[PATCH 11/11] EFI: Runtime services virtual mapping

Borislav Petkov
2013-09-19T14:56:41Z

From: Borislav Petkov <bp@suse.de>

We map the EFI regions needed for runtime services contiguously 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 way, they're mapped in a separate pagetable so that we don't
pollute the kernel namespace (you can see how the whole ioremapping and
saving and restoring of PGDs is gone now).

Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/include/asm/efi.h | 58 +++++++++++++++-------
arch/x86/include/asm/pgtable_types.h | 3 +-
arch/x86/platform/efi/efi.c | 95 +++++++++++++++++++++---------------
arch/x86/platform/efi/efi_64.c | 56 +--------------------
arch/x86/platform/efi/efi_stub_64.S | 47 ++++++++++++++++++
5 files changed, 149 insertions(+), 110 deletions(-)

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 0062a0125041..745c8d27265b 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -39,6 +39,8 @@ extern unsigned long asmlinkage efi_call_phys(void *, ...);

#else /* !CONFIG_X86_32 */

+#include <linux/sched.h>
+
#define EFI_LOADER_SIGNATURE "EL64"

extern u64 efi_call0(void *fp);
@@ -51,6 +53,21 @@ extern u64 efi_call5(void *fp, u64 arg1, u64 arg2, u64 arg3,
extern u64 efi_call6(void *fp, u64 arg1, u64 arg2, u64 arg3,
u64 arg4, u64 arg5, u64 arg6);

+/*
+ * Add low kernel mappings for passing arguments to EFI functions.
+ */
+static inline void efi_sync_low_kernel_mappings(void)
+{
+ unsigned num_pgds;
+ pgd_t *pgd = (pgd_t *)__va(real_mode_header->trampoline_pgd);
+
+ num_pgds = pgd_index(VMALLOC_START - 1) - pgd_index(PAGE_OFFSET);
+
+ memcpy(pgd + pgd_index(PAGE_OFFSET),
+ init_mm.pgd + pgd_index(PAGE_OFFSET),
+ sizeof(pgd_t) * num_pgds);
+}
+
#define efi_call_phys0(f) \
efi_call0((f))
#define efi_call_phys1(f, a1) \
@@ -69,24 +86,31 @@ 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);
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 0ecac257fb26..a83aa44bb1fb 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -382,7 +382,8 @@ 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 */
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 538c1e6b7b2c..9c54ce5b9975 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -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
@@ -60,6 +62,13 @@

static efi_char16_t efi_dummy_name[6] = { 'D', 'U', 'M', 'M', 'Y', 0 };

+/*
+ * We allocate runtime services regions top-down, starting from -4G, i.e.
+ * 0xffff_ffff_0000_0000 and limit EFI VA mapping space to 64G.
+ */
+static unsigned long efi_va = -4 * (1UL << 30);
+#define EFI_VA_END (-68 * (1UL << 30))
+
struct efi __read_mostly efi = {
.mps = EFI_INVALID_TABLE_ADDR,
.acpi = EFI_INVALID_TABLE_ADDR,
@@ -81,6 +90,16 @@ static efi_system_table_t efi_systab __initdata;
unsigned long x86_efi_facility;

/*
+ * Scratch space used for switching the pagetable in the EFI stub
+ */
+struct efi_scratch {
+ u64 r15;
+ u64 prev_cr3;
+ pgd_t *efi_pgt;
+};
+extern struct efi_scratch efi_scratch;
+
+/*
* Returns 1 if 'facility' is enabled, 0 otherwise.
*/
int efi_enabled(int facility)
@@ -797,22 +816,6 @@ void __init efi_set_executable(efi_memory_desc_t *md, bool executable)
set_memory_nx(addr, npages);
}

-static void __init runtime_code_page_mkexec(void)
-{
- efi_memory_desc_t *md;
- void *p;
-
- /* Make EFI runtime service code area executable */
- for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
- md = p;
-
- if (md->type != EFI_RUNTIME_SERVICES_CODE)
- continue;
-
- efi_set_executable(md, true);
- }
-}
-
/*
* We can't ioremap data in EFI boot services RAM, because we've already mapped
* it as RAM. So, look it up in the existing EFI memory map instead. Only
@@ -851,6 +854,23 @@ void efi_memory_uc(u64 addr, unsigned long size)
set_memory_uc(addr, npages);
}

