Re: [bigmem-patch] 4GB with Linux on IA32

Andrea Arcangeli
1999-08-16T22:47:50Z

This incremental (against bigmem-2.3.13-L) patch will fix the ptrace and
/proc/*/mem read/writes to other process VM inside the kernel.

diff -urN 2.3.13-bigmem-L/fs/proc/mem.c tmp/fs/proc/mem.c
--- 2.3.13-bigmem-L/fs/proc/mem.c Tue Jul 13 02:02:09 1999
+++ tmp/fs/proc/mem.c Tue Aug 17 00:02:48 1999
@@ -15,6 +15,9 @@
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/pgtable.h>
+#ifdef CONFIG_BIGMEM
+#include <asm/bigmem.h>
+#endif

/*
* mem_write isn't really a good idea right now. It needs
@@ -120,7 +123,13 @@
i = PAGE_SIZE-(addr & ~PAGE_MASK);
if (i > scount)
i = scount;
+#ifdef CONFIG_BIGMEM
+ page = (char *) kmap((unsigned long) page, KM_READ);
+#endif
copy_to_user(tmp, page, i);
+#ifdef CONFIG_BIGMEM
+ kunmap((unsigned long) page, KM_READ);
+#endif
addr += i;
tmp += i;
scount -= i;
@@ -177,7 +186,13 @@
i = PAGE_SIZE-(addr & ~PAGE_MASK);
if (i > count)
i = count;
+#ifdef CONFIG_BIGMEM
+ page = (unsigned long) kmap((unsigned long) page, KM_WRITE);
+#endif
copy_from_user(page, tmp, i);
+#ifdef CONFIG_BIGMEM
+ kunmap((unsigned long) page, KM_WRITE);
+#endif
addr += i;
tmp += i;
count -= i;
diff -urN 2.3.13-bigmem-L/kernel/ptrace.c tmp/kernel/ptrace.c
--- 2.3.13-bigmem-L/kernel/ptrace.c Thu Jul 22 01:07:28 1999
+++ tmp/kernel/ptrace.c Tue Aug 17 00:02:40 1999
@@ -13,6 +13,9 @@

#include <asm/pgtable.h>
#include <asm/uaccess.h>
+#ifdef CONFIG_BIGMEM
+#include <asm/bigmem.h>
+#endif

/*
* Access another process' address space, one page at a time.
@@ -52,7 +55,15 @@
dst = src;
src = buf;
}
+#ifdef CONFIG_BIGMEM
+ src = (void *) kmap((unsigned long) src, KM_READ);
+ dst = (void *) kmap((unsigned long) dst, KM_WRITE);
+#endif
memcpy(dst, src, len);
+#ifdef CONFIG_BIGMEM
+ kunmap((unsigned long) src, KM_READ);
+ kunmap((unsigned long) dst, KM_WRITE);
+#endif
}
flush_page_to_ram(page);
return len;

The /proc/*/mem read/write seems to not work though (maybe I am doing
something wrong...).

black:/home/andrea# cat /proc/1/mem
cat: /proc/1/mem: No such process

The same happens also on 2.2.11.

Andrea