x86/efi: Runtime services virtual mapping

We map the EFI regions needed for runtime services non-contiguously,
with preserved alignment on virtual addresses starting from -4G down
for a total max space of 64G. This way, we provide for stable runtime
services addresses across kernels so that a kexec'd kernel can still use
them.

Thus, they're mapped in a separate pagetable so that we don't pollute
the kernel namespace.

Add an efi= kernel command line parameter for passing miscellaneous
options and chicken bits from the command line.

While at it, add a chicken bit called "efi=old_map" which can be used as
a fallback to the old runtime services mapping method in case there's
some b0rkage with a particular EFI implementation (haha, it is hard to
hold up the sarcasm here...).

Also, add the UEFI RT VA space to Documentation/x86/x86_64/mm.txt.

Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
This commit is contained in:
Borislav Petkov 2013-10-31 17:25:08 +01:00 committed by Matt Fleming
parent 82f0712ca0
commit d2f7cbe7b2
9 changed files with 300 additions and 47 deletions

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@ -835,6 +835,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
edd= [EDD]
Format: {"off" | "on" | "skip[mbr]"}
efi= [EFI]
Format: { "old_map" }
old_map [X86-64]: switch to the old ioremap-based EFI
runtime services mapping. 32-bit still uses this one by
default.
efi_no_storage_paranoia [EFI; X86]
Using this parameter you can use more than 50% of
your efi variable storage. Use this parameter only if

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@ -28,4 +28,11 @@ reference.
Current X86-64 implementations only support 40 bits of address space,
but we support up to 46 bits. This expands into MBZ space in the page tables.
->trampoline_pgd:
We map EFI runtime services in the aforementioned PGD in the virtual
range of 64Gb (arbitrarily set, can be raised if needed)
0xffffffef00000000 - 0xffffffff00000000
-Andi Kleen, Jul 2004

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@ -1,6 +1,24 @@
#ifndef _ASM_X86_EFI_H
#define _ASM_X86_EFI_H
/*
* We map the EFI regions needed for runtime services non-contiguously,
* with preserved alignment on virtual addresses starting from -4G down
* for a total max space of 64G. This way, we provide for stable runtime
* services addresses across kernels so that a kexec'd kernel can still
* use them.
*
* This is the main reason why we're doing stable VA mappings for RT
* services.
*
* This flag is used in conjuction with a chicken bit called
* "efi=old_map" which can be used as a fallback to the old runtime
* services mapping method in case there's some b0rkage with a
* particular EFI implementation (haha, it is hard to hold up the
