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Date: Fri, 6 Jan 2017 10:44:39 +0800 From: Baoquan He <bhe@...hat.com> To: Dave Jiang <dave.jiang@...el.com>, keescook@...omium.org Cc: tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, linux-nvdimm@...1.01.org, x86@...nel.org, david@...morbit.com, linux-kernel@...r.kernel.org, dan.j.williams@...el.com Subject: Re: [PATCH v5] x86: fix kaslr and memmap collision Add Kees to let him have a look at this too. On 01/05/17 at 05:21pm, Baoquan He wrote: > On 01/04/17 at 11:29am, Dave Jiang wrote: > > CONFIG_RANDOMIZE_BASE relocates the kernel to a random base address. > > However it does not take into account the memmap= parameter passed in from > > the kernel cmdline. This results in the kernel sometimes being put in > > the middle of memmap. Teaching kaslr to not insert the kernel in > > memmap defined regions. We will support up to 4 memmap regions. Any > > additional regions will cause kaslr to disable. The mem_avoid set has > > been augmented to add up to 4 unusable regions of memmaps provided by the > > user to exclude those regions from the set of valid address range to insert > > the uncompressed kernel image. The nn@ss ranges will be skipped by the > > mem_avoid set since it indicates memory useable. > > > > Signed-off-by: Dave Jiang <dave.jiang@...el.com> > > --- > > > > v2: > > Addressing comments from Ingo. > > - Handle entire list of memmaps > > v3: > > Fix 32bit build issue > > v4: > > Addressing comments from Baoquan > > - Not exclude nn@ss ranges > > v5: > > Addressing additional comments from Baoquan > > - Update commit header and various coding style changes > > > > diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h > > index e5612f3..59c2075 100644 > > --- a/arch/x86/boot/boot.h > > +++ b/arch/x86/boot/boot.h > > @@ -332,7 +332,10 @@ int strncmp(const char *cs, const char *ct, size_t count); > > size_t strnlen(const char *s, size_t maxlen); > > unsigned int atou(const char *s); > > unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base); > > +unsigned long simple_strtoul(const char *cp, char **endp, unsigned int base); > > +long simple_strtol(const char *cp, char **endp, unsigned int base); > > size_t strlen(const char *s); > > +char *strchr(const char *s, int c); > > > > /* tty.c */ > > void puts(const char *); > > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c > > index a66854d..036b514 100644 > > --- a/arch/x86/boot/compressed/kaslr.c > > +++ b/arch/x86/boot/compressed/kaslr.c > > @@ -11,6 +11,7 @@ > > */ > > #include "misc.h" > > #include "error.h" > > +#include "../boot.h" > > > > #include <generated/compile.h> > > #include <linux/module.h> > > @@ -56,11 +57,16 @@ struct mem_vector { > > unsigned long size; > > }; > > > > +/* only supporting at most 4 unusable memmap regions with kaslr */ > > +#define MAX_MEMMAP_REGIONS 4 > > + > > enum mem_avoid_index { > > MEM_AVOID_ZO_RANGE = 0, > > MEM_AVOID_INITRD, > > MEM_AVOID_CMDLINE, > > MEM_AVOID_BOOTPARAMS, > > + MEM_AVOID_MEMMAP_BEGIN, > > + MEM_AVOID_MEMMAP_END = MEM_AVOID_MEMMAP_BEGIN + MAX_MEMMAP_REGIONS - 1, > > MEM_AVOID_MAX, > > }; > > > > @@ -77,6 +83,121 @@ 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 *endptr; /* local pointer to end of parsed string */ > > + > > + unsigned long long ret = simple_strtoull(ptr, &endptr, 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; > > +} > > + > > +static int > > +parse_memmap(char *p, unsigned long long *start, unsigned long long *size) > > +{ > > + char *oldp; > > + > > + if (!p) > > + return -EINVAL; > > + > > + /* we don't care about this option here */ > > + if (!strncmp(p, "exactmap", 8)) > > + return -EINVAL; > > + > > + oldp = p; > > + *size = _memparse(p, &p); > > + if (p == oldp) > > + 