Re: [PATCH 2/4] KASLR: Parse all memmap entries in cmdline

[Baoquan He]

On 04/18/17 at 04:32pm, Kees Cook wrote:
> On Tue, Apr 18, 2017 at 3:52 PM, Baoquan He  wrote:
> > On 04/18/17 at 01:22pm, Kees Cook wrote:
> >> > +#define COMMAND_LINE_SIZE 256
> >> > +static int handle_mem_memmap(void)
> >> > +{
> >> > +   char *args = (char *)get_cmd_line_ptr();
> >> > +   char tmp_cmdline[COMMAND_LINE_SIZE];
> >>
> >> Can't this use a dynamic allocation instead of the 256 limit?
> >
> > This is in boot/compressed code, no mm allocator built yet? Am I right?
> 
> misc.c uses malloc for phdrs, and the boot_heap is create to build an
> area for those calls, see include/linux/decompress/mm.h. I *think* it
> should be safe to use malloc here. It should be a pretty small
> allocation normally.

Yes, didn't notice this. Will use it to do dynamic malloc.
Thanks for telling!

Re: [PATCH 2/4] KASLR: Parse all memmap entries in cmdline

[Baoquan He]

On 04/18/17 at 04:32pm, Kees Cook wrote:
> On Tue, Apr 18, 2017 at 3:52 PM, Baoquan He  wrote:
> > On 04/18/17 at 01:22pm, Kees Cook wrote:
> >> > +#define COMMAND_LINE_SIZE 256
> >> > +static int handle_mem_memmap(void)
> >> > +{
> >> > +   char *args = (char *)get_cmd_line_ptr();
> >> > +   char tmp_cmdline[COMMAND_LINE_SIZE];
> >>
> >> Can't this use a dynamic allocation instead of the 256 limit?
> >
> > This is in boot/compressed code, no mm allocator built yet? Am I right?
> 
> misc.c uses malloc for phdrs, and the boot_heap is create to build an
> area for those calls, see include/linux/decompress/mm.h. I *think* it
> should be safe to use malloc here. It should be a pretty small
> allocation normally.

Yes, didn't notice this. Will use it to do dynamic malloc.
Thanks for telling!

Re: [PATCH 2/4] KASLR: Parse all memmap entries in cmdline

[Kees Cook]

On Tue, Apr 18, 2017 at 3:52 PM, Baoquan He  wrote:
> On 04/18/17 at 01:22pm, Kees Cook wrote:
>> > +#define COMMAND_LINE_SIZE 256
>> > +static int handle_mem_memmap(void)
>> > +{
>> > +   char *args = (char *)get_cmd_line_ptr();
>> > +   char tmp_cmdline[COMMAND_LINE_SIZE];
>>
>> Can't this use a dynamic allocation instead of the 256 limit?
>
> This is in boot/compressed code, no mm allocator built yet? Am I right?

misc.c uses malloc for phdrs, and the boot_heap is create to build an
area for those calls, see include/linux/decompress/mm.h. I *think* it
should be safe to use malloc here. It should be a pretty small
allocation normally.

-Kees

-- 
Kees Cook
Pixel Security

Re: [PATCH 2/4] KASLR: Parse all memmap entries in cmdline

[Kees Cook]

On Tue, Apr 18, 2017 at 3:52 PM, Baoquan He  wrote:
> On 04/18/17 at 01:22pm, Kees Cook wrote:
>> > +#define COMMAND_LINE_SIZE 256
>> > +static int handle_mem_memmap(void)
>> > +{
>> > +   char *args = (char *)get_cmd_line_ptr();
>> > +   char tmp_cmdline[COMMAND_LINE_SIZE];
>>
>> Can't this use a dynamic allocation instead of the 256 limit?
>
> This is in boot/compressed code, no mm allocator built yet? Am I right?

misc.c uses malloc for phdrs, and the boot_heap is create to build an
area for those calls, see include/linux/decompress/mm.h. I *think* it
should be safe to use malloc here. It should be a pretty small
allocation normally.

-Kees

-- 
Kees Cook
Pixel Security

Re: [PATCH 2/4] KASLR: Parse all memmap entries in cmdline

[Baoquan He]

Hi Kees,

Thanks for your reviewing!

