Hi, Ard
The approach looks good, thanks for the patchset.
Please see a few code comments inline..
On 10/24/14 at 02:39pm, Ard Biesheuvel wrote:
> In order to support kexec, the kernel needs to be able to deal with the
> state of the UEFI firmware after SetVirtualAddressMap() has been called.
> To avoid having separate code paths for non-kexec and kexec, let's move
> the call to SetVirtualAddressMap() to the stub: this will guarantee us
> that it will only be called once (since the stub is not executed during
> kexec), and ensures that the UEFI state is identical between kexec and
> normal boot.
>
> This implies that the layout of the virtual mapping needs to be created
> by the stub as well. All regions are rounded up to a naturally aligned
> multiple of 64 KB (for compatibility with 64k pages kernels) and recorded
> in the UEFI memory map. The kernel proper reads those values and installs
> the mappings in a dedicated set of page tables that are swapped in during
> UEFI Runtime Services calls.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
> arch/arm64/include/asm/efi.h | 19 +++-
> arch/arm64/kernel/efi.c | 205 +++++++++++++++++++------------------
> drivers/firmware/efi/libstub/fdt.c | 104 ++++++++++++++++++-
> 3 files changed, 224 insertions(+), 104 deletions(-)
>
> diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
> index a34fd3b12e2b..d752e5480096 100644
> --- a/arch/arm64/include/asm/efi.h
> +++ b/arch/arm64/include/asm/efi.h
> @@ -12,23 +12,32 @@ extern void efi_idmap_init(void);
> #define efi_idmap_init()
> #endif
>
> +void efi_load_rt_mapping(void);
> +void efi_unload_rt_mapping(void);
> +
> #define efi_call_virt(f, ...) \
> ({ \
> - efi_##f##_t *__f = efi.systab->runtime->f; \
> + efi_##f##_t *__f; \
> efi_status_t __s; \
> \
> - kernel_neon_begin(); \
> + kernel_neon_begin(); /* disables preemption */ \
> + efi_load_rt_mapping(); \
> + __f = efi.systab->runtime->f; \
> __s = __f(__VA_ARGS__); \
> + efi_unload_rt_mapping(); \
> kernel_neon_end(); \
> __s; \
> })
>
> #define __efi_call_virt(f, ...) \
> ({ \
> - efi_##f##_t *__f = efi.systab->runtime->f; \
> + efi_##f##_t *__f; \
> \
> - kernel_neon_begin(); \
> + kernel_neon_begin(); /* disables preemption */ \
> + efi_load_rt_mapping(); \
> + __f = efi.systab->runtime->f; \
> __f(__VA_ARGS__); \
> + efi_unload_rt_mapping(); \
> kernel_neon_end(); \
> })
>
> @@ -44,4 +53,6 @@ extern void efi_idmap_init(void);
>
> #define efi_call_early(f, ...) sys_table_arg->boottime->f(__VA_ARGS__)
>
> +#define EFI_VIRTMAP EFI_ARCH_1
> +
> #endif /* _ASM_EFI_H */
> diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
> index baab9344a32b..324398c03acd 100644
> --- a/arch/arm64/kernel/efi.c
> +++ b/arch/arm64/kernel/efi.c
> @@ -20,16 +20,21 @@
> #include <linux/of_fdt.h>
> #include <linux/sched.h>
> #include <linux/slab.h>
> +#include <linux/mm_types.h>
> +#include <linux/rbtree.h>
> +#include <linux/rwsem.h>
> +#include <linux/spinlock.h>
> +#include <linux/atomic.h>
>
> #include <asm/cacheflush.h>
> #include <asm/efi.h>
> #include <asm/tlbflush.h>
> +#include <asm/pgtable.h>
> #include <asm/mmu_context.h>
> +#include <asm/mmu.h>
>
> struct efi_memory_map memmap;
>
> -static efi_runtime_services_t *runtime;
> -
> static u64 efi_system_table;
>
> static int uefi_debug __initdata;
> @@ -69,9 +74,36 @@ static void __init efi_setup_idmap(void)
> }
> }
>
> +/*
> + * Translate a EFI virtual address into a physical address: this is necessary,
> + * as some data members of the EFI system table are virtually remapped after
> + * SetVirtualAddressMap() has been called.
> + */
> +static phys_addr_t __init efi_to_phys(unsigned long addr)
> +{
> + efi_memory_desc_t *md;
> +
> + for_each_efi_memory_desc(&memmap, md) {
> + if (!(md->attribute & EFI_MEMORY_RUNTIME))
> + continue;
> + if (md->virt_addr == 0)
> + /* no virtual mapping has been installed by the stub */
> + break;
> + if (md->virt_addr < addr &&
> + (addr - md->virt_addr) < (md->num_pages << EFI_PAGE_SHIFT))
> + return md->phys_addr + addr - md->virt_addr;
> + }
> +
> + WARN_ONCE(1, "UEFI virtual mapping incomplete or missing -- no entry found for 0x%lx\n",
> + addr);
die here instead of warn looks better, addr could be anything which does not match the virt maps.