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; > > + } > > + > > + return -EINVAL; > > +} > > + > > +static int mem_avoid_memmap(void) > > +{ > > + char arg[128]; > > + int rc = 0; > > + > > + /* see if we have any memmap areas */ > > + if (cmdline_find_option("memmap", arg, sizeof(arg)) > 0) { > > + int i = 0; > > + char *str = arg; > > + > > + while (str && (i < MAX_MEMMAP_REGIONS)) { > > + unsigned long long start, size; > > + char *k = strchr(str, ','); > > + > > + if (k) > > + *k++ = 0; > > + > > + rc = parse_memmap(str, &start, &size); > > + if (rc < 0) > > + break; > > + str = k; > > + /* a usable region that should not be skipped */ > > + if (size == 0) > > + continue; > > + > > + mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start; > > + mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size; > > + i++; > > + } > > + > > + /* more than 4 memmaps, fail kaslr */ > > + if ((i >= MAX_MEMMAP_REGIONS) && str) > > + rc = -EINVAL; > > + } > > + > > + return rc; > > +} > > + > > /* > > * 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 > > @@ -438,6 +559,12 @@ void choose_random_location(unsigned long input, > > return; > > } > > > > + /* Mark the memmap regions we need to avoid */ > > + if (mem_avoid_memmap()) { > > + warn("KASLR disabled: memmap exceeds limit of 4, giving up."); > > + return; > > + } > > theoretically, mem_avoid_memmap is doing the mem_avoid initialization > job, should be called inside mem_avoid_init(). The reason you put it > here is you want to make it cancel kaslr, both physical and virtual > address randomization, right? > > In choose_random_location(), the physical and virtual random are done > separately. You can see that later when find_random_phys_addr failed to > find a suitable random slot, it just prints a warning, virtual > randomization is still be done with calling find_random_virt_addr(). > Avoiding memmap reserved region should be physical ram issue, should we > stop the kernel virtual address randomization either? > > Kees, what do you think about this? > > > + > > boot_params->hdr.loadflags |= KASLR_FLAG; > > > > /* Prepare to add new identity pagetables on demand. */ > > diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c > > index cc3bd58..0464aaa 100644 > > --- a/arch/x86/boot/string.c > > +++ b/arch/x86/boot/string.c > > @@ -122,6 +122,31 @@ unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int bas > > } > > > > /** > > + * simple_strtoul - convert a string to an unsigned long > > + * @cp: The start of the string > > + * @endp: A pointer to the end of the parsed string will be placed here > > + * @base: The number base to use > > + */ > > +unsigned long simple_strtoul(const char *cp, char **endp, unsigned int base) > > +{ > > + return simple_strtoull(cp, endp, base); > > +} > > + > > +/** > > + * simple_strtol - convert a string to a signed long > > + * @cp: The start of the string > > + * @endp: A pointer to the end of the parsed string will be placed here > > + * @base: The number base to use > > + */ > > +long simple_strtol(const char *cp, char **endp, unsigned int base) > > +{ > > + if (*cp == '-') > > + return -simple_strtoul(cp + 1, endp, base); > > + > > + return simple_strtoul(cp, endp, base); > > +} > > + > > +/** > > * strlen - Find the length of a string > > * @s: The string to be sized > > */ > > @@ -155,3 +180,16 @@ char *strstr(const char *s1, const char *s2) > > } > > return NULL; > > } > > + > > +/** > > + * strchr - Find the first occurrence of the character c in the string s. > > + * @s: the string to be searched > > + * @c: the character to search for > > + */ > > +char *strchr(const char *s, int c) > > +{ > > + while (*s != (char)c) > > + if (*s++ == '\0') > > + return NULL; > > + return (char *)s; > > +} > >
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