[GIT PULL] x86 fixes

From: Ingo Molnar
Date: Sun Jan 11 2015 - 03:52:15 EST

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Linus,

Please pull the latest x86-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-urgent-for-linus

# HEAD: 2aba73a6146bb85d4a42386ca41dec0f4aa4b3ad Merge tag 'pr-20141223-x86-vdso' of git://git.kernel.org/pub/scm/linux/kernel/git/luto/linux into x86/urgent

Misc fixes: two vdso fixes, two kbuild fixes and a boot failure
fix with certain odd memory mappings.

Thanks,

Ingo

------------------>
Andy Lutomirski (2):
x86_64, vdso: Fix the vdso address randomization algorithm
x86, vdso: Use asm volatile in __getcpu

Bjørn Mork (1):
x86/build: Clean auto-generated processor feature files

Jan Beulich (1):
x86: Fix step size adjustment during initial memory mapping

Sylvain BERTRAND (1):
x86: Fix mkcapflags.sh bash-ism

arch/x86/boot/Makefile | 1 +
arch/x86/include/asm/vgtod.h | 6 ++++--
arch/x86/kernel/cpu/Makefile | 1 +
arch/x86/kernel/cpu/mkcapflags.sh | 2 +-
arch/x86/mm/init.c | 37 +++++++++++++++-----------------
arch/x86/vdso/vma.c | 45 +++++++++++++++++++++++++--------------
6 files changed, 53 insertions(+), 39 deletions(-)

diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index 5b016e2498f3..3db07f30636f 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -51,6 +51,7 @@ targets += cpustr.h
$(obj)/cpustr.h: $(obj)/mkcpustr FORCE
$(call if_changed,cpustr)
endif
+clean-files += cpustr.h

# ---------------------------------------------------------------------------

diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index e7e9682a33e9..f556c4843aa1 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -80,9 +80,11 @@ static inline unsigned int __getcpu(void)

/*
* Load per CPU data from GDT. LSL is faster than RDTSCP and
- * works on all CPUs.
+ * works on all CPUs. This is volatile so that it orders
+ * correctly wrt barrier() and to keep gcc from cleverly
+ * hoisting it out of the calling function.
*/
- asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
+ asm volatile ("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));

return p;
}
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index e27b49d7c922..80091ae54c2b 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -66,3 +66,4 @@ targets += capflags.c
$(obj)/capflags.c: $(cpufeature) $(src)/mkcapflags.sh FORCE
$(call if_changed,mkcapflags)
endif
+clean-files += capflags.c
diff --git a/arch/x86/kernel/cpu/mkcapflags.sh b/arch/x86/kernel/cpu/mkcapflags.sh
index e2b22df964cd..36d99a337b49 100644
--- a/arch/x86/kernel/cpu/mkcapflags.sh
+++ b/arch/x86/kernel/cpu/mkcapflags.sh
@@ -28,7 +28,7 @@ function dump_array()
# If the /* comment */ starts with a quote string, grab that.
VALUE="$(echo "$i" | sed -n 's@.*/\* *$"[^"]*"$.*\*/@\1@p')"
[ -z "$VALUE" ] && VALUE="\"$NAME\""
- [ "$VALUE" == '""' ] && continue
+ [ "$VALUE" = '""' ] && continue

# Name is uppercase, VALUE is all lowercase
VALUE="$(echo "$VALUE" | tr A-Z a-z)"
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index a97ee0801475..08a7d313538a 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -438,20 +438,20 @@ static unsigned long __init init_range_memory_mapping(
static unsigned long __init get_new_step_size(unsigned long step_size)
{
/*
- * Explain why we shift by 5 and why we don't have to worry about
- * 'step_size << 5' overflowing:
- *
- * initial mapped size is PMD_SIZE (2M).
+ * Initial mapped size is PMD_SIZE (2M).
* We can not set step_size to be PUD_SIZE (1G) yet.
* In worse case, when we cross the 1G boundary, and
* PG_LEVEL_2M is not set, we will need 1+1+512 pages (2M + 8k)
- * to map 1G range with PTE. Use 5 as shift for now.
+ * to map 1G range with PTE. Hence we use one less than the
+ * difference of page table level shifts.
*
- * Don't need to worry about overflow, on 32bit, when step_size
- * is 0, round_down() returns 0 for start, and that turns it
- * into 0x100000000ULL.
+ * Don't need to worry about overflow in the top-down case, on 32bit,
+ * when step_size is 0, round_down() returns 0 for start, and that
+ * turns it into 0x100000000ULL.
+ * In the bottom-up case, round_up(x, 0) returns 0 though too, which
+ * needs to be taken into consideration by the code below.
*/
- return step_size << 5;
+ return step_size << (PMD_SHIFT - PAGE_SHIFT - 1);
}

