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[PATCH v4 2/3] KASLR: Handle memory limit specified by memmap and mem option

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  [PATCH v4 2/3] KASLR: Handle memory limit specified by memmap and mem option Baoquan He <bhe@redhat.com> - 2017-05-09 08:00 +0200
    Re: [PATCH v4 2/3] KASLR: Handle memory limit specified by memmap and  mem option Kees Cook <keescook@chromium.org> - 2017-05-09 19:40 +0200
      Re: [PATCH v4 2/3] KASLR: Handle memory limit specified by memmap  and mem option Baoquan He <bhe@redhat.com> - 2017-05-10 02:40 +0200
    Re: [PATCH v4 2/3] KASLR: Handle memory limit specified by memmap and mem option Masayoshi Mizuma <m.mizuma@jp.fujitsu.com> - 2017-05-12 06:30 +0200
      Re: [PATCH v4 2/3] KASLR: Handle memory limit specified by memmap  and mem option Baoquan He <bhe@redhat.com> - 2017-05-12 07:10 +0200

#1637882 — [PATCH v4 2/3] KASLR: Handle memory limit specified by memmap and mem option

Option mem= will limit the max address a system can use and any memory
region above the limit will be removed.

Furthermore, memmap=nn[KMG] which has no offset specified has the same
behaviour as mem=.

KASLR needs to consider this when choosing the random position for
decompressing the kernel.

This patch implements that.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 arch/x86/boot/compressed/kaslr.c | 69 +++++++++++++++++++++++++++++-----------
 1 file changed, 51 insertions(+), 18 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 106e13b..0637e85 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -88,6 +88,10 @@ struct mem_vector {
 static bool memmap_too_large;
 
 
+/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
+unsigned long long mem_limit = ULLONG_MAX;
+
+
 enum mem_avoid_index {
 	MEM_AVOID_ZO_RANGE = 0,
 	MEM_AVOID_INITRD,
@@ -138,16 +142,24 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
 		return -EINVAL;
 
 	switch (*p) {
-	case '@':
-		/* Skip this region, usable */
-		*start = 0;
-		*size = 0;
-		return 0;
 	case '#':
 	case '$':
 	case '!':
 		*start = memparse(p + 1, &p);
 		return 0;
+	case '@':	/* Fall through: */
+		/*
+		 * memmap=nn@ss specifies usable region, should be skipped
+		 */
+		*size = 0;
+	default:
+		/*
+		 * If w/o offset, only size specified, memmap=nn[KMG] has the
+		 * same behaviour as mem=nn[KMG]. It limits the max address
+		 * system can use. Region above the limit should be avoided.
+		 */
+		*start = 0;
+		return 0;
 	}
 
 	return -EINVAL;
@@ -173,9 +185,14 @@ static void mem_avoid_memmap(char *str)
 		if (rc < 0)
 			break;
 		str = k;
-		/* A usable region that should not be skipped */
-		if (size == 0)
+
+		if (start == 0) {
+			/* Store the specified memory limit if size > 0 */
+			if (size > 0)
+				mem_limit = size;
+
 			continue;
+		}
 
 		mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start;
 		mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size;
@@ -187,19 +204,15 @@ static void mem_avoid_memmap(char *str)
 		memmap_too_large = true;
 }
 
-
-/*
- * handle_mem_memmap will also cover 'mem=' issue in next patch. Will remove
- * this note later.
- */
 static int handle_mem_memmap(void)
 {
 	char *args = (char *)get_cmd_line_ptr();
 	size_t len = strlen((char *)args);
 	char *tmp_cmdline;
 	char *param, *val;
+	u64 mem_size;
 
-	if (!strstr(args, "memmap="))
+	if (!strstr(args, "memmap=") && !strstr(args, "mem="))
 		return 0;
 
 	tmp_cmdline = malloc(len + 1);
@@ -222,8 +235,20 @@ static int handle_mem_memmap(void)
 			return -1;
 		}
 
