[PATCH] x86: e820: fix memmap kernel boot parameter

[PATCH] x86: e820: fix memmap kernel boot parameter

[Bob Liu]

Kernel boot parameter memmap=nn[KMG]$ss[KMG] is used to mark specific memory as
reserved. Region of memory to be used is from ss to ss+nn.

But I found the action of this parameter is not as expected.
I tried on two machines.
Machine1: bootcmdline in grub.cfg "memmap=800M$0x60bfdfff", but the result of
"cat /proc/cmdline" changed to "memmap=800M/bin/bashx60bfdfff" after system
booted.

Machine2: bootcmdline in grub.cfg "memmap=0x77ffffff$0x880000000", the result of
"cat /proc/cmdline" changed to "memmap=0x77ffffffx880000000".

I didn't find the root cause, I think maybe grub reserved "$0" as something
special.
Replace '$' with '%' in kernel boot parameter can fix this issue.

Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
 Documentation/kernel-parameters.txt |    6 +++---
 arch/x86/kernel/e820.c              |    2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7f9d4f5..a96c7b1 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1604,13 +1604,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			[KNL,ACPI] Mark specific memory as ACPI data.
 			Region of memory to be used, from ss to ss+nn.
 
-	memmap=nn[KMG]$ss[KMG]
+	memmap=nn[KMG]%ss[KMG]
 			[KNL,ACPI] Mark specific memory as reserved.
 			Region of memory to be used, from ss to ss+nn.
 			Example: Exclude memory from 0x18690000-0x1869ffff
-			         memmap=64K$0x18690000
+			         memmap=64K%0x18690000
 			         or
-			         memmap=0x10000$0x18690000
+			         memmap=0x10000%0x18690000
 
 	memory_corruption_check=0/1 [X86]
 			Some BIOSes seem to corrupt the first 64k of
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index d32abea..8483d45 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -869,7 +869,7 @@ static int __init parse_memmap_one(char *p)
 	} else if (*p == '#') {
 		start_at = memparse(p+1, &p);
 		e820_add_region(start_at, mem_size, E820_ACPI);
-	} else if (*p == '$') {
+	} else if (*p == '%') {
 		start_at = memparse(p+1, &p);
 		e820_add_region(start_at, mem_size, E820_RESERVED);
 	} else
-- 
1.7.10.4

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Re: [PATCH] x86: e820: fix memmap kernel boot parameter

[Dan Aloni]

On Fri, Aug 30, 2013 at 01:47:53PM +0800, Bob Liu wrote:
>[..]
> Machine2: bootcmdline in grub.cfg "memmap=0x77ffffff$0x880000000", the result of
> "cat /proc/cmdline" changed to "memmap=0x77ffffffx880000000".
> 
> I didn't find the root cause, I think maybe grub reserved "$0" as something
> special.
> Replace '$' with '%' in kernel boot parameter can fix this issue.

You are correct with the root cause, however I don't think the patch is needed.

In order to bypass grub's variable evaluation you can simply use escaping 
and replace $ with \$ in your grub config.

-- 
Dan Aloni

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Re: [PATCH] x86: e820: fix memmap kernel boot parameter

[Bob Liu]

On Fri, Aug 30, 2013 at 2:14 PM, Dan Aloni <alonid@stratoscale.com> wrote:
> On Fri, Aug 30, 2013 at 01:47:53PM +0800, Bob Liu wrote:
>>[..]
>> Machine2: bootcmdline in grub.cfg "memmap=0x77ffffff$0x880000000", the result of
>> "cat /proc/cmdline" changed to "memmap=0x77ffffffx880000000".
>>
>> I didn't find the root cause, I think maybe grub reserved "$0" as something
>> special.
>> Replace '$' with '%' in kernel boot parameter can fix this issue.
>
> You are correct with the root cause, however I don't think the patch is needed.
>
> In order to bypass grub's variable evaluation you can simply use escaping
> and replace $ with \$ in your grub config.
>

I see, thank you very much!

-- 
Regards,
--Bob

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Re: [PATCH] x86: e820: fix memmap kernel boot parameter

[H. Peter Anvin]

On 08/29/2013 10:47 PM, Bob Liu wrote:
> Kernel boot parameter memmap=nn[KMG]$ss[KMG] is used to mark specific memory as
> reserved. Region of memory to be used is from ss to ss+nn.
> 
> But I found the action of this parameter is not as expected.
> I tried on two machines.
> Machine1: bootcmdline in grub.cfg "memmap=800M$0x60bfdfff", but the result of
> "cat /proc/cmdline" changed to "memmap=800M/bin/bashx60bfdfff" after system
> booted.
> 
> Machine2: bootcmdline in grub.cfg "memmap=0x77ffffff$0x880000000", the result of
> "cat /proc/cmdline" changed to "memmap=0x77ffffffx880000000".
> 
> I didn't find the root cause, I think maybe grub reserved "$0" as something
> special.
> Replace '$' with '%' in kernel boot parameter can fix this issue.

NAK for the reasons already discussed.

	-hpa


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