[RFC/PATCH] kvm tools: Use initrd from "/boot" for distro kernels

[Pekka Enberg <penberg@xxxxxxxxxx>]

This patch implements automatic initrd detection for distro kernels.
Unfortunately, it doesn't quite produce a working environment on Fedora:

  [    0.588066] Freeing unused kernel memory: 912k freed
  [    0.588981] Write protecting the kernel read-only data: 10240k
  [    0.593634] Freeing unused kernel memory: 1332k freed
  [    0.598900] Freeing unused kernel memory: 1580k freed
  [    0.638157] dracut: dracut-009-12.fc15
  [    0.653838] udev[121]: starting version 167
  [    5.689056] dracut: Starting plymouth daemon
  plymouthd: ply-terminal.c:777: ply_terminal_set_mode: Assertion `terminal != ((void *)0)' failed.
  [    5.706055] dracut: error: unexpectedly disconnected from boot status daemon

I don't quite understand why udev starts up because we've configured kernel
parameters to boot to "/virt/init":

  [    0.000000] Command line: notsc noapic noacpi pci=conf1 reboot=k panic=1 i8042.direct=1 i8042.dumbkbd=1 i8042.nopnp=1 console=ttyS0 earlyprintk=serial i8042.noaux=1  init=/bin/sh  root=/dev/root rw rootflags=rw,trans=virtio,version=9p2000.L rootfstype=9p init=/virt/init ip=dhcp

Reported-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
Cc: Sasha Levin <levinsasha928@xxxxxxxxx>
Cc: Asias He <asias.hejun@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Pekka Enberg <penberg@xxxxxxxxxx>
---
 tools/kvm/Makefile      |    3 +-
 tools/kvm/builtin-run.c |   48 ++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/tools/kvm/Makefile b/tools/kvm/Makefile
index 20389f9..136948e 100644
--- a/tools/kvm/Makefile
+++ b/tools/kvm/Makefile
@@ -162,7 +162,8 @@ endif
 
 WARNINGS += -Wall
 WARNINGS += -Wcast-align
-WARNINGS += -Wformat=2
+WARNINGS += -Wformat
+WARNINGS += -Wformat-security
 WARNINGS += -Winit-self
 WARNINGS += -Wmissing-declarations
 WARNINGS += -Wmissing-prototypes
diff --git a/tools/kvm/builtin-run.c b/tools/kvm/builtin-run.c
index 2792650..2802e6a 100644
--- a/tools/kvm/builtin-run.c
+++ b/tools/kvm/builtin-run.c
@@ -562,6 +562,12 @@ static const char *host_kernels[] = {
 	NULL
 };
 
+static const char *host_initrds[] = {
+	"/boot/initramfs-%s.img",
+	"/boot/initrd.img-%s",
+	NULL,
+};
+
 static const char *default_kernels[] = {
 	"./bzImage",
 	"../../arch/x86/boot/bzImage",
@@ -646,7 +652,6 @@ static const char *find_kernel(void)
 {
 	const char **k;
 	struct stat st;
-	struct utsname uts;
 
 	k = &default_kernels[0];
 	while (*k) {
@@ -658,6 +663,15 @@ static const char *find_kernel(void)
 		return kernel;
 	}
 
+	return NULL;
+}
+
+static const char *find_host_kernel(void)
+{
+	const char **k;
+	struct stat st;
+	struct utsname uts;
+
 	if (uname(&uts) < 0)
 		return NULL;
 
@@ -676,6 +690,31 @@ static const char *find_kernel(void)
 	return NULL;
 }
 
+static const char *find_initrd(void)
+{
+	const char **k;
+	struct stat st;
+	struct utsname uts;
+
+	if (uname(&uts) < 0)
+		return NULL;
+
+	k = &host_initrds[0];
+	while (*k) {
+		static char initrd[PATH_MAX];
+
+		if (snprintf(initrd, PATH_MAX, *k, uts.release) < 0)
+			return NULL;
+
+		if (stat(initrd, &st) < 0 || !S_ISREG(st.st_mode)) {
+			k++;
+			continue;
+		}
+		return initrd;
+	}
+	return NULL;
+}
+
 static const char *find_vmlinux(void)
 {
 	const char **vmlinux;
@@ -741,6 +780,13 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
 		kernel_filename = find_kernel();
 
 	if (!kernel_filename) {
+		kernel_filename = find_host_kernel();
+
+		if (!initrd_filename)
+			initrd_filename = find_initrd();
+	}
+
+	if (!kernel_filename) {
 		kernel_usage_with_options();
 		return EINVAL;
 	}
-- 
1.7.6.4

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