-		if (!strcmp(param, "memmap"))
+		if (!strcmp(param, "memmap")) {
 			mem_avoid_memmap(val);
+		} else if (!strcmp(param, "mem")) {
+			char *p = val;
+
+			if (!strcmp(p, "nopentium"))
+				continue;
+			mem_size = memparse(p, &p);
+			if (mem_size == 0) {
+				free(tmp_cmdline);
+				return -EINVAL;
+			}
+			mem_limit = mem_size;
+		}
 	}
 
 	free(tmp_cmdline);
@@ -460,7 +485,8 @@ static void process_e820_entry(struct boot_e820_entry *entry,
 {
 	struct mem_vector region, overlap;
 	struct slot_area slot_area;
-	unsigned long start_orig;
+	unsigned long start_orig, end;
+	struct boot_e820_entry cur_entry;
 
 	/* Skip non-RAM entries. */
 	if (entry->type != E820_TYPE_RAM)
@@ -474,8 +500,15 @@ static void process_e820_entry(struct boot_e820_entry *entry,
 	if (entry->addr + entry->size < minimum)
 		return;
 
-	region.start = entry->addr;
-	region.size = entry->size;
+	/* Ignore entries above memory limit */
+	end = min(entry->size + entry->addr, mem_limit);
+	if (entry->addr >= end)
+		return;
+	cur_entry.addr = entry->addr;
+	cur_entry.size = end - entry->addr;
+
+	region.start = cur_entry.addr;
+	region.size = cur_entry.size;
 
 	/* Give up if slot area array is full. */
 	while (slot_area_index < MAX_SLOT_AREA) {
@@ -489,7 +522,7 @@ static void process_e820_entry(struct boot_e820_entry *entry,
 		region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
 
 		/* Did we raise the address above this e820 region? */
-		if (region.start > entry->addr + entry->size)
+		if (region.start > cur_entry.addr + cur_entry.size)
 			return;
 
 		/* Reduce size by any delta from the original address. */
-- 
2.5.5

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#1638318 — Re: [PATCH v4 2/3] KASLR: Handle memory limit specified by memmap and mem option

On Mon, May 8, 2017 at 10:57 PM, Baoquan He <bhe@redhat.com> wrote:
> Option mem= will limit the max address a system can use and any memory
> region above the limit will be removed.
>
> Furthermore, memmap=nn[KMG] which has no offset specified has the same
> behaviour as mem=.
>
> KASLR needs to consider this when choosing the random position for
> decompressing the kernel.
>
> This patch implements that.
>
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
>  arch/x86/boot/compressed/kaslr.c | 69 +++++++++++++++++++++++++++++-----------
>  1 file changed, 51 insertions(+), 18 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index 106e13b..0637e85 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -88,6 +88,10 @@ struct mem_vector {
>  static bool memmap_too_large;
>
>
> +/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
> +unsigned long long mem_limit = ULLONG_MAX;
> +
> +
>  enum mem_avoid_index {
>         MEM_AVOID_ZO_RANGE = 0,
>         MEM_AVOID_INITRD,
> @@ -138,16 +142,24 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
>                 return -EINVAL;
>
>         switch (*p) {
> -       case '@':
> -               /* Skip this region, usable */
> -               *start = 0;
> -               *size = 0;
> -               return 0;
>         case '#':
>         case '$':
>         case '!':
>                 *start = memparse(p + 1, &p);
>                 return 0;
> +       case '@':       /* Fall through: */
> +               /*
> +                * memmap=nn@ss specifies usable region, should be skipped
> +                */
> +               *size = 0;

The "fall through" comment should go here (where the break is "missing").