On 04/18/17 at 01:22pm, Kees Cook wrote:

> >  static int
> >  parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
> > @@ -142,40 +112,33 @@ parse_memmap(char *p, unsigned long long *start, 
> > unsigned long long *size)
> > return -EINVAL;
> >
> > oldp = p;
> > -   *size = _memparse(p, );
> > +   *size = memparse(p, );
> > if (p == oldp)
> > return -EINVAL;
> >
> > switch (*p) {
> > case '@':
> > /* Skip this region, usable */
> > -   *start = 0;
> > *size = 0;
> > -   return 0;
> > +   *start = 0;
> 
> Is this intentionally falling through? If so, why assign *start at all?

OOPS, this is a mistake when I split patch. Here it should not be
changed in this patch though code change is OK with patch 3/4 together.

Will change that.

> 
> > case '#':
> > case '$':
> > case '!':
> > -   *start = _memparse(p + 1, );
> > +   *start = memparse(p + 1, );
> > return 0;
> > }
> >
> > return -EINVAL;
> >  }
> >
> > -static void mem_avoid_memmap(void)
> > +static void mem_avoid_memmap(char *str)
> >  {
> > -   char arg[128];
> > int rc;
> > -   int i;
> > -   char *str;
> > +   int i = mem_avoid_memmap_index;
> >
> > -   /* See if we have any memmap areas */
> > -   rc = cmdline_find_option("memmap", arg, sizeof(arg));
> > -   if (rc <= 0)
> > +   if (i >= MAX_MEMMAP_REGIONS)
> > return;
> >
> > -   i = 0;
> > -   str = arg;
> > while (str && (i < MAX_MEMMAP_REGIONS)) {
> > int rc;
> > unsigned long long start, size;
> > @@ -196,12 +159,49 @@ static void mem_avoid_memmap(void)
> > mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size;
> > i++;
> > }
> > +   mem_avoid_memmap_index = i;
> >
> > /* More than 4 memmaps, fail kaslr */
> > if ((i >= MAX_MEMMAP_REGIONS) && str)
> > memmap_too_large = true;
> >  }
> >
> > +#define COMMAND_LINE_SIZE 256
> > +static int handle_mem_memmap(void)
> > +{
> > +   char *args = (char *)get_cmd_line_ptr();
> > +   char tmp_cmdline[COMMAND_LINE_SIZE];
> 
> Can't this use a dynamic allocation instead of the 256 limit?

This is in boot/compressed code, no mm allocator built yet? Am I right?

> 
> > +   size_t len = strlen((char *)args);
> > +   char *param, *val;
> > +
> > +   len = (len >= COMMAND_LINE_SIZE) ? COMMAND_LINE_SIZE - 1 : len;
> > +   memcpy(tmp_cmdline, args, len);
> > +   tmp_cmdline[len] = 0;
> > +   args = tmp_cmdline;
> > +
> > +   /* Chew leading spaces */
> > +   args = skip_spaces(args);
> > +
> > +   while (*args) {
> > +   int ret;
> > +
> > +   debug_putstr(args);
> > +   debug_putstr("\n");
> 
> Are these accidentally left over?

Yes, it's for debugging. Will remove.

Thanks
Baoquan

> 
> > +
> > +   args = next_arg(args, , );
> > +   /* Stop at -- */
> > +   if (!val && strcmp(param, "--") == 0) {
> > +   warn("Only '--' specified in cmdline");
> > +   return -1;
> > +   }
> > +
> > +   if (!strcmp(param, "memmap"))
> > +   mem_avoid_memmap(val);
> > +   }
> > +
> > +   return 0;
> > +}
> > +
> >  /*
> >   * In theory, KASLR can put the kernel anywhere in the range of [16M, 64T).
> >   * The mem_avoid array is used to store the ranges that need to be avoided
> > @@ -323,7 +323,7 @@ static void mem_avoid_init(unsigned long input, 
> > unsigned long input_size,
> > /* We don't need to set a mapping for setup_data. */
> >
> > /* Mark the memmap regions we need to avoid */
> > -   mem_avoid_memmap();
> > +   handle_mem_memmap();
> >
> >  #ifdef CONFIG_X86_VERBOSE_BOOTUP
> > /* Make sure video RAM can be used. */
> > diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c
> > index 5457b02..630e366 100644
> > --- a/arch/x86/boot/string.c
> > +++ b/arch/x86/boot/string.c
> > @@ -122,6 +122,14 @@ unsigned long long simple_strtoull(const char *cp, 
> > char **endp, unsigned int bas
> > return result;
> >  }
> >
> > +long simple_strtol(const char *cp, char **endp, unsigned int base)
> > +{
> > +   if (*cp == '-')
> > +   return -simple_strtoull(cp + 1, endp, base);
> > +
> > +   return simple_strtoull(cp, endp, base);
> > +}
> > +
> >  /**
> >   * strlen - Find the length of a string
> >   * @s: The string to be sized
> > --
> > 2.5.5
> >
> 
> Otherwise, yeah, this looks sensible.
> 
> -Kees
> 
> -- 
> Kees Cook
> Pixel Security

