[PATCH 40/42] x86, 64bit: remove highmap for not needed ranges

From: Yinghai Lu
Date: Tue Jul 07 2015 - 16:25:14 EST

add cleanup_highmap_late to remove highmap for initmem, around rodata, and
[_brk_end, all_end).

Kernel Layout:

[ 0.000000] .text: [0x01000000-0x0200df88]
[ 0.000000] .rodata: [0x02200000-0x02a1dfff]
[ 0.000000] .data: [0x02c00000-0x02e510ff]
[ 0.000000] .init: [0x02e53000-0x03213fff]
[ 0.000000] .bss: [0x03222000-0x0437cfff]
[ 0.000000] .brk: [0x0437d000-0x043a2fff]

Actually used brk:
[ 0.270365] memblock_reserve: [0x0000000437d000-0x00000004383fff] flags 0x0 BRK

Before patch:
---[ High Kernel Mapping ]---
0xffffffff80000000-0xffffffff81000000 16M pmd
0xffffffff81000000-0xffffffff82000000 16M ro PSE GLB x pmd
0xffffffff82000000-0xffffffff82011000 68K ro GLB x pte
0xffffffff82011000-0xffffffff82200000 1980K RW GLB x pte
0xffffffff82200000-0xffffffff82a00000 8M ro PSE GLB NX pmd
0xffffffff82a00000-0xffffffff82a1e000 120K ro GLB NX pte
0xffffffff82a1e000-0xffffffff82c00000 1928K RW GLB NX pte
0xffffffff82c00000-0xffffffff82e00000 2M RW PSE GLB NX pmd
0xffffffff82e00000-0xffffffff83000000 2M RW GLB NX pte
0xffffffff83000000-0xffffffff83200000 2M RW PSE GLB NX pmd
0xffffffff83200000-0xffffffff83400000 2M RW GLB NX pte
0xffffffff83400000-0xffffffff84400000 16M RW PSE GLB NX pmd
0xffffffff84400000-0xffffffffa0000000 444M pmd

After patch:
---[ High Kernel Mapping ]---
0xffffffff80000000-0xffffffff81000000 16M pmd
0xffffffff81000000-0xffffffff82000000 16M ro PSE GLB x pmd
0xffffffff82000000-0xffffffff82012000 72K ro GLB x pte
0xffffffff82012000-0xffffffff82200000 1976K pte
0xffffffff82200000-0xffffffff82a00000 8M ro PSE GLB NX pmd
0xffffffff82a00000-0xffffffff82a1e000 120K ro GLB NX pte
0xffffffff82a1e000-0xffffffff82c00000 1928K pte
0xffffffff82c00000-0xffffffff82e00000 2M RW PSE GLB NX pmd
0xffffffff82e00000-0xffffffff82e53000 332K RW GLB NX pte
0xffffffff82e53000-0xffffffff83000000 1716K pte
0xffffffff83000000-0xffffffff83200000 2M pmd
0xffffffff83200000-0xffffffff83214000 80K pte
0xffffffff83214000-0xffffffff83400000 1968K RW GLB NX pte
0xffffffff83400000-0xffffffff84200000 14M RW PSE GLB NX pmd
0xffffffff84200000-0xffffffff84384000 1552K RW GLB NX pte
0xffffffff84384000-0xffffffff84400000 496K pte
0xffffffff84400000-0xffffffffa0000000 444M pmd

So remove some range around rodata.

-v4: adapt it to all_end change.

Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
---
arch/x86/mm/init_64.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 62 insertions(+)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 2507b98..38aa59c 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1010,6 +1010,61 @@ void __init mem_init(void)
}

#ifdef CONFIG_DEBUG_RODATA
+static void remove_highmap_2m(unsigned long addr)
+{
+ pgd_t *pgd = pgd_offset_k(addr);
+ pud_t *pud = (pud_t *)pgd_page_vaddr(*pgd) + pud_index(addr);
+ pmd_t *pmd = (pmd_t *)pud_page_vaddr(*pud) + pmd_index(addr);
+
+ set_pmd(pmd, __pmd(0));
+}
+
+static void remove_highmap_2m_partial(unsigned long addr, unsigned long end)
+{
+ int i;
+ pgd_t *pgd = pgd_offset_k(addr);
+ pud_t *pud = (pud_t *)pgd_page_vaddr(*pgd) + pud_index(addr);
+ pmd_t *pmd = (pmd_t *)pud_page_vaddr(*pud) + pmd_index(addr);
+ pte_t *pte = (pte_t *)pmd_page_vaddr(*pmd) + pte_index(addr);
+
+ for (i = pte_index(addr); i < pte_index(end - 1) + 1; i++, pte++)
+ set_pte(pte, __pte(0));
+}
+
+static void cleanup_highmap_late(unsigned long start, unsigned long end)
+{
+ unsigned long addr;
+ unsigned long start_2m_aligned = roundup(start, PMD_SIZE);
+ unsigned long end_2m_aligned = rounddown(end, PMD_SIZE);
+
+ start = PFN_ALIGN(start);
+ end &= PAGE_MASK;
+
+ if (start >= end)
+ return;
+
+ if (start < start_2m_aligned) {
+ unsigned long tmp = min(start_2m_aligned, end);
+
+ set_memory_4k(start, (tmp - start) >> PAGE_SHIFT);
+ remove_highmap_2m_partial(start, tmp);
+ }
+
+ for (addr = start_2m_aligned; addr < end_2m_aligned; addr += PMD_SIZE)
+ remove_highmap_2m(addr);
+
+ if (start <= end_2m_aligned && end_2m_aligned < end) {
+ set_memory_4k(end_2m_aligned,
+ (end - end_2m_aligned) >> PAGE_SHIFT);
+ remove_highmap_2m_partial(end_2m_aligned, end);
+ }
+
+ subtract_range(pfn_highmapped, NR_RANGE,
+ __pa_symbol(start) >> PAGE_SHIFT,
+ __pa_symbol(end) >> PAGE_SHIFT);
+ nr_pfn_highmapped = clean_sort_range(pfn_highmapped, NR_RANGE);
+}
+
const int rodata_test_data = 0xC3;
EXPORT_SYMBOL_GPL(rodata_test_data);

@@ -1058,6 +1113,7 @@ void mark_rodata_ro(void)
unsigned long end = (unsigned long) &__end_rodata_hpage_align;
unsigned long text_end = PFN_ALIGN(&__stop___ex_table);
unsigned long rodata_end = PFN_ALIGN(&__end_rodata);
+ unsigned long data_start = PFN_ALIGN(&_sdata);
unsigned long all_end;

printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n",
@@ -1081,6 +1137,12 @@ void mark_rodata_ro(void)
all_end = roundup(_brk_end, PMD_SIZE);
set_memory_nx(rodata_start, (all_end - rodata_start) >> PAGE_SHIFT);

+ cleanup_highmap_late(text_end, rodata_start);
+ cleanup_highmap_late(rodata_end, data_start);
+ cleanup_highmap_late(PFN_ALIGN(_brk_end), all_end);
+ cleanup_highmap_late((unsigned long)(&__init_begin),
+ (unsigned long)(&__init_end));
+
rodata_test();

#ifdef CONFIG_CPA_DEBUG
--
1.8.4.5

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