+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_warning("Error mapping PA 0x%llx -> VA 0x%llx!\n",
+ md->phys_addr, va);
+}
+
/*
* This function will switch the EFI runtime services to virtual mode.
* Essentially, look through the EFI memmap and map every region that
@@ -862,10 +882,10 @@ void efi_memory_uc(u64 addr, unsigned long size)
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, new_va;
int count = 0;

efi.systab = NULL;
@@ -874,7 +894,6 @@ 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;
@@ -914,33 +933,31 @@ void __init efi_enter_virtual_mode(void)
md->type != EFI_BOOT_SERVICES_DATA)
continue;

+ /* Do the 1:1 map */
+ __map_region(md, md->phys_addr);
+
size = md->num_pages << 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);
+ new_va = efi_va - size;
+ if (new_va < EFI_VA_END) {
+ pr_warning(FW_WARN "VA address range overflow!\n");
continue;
}

+ efi_va -= size;
+
+ /* Do the VA map */
+ __map_region(md, new_va);
+ md->virt_addr = new_va;
+
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);
@@ -949,8 +966,12 @@ void __init efi_enter_virtual_mode(void)
count++;
}

+ efi_scratch.efi_pgt = (pgd_t *)(unsigned long)real_mode_header->trampoline_pgd;
+
BUG_ON(!efi.systab);

+ efi_sync_low_kernel_mappings();
+
status = phys_efi_set_virtual_address_map(
memmap.desc_size * count,
memmap.desc_size,
@@ -983,8 +1004,6 @@ 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)
- runtime_code_page_mkexec();

kfree(new_memmap);

diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 39a0e7f1f0a3..a16fa9a6cf3e 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -39,60 +39,8 @@
#include <asm/cacheflush.h>
#include <asm/fixmap.h>

-static pgd_t *save_pgd __initdata;
-static unsigned long efi_flags __initdata;
-
-static void __init early_code_mapping_set_exec(int executable)
-{
- efi_memory_desc_t *md;
- void *p;
-
- if (!(__supported_pte_mask & _PAGE_NX))
- return;
-
- /* Make EFI service code area executable */
- for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
- md = p;
- if (md->type == EFI_RUNTIME_SERVICES_CODE ||
- md->type == EFI_BOOT_SERVICES_CODE)
- efi_set_executable(md, executable);
- }
-}
-
-void __init efi_call_phys_prelog(void)
-{
- unsigned long vaddress;
- int pgd;
- int n_pgds;
-
- early_code_mapping_set_exec(1);
- local_irq_save(efi_flags);
-
- n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT), PGDIR_SIZE);
- save_pgd = kmalloc(n_pgds * sizeof(pgd_t), GFP_KERNEL);
-
- for (pgd = 0; pgd < n_pgds; pgd++) {
- save_pgd[pgd] = *pgd_offset_k(pgd * PGDIR_SIZE);
- vaddress = (unsigned long)__va(pgd * PGDIR_SIZE);
- set_pgd(pgd_offset_k(pgd * PGDIR_SIZE), *pgd_offset_k(vaddress));
- }
- __flush_tlb_all();
-}
-
-void __init efi_call_phys_epilog(void)
-{
- /*
- * After the lock is released, the original page table is restored.
- */
- int pgd;
- int n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT) , PGDIR_SIZE);
- for (pgd = 0; pgd < n_pgds; pgd++)
- set_pgd(pgd_offset_k(pgd * PGDIR_SIZE), save_pgd[pgd]);
- kfree(save_pgd);
- __flush_tlb_all();
- local_irq_restore(efi_flags);
- early_code_mapping_set_exec(0);
-}
+void __init efi_call_phys_prelog(void) {}
+void __init efi_call_phys_epilog(void) {}

void __iomem *__init efi_ioremap(unsigned long phys_addr, unsigned long size,
u32 type, u64 attribute)
diff --git a/arch/x86/platform/efi/efi_stub_64.S b/arch/x86/platform/efi/efi_stub_64.S
index 4c07ccab8146..f3bc4127f9e8 100644
--- a/arch/x86/platform/efi/efi_stub_64.S
+++ b/arch/x86/platform/efi/efi_stub_64.S
@@ -34,10 +34,41 @@
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
+ 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
+ .endm
+
+ .macro RESTORE_PGT
+ movq efi_scratch+8(%rip), %r15
+ movq %r15, %cr3
+ movq efi_scratch(%rip), %r15
+ FLUSH_TLB_ALL
+ .endm
+
ENTRY(efi_call0)
SAVE_XMM
subq $32, %rsp
+ SWITCH_PGT
call *%rdi
+ RESTORE_PGT
addq $32, %rsp
RESTORE_XMM
ret
@@ -47,7 +78,9 @@ 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 +90,9 @@ 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 +103,9 @@ 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 +117,9 @@ 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 +132,9 @@ 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 +150,14 @@ 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
--
1.8.4