Re: [PATCH] 2.4.25-rc1: Shutdown kernel on zone-alignment failure

Michael Frank
2004-02-06T22:41:20Z

Marcello,

Another thing,

The BUG() call on line 732 in mm/page_alloc.c is invalid as the BUG handler
is not initialized. It just will hang.

This updated patch fixes that as well.

Regards
Michael

diff -uN -r -X /home/mhf/sys/dont/dontdiff linux-2.4.25-rc1-Vanilla/include/linux/kernel.h linux-2.4.25-rc1-mhf176/include/linux/kernel.h
--- linux-2.4.25-rc1-Vanilla/include/linux/kernel.h 2004-02-06 17:09:26.000000000 +0800
+++ linux-2.4.25-rc1-mhf176/include/linux/kernel.h 2004-02-07 05:59:30.000000000 +0800
@@ -45,7 +45,7 @@
#define minimum_console_loglevel (console_printk[2])
#define default_console_loglevel (console_printk[3])

-# define NORET_TYPE /**/
+# define NORET_TYPE
# define ATTRIB_NORET __attribute__((noreturn))
# define NORET_AND noreturn,

@@ -104,7 +104,7 @@

extern void bust_spinlocks(int yes);
extern int oops_in_progress; /* If set, an oops, panic(), BUG() or die() is in progress */
-
+extern int force_bug; /* If set, BUG() will be forced when handler initialized */
extern int tainted;
extern const char *print_tainted(void);

diff -uN -r -X /home/mhf/sys/dont/dontdiff linux-2.4.25-rc1-Vanilla/init/main.c linux-2.4.25-rc1-mhf176/init/main.c
--- linux-2.4.25-rc1-Vanilla/init/main.c 2004-02-06 17:06:58.000000000 +0800
+++ linux-2.4.25-rc1-mhf176/init/main.c 2004-02-07 05:11:07.000000000 +0800
@@ -121,6 +121,7 @@
extern void time_init(void);
extern void softirq_init(void);

+int force_bug;
int rows, cols;

char *execute_command;
@@ -422,6 +423,14 @@
ccwcache_init();
#endif
signals_init();
+
+ /*
+ * Something went badly wrong during the early initialisation process,
+ * so lets die before doing any damage or wasting people's time
+ * running a half dead kernel.
+ */
+ if (force_bug)
+ BUG();
#ifdef CONFIG_PROC_FS
proc_root_init();
#endif
diff -uN -r -X /home/mhf/sys/dont/dontdiff linux-2.4.25-rc1-Vanilla/mm/page_alloc.c linux-2.4.25-rc1-mhf176/mm/page_alloc.c
--- linux-2.4.25-rc1-Vanilla/mm/page_alloc.c 2004-02-06 17:06:58.000000000 +0800
+++ linux-2.4.25-rc1-mhf176/mm/page_alloc.c 2004-02-07 06:36:00.000000000 +0800
@@ -726,10 +726,19 @@
unsigned long i, j;
unsigned long map_size;
unsigned long totalpages, offset, realtotalpages;
- const unsigned long zone_required_alignment = 1UL << (MAX_ORDER-1);
+ const unsigned long zone_required_alignment = 1UL << (PAGE_SHIFT + MAX_ORDER-1);
+ unsigned long zone_bad_alignment;

- if (zone_start_paddr & ~PAGE_MASK)
- BUG();
+ /*
+ * We abort when physical address is bad. arch/mm/init.c should catch it
+ * if not, setup/main.c will
+ */
+ if (zone_start_paddr & ~PAGE_MASK) {
+ printk("FATAL ERROR: wrong zone physical start address at: 0x%lx"
+ " - will force kernel BUG\n", zone_start_paddr);
+ force_bug = 1;
+ return;
+ }

totalpages = 0;
for (i = 0; i < MAX_NR_ZONES; i++) {
@@ -741,7 +750,8 @@
for (i = 0; i < MAX_NR_ZONES; i++)
realtotalpages -= zholes_size[i];

- printk("On node %d totalpages: %lu\n", nid, realtotalpages);
+ printk("On node %d totalpages: %lu, zones aligned at: 0x%lx\n",
+ nid, realtotalpages,zone_required_alignment);

/*
* Some architectures (with lots of mem and discontinous memory
@@ -774,7 +784,20 @@
if (zholes_size)
realsize -= zholes_size[j];

- printk("zone(%lu): %lu pages.\n", j, size);
+ printk("zone(%lu): %lu pages, physical start address at: 0x%lx\n",
+ j, size,zone_start_paddr);
+
+ /*
+ * Here the alignment of a zone is checked. Should alignment
+ * be wrong, all that can be done is to print an error message
+ * and defer the the BUG handler as it is not yet initialized.
+ */
+ if ((zone_bad_alignment = (zone_start_paddr & (zone_required_alignment-1)))) {
+ printk("zone(%lu): FATAL ERROR: wrong zone alignment: 0x%lx"
+ " - will force kernel BUG\n",
+ j,zone_bad_alignment);
+ force_bug = 1;
+ }
zone->size = size;
zone->realsize = realsize;
zone->name = zone_names[j];
@@ -784,7 +807,6 @@
zone->need_balance = 0;
zone->nr_active_pages = zone->nr_inactive_pages = 0;

-
if (!size)
continue;

@@ -837,8 +859,6 @@
zone->zone_start_mapnr = offset;
zone->zone_start_paddr = zone_start_paddr;

- if ((zone_start_paddr >> PAGE_SHIFT) & (zone_required_alignment-1))
- printk("BUG: wrong zone alignment, it will crash\n");

/*
* Initially all pages are reserved - free ones are freed