> + return addr;
> +}
> +
> static int __init uefi_init(void)
> {
> efi_char16_t *c16;
> + void *config_tables;
> + u64 table_size;
> char vendor[100] = "unknown";
> int i, retval;
>
> @@ -99,7 +131,7 @@ static int __init uefi_init(void)
> efi.systab->hdr.revision & 0xffff);
>
> /* Show what we know for posterity */
> - c16 = early_memremap(efi.systab->fw_vendor,
> + c16 = early_memremap(efi_to_phys(efi.systab->fw_vendor),
> sizeof(vendor));
> if (c16) {
> for (i = 0; i < (int) sizeof(vendor) - 1 && *c16; ++i)
> @@ -112,8 +144,14 @@ static int __init uefi_init(void)
> efi.systab->hdr.revision >> 16,
> efi.systab->hdr.revision & 0xffff, vendor);
>
> - retval = efi_config_init(NULL);
> + table_size = sizeof(efi_config_table_64_t) * efi.systab->nr_tables;
> + config_tables = early_memremap(efi_to_phys(efi.systab->tables),
> + table_size);
There should be error handling for early_memremap.
> +
> + retval = efi_config_parse_tables(config_tables,
> + efi.systab->nr_tables, NULL);
>
> + early_memunmap(config_tables, table_size);
> out:
> early_memunmap(efi.systab, sizeof(efi_system_table_t));
> return retval;
> @@ -319,60 +357,64 @@ void __init efi_init(void)
> reserve_regions();
> }
>
> +static pgd_t efi_pgd[PTRS_PER_PGD] __page_aligned_bss;
> +
> +static struct mm_struct efi_mm = {
> + .mm_rb = RB_ROOT,
> + .pgd = efi_pgd,
> + .mm_users = ATOMIC_INIT(2),
> + .mm_count = ATOMIC_INIT(1),
> + .mmap_sem = __RWSEM_INITIALIZER(efi_mm.mmap_sem),
> + .page_table_lock = __SPIN_LOCK_UNLOCKED(efi_mm.page_table_lock),
> + .mmlist = LIST_HEAD_INIT(efi_mm.mmlist),
> + INIT_MM_CONTEXT(efi_mm)
> +};
> +
> void __init efi_idmap_init(void)
> {
> + efi_memory_desc_t *md;
> +
> if (!efi_enabled(EFI_BOOT))
> return;
>
> /* boot time idmap_pg_dir is incomplete, so fill in missing parts */
> efi_setup_idmap();
> -}
> -
> -static int __init remap_region(efi_memory_desc_t *md, void **new)
> -{
> - u64 paddr, vaddr, npages, size;
> -
> - paddr = md->phys_addr;
> - npages = md->num_pages;
> - memrange_efi_to_native(&paddr, &npages);
> - size = npages << PAGE_SHIFT;
> -
> - if (is_normal_ram(md))
> - vaddr = (__force u64)ioremap_cache(paddr, size);
> - else
> - vaddr = (__force u64)ioremap(paddr, size);
>
> - if (!vaddr) {
> - pr_err("Unable to remap 0x%llx pages @ %p\n",
> - npages, (void *)paddr);
> - return 0;
> - }
> + for_each_efi_memory_desc(&memmap, md) {
> + u64 paddr, npages, size;
>
> - /* adjust for any rounding when EFI and system pagesize differs */
> - md->virt_addr = vaddr + (md->phys_addr - paddr);
> + if (!(md->attribute & EFI_MEMORY_RUNTIME))
> + continue;
> + if (md->virt_addr == 0)
> + /* no virtual mapping has been installed by the stub */
> + return;
>
> - if (uefi_debug)
> - pr_info(" EFI remap 0x%012llx => %p\n",
> - md->phys_addr, (void *)md->virt_addr);
> + paddr = md->phys_addr;
> + npages = md->num_pages;
> + memrange_efi_to_native(&paddr, &npages);
> + size = npages << PAGE_SHIFT;
>
> - memcpy(*new, md, memmap.desc_size);
> - *new += memmap.desc_size;
> + if (uefi_debug)
> + pr_info(" EFI remap 0x%012llx => %p\n",
> + md->phys_addr, (void *)md->virt_addr);
>
> - return 1;
> + /*
> + * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
> + * executable, everything else can be mapped with the XN bits
> + * set. Unfortunately, we cannot map those code regions write
> + * protect, as they may contain read-write .data sections as
> + * well.
