_restorer) { + act2.sa_flags |= SA_RESTORER; + act2.sa_restorer = __arch_restore_rt; + } + + ret = sys_sigaction(signum, &act2, oldact); + if (ret < 0) { + SET_ERRNO(-ret); + ret = -1; + } + return ret; +#else + /* + * TODO: Implement sa_restorer ("signal trampoline") for + * other architectures. + */ + SET_ERRNO(ENOSYS); + return -1; +#endif +} +

/* * int stat(const char *path, struct stat *buf);

From: Ammar Faizi ammarfaizi2@gnuweeb.org

This commit adds getpagesize() function implementation.

The getpagesize() syscall doesn't always exist on the Linux syscall table. Only specific architectures have this syscall.

Implementation detail: Some architectures use a fixed page size, like x86. We can hard-code the page size value on such architectures.

Some other architectures may use different page sizes. For example, Linux aarch64 supports three values of page size: 4K, 16K, and 64K which are selected at kernel compilation time. The kernel stores the used page size in the auxiliary vector. The auxiliary vector can be obtained from /proc/self/auxv at AT_PAGESZ key-value-pair. /proc/self/auxv is available on all architectures.

Once we obtain the page size info, cache the value in a static variable to avoid traversing the auxiliary vector again in the next getpagesize() call. The page size should never change during kernel uptime.

Link: https://lwn.net/Articles/519085 Link: https://github.com/torvalds/linux/blob/v6.1/fs/binfmt_elf.c#L260 Signed-off-by: Ammar Faizi ammarfaizi2@gnuweeb.org --- tools/include/nolibc/sys.h | 114 +++++++++++++++++++++++++++++++++++++ 1 file changed, 114 insertions(+)

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h index ca348939eb50..e9e3640c36e1 100644 --- a/tools/include/nolibc/sys.h +++ b/tools/include/nolibc/sys.h @@ -18,6 +18,7 @@ #include <linux/fs.h> #include <linux/loop.h> #include <linux/time.h> +#include <linux/auxvec.h>

#include "arch.h" #include "errno.h" @@ -407,6 +408,119 @@ int getdents64(int fd, struct linux_dirent64 *dirp, int count) return ret; }

+/* + * The getpagesize() syscall doesn't always exist on the Linux syscall + * table. Only specific architectures have this syscall. + * + * Implementation detail: + * Some architectures use a fixed page size, like x86. We can hard-code + * the page size value on such architectures. + * + * Some other architectures may use different page sizes. For example, + * Linux aarch64 supports three values of page size: 4K, 16K, and 64K + * which are selected at kernel compilation time. The kernel stores the + * used page size in the auxiliary vector. The auxiliary vector can be + * obtained from /proc/self/auxv at AT_PAGESZ key-val-pair. + * /proc/self/auxv is available on all architectures. + * + * Once we obtain the page size info, cache the value in a static + * variable to avoid traversing the auxiliary vector again in the next + * getpagesize() call. The page size should never change during kernel + * uptime. + * + * Link: https://lwn.net/Articles/519085 + * Link: https://github.com/torvalds/linux/blob/v6.1/fs/binfmt_elf.c#L260 + * + * + * long getpagesize(void); + * + */ + +#if defined(__x86_64__) || defined(__i386__) || defined(__i486__) || defined(__i586__) || defined(__i686__) +__attribute__((unused)) +static inline long getpagesize(void) +{ + /* + * x86 family is always 4K page. Don't bother + * reading the auxiliary vector. + */ + return 4096; +} +#else +static int sys_open(const char *path, int flags, mode_t mode); +static ssize_t sys_read(int fd, void *buf, size_t count); + +/* + * This function works for all architectures. + */ +static long sys_getpagesize(void) +{ + uint64_t buf[2] = {0, 0}; + long ret; + int fd; + + + fd = sys_open("/proc/self/auxv", O_RDONLY, 0); + if (fd < 0) + return fd; + + while (1) { + ssize_t x; + + x = sys_read(fd, buf, sizeof(buf)); + if (x < 0) { + ret = x; + break; + } + + if (__builtin_expect(x == 0, 0)) { + /* + * We've reached the end of the auxiliary + * vector, but can't find the AT_PAGESZ + * entry. + */ + ret = -ENOENT; + break; + } + + /* + * buf[0] is the key. + * buf[1] is the value. + */ + if (buf[0] == AT_PAGESZ) { + ret = buf[1]; + break; + } + } + + sys_close(fd); + return ret; +} + +__attribute__((unused)) +static long getpagesize(void) +{ + static long cached; + long ret; + + /* + * No need to read the auxv for the second + * getpagesize() call. + */ + if (__builtin_expect(cached != 0, 1)) + return cached; + + ret = sys_getpagesize(); + if (ret < 0) { + SET_ERRNO(-ret); + ret = -1; + } else { + cached = ret; + } + return ret; +} +#endif +