> +       default:
> +               /*
> +                * If w/o offset, only size specified, memmap=nn[KMG] has the
> +                * same behaviour as mem=nn[KMG]. It limits the max address
> +                * system can use. Region above the limit should be avoided.
> +                */
> +               *start = 0;
> +               return 0;
>         }
>
>         return -EINVAL;
> @@ -173,9 +185,14 @@ static void mem_avoid_memmap(char *str)
>                 if (rc < 0)
>                         break;
>                 str = k;
> -               /* A usable region that should not be skipped */
> -               if (size == 0)
> +
> +               if (start == 0) {
> +                       /* Store the specified memory limit if size > 0 */
> +                       if (size > 0)
> +                               mem_limit = size;
> +
>                         continue;
> +               }
>
>                 mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start;
>                 mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size;
> @@ -187,19 +204,15 @@ static void mem_avoid_memmap(char *str)
>                 memmap_too_large = true;
>  }
>
> -
> -/*
> - * handle_mem_memmap will also cover 'mem=' issue in next patch. Will remove
> - * this note later.
> - */
>  static int handle_mem_memmap(void)
>  {
>         char *args = (char *)get_cmd_line_ptr();
>         size_t len = strlen((char *)args);
>         char *tmp_cmdline;
>         char *param, *val;
> +       u64 mem_size;
>
> -       if (!strstr(args, "memmap="))
> +       if (!strstr(args, "memmap=") && !strstr(args, "mem="))
>                 return 0;
>
>         tmp_cmdline = malloc(len + 1);
> @@ -222,8 +235,20 @@ static int handle_mem_memmap(void)
>                         return -1;
>                 }
>
> -               if (!strcmp(param, "memmap"))
> +               if (!strcmp(param, "memmap")) {
>                         mem_avoid_memmap(val);
> +               } else if (!strcmp(param, "mem")) {
> +                       char *p = val;
> +
> +                       if (!strcmp(p, "nopentium"))
> +                               continue;
> +                       mem_size = memparse(p, &p);
> +                       if (mem_size == 0) {
> +                               free(tmp_cmdline);
> +                               return -EINVAL;
> +                       }
> +                       mem_limit = mem_size;
> +               }
>         }
>
>         free(tmp_cmdline);
> @@ -460,7 +485,8 @@ static void process_e820_entry(struct boot_e820_entry *entry,
>  {
>         struct mem_vector region, overlap;
>         struct slot_area slot_area;
> -       unsigned long start_orig;
> +       unsigned long start_orig, end;
> +       struct boot_e820_entry cur_entry;
>
>         /* Skip non-RAM entries. */
>         if (entry->type != E820_TYPE_RAM)
> @@ -474,8 +500,15 @@ static void process_e820_entry(struct boot_e820_entry *entry,
>         if (entry->addr + entry->size < minimum)
>                 return;
>
> -       region.start = entry->addr;
> -       region.size = entry->size;
> +       /* Ignore entries above memory limit */
> +       end = min(entry->size + entry->addr, mem_limit);
> +       if (entry->addr >= end)
> +               return;
> +       cur_entry.addr = entry->addr;
> +       cur_entry.size = end - entry->addr;
> +
> +       region.start = cur_entry.addr;
> +       region.size = cur_entry.size;
>
>         /* Give up if slot area array is full. */
>         while (slot_area_index < MAX_SLOT_AREA) {
> @@ -489,7 +522,7 @@ static void process_e820_entry(struct boot_e820_entry *entry,
>                 region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
>
>                 /* Did we raise the address above this e820 region? */
> -               if (region.start > entry->addr + entry->size)
> +               if (region.start > cur_entry.addr + cur_entry.size)
>                         return;
>
>                 /* Reduce size by any delta from the original address. */
> --
> 2.5.5
>

Otherwise looks fine to me!

-Kees

-- 
Kees Cook
Pixel Security

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#1638468 — Re: [PATCH v4 2/3] KASLR: Handle memory limit specified by memmap and mem option

On 05/09/17 at 10:39am, Kees Cook wrote:
> On Mon, May 8, 2017 at 10:57 PM, Baoquan He <bhe@redhat.com> wrote:
> > Option mem= will limit the max address a system can use and any memory
> > region above the limit will be removed.
> >
> > Furthermore, memmap=nn[KMG] which has no offset specified has the same
> > behaviour as mem=.
> >
> > KASLR needs to consider this when choosing the random position for
> > decompressing the kernel.
> >
> > This patch implements that.
> >
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > ---
> >  arch/x86/boot/compressed/kaslr.c | 69 +++++++++++++++++++++++++++++-----------
> >  1 file changed, 51 insertions(+), 18 deletions(-)
> >
> > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> > index 106e13b..0637e85 100644
> > --- a/arch/x86/boot/compressed/kaslr.c
> > +++ b/arch/x86/boot/compressed/kaslr.c
> > @@ -88,6 +88,10 @@ struct mem_vector {
> >  static bool memmap_too_large;
> >
> >
> > +/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
> > +unsigned long long mem_limit = ULLONG_MAX;
> > +
> > +
> >  enum mem_avoid_index {
> >         MEM_AVOID_ZO_RANGE = 0,
> >         MEM_AVOID_INITRD,
> > @@ -138,16 +142,24 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
> >                 return -EINVAL;
> >
> >         switch (*p) {
> > -       case '@':
> > -               /* Skip this region, usable */
> > -               *start = 0;
> > -               *size = 0;
> > -               return 0;
> >         case '#':
> >         case '$':
> >         case '!':
> >                 *start = memparse(p + 1, &p);
> >                 return 0;
> > +       case '@':       /* Fall through: */
> > +               /*
> > +                * memmap=nn@ss specifies usable region, should be skipped
> > +                */
> > +               *size = 0;
> 
> The "fall through" comment should go here (where the break is "missing").

