detect Xen dom0 properly to avoid conflict with pv_on_hvm domU

A Xen HVM guest with PV drivers loaded has also a /proc/xen directory. But such a guest is an ordinary PC and the special handling for dom0 breaks kdump in this environment.
Test for /proc/xen/capabilities instead and cache the result.

Also make two variables static, they are only used in this file.

Signed-off-by Olaf Hering <[email protected]>

---
 kexec/crashdump-xen.c |   15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

Index: kexec-tools-0.8.15/kexec/crashdump-xen.c
===================================================================

kexec/crashdump-xen.c +7 -3

 int xen_present(void)
 {
-	struct stat buf;
-
-	return stat("/proc/xen", &buf) == 0;
+	if (!is_dom0) {
+		if (access("/proc/xen/capabilities", F_OK) == 0)
+			is_dom0 = 1;
+		else
+			is_dom0 = -1;
+	}
+	return is_dom0 > 0;
 }
 
 unsigned long xen_architecture(struct crash_elf_info *elf_info)
 

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Quoted 1 line · Olaf Hering

+static int is_dom0;

I think you need to explicitly initialise is_dom0 to 0.

Alternatively, is it really such a burden to call access() each time xen_present() is called? (I'm ambivalent with regards to this).

Quoted 5 lines · Simon Horman

Quoted 1 line · Olaf Hering

+static int is_dom0;

I think you need to explicitly initialise is_dom0 to 0.

Globals are always initialized to zero, its a C language thing.

Quoted 2 lines

Alternatively, is it really such a burden to call access() each time xen_present() is called? (I'm ambivalent with regards to this).

Probably not, its called a dozen times in my testing.