[flashrom] [PATCH] Hack libpci not to exit(1) during init if PCI does not work

[Carl-Daniel Hailfinger]

New version: Should work for the internal programmer as well.

TODO: Add sane error handling to pcidev_init() and its callers.

libpci unhelpfully calls exit(1) instead of reporting an error if init
fails.
Fortunately, that part of libpci has not changed since the year 2000, so
we can use a really evil hack to avoid that.
We supply an alternative error printing function (which does not
exit(1)) and this function detects which error is happening and hacks
internal libpci structures in a way that avoids a later segfault due to
NULL pointer dereference.

We MUST absolutely make sure that pci_init() in libpci will not change
or this hack will explode spectacularly. Once we decide that this hack
is the way to go, notifying the libpci maintainer is essential.

To check if the hack works, run "flashrom -V" and respond to this mail
with the output.
If you don't have working PCI access, you should get a message near the
end which says that programmer initialization failed.
If you have working PCI access, the patch should not change anything.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net>

Index: flashrom-libpci_hack_avoid_exit1_during_init/pcidev.c
===================================================================
--- flashrom-libpci_hack_avoid_exit1_during_init/pcidev.c	(Revision 1362)
+++ flashrom-libpci_hack_avoid_exit1_during_init/pcidev.c	(Arbeitskopie)
@@ -21,6 +21,8 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <stdio.h>
+#include <stdarg.h>
 #include "flash.h"
 #include "programmer.h"
 
@@ -188,6 +190,77 @@
 	return 0;
 }
 
+/* Ugliest hack ever in flashrom! Should work for all libpci versions released
+ * in the year 2000 or later. Checked to make sense until at least version
+ * 3.1.8-test1.
+ */
+static void fake_libpci_method_init(struct pci_access *foo)
+{
+	msg_pinfo("Working around another pcilib crash\n");
+	return;
+}
+
+static struct {
+  char *name;	/* name in all libpci versions */
+  char *dummy1; /* Only present in some libpci versions */
+  void *dummy2;
+  void (*init1)(struct pci_access *); /* init in older versions */
+  void (*init2)(struct pci_access *); /* init in newer versions */
+  void *dummy3;
+  void *dummy4;
+  void *dummy5;
+  void *dummy6;
+  void *dummy7;
+  void *dummy8;
+  void *dummy9;
+  void *dummy10;
+} fake_libpci_methods = {
+	.name = "None",
+	.init1 = &fake_libpci_method_init,
+	.init2 = &fake_libpci_method_init,
+};
+
+static int pci_init_failed = 0;
+
+static void my_libpci_generic_error(char *msg, ...)
+{
+	va_list ap;
+
+	msg_pinfo("pcilib: ");
+	va_start(ap, msg);
+	vprintf(msg, ap);
+	va_end(ap);
+	msg_pinfo("\n");
+	if (!strcmp(msg, "Cannot find any working access method.")) {
+		/* Workaround for crash, very ugly. */
+		msg_pinfo("Working around pcilib crash\n");
+		pacc->methods = (void *)&fake_libpci_methods;
+		pci_init_failed = 1;
+	} else {
+		/* Any error in libpci would result in exit(1) by default. */
+		exit(1);
+	}
+}
+
+/* Wrapper for libpci pci_init() which simply calls exit(1) on error. */
+int flashrom_pci_init(void)
+{
+	/* Allocate the pci_access structure. */
+	pacc = pci_alloc();     
+	/* Hook the error printing function which would exit(1). */
+	pacc->error = &my_libpci_generic_error;
+	/* Initialize the PCI library. */
+	pci_init(pacc);
+	/* pci_init returns void, so we have to get any error status from the
+	 * hooked pacc->error which updates pci_init_failed.
+	 */
+	if (pci_init_failed) {
+		pci_cleanup(pacc);
+		return 1;
+	}
+	return 0;
+}
+
 uintptr_t pcidev_init(int bar, const struct pcidev_status *devs)
 {
 	struct pci_dev *dev;
@@ -197,8 +270,9 @@
 	int found = 0;
 	uintptr_t addr = 0, curaddr = 0;
 
-	pacc = pci_alloc();     /* Get the pci_access structure */
-	pci_init(pacc);         /* Initialize the PCI library */
+	if (flashrom_pci_init())
+		return 1;
+
 	pci_scan_bus(pacc);     /* We want to get the list of devices */
 	pci_filter_init(pacc, &filter);
 
Index: flashrom-libpci_hack_avoid_exit1_during_init/internal.c
===================================================================
--- flashrom-libpci_hack_avoid_exit1_during_init/internal.c	(Revision 1362)
+++ flashrom-libpci_hack_avoid_exit1_during_init/internal.c	(Arbeitskopie)
@@ -192,10 +192,8 @@
 	 */
 	buses_supported = CHIP_BUSTYPE_NONSPI;
 
-	/* Initialize PCI access for flash enables */
-	pacc = pci_alloc();	/* Get the pci_access structure */
-	/* Set all options you want -- here we stick with the defaults */
-	pci_init(pacc);		/* Initialize the PCI library */
+	if (flashrom_pci_init())
+		return 1;
 	pci_scan_bus(pacc);	/* We want to get the list of devices */
 
 	if (processor_flash_enable()) {
Index: flashrom-libpci_hack_avoid_exit1_during_init/programmer.h
===================================================================
--- flashrom-libpci_hack_avoid_exit1_during_init/programmer.h	(Revision 1362)
+++ flashrom-libpci_hack_avoid_exit1_during_init/programmer.h	(Arbeitskopie)
@@ -225,6 +225,7 @@
 };
 uintptr_t pcidev_validate(struct pci_dev *dev, int bar, const struct pcidev_status *devs);
 uintptr_t pcidev_init(int bar, const struct pcidev_status *devs);
+int flashrom_pci_init(void);
 /* rpci_write_* are reversible writes. The original PCI config space register
  * contents will be restored on shutdown.
  */


-- 
http://www.hailfinger.org/