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From:   Ammar Faizi <ammarfaizi2@gnuweeb.org>
To:     Willy Tarreau <w@1wt.eu>
Cc:     Ammar Faizi <ammarfaizi2@gnuweeb.org>,
        Shuah Khan <shuah@kernel.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Sven Schnelle <svens@linux.ibm.com>,
        Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>,
        GNU/Weeb Mailing List <gwml@vger.gnuweeb.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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        <linux-kselftest@vger.kernel.org>
Subject: [PATCH v1 2/3] nolibc/sys: Implement `getpagesize(2)` function
Date:   Sun,  8 Jan 2023 20:08:51 +0700
Message-Id: <20230108130853.840948-3-ammar.faizi@intel.com>
In-Reply-To: <20230108130853.840948-1-ammar.faizi@intel.com>
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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);
-- 
Ammar Faizi