Ah, OK, will change and repost after patch 1/3 reviewing. Thanks a lot!

> 
> > +       default:
> > +               /*
> > +                * If w/o offset, only size specified, memmap=nn[KMG] has the
> > +                * same behaviour as mem=nn[KMG]. It limits the max address
> > +                * system can use. Region above the limit should be avoided.
> > +                */
> > +               *start = 0;
> > +               return 0;
> >         }
> >
> >         return -EINVAL;
> > @@ -173,9 +185,14 @@ static void mem_avoid_memmap(char *str)
> >                 if (rc < 0)
> >                         break;
> >                 str = k;
> > -               /* A usable region that should not be skipped */
> > -               if (size == 0)
> > +
> > +               if (start == 0) {
> > +                       /* Store the specified memory limit if size > 0 */
> > +                       if (size > 0)
> > +                               mem_limit = size;
> > +
> >                         continue;
> > +               }
> >
> >                 mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start;
> >                 mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size;
> > @@ -187,19 +204,15 @@ static void mem_avoid_memmap(char *str)
> >                 memmap_too_large = true;
> >  }
> >
> > -
> > -/*
> > - * handle_mem_memmap will also cover 'mem=' issue in next patch. Will remove
> > - * this note later.
> > - */
> >  static int handle_mem_memmap(void)
> >  {
> >         char *args = (char *)get_cmd_line_ptr();
> >         size_t len = strlen((char *)args);
> >         char *tmp_cmdline;
> >         char *param, *val;
> > +       u64 mem_size;
> >
> > -       if (!strstr(args, "memmap="))
> > +       if (!strstr(args, "memmap=") && !strstr(args, "mem="))
> >                 return 0;
> >
> >         tmp_cmdline = malloc(len + 1);
> > @@ -222,8 +235,20 @@ static int handle_mem_memmap(void)
> >                         return -1;
> >                 }
> >
> > -               if (!strcmp(param, "memmap"))
> > +               if (!strcmp(param, "memmap")) {
> >                         mem_avoid_memmap(val);
> > +               } else if (!strcmp(param, "mem")) {
> > +                       char *p = val;
> > +
> > +                       if (!strcmp(p, "nopentium"))
> > +                               continue;
> > +                       mem_size = memparse(p, &p);
> > +                       if (mem_size == 0) {
> > +                               free(tmp_cmdline);
> > +                               return -EINVAL;
> > +                       }
> > +                       mem_limit = mem_size;
> > +               }
> >         }
> >
> >         free(tmp_cmdline);
> > @@ -460,7 +485,8 @@ static void process_e820_entry(struct boot_e820_entry *entry,
> >  {
> >         struct mem_vector region, overlap;
> >         struct slot_area slot_area;
> > -       unsigned long start_orig;
> > +       unsigned long start_orig, end;
> > +       struct boot_e820_entry cur_entry;
> >
> >         /* Skip non-RAM entries. */
> >         if (entry->type != E820_TYPE_RAM)
> > @@ -474,8 +500,15 @@ static void process_e820_entry(struct boot_e820_entry *entry,
> >         if (entry->addr + entry->size < minimum)
> >                 return;
> >
> > -       region.start = entry->addr;
> > -       region.size = entry->size;
> > +       /* Ignore entries above memory limit */
> > +       end = min(entry->size + entry->addr, mem_limit);
> > +       if (entry->addr >= end)
> > +               return;
> > +       cur_entry.addr = entry->addr;
> > +       cur_entry.size = end - entry->addr;
> > +
> > +       region.start = cur_entry.addr;
> > +       region.size = cur_entry.size;
> >
> >         /* Give up if slot area array is full. */
> >         while (slot_area_index < MAX_SLOT_AREA) {
> > @@ -489,7 +522,7 @@ static void process_e820_entry(struct boot_e820_entry *entry,
> >                 region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
> >
> >                 /* Did we raise the address above this e820 region? */
> > -               if (region.start > entry->addr + entry->size)
> > +               if (region.start > cur_entry.addr + cur_entry.size)
> >                         return;
> >
> >                 /* Reduce size by any delta from the original address. */
> > --
> > 2.5.5
> >
> 
> Otherwise looks fine to me!
> 
> -Kees
> 
> -- 
> Kees Cook
> Pixel Security