/* * pid_t getpgid(pid_t pid);

From: Ammar Faizi ammarfaizi2@gnuweeb.org

Ensure the fork() function can create a child process. Also, when the child exits, the parent must be able to get the child's exit code via waitpid().

Signed-off-by: Ammar Faizi ammarfaizi2@gnuweeb.org --- tools/testing/selftests/nolibc/nolibc-test.c | 45 ++++++++++++++++++++ 1 file changed, 45 insertions(+)

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c index 8d69f8a0f35a..309cabbddeec 100644 --- a/tools/testing/selftests/nolibc/nolibc-test.c +++ b/tools/testing/selftests/nolibc/nolibc-test.c @@ -442,6 +442,50 @@ int test_getdents64(const char *dir) return ret; }

+/* + * Test fork(). + * Make sure the exit code can be read from the parent process. + */ +static int test_fork_and_exit(int expected_code) +{ + int status; + int code; + pid_t ret; + pid_t p; + + p = fork(); + if (p < 0) + return p; + + if (!p) + exit(expected_code); + + do { + ret = waitpid(p, &status, 0); + if (ret < 0) + return ret; + } while (!WIFEXITED(status)); + + code = WEXITSTATUS(status); + if (code != expected_code) { + printf("test_fork_and_exit(): waitpid(): Invalid exit code: %d; expected = %d\n", code, expected_code); + return -1; + } + + return 0; +} + +static int test_fork(void) +{ + int i; + + for (i = 0; i < 255; i++) { + if (test_fork_and_exit(i)) + return -1; + } + return 0; +} + /* Run syscall tests between IDs <min> and <max>. * Return 0 on success, non-zero on failure. */ @@ -494,6 +538,7 @@ int run_syscall(int min, int max) CASE_TEST(dup3_0); tmp = dup3(0, 100, 0); EXPECT_SYSNE(1, tmp, -1); close(tmp); break; CASE_TEST(dup3_m1); tmp = dup3(-1, 100, 0); EXPECT_SYSER(1, tmp, -1, EBADF); if (tmp != -1) close(tmp); break; CASE_TEST(execve_root); EXPECT_SYSER(1, execve("/", (char*[]){ [0] = "/", [1] = NULL }, NULL), -1, EACCES); break; + CASE_TEST(fork); EXPECT_SYSZR(1, test_fork()); break; CASE_TEST(getdents64_root); EXPECT_SYSNE(1, test_getdents64("/"), -1); break; CASE_TEST(getdents64_null); EXPECT_SYSER(1, test_getdents64("/dev/null"), -1, ENOTDIR); break; CASE_TEST(gettimeofday_null); EXPECT_SYSZR(1, gettimeofday(NULL, NULL)); break;

From: Ammar Faizi ammarfaizi2@gnuweeb.org

Just like the sigaction() selftest, but for signal().

Signed-off-by: Ammar Faizi ammarfaizi2@gnuweeb.org --- tools/testing/selftests/nolibc/nolibc-test.c | 84 +++++++++++++++++--- 1 file changed, 72 insertions(+), 12 deletions(-)

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c index 562766e0f63c..a65cc6b83779 100644 --- a/tools/testing/selftests/nolibc/nolibc-test.c +++ b/tools/testing/selftests/nolibc/nolibc-test.c @@ -488,7 +488,7 @@ static int test_fork(void)

static volatile int g_test_sig;

-static void test_sigaction_signal_handler(int sig) +static void test_signal_handler(int sig) { g_test_sig = sig; } @@ -496,7 +496,7 @@ static void test_sigaction_signal_handler(int sig) static int test_sigaction_sig(int sig) { const struct sigaction new = { - .sa_handler = test_sigaction_signal_handler + .sa_handler = test_signal_handler }; struct sigaction old; int ret; @@ -517,7 +517,7 @@ static int test_sigaction_sig(int sig) kill(getpid(), sig);

