Extend KCORE_TEXT to cover the pages between _text and _stext,
to allow examining some important page table pages.
`readelf -a` output on x86_64 before and after patch:
Type Offset VirtAddr PhysAddr
before LOAD 0x00007fff8100c000 0xffffffff81009000 0x0000000000000000
after LOAD 0x00007fff81003000 0xffffffff81000000 0x0000000000000000
The newly covered pages are:
0xffffffff81000000 <startup_64> etc.
0xffffffff81001000 <init_level4_pgt>
0xffffffff81002000 <level3_ident_pgt>
0xffffffff81003000 <level3_kernel_pgt>
0xffffffff81004000 <level2_fixmap_pgt>
0xffffffff81005000 <level1_fixmap_pgt>
0xffffffff81006000 <level2_ident_pgt>
0xffffffff81007000 <level2_kernel_pgt>
0xffffffff81008000 <level2_spare_pgt>
Before patch, /proc/kcore shows outdated contents for the above page
table pages, for example:
(gdb) p level3_ident_pgt
$1 = {<text variable, no debug info>} 0xffffffff81002000 <level3_ident_pgt>
(gdb) p/x *((pud_t *)&level3_ident_pgt)@512
$2 = {{pud = 0x1006063}, {pud = 0x0} <repeats 511 times>}
while the real content is:
root@hp /home/wfg# hexdump -s 0x1002000 -n 4096 /dev/mem
1002000 6063 0100 0000 0000 8067 0000 0000 0000
1002010 0000 0000 0000 0000 0000 0000 0000 0000
*
1003000
That is, on a x86_64 box with 2GB memory, we can see first-1GB / full-2GB
identity mapping before/after patch:
(gdb) p/x *((pud_t *)&level3_ident_pgt)@512
before $1 = {{pud = 0x1006063}, {pud = 0x0} <repeats 511 times>}
after $1 = {{pud = 0x1006063}, {pud = 0x8067}, {pud = 0x0} <repeats 510 times>}
Obviously the content before patch is wrong.
CC: Andi Kleen <andi@xxxxxxxxxxxxxx>
CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
fs/proc/kcore.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- linux-2.6.orig/fs/proc/kcore.c 2010-04-15 12:27:54.000000000 +0800
+++ linux-2.6/fs/proc/kcore.c 2010-04-15 12:44:05.000000000 +0800
@@ -587,7 +587,7 @@ static struct kcore_list kcore_text;
*/
static void __init proc_kcore_text_init(void)
{
- kclist_add(&kcore_text, _stext, _end - _stext, KCORE_TEXT);
+ kclist_add(&kcore_text, _text, _end - _text, KCORE_TEXT);
}
#else
static void __init proc_kcore_text_init(void)
--
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