/**
@@ -471,7 +471,6 @@ static void __init memory_map_top_down(unsigned long map_start,
unsigned long step_size;
unsigned long addr;
unsigned long mapped_ram_size = 0;
- unsigned long new_mapped_ram_size;

/* xen has big range in reserved near end of ram, skip it at first.*/
addr = memblock_find_in_range(map_start, map_end, PMD_SIZE, PMD_SIZE);
@@ -496,14 +495,12 @@ static void __init memory_map_top_down(unsigned long map_start,
start = map_start;
} else
start = map_start;
- new_mapped_ram_size = init_range_memory_mapping(start,
+ mapped_ram_size += init_range_memory_mapping(start,
last_start);
last_start = start;
min_pfn_mapped = last_start >> PAGE_SHIFT;
- /* only increase step_size after big range get mapped */
- if (new_mapped_ram_size > mapped_ram_size)
+ if (mapped_ram_size >= step_size)
step_size = get_new_step_size(step_size);
- mapped_ram_size += new_mapped_ram_size;
}

if (real_end < map_end)
@@ -524,7 +521,7 @@ static void __init memory_map_top_down(unsigned long map_start,
static void __init memory_map_bottom_up(unsigned long map_start,
unsigned long map_end)
{
- unsigned long next, new_mapped_ram_size, start;
+ unsigned long next, start;
unsigned long mapped_ram_size = 0;
/* step_size need to be small so pgt_buf from BRK could cover it */
unsigned long step_size = PMD_SIZE;
@@ -539,19 +536,19 @@ static void __init memory_map_bottom_up(unsigned long map_start,
* for page table.
*/
while (start < map_end) {
- if (map_end - start > step_size) {
+ if (step_size && map_end - start > step_size) {
next = round_up(start + 1, step_size);
if (next > map_end)
next = map_end;
- } else
+ } else {
next = map_end;
+ }

- new_mapped_ram_size = init_range_memory_mapping(start, next);
+ mapped_ram_size += init_range_memory_mapping(start, next);
start = next;

- if (new_mapped_ram_size > mapped_ram_size)
+ if (mapped_ram_size >= step_size)
step_size = get_new_step_size(step_size);
- mapped_ram_size += new_mapped_ram_size;
}
}

diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c
index 009495b9ab4b..1c9f750c3859 100644
--- a/arch/x86/vdso/vma.c
+++ b/arch/x86/vdso/vma.c
@@ -41,12 +41,17 @@ void __init init_vdso_image(const struct vdso_image *image)

struct linux_binprm;

-/* Put the vdso above the (randomized) stack with another randomized offset.
- This way there is no hole in the middle of address space.
- To save memory make sure it is still in the same PTE as the stack top.
- This doesn't give that many random bits.
-
- Only used for the 64-bit and x32 vdsos. */
+/*
+ * Put the vdso above the (randomized) stack with another randomized
+ * offset. This way there is no hole in the middle of address space.
+ * To save memory make sure it is still in the same PTE as the stack
+ * top. This doesn't give that many random bits.
+ *
+ * Note that this algorithm is imperfect: the distribution of the vdso
+ * start address within a PMD is biased toward the end.
+ *
+ * Only used for the 64-bit and x32 vdsos.
+ */
static unsigned long vdso_addr(unsigned long start, unsigned len)
{
#ifdef CONFIG_X86_32
@@ -54,22 +59,30 @@ static unsigned long vdso_addr(unsigned long start, unsigned len)
#else
unsigned long addr, end;
unsigned offset;
- end = (start + PMD_SIZE - 1) & PMD_MASK;
+
+ /*
+ * Round up the start address. It can start out unaligned as a result
+ * of stack start randomization.
+ */
+ start = PAGE_ALIGN(start);
+
+ /* Round the lowest possible end address up to a PMD boundary. */
+ end = (start + len + PMD_SIZE - 1) & PMD_MASK;
if (end >= TASK_SIZE_MAX)
end = TASK_SIZE_MAX;
end -= len;
- /* This loses some more bits than a modulo, but is cheaper */
- offset = get_random_int() & (PTRS_PER_PTE - 1);
- addr = start + (offset << PAGE_SHIFT);
- if (addr >= end)
- addr = end;
+
+ if (end > start) {
+ offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
+ addr = start + (offset << PAGE_SHIFT);
+ } else {
+ addr = start;
+ }

/*
- * page-align it here so that get_unmapped_area doesn't
- * align it wrongfully again to the next page. addr can come in 4K
- * unaligned here as a result of stack start randomization.
+ * Forcibly align the final address in case we have a hardware
+ * issue that requires alignment for performance reasons.
*/
- addr = PAGE_ALIGN(addr);
addr = align_vdso_addr(addr);

return addr;
--
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Next message: Oded Gabbay: "[BUG] 3.19-rc3+ - mm: prevent endless growth of anon_vma hierarchy"
Previous message: Ingo Molnar: "[GIT PULL] scheduler fixes"
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