* sarcasm here...).
*/
#define EFI_OLD_MEMMAP EFI_ARCH_1
#ifdef CONFIG_X86_32
#define EFI_LOADER_SIGNATURE "EL32"
@ -69,24 +87,31 @@ extern u64 efi_call6(void *fp, u64 arg1, u64 arg2, u64 arg3,
efi_call6((f), (u64)(a1), (u64)(a2), (u64)(a3), \
(u64)(a4), (u64)(a5), (u64)(a6))
#define _efi_call_virtX(x, f, ...) \
({ \
efi_status_t __s; \
\
efi_sync_low_kernel_mappings(); \
preempt_disable(); \
__s = efi_call##x((void *)efi.systab->runtime->f, __VA_ARGS__); \
preempt_enable(); \
__s; \
})
#define efi_call_virt0(f) \
efi_call0((efi.systab->runtime->f))
#define efi_call_virt1(f, a1) \
efi_call1((efi.systab->runtime->f), (u64)(a1))
#define efi_call_virt2(f, a1, a2) \
efi_call2((efi.systab->runtime->f), (u64)(a1), (u64)(a2))
#define efi_call_virt3(f, a1, a2, a3) \
efi_call3((efi.systab->runtime->f), (u64)(a1), (u64)(a2), \
(u64)(a3))
#define efi_call_virt4(f, a1, a2, a3, a4) \
efi_call4((efi.systab->runtime->f), (u64)(a1), (u64)(a2), \
(u64)(a3), (u64)(a4))
#define efi_call_virt5(f, a1, a2, a3, a4, a5) \
efi_call5((efi.systab->runtime->f), (u64)(a1), (u64)(a2), \
(u64)(a3), (u64)(a4), (u64)(a5))
#define efi_call_virt6(f, a1, a2, a3, a4, a5, a6) \
efi_call6((efi.systab->runtime->f), (u64)(a1), (u64)(a2), \
(u64)(a3), (u64)(a4), (u64)(a5), (u64)(a6))
_efi_call_virtX(0, f)
#define efi_call_virt1(f, a1) \
_efi_call_virtX(1, f, (u64)(a1))
#define efi_call_virt2(f, a1, a2) \
_efi_call_virtX(2, f, (u64)(a1), (u64)(a2))
#define efi_call_virt3(f, a1, a2, a3) \
_efi_call_virtX(3, f, (u64)(a1), (u64)(a2), (u64)(a3))
#define efi_call_virt4(f, a1, a2, a3, a4) \
_efi_call_virtX(4, f, (u64)(a1), (u64)(a2), (u64)(a3), (u64)(a4))
#define efi_call_virt5(f, a1, a2, a3, a4, a5) \
_efi_call_virtX(5, f, (u64)(a1), (u64)(a2), (u64)(a3), (u64)(a4), (u64)(a5))
#define efi_call_virt6(f, a1, a2, a3, a4, a5, a6) \
_efi_call_virtX(6, f, (u64)(a1), (u64)(a2), (u64)(a3), (u64)(a4), (u64)(a5), (u64)(a6))
extern void __iomem *efi_ioremap(unsigned long addr, unsigned long size,
u32 type, u64 attribute);
@ -95,12 +120,17 @@ extern void __iomem *efi_ioremap(unsigned long addr, unsigned long size,
extern int add_efi_memmap;
extern unsigned long x86_efi_facility;
extern struct efi_scratch efi_scratch;
extern void efi_set_executable(efi_memory_desc_t *md, bool executable);
extern int efi_memblock_x86_reserve_range(void);
extern void efi_call_phys_prelog(void);
extern void efi_call_phys_epilog(void);
extern void efi_unmap_memmap(void);
extern void efi_memory_uc(u64 addr, unsigned long size);
extern void __init efi_map_region(efi_memory_desc_t *md);
extern void efi_sync_low_kernel_mappings(void);
extern void efi_setup_page_tables(void);
extern void __init old_map_region(efi_memory_desc_t *md);
#ifdef CONFIG_EFI