Re: [PATCH 2/4] KASLR: Parse all memmap entries in cmdline

[Baoquan He]

Hi Kees,

Thanks for your reviewing!

On 04/18/17 at 01:22pm, Kees Cook wrote:

> >  static int
> >  parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
> > @@ -142,40 +112,33 @@ parse_memmap(char *p, unsigned long long *start, 
> > unsigned long long *size)
> > return -EINVAL;
> >
> > oldp = p;
> > -   *size = _memparse(p, );
> > +   *size = memparse(p, );
> > if (p == oldp)
> > return -EINVAL;
> >
> > switch (*p) {
> > case '@':
> > /* Skip this region, usable */
> > -   *start = 0;
> > *size = 0;
> > -   return 0;
> > +   *start = 0;
> 
> Is this intentionally falling through? If so, why assign *start at all?

OOPS, this is a mistake when I split patch. Here it should not be
changed in this patch though code change is OK with patch 3/4 together.

Will change that.

> 
> > case '#':
> > case '$':
> > case '!':
> > -   *start = _memparse(p + 1, );
> > +   *start = memparse(p + 1, );
> > return 0;
> > }
> >
> > return -EINVAL;
> >  }
> >
> > -static void mem_avoid_memmap(void)
> > +static void mem_avoid_memmap(char *str)
> >  {
> > -   char arg[128];
> > int rc;
> > -   int i;
> > -   char *str;
> > +   int i = mem_avoid_memmap_index;
> >
> > -   /* See if we have any memmap areas */
> > -   rc = cmdline_find_option("memmap", arg, sizeof(arg));
> > -   if (rc <= 0)
> > +   if (i >= MAX_MEMMAP_REGIONS)
> > return;
> >
> > -   i = 0;
> > -   str = arg;
> > while (str && (i < MAX_MEMMAP_REGIONS)) {
> > int rc;
> > unsigned long long start, size;
> > @@ -196,12 +159,49 @@ static void mem_avoid_memmap(void)
> > mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size;
> > i++;
> > }
> > +   mem_avoid_memmap_index = i;
> >
> > /* More than 4 memmaps, fail kaslr */
> > if ((i >= MAX_MEMMAP_REGIONS) && str)
> > memmap_too_large = true;
> >  }
> >
> > +#define COMMAND_LINE_SIZE 256
> > +static int handle_mem_memmap(void)
> > +{
> > +   char *args = (char *)get_cmd_line_ptr();
> > +   char tmp_cmdline[COMMAND_LINE_SIZE];
> 
> Can't this use a dynamic allocation instead of the 256 limit?

This is in boot/compressed code, no mm allocator built yet? Am I right?

> 
> > +   size_t len = strlen((char *)args);
> > +   char *param, *val;
> > +
> > +   len = (len >= COMMAND_LINE_SIZE) ? COMMAND_LINE_SIZE - 1 : len;
> > +   memcpy(tmp_cmdline, args, len);
> > +   tmp_cmdline[len] = 0;
> > +   args = tmp_cmdline;
> > +
> > +   /* Chew leading spaces */
> > +   args = skip_spaces(args);
> > +
> > +   while (*args) {
> > +   int ret;
> > +
> > +   debug_putstr(args);
> > +   debug_putstr("\n");
> 
> Are these accidentally left over?

Yes, it's for debugging. Will remove.