/* - * test_sigaction_signal_handler() must set @g_test_sig to @sig. + * test_signal_handler() must set @g_test_sig to @sig. */ if (g_test_sig != sig) { printf("test_sigaction_sig(%d): Invalid g_test_sig value (%d != %d)\n", sig, g_test_sig, sig); @@ -536,20 +536,74 @@ static int test_sigaction_sig(int sig) return 0; }

+static int test_signal_sig(int sig) +{ + sighandler_t old; + + /* + * Set the signal handler. + */ + old = signal(sig, test_signal_handler); + if (old == SIG_ERR) { + printf("test_signal_sig(%d): Failed to set a signal handler\n", sig); + return -1; + } + + /* + * Test the signal handler. + */ + g_test_sig = 0; + kill(getpid(), sig); + + /* + * test_signal_handler() must set @g_test_sig to @sig. + */ + if (g_test_sig != sig) { + printf("test_signal_sig(%d): Invalid g_test_sig value (%d != %d)\n", sig, g_test_sig, sig); + return -1; + } + + /* + * Restore the original signal handler. + */ + old = signal(sig, old); + if (old == SIG_ERR) { + printf("test_signal_sig(%d): Failed to restore the signal handler\n", sig); + return -1; + } + + return 0; +} + +static const int g_sig_to_test[] = { + SIGINT, + SIGHUP, + SIGTERM, + SIGQUIT, + SIGSEGV +}; + static int test_sigaction(void) { - static const int sig_to_test[] = { - SIGINT, - SIGHUP, - SIGTERM, - SIGQUIT, - SIGSEGV - }; size_t i; int ret;

- for (i = 0; i < (sizeof(sig_to_test) / sizeof(sig_to_test[0])); i++) { - ret = test_sigaction_sig(sig_to_test[i]); + for (i = 0; i < (sizeof(g_sig_to_test) / sizeof(g_sig_to_test[0])); i++) { + ret = test_sigaction_sig(g_sig_to_test[i]); + if (ret) + return ret; + } + + return 0; +} + +static int test_signal(void) +{ + size_t i; + int ret; + + for (i = 0; i < (sizeof(g_sig_to_test) / sizeof(g_sig_to_test[0])); i++) { + ret = test_signal_sig(g_sig_to_test[i]); if (ret) return ret; } @@ -566,6 +620,11 @@ static int should_test_sigaction(void) #endif }

+static int should_test_signal(void) +{ + return should_test_sigaction(); +} + /* Run syscall tests between IDs <min> and <max>. * Return 0 on success, non-zero on failure. */ @@ -647,6 +706,7 @@ int run_syscall(int min, int max) CASE_TEST(select_stdout); EXPECT_SYSNE(1, ({ fd_set fds; FD_ZERO(&fds); FD_SET(1, &fds); select(2, NULL, &fds, NULL, NULL); }), -1); break; CASE_TEST(select_fault); EXPECT_SYSER(1, select(1, (void *)1, NULL, NULL, 0), -1, EFAULT); break; CASE_TEST(sigaction); EXPECT_SYSZR(should_test_sigaction(), test_sigaction()); break; + CASE_TEST(signal); EXPECT_SYSZR(should_test_signal(), test_signal()); break; CASE_TEST(stat_blah); EXPECT_SYSER(1, stat("/proc/self/blah", &stat_buf), -1, ENOENT); break; CASE_TEST(stat_fault); EXPECT_SYSER(1, stat(NULL, &stat_buf), -1, EFAULT); break; CASE_TEST(symlink_root); EXPECT_SYSER(1, symlink("/", "/"), -1, EEXIST); break;

Hi Ammar,

On Thu, Dec 22, 2022 at 08:46:15PM +0700, Ammar Faizi wrote:

I agree with following the @envp pointer to get the auxv. I was trying to wire up a new function '__start' (with double underscores) written in C that accepts @argc, @argv and @envp. Then it calls 'main'. Then we call '__start' instead of 'main' from '_start'. This way, we can arrange nolibc-defined data without touching Assembly much in '__start' (before main).

But then I noticed that it wouldn't work because we may have users who define the 'main' function differently, e.g.:

int main(void);
int main(int argc, char **argv);
int main(int argc, char **argv, char **envp);

So '__start' can't call main. We still need to call the main from the inline Assembly (from '_start').