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@ -379,7 +379,8 @@ static inline void update_page_count(int level, unsigned long pages) { }
*/
extern pte_t *lookup_address(unsigned long address, unsigned int *level);
extern phys_addr_t slow_virt_to_phys(void *__address);
extern int kernel_map_pages_in_pgd(pgd_t *pgd, u64 pfn, unsigned long address,
unsigned numpages, unsigned long page_flags);
#endif /* !__ASSEMBLY__ */
#endif /* _ASM_X86_PGTABLE_DEFS_H */

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@ -12,6 +12,8 @@
* Bibo Mao <bibo.mao@intel.com>
* Chandramouli Narayanan <mouli@linux.intel.com>
* Huang Ying <ying.huang@intel.com>
* Copyright (C) 2013 SuSE Labs
* Borislav Petkov <bp@suse.de> - runtime services VA mapping
*
* Copied from efi_32.c to eliminate the duplicated code between EFI
* 32/64 support code. --ying 2007-10-26
@ -745,21 +747,56 @@ void efi_memory_uc(u64 addr, unsigned long size)
set_memory_uc(addr, npages);
}
void __init old_map_region(efi_memory_desc_t *md)
{
u64 start_pfn, end_pfn, end;
unsigned long size;
void *va;
start_pfn = PFN_DOWN(md->phys_addr);
size = md->num_pages << PAGE_SHIFT;
end = md->phys_addr + size;
end_pfn = PFN_UP(end);
if (pfn_range_is_mapped(start_pfn, end_pfn)) {
va = __va(md->phys_addr);
if (!(md->attribute & EFI_MEMORY_WB))
efi_memory_uc((u64)(unsigned long)va, size);
} else
va = efi_ioremap(md->phys_addr, size,
md->type, md->attribute);
md->virt_addr = (u64) (unsigned long) va;
if (!va)
pr_err("ioremap of 0x%llX failed!\n",
(unsigned long long)md->phys_addr);
}
/*
* This function will switch the EFI runtime services to virtual mode.
* Essentially, look through the EFI memmap and map every region that
* has the runtime attribute bit set in its memory descriptor and update
* that memory descriptor with the virtual address obtained from ioremap().
* This enables the runtime services to be called without having to
* Essentially, we look through the EFI memmap and map every region that
* has the runtime attribute bit set in its memory descriptor into the
* ->trampoline_pgd page table using a top-down VA allocation scheme.
*
* The old method which used to update that memory descriptor with the
* virtual address obtained from ioremap() is still supported when the
* kernel is booted with efi=old_map on its command line. Same old
* method enabled the runtime services to be called without having to
* thunk back into physical mode for every invocation.
*
* The new method does a pagetable switch in a preemption-safe manner
* so that we're in a different address space when calling a runtime
* function. For function arguments passing we do copy the PGDs of the
* kernel page table into ->trampoline_pgd prior to each call.
*/
void __init efi_enter_virtual_mode(void)
{
efi_memory_desc_t *md, *prev_md = NULL;
efi_status_t status;
void *p, *new_memmap = NULL;
unsigned long size;
u64 end, systab, start_pfn, end_pfn;
void *p, *va, *new_memmap = NULL;
efi_status_t status;
u64 end, systab;
int count = 0;
efi.systab = NULL;
@ -768,7 +805,6 @@ void __init efi_enter_virtual_mode(void)
* We don't do virtual mode, since we don't do runtime services, on
* non-native EFI
*/
if (!efi_is_native()) {
efi_unmap_memmap();
return;
@ -799,6 +835,7 @@ void __init efi_enter_virtual_mode(void)
continue;
}
prev_md = md;
}
for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
@ -808,33 +845,18 @@ void __init efi_enter_virtual_mode(void)
md->type != EFI_BOOT_SERVICES_DATA)
continue;
efi_map_region(md);
size = md->num_pages << EFI_PAGE_SHIFT;
end = md->phys_addr + size;
start_pfn = PFN_DOWN(md->phys_addr);
end_pfn = PFN_UP(end);
if (pfn_range_is_mapped(start_pfn, end_pfn)) {
va = __va(md->phys_addr);
if (!(md->attribute & EFI_MEMORY_WB))
efi_memory_uc((u64)(unsigned long)va, size);
} else
va = efi_ioremap(md->phys_addr, size,
md->type, md->attribute);
md->virt_addr = (u64) (unsigned long) va;
if (!va) {
pr_err("ioremap of 0x%llX failed!\n",
(unsigned long long)md->phys_addr);
continue;
}
systab = (u64) (unsigned long) efi_phys.systab;
if (md->phys_addr <= systab && systab < end) {
systab += md->virt_addr - md->phys_addr;
efi.systab = (efi_system_table_t *) (unsigned long) systab;
}
new_memmap = krealloc(new_memmap,
(count + 1) * memmap.desc_size,
GFP_KERNEL);
@ -845,6 +867,9 @@ void __init efi_enter_virtual_mode(void)
BUG_ON(!efi.systab);
efi_setup_page_tables();
efi_sync_low_kernel_mappings();
status = phys_efi_set_virtual_address_map(
memmap.desc_size * count,
memmap.desc_size,
@ -877,7 +902,8 @@ void __init efi_enter_virtual_mode(void)
efi.query_variable_info = virt_efi_query_variable_info;
efi.update_capsule = virt_efi_update_capsule;
efi.query_capsule_caps = virt_efi_query_capsule_caps;
if (__supported_pte_mask & _PAGE_NX)
if (efi_enabled(EFI_OLD_MEMMAP) && (__supported_pte_mask & _PAGE_NX))
runtime_code_page_mkexec();
kfree(new_memmap);
@ -1007,3 +1033,15 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
return EFI_SUCCESS;
}
EXPORT_SYMBOL_GPL(efi_query_variable_store);
static int __init parse_efi_cmdline(char *str)
{
if (*str == '=')
str++;
if (!strncmp(str, "old_map", 7))
set_bit(EFI_OLD_MEMMAP, &x86_efi_facility);
return 0;
}
early_param("efi", parse_efi_cmdline);