Thanks
Baoquan

> 
> > +
> > +   args = next_arg(args, , );
> > +   /* Stop at -- */
> > +   if (!val && strcmp(param, "--") == 0) {
> > +   warn("Only '--' specified in cmdline");
> > +   return -1;
> > +   }
> > +
> > +   if (!strcmp(param, "memmap"))
> > +   mem_avoid_memmap(val);
> > +   }
> > +
> > +   return 0;
> > +}
> > +
> >  /*
> >   * In theory, KASLR can put the kernel anywhere in the range of [16M, 64T).
> >   * The mem_avoid array is used to store the ranges that need to be avoided
> > @@ -323,7 +323,7 @@ static void mem_avoid_init(unsigned long input, 
> > unsigned long input_size,
> > /* We don't need to set a mapping for setup_data. */
> >
> > /* Mark the memmap regions we need to avoid */
> > -   mem_avoid_memmap();
> > +   handle_mem_memmap();
> >
> >  #ifdef CONFIG_X86_VERBOSE_BOOTUP
> > /* Make sure video RAM can be used. */
> > diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c
> > index 5457b02..630e366 100644
> > --- a/arch/x86/boot/string.c
> > +++ b/arch/x86/boot/string.c
> > @@ -122,6 +122,14 @@ unsigned long long simple_strtoull(const char *cp, 
> > char **endp, unsigned int bas
> > return result;
> >  }
> >
> > +long simple_strtol(const char *cp, char **endp, unsigned int base)
> > +{
> > +   if (*cp == '-')
> > +   return -simple_strtoull(cp + 1, endp, base);
> > +
> > +   return simple_strtoull(cp, endp, base);
> > +}
> > +
> >  /**
> >   * strlen - Find the length of a string
> >   * @s: The string to be sized
> > --
> > 2.5.5
> >
> 
> Otherwise, yeah, this looks sensible.
> 
> -Kees
> 
> -- 
> Kees Cook
> Pixel Security

Re: [PATCH 2/4] KASLR: Parse all memmap entries in cmdline

[Kees Cook]

