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Subject[PATCH V1 2/6] x86/efi: Remove __init attribute from memory mapping functions
Date
From: Sai Praneeth <sai.praneeth.prakhya@intel.com>

Buggy firmware could illegally access EFI_BOOT_SERVICES_CODE/DATA
regions even after the kernel has assumed control of the platform. When
"CONFIG_EFI_WARN_ON_ILLEGAL_ACCESSES" is enabled, the efi page fault
handler will detect/fixup these illegal accesses. The below modified
functions are used by the page fault handler to fixup illegal accesses
to EFI_BOOT_SERVICES_CODE/DATA regions. As the page fault handler is
present during/after kernel boot it doesn't have an __init attribute,
but the below functions have it and thus during kernel build, "WARNING:
modpost: Found * section mismatch(es)" build warning is observed. To fix
it, remove __init attribute for all these functions.

In order to not keep these functions needlessly when
"CONFIG_EFI_WARN_ON_ILLEGAL_ACCESSES" is not selected, add a new
__efi_init_fixup attribute whose value changes based on whether the
config option is selected or not.

Suggested-by: Matt Fleming <matt@codeblueprint.co.uk>
Based-on-code-from: Ricardo Neri <ricardo.neri@intel.com>
Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Lee Chun-Yi <jlee@suse.com>
Cc: Al Stone <astone@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Bhupesh Sharma <bhsharma@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
arch/x86/include/asm/efi.h | 11 ++++++-----
arch/x86/platform/efi/efi.c | 4 ++--
arch/x86/platform/efi/efi_32.c | 2 +-
arch/x86/platform/efi/efi_64.c | 9 +++++----
drivers/firmware/efi/efi.c | 6 +++---
include/linux/efi.h | 16 ++++++++++++++--
6 files changed, 31 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index cec5fae23eb3..9b70743400f3 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -103,8 +103,9 @@ struct efi_scratch {
preempt_enable(); \
})

-extern void __iomem *__init efi_ioremap(unsigned long addr, unsigned long size,
- u32 type, u64 attribute);
+extern void __iomem *__efi_init_fixup efi_ioremap(unsigned long addr,
+ unsigned long size, u32 type,
+ u64 attribute);

#ifdef CONFIG_KASAN
/*
@@ -126,13 +127,13 @@ extern int __init efi_memblock_x86_reserve_range(void);
extern pgd_t * __init efi_call_phys_prolog(void);
extern void __init efi_call_phys_epilog(pgd_t *save_pgd);
extern void __init efi_print_memmap(void);
-extern void __init efi_memory_uc(u64 addr, unsigned long size);
-extern void __init efi_map_region(efi_memory_desc_t *md);
+extern void __efi_init_fixup efi_memory_uc(u64 addr, unsigned long size);
+extern void __efi_init_fixup efi_map_region(efi_memory_desc_t *md);
extern void __init efi_map_region_fixed(efi_memory_desc_t *md);
extern void efi_sync_low_kernel_mappings(void);
extern int __init efi_alloc_page_tables(void);
extern int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages);
-extern void __init old_map_region(efi_memory_desc_t *md);
+extern void __efi_init_fixup old_map_region(efi_memory_desc_t *md);
extern void __init runtime_code_page_mkexec(void);
extern void __init efi_runtime_update_mappings(void);
extern void __init efi_dump_pagetable(void);
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 9061babfbc83..439c2c40bf03 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -572,7 +572,7 @@ void __init runtime_code_page_mkexec(void)
}
}

-void __init efi_memory_uc(u64 addr, unsigned long size)
+void __efi_init_fixup efi_memory_uc(u64 addr, unsigned long size)
{
unsigned long page_shift = 1UL << EFI_PAGE_SHIFT;
u64 npages;
@@ -582,7 +582,7 @@ void __init efi_memory_uc(u64 addr, unsigned long size)
set_memory_uc(addr, npages);
}

-void __init old_map_region(efi_memory_desc_t *md)
+void __efi_init_fixup old_map_region(efi_memory_desc_t *md)
{
u64 start_pfn, end_pfn, end;
unsigned long size;
diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c
index 324b93328b37..8f31452bd204 100644
--- a/arch/x86/platform/efi/efi_32.c
+++ b/arch/x86/platform/efi/efi_32.c
@@ -58,7 +58,7 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
return 0;
}

-void __init efi_map_region(efi_memory_desc_t *md)
+void __efi_init_fixup efi_map_region(efi_memory_desc_t *md)
{
old_map_region(md);
}
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 448267f1c073..a04298312fdd 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -408,7 +408,7 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
return 0;
}

-static void __init __map_region(efi_memory_desc_t *md, u64 va)
+static void __efi_init_fixup __map_region(efi_memory_desc_t *md, u64 va)
{
unsigned long flags = _PAGE_RW;
unsigned long pfn;
@@ -426,7 +426,7 @@ static void __init __map_region(efi_memory_desc_t *md, u64 va)
md->phys_addr, va);
}

-void __init efi_map_region(efi_memory_desc_t *md)
+void __efi_init_fixup efi_map_region(efi_memory_desc_t *md)
{
unsigned long size = md->num_pages << PAGE_SHIFT;
u64 pa = md->phys_addr;
@@ -488,8 +488,9 @@ void __init efi_map_region_fixed(efi_memory_desc_t *md)
__map_region(md, md->virt_addr);
}

-void __iomem *__init efi_ioremap(unsigned long phys_addr, unsigned long size,
- u32 type, u64 attribute)
+void __iomem *__efi_init_fixup efi_ioremap(unsigned long phys_addr,
+ unsigned long size, u32 type,
+ u64 attribute)
{
unsigned long last_map_pfn;

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index d8a33a781a57..7bc3fac7bfe0 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -768,7 +768,7 @@ int __init efi_get_fdt_params(struct efi_fdt_params *params)
}
#endif /* CONFIG_EFI_PARAMS_FROM_FDT */

-static __initdata char memory_type_name[][20] = {
+static __efi_initdata_fixup char memory_type_name[][20] = {
"Reserved",
"Loader Code",
"Loader Data",
@@ -786,8 +786,8 @@ static __initdata char memory_type_name[][20] = {
"Persistent Memory",
};

-char * __init efi_md_typeattr_format(char *buf, size_t size,
- const efi_memory_desc_t *md)
+char * __efi_init_fixup efi_md_typeattr_format(char *buf, size_t size,
+ const efi_memory_desc_t *md)
{
char *pos;
int type_len;
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 855992b15269..169b5837c72c 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1107,11 +1107,23 @@ extern int efi_memattr_apply_permissions(struct mm_struct *mm,
for_each_efi_memory_desc_in_map(&efi.memmap, md)

/*
+ * __efi_init_fixup - if CONFIG_EFI_WARN_ON_ILLEGAL_ACCESSES is enabled,
+ * remove __init modifier.
+ */
+#ifdef CONFIG_EFI_WARN_ON_ILLEGAL_ACCESSES
+#define __efi_init_fixup
+#define __efi_initdata_fixup
+#else
+#define __efi_init_fixup __init
+#define __efi_initdata_fixup __initdata
+#endif
+
+/*
* Format an EFI memory descriptor's type and attributes to a user-provided
* character buffer, as per snprintf(), and return the buffer.
*/
-char * __init efi_md_typeattr_format(char *buf, size_t size,
- const efi_memory_desc_t *md);
+char * __efi_init_fixup efi_md_typeattr_format(char *buf, size_t size,
+ const efi_memory_desc_t *md);

/**
* efi_range_is_wc - check the WC bit on an address range
--
2.7.4
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