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@ -37,9 +37,16 @@
* claim EFI runtime service handler exclusively and to duplicate a memory in
* low memory space say 0 - 3G.
*/
static unsigned long efi_rt_eflags;
void efi_sync_low_kernel_mappings(void) {}
void efi_setup_page_tables(void) {}
void __init efi_map_region(efi_memory_desc_t *md)
{
old_map_region(md);
}
void efi_call_phys_prelog(void)
{
struct desc_ptr gdt_descr;

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@ -38,10 +38,28 @@
#include <asm/efi.h>
#include <asm/cacheflush.h>
#include <asm/fixmap.h>
#include <asm/realmode.h>
static pgd_t *save_pgd __initdata;
static unsigned long efi_flags __initdata;
/*
* We allocate runtime services regions bottom-up, starting from -4G, i.e.
* 0xffff_ffff_0000_0000 and limit EFI VA mapping space to 64G.
*/
static u64 efi_va = -4 * (1UL << 30);
#define EFI_VA_END (-68 * (1UL << 30))
/*
* Scratch space used for switching the pagetable in the EFI stub
*/
struct efi_scratch {
u64 r15;
u64 prev_cr3;
pgd_t *efi_pgt;
bool use_pgd;
};
static void __init early_code_mapping_set_exec(int executable)
{
efi_memory_desc_t *md;
@ -65,6 +83,9 @@ void __init efi_call_phys_prelog(void)
int pgd;
int n_pgds;
if (!efi_enabled(EFI_OLD_MEMMAP))
return;
early_code_mapping_set_exec(1);
local_irq_save(efi_flags);
@ -86,6 +107,10 @@ void __init efi_call_phys_epilog(void)
*/
int pgd;
int n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT) , PGDIR_SIZE);
if (!efi_enabled(EFI_OLD_MEMMAP))
return;
for (pgd = 0; pgd < n_pgds; pgd++)
set_pgd(pgd_offset_k(pgd * PGDIR_SIZE), save_pgd[pgd]);
kfree(save_pgd);
@ -94,6 +119,90 @@ void __init efi_call_phys_epilog(void)
early_code_mapping_set_exec(0);
}
/*
* Add low kernel mappings for passing arguments to EFI functions.
*/
void efi_sync_low_kernel_mappings(void)
{
unsigned num_pgds;
pgd_t *pgd = (pgd_t *)__va(real_mode_header->trampoline_pgd);
if (efi_enabled(EFI_OLD_MEMMAP))
return;
num_pgds = pgd_index(MODULES_END - 1) - pgd_index(PAGE_OFFSET);
memcpy(pgd + pgd_index(PAGE_OFFSET),
init_mm.pgd + pgd_index(PAGE_OFFSET),
sizeof(pgd_t) * num_pgds);
}
void efi_setup_page_tables(void)
{
efi_scratch.efi_pgt = (pgd_t *)(unsigned long)real_mode_header->trampoline_pgd;
if (!efi_enabled(EFI_OLD_MEMMAP))
efi_scratch.use_pgd = true;
}
static void __init __map_region(efi_memory_desc_t *md, u64 va)
{
pgd_t *pgd = (pgd_t *)__va(real_mode_header->trampoline_pgd);
unsigned long pf = 0, size;
u64 end;
if (!(md->attribute & EFI_MEMORY_WB))
pf |= _PAGE_PCD;
size = md->num_pages << PAGE_SHIFT;
end = va + size;
if (kernel_map_pages_in_pgd(pgd, md->phys_addr, va, md->num_pages, pf))
pr_warn("Error mapping PA 0x%llx -> VA 0x%llx!\n",
md->phys_addr, va);
}
void __init efi_map_region(efi_memory_desc_t *md)
{
unsigned long size = md->num_pages << PAGE_SHIFT;
u64 pa = md->phys_addr;
if (efi_enabled(EFI_OLD_MEMMAP))
return old_map_region(md);
/*
* Make sure the 1:1 mappings are present as a catch-all for b0rked
* firmware which doesn't update all internal pointers after switching
* to virtual mode and would otherwise crap on us.
*/
__map_region(md, md->phys_addr);
efi_va -= size;
/* Is PA 2M-aligned? */
if (!(pa & (PMD_SIZE - 1))) {
efi_va &= PMD_MASK;
} else {
u64 pa_offset = pa & (PMD_SIZE - 1);
u64 prev_va = efi_va;
/* get us the same offset within this 2M page */
efi_va = (efi_va & PMD_MASK) + pa_offset;
if (efi_va > prev_va)
efi_va -= PMD_SIZE;
}
if (efi_va < EFI_VA_END) {
pr_warn(FW_WARN "VA address range overflow!\n");
return;
}
/* Do the VA map */
__map_region(md, efi_va);
md->virt_addr = efi_va;
}
void __iomem *__init efi_ioremap(unsigned long phys_addr, unsigned long size,
u32 type, u64 attribute)
{