On Mon, Apr 17, 2017 at 6:34 AM, Baoquan He  wrote:
> In commit f28442497b5c ("x86/boot: Fix KASLR and memmap= collision"),
> memmap= option is parsed so that kaslr can avoid those reserved
> regions. It uses cmdline_find_option to get the value if memmap=
> is specified, however the problem is cmdline_find_option can only
> find the last entry if multiple memmap entries are provided. This
> is not correct.
>
> In this patch, the whole cmdline will be scanned to search each
> memmap, all of them will be parsed and handled.
>
> Signed-off-by: Baoquan He 
> Cc: "H. Peter Anvin" 
> Cc: Thomas Gleixner 
> Cc: Ingo Molnar 
> Cc: x...@kernel.org
> Cc: Kees Cook 
> Cc: Baoquan He 
> Cc: Yinghai Lu 
> Cc: Borislav Petkov 
> ---
>  arch/x86/boot/compressed/cmdline.c |   2 +-
>  arch/x86/boot/compressed/kaslr.c   | 112 
> ++---
>  arch/x86/boot/string.c |   8 +++
>  3 files changed, 65 insertions(+), 57 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/cmdline.c 
> b/arch/x86/boot/compressed/cmdline.c
> index 73ccf63..9dc1ce6 100644
> --- a/arch/x86/boot/compressed/cmdline.c
> +++ b/arch/x86/boot/compressed/cmdline.c
> @@ -13,7 +13,7 @@ static inline char rdfs8(addr_t addr)
> return *((char *)(fs + addr));
>  }
>  #include "../cmdline.c"
> -static unsigned long get_cmd_line_ptr(void)
> +unsigned long get_cmd_line_ptr(void)
>  {
> unsigned long cmd_line_ptr = boot_params->hdr.cmd_line_ptr;
>
> diff --git a/arch/x86/boot/compressed/kaslr.c 
> b/arch/x86/boot/compressed/kaslr.c
> index 8b7c9e7..36ab429 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -9,14 +9,16 @@
>   * contain the entire properly aligned running kernel image.
>   *
>   */
> +
> +#define BOOT_CTYPE_H
>  #include "misc.h"
>  #include "error.h"
> -#include "../boot.h"
>
>  #include 
>  #include 
>  #include 
>  #include 
> +#include 
>  #include 
>
>  /* Simplified build-specific string for starting entropy. */
> @@ -61,6 +63,9 @@ struct mem_vector {
>  #define MAX_MEMMAP_REGIONS 4
>
>  static bool memmap_too_large;
> +int mem_avoid_memmap_index;
> +extern unsigned long get_cmd_line_ptr(void);
> +
>
>  enum mem_avoid_index {
> MEM_AVOID_ZO_RANGE = 0,
> @@ -85,49 +90,14 @@ static bool mem_overlaps(struct mem_vector *one, struct 
> mem_vector *two)
> return true;
>  }
>
> -/**
> - * _memparse - Parse a string with mem suffixes into a number
> - * @ptr: Where parse begins
> - * @retptr: (output) Optional pointer to next char after parse completes
> - *
> - * Parses a string into a number.  The number stored at @ptr is
> - * potentially suffixed with K, M, G, T, P, E.
> - */
> -static unsigned long long _memparse(const char *ptr, char **retptr)
> +char *skip_spaces(const char *str)
>  {
> -   char *endptr;   /* Local pointer to end of parsed string */
> -
> -   unsigned long long ret = simple_strtoull(ptr, , 0);
> -
> -   switch (*endptr) {
> -   case 'E':
> -   case 'e':
> -   ret <<= 10;
> -   case 'P':
> -   case 'p':
> -   ret <<= 10;
> -   case 'T':
> -   case 't':
> -   ret <<= 10;
> -   case 'G':
> -   case 'g':
> -   ret <<= 10;
> -   case 'M':
> -   case 'm':
> -   ret <<= 10;
> -   case 'K':
> -   case 'k':
> -   ret <<= 10;
> -   endptr++;
> -   default:
> -   break;
> -   }
> -
> -   if (retptr)
> -   *retptr = endptr;
> -
> -   return ret;
> +   while (isspace(*str))
> +   ++str;
> +   return (char *)str;
>  }
> +#include "../../../../lib/ctype.c"
> +#include "../../../../lib/cmdline.c"
>
>  static int
>  parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
> @@ -142,40 +112,33 @@ parse_memmap(char *p, unsigned long long *start, 
> unsigned long long *size)
> return -EINVAL;
>
> oldp = p;
> -   *size = _memparse(p, );
> +   *size = memparse(p, );
> if (p == oldp)
> return -EINVAL;
>
> switch (*p) {
> case '@':
> /* Skip this region, usable */
> -   *start = 0;
> *size = 0;
> -   return 0;
> +   *start = 0;

Is this intentionally falling through? If so, why assign *start at all?

> case '#':
> case '$':
> case '!':
> -   *start = _memparse(p + 1, );
> +   *start = memparse(p + 1, );
> return 0;
> }
>
> return -EINVAL;
>  }
>
> -static void mem_avoid_memmap(void)
> +static void mem_avoid_memmap(char *str)
>  {
> -   char arg[128];
> int rc;
> -   int i;
> -   char *str;
> +   

Re: [PATCH 2/4] KASLR: Parse all memmap entries in cmdline

[Kees Cook]