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#1640194

Hi Baoquan,

Thank you for fixing!
I confirmed that the kernel is located within mem= address.

Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>

Regards,
Masayoshi Mizuma

On Tue, 9 May 2017 13:57:51 +0800 Baoquan He wrote:

> Option mem= will limit the max address a system can use and any memory
> region above the limit will be removed.
> 
> Furthermore, memmap=nn[KMG] which has no offset specified has the same
> behaviour as mem=.
> 
> KASLR needs to consider this when choosing the random position for
> decompressing the kernel.
> 
> This patch implements that.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
>  arch/x86/boot/compressed/kaslr.c | 69 +++++++++++++++++++++++++++++-----------
>  1 file changed, 51 insertions(+), 18 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index 106e13b..0637e85 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -88,6 +88,10 @@ struct mem_vector {
>  static bool memmap_too_large;
>  
>  
> +/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
> +unsigned long long mem_limit = ULLONG_MAX;
> +
> +
>  enum mem_avoid_index {
>  	MEM_AVOID_ZO_RANGE = 0,
>  	MEM_AVOID_INITRD,
> @@ -138,16 +142,24 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
>  		return -EINVAL;
>  
>  	switch (*p) {
> -	case '@':
> -		/* Skip this region, usable */
> -		*start = 0;
> -		*size = 0;
> -		return 0;
>  	case '#':
>  	case '$':
>  	case '!':
>  		*start = memparse(p + 1, &p);
>  		return 0;
> +	case '@':	/* Fall through: */
> +		/*
> +		 * memmap=nn@ss specifies usable region, should be skipped
> +		 */
> +		*size = 0;
> +	default:
> +		/*
> +		 * If w/o offset, only size specified, memmap=nn[KMG] has the
> +		 * same behaviour as mem=nn[KMG]. It limits the max address
> +		 * system can use. Region above the limit should be avoided.
> +		 */
> +		*start = 0;
> +		return 0;
>  	}
>  
>  	return -EINVAL;
> @@ -173,9 +185,14 @@ static void mem_avoid_memmap(char *str)
>  		if (rc < 0)
>  			break;
>  		str = k;
> -		/* A usable region that should not be skipped */
> -		if (size == 0)
> +
> +		if (start == 0) {
> +			/* Store the specified memory limit if size > 0 */
> +			if (size > 0)
> +				mem_limit = size;
> +
>  			continue;
> +		}
>  
>  		mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start;
>  		mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size;
> @@ -187,19 +204,15 @@ static void mem_avoid_memmap(char *str)
>  		memmap_too_large = true;
>  }
>  
> -
> -/*
> - * handle_mem_memmap will also cover 'mem=' issue in next patch. Will remove
> - * this note later.
> - */
>  static int handle_mem_memmap(void)
>  {
>  	char *args = (char *)get_cmd_line_ptr();
>  	size_t len = strlen((char *)args);
>  	char *tmp_cmdline;
>  	char *param, *val;
> +	u64 mem_size;
>  
> -	if (!strstr(args, "memmap="))
> +	if (!strstr(args, "memmap=") && !strstr(args, "mem="))
>  		return 0;
>  
>  	tmp_cmdline = malloc(len + 1);
> @@ -222,8 +235,20 @@ static int handle_mem_memmap(void)
>  			return -1;
>  		}
>  
> -		if (!strcmp(param, "memmap"))
> +		if (!strcmp(param, "memmap")) {
>  			mem_avoid_memmap(val);
> +		} else if (!strcmp(param, "mem")) {
> +			char *p = val;
> +
> +			if (!strcmp(p, "nopentium"))
> +				continue;
> +			mem_size = memparse(p, &p);
> +			if (mem_size == 0) {
> +				free(tmp_cmdline);
> +				return -EINVAL;
> +			}
> +			mem_limit = mem_size;
> +		}
>  	}
>  
>  	free(tmp_cmdline);
> @@ -460,7 +485,8 @@ static void process_e820_entry(struct boot_e820_entry *entry,
>  {
>  	struct mem_vector region, overlap;
>  	struct slot_area slot_area;
> -	unsigned long start_orig;
> +	unsigned long start_orig, end;
> +	struct boot_e820_entry cur_entry;
>  
>  	/* Skip non-RAM entries. */
>  	if (entry->type != E820_TYPE_RAM)
> @@ -474,8 +500,15 @@ static void process_e820_entry(struct boot_e820_entry *entry,
>  	if (entry->addr + entry->size < minimum)
>  		return;
>  
> -	region.start = entry->addr;
> -	region.size = entry->size;
> +	/* Ignore entries above memory limit */
> +	end = min(entry->size + entry->addr, mem_limit);
> +	if (entry->addr >= end)
> +		return;
> +	cur_entry.addr = entry->addr;
> +	cur_entry.size = end - entry->addr;
> +
> +	region.start = cur_entry.addr;
> +	region.size = cur_entry.size;
>  
>  	/* Give up if slot area array is full. */
>  	while (slot_area_index < MAX_SLOT_AREA) {
> @@ -489,7 +522,7 @@ static void process_e820_entry(struct boot_e820_entry *entry,
>  		region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
>  
>  		/* Did we raise the address above this e820 region? */
> -		if (region.start > entry->addr + entry->size)
> +		if (region.start > cur_entry.addr + cur_entry.size)
>  			return;
>  
>  		/* Reduce size by any delta from the original address. */
> -- 
> 2.5.5
> 