Yes, and quite frankly I prefer to make that the least complicated. Doing just a simple loop in the _start code is trivial. The main concern was to store the data. Till now we had an optional .bss section, we didn't save environ and errno was optional. But let's be honest, while it does allow for writing the smallest programs, most programs will have at least one global variable and will get this section anyway, so we don't save anything in practice. This concern used to be valid when I was making tiny executables when running on floppies where each byte mattered, but now that's pointless.

Thus what I'm proposing is to switch to weak symbol definitions for errno, environ, and auxv. I did a quick test to make sure that the same symbol was properly used when accessed from two units and that's OK, I'm seeing the same instance for all of them (which is better than the current situation where errno is static, hence per-unit).

My quick-and-dirty test looks like this:

diff --git a/arch-x86_64.h b/arch-x86_64.h index e780fdf..73f7b5f 100644 --- a/arch-x86_64.h +++ b/arch-x86_64.h @@ -209,6 +209,9 @@ struct sys_stat_struct { _ret; \ })

+char **environ __attribute__((weak,unused)); +long *auxv __attribute__((weak,unused)); + /* startup code */ /* * x86-64 System V ABI mandates: @@ -218,11 +221,17 @@ struct sys_stat_struct { */ asm(".section .text\n" ".weak _start\n" "_start:\n" "pop %rdi\n" // argc (first arg, %rdi) "mov %rsp, %rsi\n" // argv[] (second arg, %rsi) "lea 8(%rsi,%rdi,8),%rdx\n" // then a NULL then envp (third arg, %rdx) + "mov %rdx, environ\n" // save environ "xor %ebp, %ebp\n" // zero the stack frame + "mov %rdx, %rax\n" // search for auxv (follows NULL after last en> + "0: add $8, %rax\n" + " cmp -8(%rax), %rbp\n" + " jnz 0b\n" + "mov %rax, auxv\n" // save auxv "and $-16, %rsp\n" // x86 ABI : esp must be 16-byte aligned befor> "call main\n" // main() returns the status code, we'll exit > "mov %eax, %edi\n" // retrieve exit code (32 bit)

diff --git a/errno.h b/errno.h index df0e473..9781077 100644 --- a/errno.h +++ b/errno.h @@ -29,7 +29,8 @@ #include <asm/errno.h>

/* this way it will be removed if unused */ -static int errno; +//static int errno; +int errno __attribute__((weak));

#ifndef NOLIBC_IGNORE_ERRNO #define SET_ERRNO(v) do { errno = (v); } while (0)

$ cat a.c #include "nolibc.h"

extern void b(void);

int main(int argc, char **argv, char **envp) { //environ = envp; errno = 1234; printf("main(): errno=%d env(TERM)=%s auxv=%p auxv[0].t=0x%lx auxv[0].v=0x%lx\n", errno, getenv("TERM"), auxv, auxv?auxv[0]:0, auxv?auxv[1]:0); b(); return 0; }

$ cat b.c #include "nolibc.h"

void b(void) { long *v = auxv;

printf("b(): errno=%d env(TERM)=%s auxv=%p auxv[0].t=0x%lx auxv[0].v=0x%lx\n", errno, getenv("TERM"), auxv, auxv?auxv[0]:0, auxv?auxv[1]:0);

printf("auxv:\n"); while (v && v[0]) { printf(" 0x%lx: 0x%lx\n", v[0], v[1]); v += 2; } }

$ gcc -Os -fno-asynchronous-unwind-tables -include /g/public/nolibc/nolibc.h -Wall -nostdlib -static -o ab a.c b.c

$ nm --size ab 0000000000000004 V errno 0000000000000008 V auxv 0000000000000008 V environ 0000000000000014 W memset 0000000000000018 W memcpy 0000000000000018 W raise 000000000000001b W abort 0000000000000030 W memmove 0000000000000053 t u64toa_r 0000000000000053 t u64toa_r 0000000000000082 T main 00000000000000a4 T b 0000000000000289 t printf 000000000000028c t printf.constprop.0