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@ -34,10 +34,47 @@
mov %rsi, %cr0; \
mov (%rsp), %rsp
/* stolen from gcc */
.macro FLUSH_TLB_ALL
movq %r15, efi_scratch(%rip)
movq %r14, efi_scratch+8(%rip)
movq %cr4, %r15
movq %r15, %r14
andb $0x7f, %r14b
movq %r14, %cr4
movq %r15, %cr4
movq efi_scratch+8(%rip), %r14
movq efi_scratch(%rip), %r15
.endm
.macro SWITCH_PGT
cmpb $0, efi_scratch+24(%rip)
je 1f
movq %r15, efi_scratch(%rip) # r15
# save previous CR3
movq %cr3, %r15
movq %r15, efi_scratch+8(%rip) # prev_cr3
movq efi_scratch+16(%rip), %r15 # EFI pgt
movq %r15, %cr3
1:
.endm
.macro RESTORE_PGT
cmpb $0, efi_scratch+24(%rip)
je 2f
movq efi_scratch+8(%rip), %r15
movq %r15, %cr3
movq efi_scratch(%rip), %r15
FLUSH_TLB_ALL
2:
.endm
ENTRY(efi_call0)
SAVE_XMM
subq $32, %rsp
SWITCH_PGT
call *%rdi
RESTORE_PGT
addq $32, %rsp
RESTORE_XMM
ret
@ -47,7 +84,9 @@ ENTRY(efi_call1)
SAVE_XMM
subq $32, %rsp
mov %rsi, %rcx
SWITCH_PGT
call *%rdi
RESTORE_PGT
addq $32, %rsp
RESTORE_XMM
ret
@ -57,7 +96,9 @@ ENTRY(efi_call2)
SAVE_XMM
subq $32, %rsp
mov %rsi, %rcx
SWITCH_PGT
call *%rdi
RESTORE_PGT
addq $32, %rsp
RESTORE_XMM
ret
@ -68,7 +109,9 @@ ENTRY(efi_call3)
subq $32, %rsp
mov %rcx, %r8
mov %rsi, %rcx
SWITCH_PGT
call *%rdi
RESTORE_PGT
addq $32, %rsp
RESTORE_XMM
ret
@ -80,7 +123,9 @@ ENTRY(efi_call4)
mov %r8, %r9
mov %rcx, %r8
mov %rsi, %rcx
SWITCH_PGT
call *%rdi
RESTORE_PGT
addq $32, %rsp
RESTORE_XMM
ret
@ -93,7 +138,9 @@ ENTRY(efi_call5)
mov %r8, %r9
mov %rcx, %r8
mov %rsi, %rcx
SWITCH_PGT
call *%rdi
RESTORE_PGT
addq $48, %rsp
RESTORE_XMM
ret
@ -109,8 +156,15 @@ ENTRY(efi_call6)
mov %r8, %r9
mov %rcx, %r8
mov %rsi, %rcx
SWITCH_PGT
call *%rdi
RESTORE_PGT
addq $48, %rsp
RESTORE_XMM
ret
ENDPROC(efi_call6)
.data
ENTRY(efi_scratch)
.fill 3,8,0
.byte 0

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@ -653,6 +653,7 @@ extern int __init efi_setup_pcdp_console(char *);
#define EFI_RUNTIME_SERVICES 3 /* Can we use runtime services? */
#define EFI_MEMMAP 4 /* Can we use EFI memory map? */
#define EFI_64BIT 5 /* Is the firmware 64-bit? */
#define EFI_ARCH_1 6 /* First arch-specific bit */
#ifdef CONFIG_EFI
# ifdef CONFIG_X86