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#1640201 — Re: [PATCH v4 2/3] KASLR: Handle memory limit specified by memmap and mem option

On 05/12/17 at 01:15pm, Masayoshi Mizuma wrote:
> Hi Baoquan,
> 
> Thank you for fixing!
> I confirmed that the kernel is located within mem= address.
> 
> Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>

Thanks for your testing!

I will post v5 according to comments from Thomas and Kees. Since no
functionality code change, will add your Tested-by.

Thanks
Baoquan

> 
> On Tue, 9 May 2017 13:57:51 +0800 Baoquan He wrote:
> 
> > Option mem= will limit the max address a system can use and any memory
> > region above the limit will be removed.
> > 
> > Furthermore, memmap=nn[KMG] which has no offset specified has the same
> > behaviour as mem=.
> > 
> > KASLR needs to consider this when choosing the random position for
> > decompressing the kernel.
> > 
> > This patch implements that.
> > 
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > ---
> >  arch/x86/boot/compressed/kaslr.c | 69 +++++++++++++++++++++++++++++-----------
> >  1 file changed, 51 insertions(+), 18 deletions(-)
> > 
> > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> > index 106e13b..0637e85 100644
> > --- a/arch/x86/boot/compressed/kaslr.c
> > +++ b/arch/x86/boot/compressed/kaslr.c
> > @@ -88,6 +88,10 @@ struct mem_vector {
> >  static bool memmap_too_large;
> >  
> >  
> > +/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
> > +unsigned long long mem_limit = ULLONG_MAX;
> > +
> > +
> >  enum mem_avoid_index {
> >  	MEM_AVOID_ZO_RANGE = 0,
> >  	MEM_AVOID_INITRD,
> > @@ -138,16 +142,24 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
> >  		return -EINVAL;
> >  
> >  	switch (*p) {
> > -	case '@':
> > -		/* Skip this region, usable */
> > -		*start = 0;
> > -		*size = 0;
> > -		return 0;
> >  	case '#':
> >  	case '$':
> >  	case '!':
> >  		*start = memparse(p + 1, &p);
> >  		return 0;
> > +	case '@':	/* Fall through: */
> > +		/*
> > +		 * memmap=nn@ss specifies usable region, should be skipped
> > +		 */
> > +		*size = 0;
> > +	default:
> > +		/*
> > +		 * If w/o offset, only size specified, memmap=nn[KMG] has the
> > +		 * same behaviour as mem=nn[KMG]. It limits the max address
> > +		 * system can use. Region above the limit should be avoided.
> > +		 */
> > +		*start = 0;
> > +		return 0;
> >  	}
> >  
> >  	return -EINVAL;
> > @@ -173,9 +185,14 @@ static void mem_avoid_memmap(char *str)
> >  		if (rc < 0)
> >  			break;
> >  		str = k;
> > -		/* A usable region that should not be skipped */
> > -		if (size == 0)
> > +
> > +		if (start == 0) {
> > +			/* Store the specified memory limit if size > 0 */
> > +			if (size > 0)
> > +				mem_limit = size;
> > +
> >  			continue;
> > +		}