$ ./ab main(): errno=1234 env(TERM)=xterm auxv=0x7ffdd0c31df8 auxv[0].t=0x21 auxv[0].v=0x7ffdd0d56000 b(): errno=1234 env(TERM)=xterm auxv=0x7ffdd0c31df8 auxv[0].t=0x21 auxv[0].v=0x7ffdd0d56000 auxv: 0x21: 0x7ffdd0d56000 0x10: 0xbfebfbff 0x6: 0x1000 0x11: 0x64 0x3: 0x400040 0x4: 0x38 0x5: 0x7 0x7: 0x0 0x8: 0x0 0x9: 0x401082 0xb: 0x1fd 0xc: 0x1fd 0xd: 0x64 0xe: 0x64 0x17: 0x0 0x19: 0x7ffdd0c31f39 0x1a: 0x2 0x1f: 0x7ffdd0c33ff3 0xf: 0x7ffdd0c31f49

Note that I could verify that some of the entries above are valid (e.g. "x86_64" in 0xf = AT_PLATFORM).

Thus now my focus will be on storing these variables where relevant for all archs, so that your getauxval() implementation works on top of it. It will be much cleaner and will also improve programs' ease of implementation and reliability.

Cheers, Willy

PS: maybe we should trim the Cc list for future exchanges.

From: Ammar Faizi ammarfaizi2@gnuweeb.org

This function returns the page size used by the running kernel. The page size value is taken from the auxiliary vector at 'AT_PAGESZ' key.

'getpagesize(2)' is assumed as a syscall becuase the manpage placement of this function is in entry 2 ('man 2 getpagesize') despite there is no real 'getpagesize(2)' syscall in the Linux syscall table. Define this function in 'sys.h'.

Signed-off-by: Ammar Faizi ammarfaizi2@gnuweeb.org ---

Side note: This function calls 'getauxval(3)' function that's defined in 'stdlib.h', but since most functions in 'stdlib.h' needs 'sys.h', the 'sys.h' is always included first. Therefore, we need a forward declaration of 'getauxval(3)' in sys.h.

tools/include/nolibc/sys.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h index 3db1dd8c74ee..acf7cf438010 100644 --- a/tools/include/nolibc/sys.h +++ b/tools/include/nolibc/sys.h @@ -18,6 +18,7 @@ #include <linux/fs.h> #include <linux/loop.h> #include <linux/time.h> +#include <linux/auxvec.h>

#include "arch.h" #include "errno.h" @@ -498,6 +499,26 @@ pid_t gettid(void) return sys_gettid(); }

+static unsigned long getauxval(unsigned long key); + +/* + * long getpagesize(void); + */ + +static __attribute__((unused)) +long getpagesize(void) +{ + long ret; + + ret = getauxval(AT_PAGESZ); + if (!ret) { + SET_ERRNO(ENOENT); + return -1; + } + + return ret; +} +

/* * int gettimeofday(struct timeval *tv, struct timezone *tz);

From: Ammar Faizi ammarfaizi2@gnuweeb.org

signal() function is the simpler version of sigaction(). Unlike sigaction(), which fully controls the `struct sigaction`, the caller only cares about the sa_handler when calling the signal() function. signal() internally calls sigaction().

Signed-off-by: Ammar Faizi ammarfaizi2@gnuweeb.org --- tools/include/nolibc/sys.h | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h index 7d594155e77f..54e51f154b1f 100644 --- a/tools/include/nolibc/sys.h +++ b/tools/include/nolibc/sys.h @@ -1119,6 +1119,31 @@ int sigaction(int signum, const struct sigaction *act, struct sigaction *oldact) return ret; }

+/* + * sighandler_t signal(int signum, sighandler_t handler); + */ + +static __attribute__((unused)) +sighandler_t signal(int signum, sighandler_t handler) +{ + const struct sigaction act = { + .sa_handler = handler, + .sa_flags = SA_RESTORER, + .sa_restorer = __restore_rt + }; + sighandler_t old_sah; + struct sigaction old; + int ret; + + ret = sys_sigaction(signum, &act, &old); + if (ret < 0) { + SET_ERRNO(-ret); + old_sah = SIG_ERR; + } else { + old_sah = old.sa_handler; + } + return old_sah; +}

/* * int stat(const char *path, struct stat *buf);

From: Ammar Faizi ammarfaizi2@gnuweeb.org

Test the sigaction() function implementation. Test steps:

- Set a signal handler. - Then send a signal to itself using the kill() syscall. - The program has to survive and store the caught signal number in a volatile global variable. - Validate the volatile global variable value. - Restore the original signal handler.

