[PATCH RFC] ARM: option for loading modules into vmalloc area
From: Konstantin Khlebnikov
Date: Tue Nov 18 2014 - 12:21:54 EST
Usually modules are loaded into small area prior to the kernel
text because they are linked with the kernel using short calls.
Compile-time instrumentation like GCOV or KASAN bloats code a lot,
and as a result huge modules no longer fit into reserved area.
This patch adds option CONFIG_MODULES_USE_VMALLOC which lifts
limitation on amount of loaded modules. It links modules using
long-calls (option -mlong-calls) and loads them into vmalloc area.
In few places exported symbols are called from inline assembly.
This patch adds macro for such call sites: __asmbl and __asmbl_clobber.
Call turns into single 'bl' or sequence 'movw; movt; blx' depending on
context and state of config option.
Unfortunately this option isn't compatible with CONFIG_FUNCTION_TRACER.
Compiler emits short calls to profiling function despite of -mlong-calls.
This is a bug in GCC, but ftrace anyway needs an update to handle this.
Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@xxxxxxxxxxx>
---
arch/arm/Kconfig | 20 ++++++++++++++++++++
arch/arm/Makefile | 4 ++++
arch/arm/include/asm/compiler.h | 13 +++++++++++++
arch/arm/include/asm/div64.h | 2 +-
arch/arm/include/asm/memory.h | 11 +++++++++++
arch/arm/include/asm/uaccess.h | 16 ++++++++--------
arch/arm/kernel/module.c | 2 ++
arch/arm/mm/dump.c | 10 +++++++++-
arch/arm/mm/init.c | 2 ++
arch/arm/mm/mmu.c | 7 +++----
arch/arm/mm/pgd.c | 5 +++--
11 files changed, 76 insertions(+), 16 deletions(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 89c4b5c..7fc4b22 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1686,6 +1686,26 @@ config HIGHPTE
bool "Allocate 2nd-level pagetables from highmem"
depends on HIGHMEM
+config MODULES_USE_LONG_CALLS
+ bool
+ help
+ Use long calls for calling exported symbols.
+
+config MODULES_USE_VMALLOC
+ bool "Put modules into vmalloc area"
+ select MODULES_USE_LONG_CALLS
+ depends on MMU && MODULES
+ depends on !XIP_KERNEL
+ depends on !FUNCTION_TRACER
+ help
+ Usually modules are loaded into small area prior to the kernel text
+ because they are linked with the kernel using short calls.
+
+ This option enables long calls and moves modules into vmalloc area.
+ This allows to load more modules but adds some perfromance penalty.
+
+ If unsure, say n.
+
config HW_PERF_EVENTS
bool "Enable hardware performance counter support for perf events"
depends on PERF_EVENTS
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 034a949..64541db 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -117,6 +117,10 @@ CFLAGS_ISA :=$(call cc-option,-marm,)
AFLAGS_ISA :=$(CFLAGS_ISA)
endif
+ifeq ($(CONFIG_MODULES_USE_LONG_CALLS),y)
+CFLAGS_MODULE += -mlong-calls
+endif
+
# Need -Uarm for gcc < 3.x
KBUILD_CFLAGS +=$(CFLAGS_ABI) $(CFLAGS_ISA) $(arch-y) $(tune-y) $(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,)) -msoft-float -Uarm
KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_ISA) $(arch-y) $(tune-y) -include asm/unified.h -msoft-float
diff --git a/arch/arm/include/asm/compiler.h b/arch/arm/include/asm/compiler.h
index 8155db2..d953067 100644
--- a/arch/arm/include/asm/compiler.h
+++ b/arch/arm/include/asm/compiler.h
@@ -11,5 +11,18 @@
*/
#define __asmeq(x, y) ".ifnc " x "," y " ; .err ; .endif\n\t"
+/*
+ * This is used for calling exported symbols from inline assembly code.