> >  
> >  		mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start;
> >  		mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size;
> > @@ -187,19 +204,15 @@ static void mem_avoid_memmap(char *str)
> >  		memmap_too_large = true;
> >  }
> >  
> > -
> > -/*
> > - * handle_mem_memmap will also cover 'mem=' issue in next patch. Will remove
> > - * this note later.
> > - */
> >  static int handle_mem_memmap(void)
> >  {
> >  	char *args = (char *)get_cmd_line_ptr();
> >  	size_t len = strlen((char *)args);
> >  	char *tmp_cmdline;
> >  	char *param, *val;
> > +	u64 mem_size;
> >  
> > -	if (!strstr(args, "memmap="))
> > +	if (!strstr(args, "memmap=") && !strstr(args, "mem="))
> >  		return 0;
> >  
> >  	tmp_cmdline = malloc(len + 1);
> > @@ -222,8 +235,20 @@ static int handle_mem_memmap(void)
> >  			return -1;
> >  		}
> >  
> > -		if (!strcmp(param, "memmap"))
> > +		if (!strcmp(param, "memmap")) {
> >  			mem_avoid_memmap(val);
> > +		} else if (!strcmp(param, "mem")) {
> > +			char *p = val;
> > +
> > +			if (!strcmp(p, "nopentium"))
> > +				continue;
> > +			mem_size = memparse(p, &p);
> > +			if (mem_size == 0) {
> > +				free(tmp_cmdline);
> > +				return -EINVAL;
> > +			}
> > +			mem_limit = mem_size;
> > +		}
> >  	}
> >  
> >  	free(tmp_cmdline);
> > @@ -460,7 +485,8 @@ static void process_e820_entry(struct boot_e820_entry *entry,
> >  {
> >  	struct mem_vector region, overlap;
> >  	struct slot_area slot_area;
> > -	unsigned long start_orig;
> > +	unsigned long start_orig, end;
> > +	struct boot_e820_entry cur_entry;
> >  
> >  	/* Skip non-RAM entries. */
> >  	if (entry->type != E820_TYPE_RAM)
> > @@ -474,8 +500,15 @@ static void process_e820_entry(struct boot_e820_entry *entry,
> >  	if (entry->addr + entry->size < minimum)
> >  		return;
> >  
> > -	region.start = entry->addr;
> > -	region.size = entry->size;
> > +	/* Ignore entries above memory limit */
> > +	end = min(entry->size + entry->addr, mem_limit);
> > +	if (entry->addr >= end)
> > +		return;
> > +	cur_entry.addr = entry->addr;
> > +	cur_entry.size = end - entry->addr;
> > +
> > +	region.start = cur_entry.addr;
> > +	region.size = cur_entry.size;
> >  
> >  	/* Give up if slot area array is full. */
> >  	while (slot_area_index < MAX_SLOT_AREA) {
> > @@ -489,7 +522,7 @@ static void process_e820_entry(struct boot_e820_entry *entry,
> >  		region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
> >  
> >  		/* Did we raise the address above this e820 region? */
> > -		if (region.start > entry->addr + entry->size)
> > +		if (region.start > cur_entry.addr + cur_entry.size)
> >  			return;
> >  
> >  		/* Reduce size by any delta from the original address. */
> > -- 
> > 2.5.5
> > 
> 

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