From ab1d521db39bf4371c7db96e8a0fcd4857ee70ed Mon Sep 17 00:00:00 2001
From: Roland McGrath <roland@gnu.org>
Date: Thu, 7 Apr 2005 20:57:41 +0000
Subject: * sysdeps/unix/sysv/linux/dl-osinfo.h (_dl_discover_osversion)

	[(NEED_DL_SYSINFO || NEED_DL_SYSINFO_DSO) && SHARED]: Scan
	GLRO(dl_sysinfo_map) for PT_NOTE giving Linux kernel version,
	we can skip the uname call if it's there.
	* sysdeps/generic/dl-sysdep.c (_dl_sysdep_start): Don't use
	DL_SYSDEP_OSCHECK here.
	* elf/rtld.c (dl_main) [DL_SYSDEP_OSCHECK]: Do it here instead.

	* sysdeps/generic/ldsodefs.h (struct rtld_global_ro):
	Add _dl_sysinfo_map.
	* elf/rtld.c (dl_main): Don't call _dl_init_paths early in the
	rtld_is_main case.  Call it unconditionally later.
	Move GLRO(dl_sysinfo_dso) handling earlier, before _dl_init_paths call.
	Initialize GLRO(dl_sysinfo_map).
	* elf/dl-load.c (open_path): Bail out if _dl_init_paths wasn't called.
	* sysdeps/generic/dl-sysdep.c (_DL_FIRST_EXTRA): New macro.
	(_dl_important_hwcaps)
	[(NEED_DL_SYSINFO || NEED_DL_SYSINFO_DSO) && SHARED]: Scan
	GLRO(dl_sysinfo_map) for PT_NOTE giving synthetic hwcap names
	and bit values.
	* elf/ldconfig.c (_DL_FIRST_EXTRA): New macro.
	(hwcap_extra): New static variable.
	(is_hwcap_platform): Check hwcap_extra for a matching name.
	Remove tls special case.
	(path_hwcap): Likewise.
	(parse_conf): Parse "hwcap" directive to define synthetic hwcap bits
	and their names, stored in hwcap_extra.
	(main) [USE_TLS]: Initialize final synthetic hwcap bit as "tls".

	* sysdeps/generic/ldsodefs.h (struct rtld_global_ro): Use uint64_t for
	_dl_hwcap and _dl_hwcap_mask.
	* sysdeps/generic/dl-sysdep.c (_dl_sysdep_start): Cast a_val for
	AT_HWCAP to unsigned long int.
	* elf/dl-support.c (_dl_aux_init): Likewise.
	(_dl_hwcap): Update defn.

	* elf/cache.c (print_entry): Pad hwcap value with 0s in diagnostic.
	* elf/ldconfig.c (search_dir): Likewise.
---
 sysdeps/unix/sysv/linux/dl-osinfo.h | 39 +++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

(limited to 'sysdeps/unix/sysv/linux/dl-osinfo.h')

diff --git a/sysdeps/unix/sysv/linux/dl-osinfo.h b/sysdeps/unix/sysv/linux/dl-osinfo.h
index dfb4cde72d..befa804cb1 100644
--- a/sysdeps/unix/sysv/linux/dl-osinfo.h
+++ b/sysdeps/unix/sysv/linux/dl-osinfo.h
@@ -43,6 +43,45 @@ dl_fatal (const char *str)
 static inline int __attribute__ ((always_inline))
 _dl_discover_osversion (void)
 {
+#if (defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO) && defined SHARED
+  if (GLRO(dl_sysinfo_map) != NULL)
+    {
+      /* If the kernel-supplied DSO contains a note indicating the kernel's
+	 version, we don't need to call uname or parse any strings.  */
+
+      static const struct
+      {
+	ElfW(Word) vendorlen;
+	ElfW(Word) datalen;
+	ElfW(Word) type;
+	char vendor[8];
+      } expected_note = { sizeof "Linux", sizeof (ElfW(Word)), 0, "Linux" };
+      const ElfW(Phdr) *const phdr = GLRO(dl_sysinfo_map)->l_phdr;
+      const ElfW(Word) phnum = GLRO(dl_sysinfo_map)->l_phnum;
+      for (uint_fast16_t i = 0; i < phnum; ++i)
+	if (phdr[i].p_type == PT_NOTE)
+	  {
+	    const ElfW(Addr) start = (phdr[i].p_vaddr
+				      + GLRO(dl_sysinfo_map)->l_addr);
+	    const struct
+	    {
+	      ElfW(Word) vendorlen;
+	      ElfW(Word) datalen;
+	      ElfW(Word) type;
+	    } *note = (const void *) start;
+	    while ((ElfW(Addr)) (note + 1) - start < phdr[i].p_memsz)
+	      {
+		if (!memcmp (note, &expected_note, sizeof expected_note))
+		  return *(const ElfW(Word) *) ((const void *) note
+						+ sizeof expected_note);
+#define ROUND(len) (((len) + sizeof (ElfW(Word)) - 1) & -sizeof (ElfW(Word)))
+		note = ((const void *) (note + 1)
+			+ ROUND (note->vendorlen) + ROUND (note->datalen));
+	      }
+	  }
+    }
+#endif
+
   char bufmem[64];
   char *buf = bufmem;
   unsigned int version;
-- 
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