+ */
+#if defined(MODULE) && defined(CONFIG_MODULES_USE_LONG_CALLS)
+#define __asmbl(cond, reg, target) \
+ "movw " reg ", #:lower16:" target "\n\t" \
+ "movt " reg ", #:upper16:" target "\n\t" \
+ "blx" cond " " reg "\n\t"
+#define __asmbl_clobber(reg) ,reg
+#else
+#define __asmbl(cond, reg, target) "bl" cond " " target"\n\t"
+#define __asmbl_clobber(reg)
+#endif
#endif /* __ASM_ARM_COMPILER_H */
diff --git a/arch/arm/include/asm/div64.h b/arch/arm/include/asm/div64.h
index 662c7bd..fc7548d 100644
--- a/arch/arm/include/asm/div64.h
+++ b/arch/arm/include/asm/div64.h
@@ -38,7 +38,7 @@
__asmeq("%1", "r2") \
__asmeq("%2", "r0") \
__asmeq("%3", "r4") \
- "bl __do_div64" \
+ __asmbl("", "ip", "__do_div64") \
: "=r" (__rem), "=r" (__res) \
: "r" (__n), "r" (__base) \
: "ip", "lr", "cc"); \
diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index e731018..17745c2 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -47,6 +47,15 @@
*/
#define TASK_SIZE_26 (UL(1) << 26)
+#ifdef CONFIG_MODULES_USE_VMALLOC
+/*
+ * Modules might be anywhere in the vmalloc area.
+ */
+#define MODULES_VADDR VMALLOC_START
+#define MODULES_END VMALLOC_END
+
+#else /* CONFIG_MODULES_USE_VMALLOC */
+
/*
* The module space lives between the addresses given by TASK_SIZE
* and PAGE_OFFSET - it must be within 32MB of the kernel text.
@@ -71,6 +80,8 @@
#define MODULES_END (PAGE_OFFSET)
#endif
+#endif /* CONFIG_MODULES_USE_VMALLOC */
+
/*
* The XIP kernel gets mapped at the bottom of the module vm area.
* Since we use sections to map it, this macro replaces the physical address
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 4767eb9..c4c8d26 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -113,21 +113,21 @@ extern int __get_user_64t_1(void *);
extern int __get_user_64t_2(void *);
extern int __get_user_64t_4(void *);
-#define __GUP_CLOBBER_1 "lr", "cc"
+#define __GUP_CLOBBER_1 "lr", "cc" __asmbl_clobber("ip")
#ifdef CONFIG_CPU_USE_DOMAINS
#define __GUP_CLOBBER_2 "ip", "lr", "cc"
#else
-#define __GUP_CLOBBER_2 "lr", "cc"
+#define __GUP_CLOBBER_2 "lr", "cc" __asmbl_clobber("ip")
#endif
-#define __GUP_CLOBBER_4 "lr", "cc"
-#define __GUP_CLOBBER_32t_8 "lr", "cc"
-#define __GUP_CLOBBER_8 "lr", "cc"
+#define __GUP_CLOBBER_4 "lr", "cc" __asmbl_clobber("ip")
+#define __GUP_CLOBBER_32t_8 "lr", "cc" __asmbl_clobber("ip")
+#define __GUP_CLOBBER_8 "lr", "cc" __asmbl_clobber("ip")
#define __get_user_x(__r2,__p,__e,__l,__s) \
__asm__ __volatile__ ( \
__asmeq("%0", "r0") __asmeq("%1", "r2") \
__asmeq("%3", "r1") \
- "bl __get_user_" #__s \
+ __asmbl("", "ip", "__get_user_" #__s) \
: "=&r" (__e), "=r" (__r2) \
: "0" (__p), "r" (__l) \
: __GUP_CLOBBER_##__s)
@@ -149,7 +149,7 @@ extern int __get_user_64t_4(void *);
__asm__ __volatile__ ( \
__asmeq("%0", "r0") __asmeq("%1", "r2") \
__asmeq("%3", "r1") \
- "bl __get_user_64t_" #__s \
+ __asmbl("", "ip", "__get_user_64t_" #__s) \
: "=&r" (__e), "=r" (__r2) \
: "0" (__p), "r" (__l) \
: __GUP_CLOBBER_##__s)
@@ -211,7 +211,7 @@ extern int __put_user_8(void *, unsigned long long);
__asm__ __volatile__ ( \
__asmeq("%0", "r0") __asmeq("%2", "r2") \
__asmeq("%3", "r1") \
- "bl __put_user_" #__s \
+ __asmbl("", "ip", "__put_user_" #__s) \
: "=&r" (__e) \
: "0" (__p), "r" (__r2), "r" (__l) \
: "ip", "lr", "cc")
diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
index 6a4dffe..081da90 100644
--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c
@@ -38,12 +38,14 @@
#endif
#ifdef CONFIG_MMU
+#ifndef CONFIG_MODULES_USE_VMALLOC
void *module_alloc(unsigned long size)
{
return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
GFP_KERNEL, PAGE_KERNEL_EXEC, NUMA_NO_NODE,
__builtin_return_address(0));
}
+#endif /* CONFIG_MODULES_USE_VMALLOC */
#endif
int
diff --git a/arch/arm/mm/dump.c b/arch/arm/mm/dump.c
index 5942493..d4d4f75d 100644
--- a/arch/arm/mm/dump.c
+++ b/arch/arm/mm/dump.c
@@ -19,6 +19,7 @@
#include <asm/fixmap.h>
#include <asm/pgtable.h>
+#include <asm/highmem.h>
struct addr_marker {
unsigned long start_address;
@@ -26,7 +27,12 @@ struct addr_marker {
};
static struct addr_marker address_markers[] = {
+#ifndef CONFIG_MODULES_USE_VMALLOC
{ MODULES_VADDR, "Modules" },
+#endif
+#ifdef CONFIG_HIGHMEM
+ { PKMAP_BASE, "Page kmap" },
+#endif
{ PAGE_OFFSET, "Kernel Mapping" },
{ 0, "vmalloc() Area" },
{ VMALLOC_END, "vmalloc() End" },
@@ -356,7 +362,9 @@ static int ptdump_init(void)
for (j = 0; j < pg_level[i].num; j++)
pg_level[i].mask |= pg_level[i].bits[j].mask;
- address_markers[2].start_address = VMALLOC_START;
+ i = 1 + !IS_ENABLED(CONFIG_MODULES_USE_VMALLOC) +
+ !!IS_ENABLED(CONFIG_HIGHMEM);
+ address_markers[i].start_address = VMALLOC_START;
pe = debugfs_create_file("kernel_page_tables", 0400, NULL, NULL,
&ptdump_fops);
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 9481f85..985aed8 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -595,7 +595,9 @@ void __init mem_init(void)
* be detected at build time already.
*/
#ifdef CONFIG_MMU
+#ifndef CONFIG_MODULES_USE_VMALLOC
BUILD_BUG_ON(TASK_SIZE > MODULES_VADDR);
+#endif
BUG_ON(TASK_SIZE > MODULES_VADDR);
#endif
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 9d2cdda..9e0c4f4 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1161,16 +1161,15 @@ void __init sanity_check_meminfo(void)
static inline void prepare_page_table(void)
{
- unsigned long addr;
+ unsigned long addr = 0;
phys_addr_t end;
/*
* Clear out all the mappings below the kernel image.
*/
- for (addr = 0; addr < MODULES_VADDR; addr += PMD_SIZE)
- pmd_clear(pmd_off_k(addr));
-
#ifdef CONFIG_XIP_KERNEL
+ for ( ; addr < MODULES_VADDR; addr += PMD_SIZE)
+ pmd_clear(pmd_off_k(addr));
/* The XIP kernel is mapped in the module area -- skip over it */
addr = ((unsigned long)_etext + PMD_SIZE - 1) & PMD_MASK;
#endif
diff --git a/arch/arm/mm/pgd.c b/arch/arm/mm/pgd.c
index 3fbcb5a..ce23923 100644
--- a/arch/arm/mm/pgd.c
+++ b/arch/arm/mm/pgd.c
@@ -57,11 +57,11 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
clean_dcache_area(new_pgd, TTBR0_PTRS_PER_PGD * sizeof(pgd_t));
#ifdef CONFIG_ARM_LPAE
+#if defined(CONFIG_HIGHMEM) || !defined(CONFIG_MODULES_USE_VMALLOC)
/*
* Allocate PMD table for modules and pkmap mappings.
*/
- new_pud = pud_alloc(mm, new_pgd + pgd_index(MODULES_VADDR),
- MODULES_VADDR);
+ new_pud = pud_alloc(mm, new_pgd + pgd_index(PKMAP_BASE), PKMAP_BASE);
if (!new_pud)
goto no_pud;
@@ -69,6 +69,7 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
if (!new_pmd)
goto no_pmd;
#endif
+#endif
if (!vectors_high()) {
/*
--
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