> + */
> + create_pgd_mapping(&efi_mm, paddr, md->virt_addr, size,
> + !is_normal_ram(md),
> + md->type != EFI_RUNTIME_SERVICES_CODE);
> + }
> + set_bit(EFI_VIRTMAP, &efi.flags);
> }
>
> -/*
> - * Switch UEFI from an identity map to a kernel virtual map
> - */
> static int __init arm64_enter_virtual_mode(void)
> {
> - efi_memory_desc_t *md;
> - phys_addr_t virtmap_phys;
> - void *virtmap, *virt_md;
> - efi_status_t status;
> u64 mapsize;
> - int count = 0;
> - unsigned long flags;
>
> if (!efi_enabled(EFI_MEMMAP))
> return 0;
> @@ -393,79 +435,28 @@ static int __init arm64_enter_virtual_mode(void)
>
> efi.memmap = &memmap;
>
> - /* Map the runtime regions */
> - virtmap = kmalloc(mapsize, GFP_KERNEL);
> - if (!virtmap) {
> - pr_err("Failed to allocate EFI virtual memmap\n");
> - return -1;
> - }
> - virtmap_phys = virt_to_phys(virtmap);
> - virt_md = virtmap;
> -
> - for_each_efi_memory_desc(&memmap, md) {
> - if (!(md->attribute & EFI_MEMORY_RUNTIME))
> - continue;
> - if (!remap_region(md, &virt_md))
> - goto err_unmap;
> - ++count;
> - }
> -
> - efi.systab = (__force void *)efi_lookup_mapped_addr(efi_system_table);
> + efi.systab = (__force void *)ioremap_cache(efi_system_table,
> + sizeof(efi_system_table_t));
> if (!efi.systab) {
> - /*
> - * If we have no virtual mapping for the System Table at this
> - * point, the memory map doesn't cover the physical offset where
> - * it resides. This means the System Table will be inaccessible
> - * to Runtime Services themselves once the virtual mapping is
> - * installed.
> - */
> - pr_err("Failed to remap EFI System Table -- buggy firmware?\n");
> - goto err_unmap;
> + pr_err("Failed to remap EFI System Table\n");
> + return -1;
> }
> set_bit(EFI_SYSTEM_TABLES, &efi.flags);
>
> - local_irq_save(flags);
> - cpu_switch_mm(idmap_pg_dir, &init_mm);
> -
> - /* Call SetVirtualAddressMap with the physical address of the map */
> - runtime = efi.systab->runtime;
> - efi.set_virtual_address_map = runtime->set_virtual_address_map;
> -
> - status = efi.set_virtual_address_map(count * memmap.desc_size,
> - memmap.desc_size,
> - memmap.desc_version,
> - (efi_memory_desc_t *)virtmap_phys);
> - cpu_set_reserved_ttbr0();
> - flush_tlb_all();
> - local_irq_restore(flags);
> -
> - kfree(virtmap);
> -
> free_boot_services();
>
> - if (status != EFI_SUCCESS) {
> - pr_err("Failed to set EFI virtual address map! [%lx]\n",
> - status);
> + if (!efi_enabled(EFI_VIRTMAP)) {
> + pr_err("No UEFI virtual mapping was installed -- runtime services will not be available\n");
> return -1;
> }
>
> /* Set up runtime services function pointers */
> - runtime = efi.systab->runtime;
> efi_native_runtime_setup();
> set_bit(EFI_RUNTIME_SERVICES, &efi.flags);
>
> efi.runtime_version = efi.systab->hdr.revision;
>
> return 0;
> -
> -err_unmap:
> - /* unmap all mappings that succeeded: there are 'count' of those */
> - for (virt_md = virtmap; count--; virt_md += memmap.desc_size) {
> - md = virt_md;
> - iounmap((__force void __iomem *)md->virt_addr);
> - }
> - kfree(virtmap);
> - return -1;
> }
> early_initcall(arm64_enter_virtual_mode);
>
> @@ -482,3 +473,21 @@ static int __init arm64_dmi_init(void)
> return 0;
> }
> core_initcall(arm64_dmi_init);
> +
> +static void efi_set_pgd(struct mm_struct *mm)
> +{
> + cpu_switch_mm(mm->pgd, mm);
> + flush_tlb_all();
> + if (icache_is_aivivt())
> + __flush_icache_all();
> +}
> +
> +void efi_load_rt_mapping(void)
> +{
> + efi_set_pgd(&efi_mm);
> +}
> +
> +void efi_unload_rt_mapping(void)
> +{
> + efi_set_pgd(current->active_mm);
> +}
> diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
> index c846a9608cbd..9a5f6e54a423 100644
> --- a/drivers/firmware/efi/libstub/fdt.c
> +++ b/drivers/firmware/efi/libstub/fdt.c
> @@ -168,6 +168,68 @@ fdt_set_fail:
> #endif
>
> /*
> + * This is the base address at which to start allocating virtual memory ranges
> + * for UEFI Runtime Services. This is a userland range so that we can use any
> + * allocation we choose, and eliminate the risk of a conflict after kexec.