On Mon, Apr 17, 2017 at 6:34 AM, Baoquan He  wrote:
> In commit f28442497b5c ("x86/boot: Fix KASLR and memmap= collision"),
> memmap= option is parsed so that kaslr can avoid those reserved
> regions. It uses cmdline_find_option to get the value if memmap=
> is specified, however the problem is cmdline_find_option can only
> find the last entry if multiple memmap entries are provided. This
> is not correct.
>
> In this patch, the whole cmdline will be scanned to search each
> memmap, all of them will be parsed and handled.
>
> Signed-off-by: Baoquan He 
> Cc: "H. Peter Anvin" 
> Cc: Thomas Gleixner 
> Cc: Ingo Molnar 
> Cc: x...@kernel.org
> Cc: Kees Cook 
> Cc: Baoquan He 
> Cc: Yinghai Lu 
> Cc: Borislav Petkov 
> ---
>  arch/x86/boot/compressed/cmdline.c |   2 +-
>  arch/x86/boot/compressed/kaslr.c   | 112 
> ++---
>  arch/x86/boot/string.c |   8 +++
>  3 files changed, 65 insertions(+), 57 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/cmdline.c 
> b/arch/x86/boot/compressed/cmdline.c
> index 73ccf63..9dc1ce6 100644
> --- a/arch/x86/boot/compressed/cmdline.c
> +++ b/arch/x86/boot/compressed/cmdline.c
> @@ -13,7 +13,7 @@ static inline char rdfs8(addr_t addr)
> return *((char *)(fs + addr));
>  }
>  #include "../cmdline.c"
> -static unsigned long get_cmd_line_ptr(void)
> +unsigned long get_cmd_line_ptr(void)
>  {
> unsigned long cmd_line_ptr = boot_params->hdr.cmd_line_ptr;
>
> diff --git a/arch/x86/boot/compressed/kaslr.c 
> b/arch/x86/boot/compressed/kaslr.c
> index 8b7c9e7..36ab429 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -9,14 +9,16 @@
>   * contain the entire properly aligned running kernel image.
>   *
>   */
> +
> +#define BOOT_CTYPE_H
>  #include "misc.h"
>  #include "error.h"
> -#include "../boot.h"
>
>  #include 
>  #include 
>  #include 
>  #include 
> +#include 
>  #include 
>
>  /* Simplified build-specific string for starting entropy. */
> @@ -61,6 +63,9 @@ struct mem_vector {
>  #define MAX_MEMMAP_REGIONS 4
>
>  static bool memmap_too_large;
> +int mem_avoid_memmap_index;
> +extern unsigned long get_cmd_line_ptr(void);
> +
>
>  enum mem_avoid_index {
> MEM_AVOID_ZO_RANGE = 0,
> @@ -85,49 +90,14 @@ static bool mem_overlaps(struct mem_vector *one, struct 
> mem_vector *two)
> return true;
>  }
>
> -/**
> - * _memparse - Parse a string with mem suffixes into a number
> - * @ptr: Where parse begins
> - * @retptr: (output) Optional pointer to next char after parse completes
> - *
> - * Parses a string into a number.  The number stored at @ptr is
> - * potentially suffixed with K, M, G, T, P, E.
> - */
> -static unsigned long long _memparse(const char *ptr, char **retptr)
> +char *skip_spaces(const char *str)
>  {
> -   char *endptr;   /* Local pointer to end of parsed string */
> -
> -   unsigned long long ret = simple_strtoull(ptr, , 0);
> -
> -   switch (*endptr) {
> -   case 'E':
> -   case 'e':
> -   ret <<= 10;
> -   case 'P':
> -   case 'p':
> -   ret <<= 10;
> -   case 'T':
> -   case 't':
> -   ret <<= 10;
> -   case 'G':
> -   case 'g':
> -   ret <<= 10;
> -   case 'M':
> -   case 'm':
> -   ret <<= 10;
> -   case 'K':
> -   case 'k':
> -   ret <<= 10;
> -   endptr++;
> -   default:
> -   break;
> -   }
> -
> -   if (retptr)
> -   *retptr = endptr;
> -
> -   return ret;
> +   while (isspace(*str))
> +   ++str;
> +   return (char *)str;
>  }
> +#include "../../../../lib/ctype.c"
> +#include "../../../../lib/cmdline.c"
>
>  static int
>  parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
> @@ -142,40 +112,33 @@ parse_memmap(char *p, unsigned long long *start, 
> unsigned long long *size)
> return -EINVAL;
>
> oldp = p;
> -   *size = _memparse(p, );
> +   *size = memparse(p, );
> if (p == oldp)
> return -EINVAL;
>
> switch (*p) {
> case '@':
> /* Skip this region, usable */
> -   *start = 0;
> *size = 0;
> -   return 0;
> +   *start = 0;

Is this intentionally falling through? If so, why assign *start at all?

> case '#':
> case '$':
> case '!':
> -   *start = _memparse(p + 1, );
> +   *start = memparse(p + 1, );
> return 0;
> }
>
> return -EINVAL;
>  }
>
> -static void mem_avoid_memmap(void)
> +static void mem_avoid_memmap(char *str)
>  {
> -   char arg[128];
> int rc;
> -   int i;
> -   char *str;
> +   int i = mem_avoid_memmap_index;
>
> -   /* See if we have any memmap areas */
> -   rc = cmdline_find_option("memmap", arg, sizeof(arg));
> -   if (rc