[PATCH -v2] EFI: Runtime services virtual mapping

Borislav Petkov
2013-09-21T11:39:29Z

On Thu, Sep 19, 2013 at 04:54:54PM +0200, Borislav Petkov wrote:
> From: Borislav Petkov <bp-l3A5Bk7waGM@public.gmane.org>
>
> 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).

Ok, this one was not so good, let's try again:

This time I saved 32-bit and am switching the pagetable only after
having built it properly. This boots fine again on baremetal and on OVMF
with Matt's handover flags fix from yesterday.

Also, I've uploaded the whole series to
git://git.kernel.org/pub/scm/linux/kernel/git/bp/bp.git, branch
efi-experimental

("-experimental" doesn't trigger Fengguang's robot :-))

Good luck! :-)

---
>From 880fcee20209a122eda846e7f109776ed1c56de5 Mon Sep 17 00:00:00 2001
From: Borislav Petkov <bp-l3A5Bk7waGM@public.gmane.org>
Date: Wed, 18 Sep 2013 17:35:42 +0200
Subject: [PATCH] EFI: Runtime services virtual mapping

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-l3A5Bk7waGM@public.gmane.org>
---
arch/x86/include/asm/efi.h | 43 ++++++++++--------
arch/x86/include/asm/pgtable_types.h | 3 +-
arch/x86/platform/efi/efi.c | 68 ++++++++++++-----------------
arch/x86/platform/efi/efi_32.c | 29 +++++++++++-
arch/x86/platform/efi/efi_64.c | 85 +++++++++++++++++++-----------------
arch/x86/platform/efi/efi_stub_64.S | 53 ++++++++++++++++++++++
6 files changed, 181 insertions(+), 100 deletions(-)

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 0062a0125041..9a99e0499e4b 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -69,24 +69,31 @@ 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);
@@ -101,6 +108,8 @@ 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);

#ifdef CONFIG_EFI

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..90459f5f587c 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -12,6 +12,8 @@
* Bibo Mao <bibo.mao-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
* Chandramouli Narayanan <mouli-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
* Huang Ying <ying.huang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
+ * Copyright (C) 2013 SuSE Labs
+ * Borislav Petkov <bp-l3A5Bk7waGM@public.gmane.org> - runtime services VA mapping
*
* Copied from efi_32.c to eliminate the duplicated code between EFI
* 32/64 support code. --ying 2007-10-26
@@ -81,6 +83,17 @@ 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;
+ bool use_pgd;
+};
+extern struct efi_scratch efi_scratch;
+
+/*
* Returns 1 if 'facility' is enabled, 0 otherwise.
*/
int efi_enabled(int facility)
@@ -797,22 +810,6 @@ 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
@@ -862,10 +859,10 @@ 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;
int count = 0;

efi.systab = NULL;
@@ -874,7 +871,6 @@ 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 +910,18 @@ void __init efi_enter_virtual_mode(void)
md->type != EFI_BOOT_SERVICES_DATA)
continue;

+ efi_map_region(md);
+
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);
- 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);
@@ -949,8 +930,15 @@ void __init efi_enter_virtual_mode(void)
count++;
}

+#ifdef CONFIG_X86_64
+ efi_scratch.efi_pgt = (pgd_t *)(unsigned long)real_mode_header->trampoline_pgd;
+ efi_scratch.use_pgd = true;
+#endif
+
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 +971,6 @@ 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_32.c b/arch/x86/platform/efi/efi_32.c
index 40e446941dd7..661663b08eaf 100644
--- a/arch/x86/platform/efi/efi_32.c
+++ b/arch/x86/platform/efi/efi_32.c
@@ -37,9 +37,36 @@
* 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 __init efi_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);
+}
+
void efi_call_phys_prelog(void)
{
struct desc_ptr gdt_descr;
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 39a0e7f1f0a3..db5230dd350e 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -39,59 +39,64 @@
#include <asm/cacheflush.h>
#include <asm/fixmap.h>

-static pgd_t *save_pgd __initdata;
-static unsigned long efi_flags __initdata;
+void __init efi_call_phys_prelog(void) {}
+void __init efi_call_phys_epilog(void) {}

-static void __init early_code_mapping_set_exec(int executable)
+/*
+ * Add low kernel mappings for passing arguments to EFI functions.
+ */
+void efi_sync_low_kernel_mappings(void)
{
- efi_memory_desc_t *md;
- void *p;
+ unsigned num_pgds;
+ pgd_t *pgd = (pgd_t *)__va(real_mode_header->trampoline_pgd);

- if (!(__supported_pte_mask & _PAGE_NX))
- return;
+ num_pgds = pgd_index(VMALLOC_START - 1) - pgd_index(PAGE_OFFSET);

- /* 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);
- }
+ memcpy(pgd + pgd_index(PAGE_OFFSET),
+ init_mm.pgd + pgd_index(PAGE_OFFSET),
+ sizeof(pgd_t) * num_pgds);
}

-void __init efi_call_phys_prelog(void)
+/*
+ * 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 u64 efi_va = -4 * (1UL << 30);
+#define EFI_VA_END (-68 * (1UL << 30))
+
+static void __init __map_region(efi_memory_desc_t *md, u64 va)
{
- unsigned long vaddress;
- int pgd;
- int n_pgds;
+ pgd_t *pgd = (pgd_t *)__va(real_mode_header->trampoline_pgd);
+ unsigned long pf = 0, size;
+ u64 end;

- early_code_mapping_set_exec(1);
- local_irq_save(efi_flags);
+ if (!(md->attribute & EFI_MEMORY_WB))
+ pf |= _PAGE_PCD;

- n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT), PGDIR_SIZE);
- save_pgd = kmalloc(n_pgds * sizeof(pgd_t), GFP_KERNEL);
+ size = md->num_pages << PAGE_SHIFT;
+ end = va + size;

- 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();
+ 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);
}

-void __init efi_call_phys_epilog(void)
+void __init efi_map_region(efi_memory_desc_t *md)
{
- /*
- * 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);
+ unsigned long size = md->num_pages << PAGE_SHIFT;
+
+ efi_va -= size;
+ if (efi_va < EFI_VA_END) {
+ pr_warning(FW_WARN "VA address range overflow!\n");
+ return;
+ }
+
+ /* Do the 1:1 map */
+ __map_region(md, md->phys_addr);
+
+ /* 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,
diff --git a/arch/x86/platform/efi/efi_stub_64.S b/arch/x86/platform/efi/efi_stub_64.S
index 4c07ccab8146..2bb9714bf713 100644
--- a/arch/x86/platform/efi/efi_stub_64.S
+++ b/arch/x86/platform/efi/efi_stub_64.S
@@ -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 +156,14 @@ 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

--
Regards/Gruss,
Boris.

Sent from a fat crate under my desk. Formatting is fine.
--