From mboxrd@z Thu Jan 1 00:00:00 1970 From: ard.biesheuvel@linaro.org (Ard Biesheuvel) Date: Wed, 15 Apr 2015 17:34:23 +0200 Subject: [PATCH v4 12/13] arm64: allow kernel Image to be loaded anywhere in physical memory In-Reply-To: <1429112064-19952-1-git-send-email-ard.biesheuvel@linaro.org> References: <1429112064-19952-1-git-send-email-ard.biesheuvel@linaro.org> Message-ID: <1429112064-19952-13-git-send-email-ard.biesheuvel@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org This relaxes the kernel Image placement requirements, so that it may be placed at any 2 MB aligned offset in physical memory. This is accomplished by ignoring PHYS_OFFSET when installing memblocks, and accounting for the apparent virtual offset of the kernel Image (in addition to the 64 MB that is is moved below PAGE_OFFSET). As a result, virtual address references below PAGE_OFFSET are correctly mapped onto physical references into the kernel Image regardless of where it sits in memory. Signed-off-by: Ard Biesheuvel --- Documentation/arm64/booting.txt | 20 ++++++++++---------- arch/arm64/mm/Makefile | 1 + arch/arm64/mm/init.c | 38 +++++++++++++++++++++++++++++++++++--- arch/arm64/mm/mmu.c | 24 ++++++++++++++++++++++-- 4 files changed, 68 insertions(+), 15 deletions(-) diff --git a/Documentation/arm64/booting.txt b/Documentation/arm64/booting.txt index 53f18e13d51c..7bd9feedb6f9 100644 --- a/Documentation/arm64/booting.txt +++ b/Documentation/arm64/booting.txt @@ -113,16 +113,16 @@ Header notes: depending on selected features, and is effectively unbound. The Image must be placed text_offset bytes from a 2MB aligned base -address near the start of usable system RAM and called there. Memory -below that base address is currently unusable by Linux, and therefore it -is strongly recommended that this location is the start of system RAM. -At least image_size bytes from the start of the image must be free for -use by the kernel. - -Any memory described to the kernel (even that below the 2MB aligned base -address) which is not marked as reserved from the kernel e.g. with a -memreserve region in the device tree) will be considered as available to -the kernel. +address anywhere in usable system RAM and called there. At least +image_size bytes from the start of the image must be free for use +by the kernel. +NOTE: versions prior to v4.2 cannot make use of memory below the +physical offset of the Image so it is recommended that the Image be +placed as close as possible to the start of system RAM. + +Any memory described to the kernel which is not marked as reserved from +the kernel (e.g., with a memreserve region in the device tree) will be +considered as available to the kernel. Before jumping into the kernel, the following conditions must be met: diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile index 9d84feb41a16..49e90bab4d57 100644 --- a/arch/arm64/mm/Makefile +++ b/arch/arm64/mm/Makefile @@ -6,3 +6,4 @@ obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o obj-$(CONFIG_ARM64_PTDUMP) += dump.o CFLAGS_mmu.o := -I$(srctree)/scripts/dtc/libfdt/ +CFLAGS_init.o := -DTEXT_OFFSET=$(TEXT_OFFSET) diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 0e7d9a2aad39..98a009885229 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -157,6 +157,38 @@ static int __init early_mem(char *p) } early_param("mem", early_mem); +static void enforce_memory_limit(void) +{ + const phys_addr_t kstart = __pa(_text) - TEXT_OFFSET; + const phys_addr_t kend = round_up(__pa(_end), SZ_2M); + const u64 ksize = kend - kstart; + struct memblock_region *reg; + + if (likely(memory_limit == (phys_addr_t)ULLONG_MAX)) + return; + + if (WARN(memory_limit < ksize, "mem= limit is unreasonably low")) + return; + + /* + * We have to make sure that the kernel image is still covered by + * memblock after we apply the memory limit, even if the kernel image + * is high up in physical memory. So if the kernel image becomes + * inaccessible after the limit is applied, we will lower the limit + * so that it compensates for the kernel image and reapply it. That way, + * we can add back the kernel image region and still honor the limit. + */ + memblock_enforce_memory_limit(memory_limit); + + for_each_memblock(memory, reg) + if (reg->base <= kstart && reg->base + reg->size >= kend) + /* kernel image still accessible -> we're done */ + return; + + memblock_enforce_memory_limit(memory_limit - ksize); + memblock_add(kstart, ksize); +} + void __init arm64_memblock_init(void) { /* @@ -165,10 +197,10 @@ void __init arm64_memblock_init(void) */ const s64 linear_region_size = -(s64)PAGE_OFFSET; - memblock_remove(0, memstart_addr); - memblock_remove(memstart_addr + linear_region_size, ULLONG_MAX); + memblock_remove(round_down(memblock_start_of_DRAM(), SZ_1G) + + linear_region_size, ULLONG_MAX); - memblock_enforce_memory_limit(memory_limit); + enforce_memory_limit(); /* * Register the kernel text, kernel data, initrd, and initial diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index c07ba8bdd8ed..1487824c5896 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -409,10 +409,30 @@ static void __init bootstrap_linear_mapping(unsigned long va_offset) static void __init map_mem(void) { struct memblock_region *reg; + u64 new_memstart_addr = memblock_start_of_DRAM(); + u64 new_va_offset; - bootstrap_linear_mapping(KIMAGE_OFFSET); + /* + * Select a suitable value for the base of physical memory. + * This should be below the lowest usable physical memory + * address, and aligned to PUD/PMD size so that we can map + * it efficiently. + */ + if (IS_ENABLED(CONFIG_ARM64_64K_PAGES)) + new_memstart_addr &= PMD_MASK; + else + new_memstart_addr &= PUD_MASK; + + /* + * Calculate the offset between the kernel text mapping that exists + * outside of the linear mapping, and its mapping in the linear region. + */ + new_va_offset = memstart_addr - new_memstart_addr + phys_offset_bias; + + bootstrap_linear_mapping(new_va_offset); - kernel_va_offset = KIMAGE_OFFSET; + memstart_addr = new_memstart_addr; + kernel_va_offset = new_va_offset; phys_offset_bias = 0; /* map all the memory banks */ -- 1.8.3.2