Signed-off-by: Ammar Faizi ammarfaizi2@gnuweeb.org --- tools/testing/selftests/nolibc/nolibc-test.c | 127 +++++++++++++++++++ 1 file changed, 127 insertions(+)

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c index cb6ec9f71aae..946ed0132f93 100644 --- a/tools/testing/selftests/nolibc/nolibc-test.c +++ b/tools/testing/selftests/nolibc/nolibc-test.c @@ -515,6 +515,131 @@ static int test_fork(void) return 0; }

+static volatile int g_test_sig; + +static void test_signal_handler(int sig) +{ + g_test_sig = sig; +} + +static int test_sigaction_sig(int sig) +{ + const struct sigaction new = { + .sa_handler = test_signal_handler + }; + struct sigaction old; + int ret; + + /* + * Set the signal handler. + */ + ret = sigaction(sig, &new, &old); + if (ret) { + printf("test_sigaction_sig(%d): Failed to set a signal handler\n", sig); + return ret; + } + + /* + * Test the signal handler. + */ + g_test_sig = 0; + kill(getpid(), sig); + + /* + * test_signal_handler() must set @g_test_sig to @sig. + */ + if (g_test_sig != sig) { + printf("test_sigaction_sig(%d): Invalid g_test_sig value (%d != %d)\n", sig, g_test_sig, sig); + return -1; + } + + /* + * Restore the original signal handler. + */ + ret = sigaction(sig, &old, NULL); + if (ret) { + printf("test_sigaction_sig(%d): Failed to restore the signal handler\n", sig); + return ret; + } + + return 0; +} + +static int test_signal_sig(int sig) +{ + sighandler_t old; + + /* + * Set the signal handler. + */ + old = signal(sig, test_signal_handler); + if (old == SIG_ERR) { + printf("test_signal_sig(%d): Failed to set a signal handler\n", sig); + return -1; + } + + /* + * Test the signal handler. + */ + g_test_sig = 0; + kill(getpid(), sig); + + /* + * test_signal_handler() must set @g_test_sig to @sig. + */ + if (g_test_sig != sig) { + printf("test_signal_sig(%d): Invalid g_test_sig value (%d != %d)\n", sig, g_test_sig, sig); + return -1; + } + + /* + * Restore the original signal handler. + */ + old = signal(sig, old); + if (old == SIG_ERR) { + printf("test_signal_sig(%d): Failed to restore the signal handler\n", sig); + return -1; + } + + return 0; +} + +static const int g_sig_to_test[] = { + SIGINT, + SIGHUP, + SIGTERM, + SIGQUIT, + SIGSEGV +}; + +static int test_sigaction(void) +{ + size_t i; + int ret; + + for (i = 0; i < (sizeof(g_sig_to_test) / sizeof(g_sig_to_test[0])); i++) { + ret = test_sigaction_sig(g_sig_to_test[i]); + if (ret) + return ret; + } + + return 0; +} + +static int test_signal(void) +{ + size_t i; + int ret; + + for (i = 0; i < (sizeof(g_sig_to_test) / sizeof(g_sig_to_test[0])); i++) { + ret = test_signal_sig(g_sig_to_test[i]); + if (ret) + return ret; + } + + return 0; +} + /* Run syscall tests between IDs <min> and <max>. * Return 0 on success, non-zero on failure. */ @@ -596,6 +721,8 @@ int run_syscall(int min, int max) CASE_TEST(select_null); EXPECT_SYSZR(1, ({ struct timeval tv = { 0 }; select(0, NULL, NULL, NULL, &tv); })); break; CASE_TEST(select_stdout); EXPECT_SYSNE(1, ({ fd_set fds; FD_ZERO(&fds); FD_SET(1, &fds); select(2, NULL, &fds, NULL, NULL); }), -1); break; CASE_TEST(select_fault); EXPECT_SYSER(1, select(1, (void *)1, NULL, NULL, 0), -1, EFAULT); break; + CASE_TEST(sigaction); EXPECT_SYSZR(1, test_sigaction()); break; + CASE_TEST(signal); EXPECT_SYSZR(1, test_signal()); break; CASE_TEST(stat_blah); EXPECT_SYSER(1, stat("/proc/self/blah", &stat_buf), -1, ENOENT); break; CASE_TEST(stat_fault); EXPECT_SYSER(1, stat(NULL, &stat_buf), -1, EFAULT); break; CASE_TEST(symlink_root); EXPECT_SYSER(1, symlink("/", "/"), -1, EEXIST); break;