> + */
> +#define EFI_RT_VIRTUAL_BASE 0x40000000
> +
> +static void update_memory_map(efi_memory_desc_t *memory_map,
> + unsigned long map_size, unsigned long desc_size,
> + int *count)
> +{
> + u64 efi_virt_base = EFI_RT_VIRTUAL_BASE;
> + union {
> + efi_memory_desc_t entry;
> + u8 pad[desc_size];
> + } *p, *q, tmp;
> + int i = map_size / desc_size;
> +
> + p = (void *)memory_map;
> + for (q = p; i >= 0; i--, q++) {
> + u64 paddr, size;
> +
> + if (!(q->entry.attribute & EFI_MEMORY_RUNTIME))
> + continue;
> +
> + /*
> + * Swap the entries around so that all EFI_MEMORY_RUNTIME
> + * entries bubble to the top. This will allow us to reuse the
> + * table as input to SetVirtualAddressMap().
> + */
> + if (q != p) {
> + tmp = *p;
> + *p = *q;
> + *q = tmp;
> + }
> +
> + /*
> + * Make the mapping compatible with 64k pages: this allows
> + * a 4k page size kernel to kexec a 64k page size kernel and
> + * vice versa.
> + */
> + paddr = round_down(p->entry.phys_addr, SZ_64K);
> + size = round_up(p->entry.num_pages * EFI_PAGE_SIZE +
> + p->entry.phys_addr - paddr, SZ_64K);
> +
> + /*
> + * Avoid wasting memory on PTEs by choosing a virtual base that
> + * is compatible with section mappings if this region has the
> + * appropriate size and physical alignment. (Sections are 2 MB
> + * on 4k granule kernels)
> + */
> + if (IS_ALIGNED(p->entry.phys_addr, SZ_2M) && size >= SZ_2M)
> + efi_virt_base = round_up(efi_virt_base, SZ_2M);
> +
> + p->entry.virt_addr = efi_virt_base + p->entry.phys_addr - paddr;
> + efi_virt_base += size;
> +
> + ++p;
> + ++*count;
> + }
> +}
> +
> +/*
> * Allocate memory for a new FDT, then add EFI, commandline, and
> * initrd related fields to the FDT. This routine increases the
> * FDT allocation size until the allocated memory is large
> @@ -196,6 +258,7 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
> efi_memory_desc_t *memory_map;
> unsigned long new_fdt_size;
> efi_status_t status;
> + int runtime_entry_count = 0;
>
> /*
> * Estimate size of new FDT, and allocate memory for it. We
> @@ -248,12 +311,49 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
> }
> }
>
> + /*
> + * Update the memory map with virtual addresses, and reorder the entries
> + * so that we can pass it straight into SetVirtualAddressMap()
> + */
> + update_memory_map(memory_map, map_size, desc_size,
> + &runtime_entry_count);
> +
> /* Now we are ready to exit_boot_services.*/
> status = sys_table->boottime->exit_boot_services(handle, mmap_key);
>
> + if (status == EFI_SUCCESS) {
> + efi_set_virtual_address_map_t *svam;
> +
> + /* Install the new virtual address map */
> + svam = sys_table->runtime->set_virtual_address_map;
> + status = svam(runtime_entry_count * desc_size, desc_size,
> + desc_ver, memory_map);
>
> - if (status == EFI_SUCCESS)
> - return status;
> + /*
> + * We are beyond the point of no return here, so if the call to
> + * SetVirtualAddressMap() failed, we need to signal that to the
> + * incoming kernel but proceed normally otherwise.
> + */
> + if (status != EFI_SUCCESS) {
> + int i;
> +
> + /*
> + * Set the virtual address field of all
> + * EFI_MEMORY_RUNTIME entries to 0. This will signal
> + * the incoming kernel that no virtual translation has
> + * been installed.
> + */
> + for (i = 0; i < map_size; i += desc_size) {
> + efi_memory_desc_t *p;
> +
> + p = (efi_memory_desc_t *)((u8 *)memory_map + i);
> + if (!(p->attribute & EFI_MEMORY_RUNTIME))
> + break;
should it be continue instead of break?
> + p->virt_addr = 0;
In X86 kernel panics in case set_virtual_address_map, Matt mentioned that it's
not reasonable to continue. But for arm64 I'm not sure it's same case.
> + }
> + }
> + return EFI_SUCCESS;
> + }
>
> pr_efi_err(sys_table, "Exit boot services failed.\n");
>
> --
> 1.8.3.2
>
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