MIPS: Preliminary VDSO

This is a preliminary patch to add a vdso to all user processes.  Still
missing are ELF headers and .eh_frame information.  But it is enough to
allow us to move signal trampolines off of the stack.  Note that emulation
of branch delay slots in the FPU emulator still requires the stack.

We allocate a single page (the vdso) and write all possible signal
trampolines into it.  The stack is moved down by one page and the vdso is
mapped into this space.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/975/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
index 1184f6eea98b7dd831599c97a19efbed14ce020b..ea77a42c5f8cb1bfc6ae03e131b60dde810f87bf 100644 (file)
--- a/arch/mips/include/asm/elf.h
+++ b/arch/mips/include/asm/elf.h
@@ -368,4 +368,8 @@ extern const char *__elf_platform;
 #define ELF_ET_DYN_BASE         (TASK_SIZE / 3 * 2)
 #endif
 
+#define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1
+struct linux_binprm;
+extern int arch_setup_additional_pages(struct linux_binprm *bprm,
+                                      int uses_interp);
 #endif /* _ASM_ELF_H */

diff --git a/arch/mips/include/asm/mmu.h b/arch/mips/include/asm/mmu.h
index 4063edd79623c89ba9eb2e5b4c8f0d69e4063191..c436138945a84dca9f1f311e54a801090c396853 100644 (file)
--- a/arch/mips/include/asm/mmu.h
+++ b/arch/mips/include/asm/mmu.h
@@ -1,6 +1,9 @@
 #ifndef __ASM_MMU_H
 #define __ASM_MMU_H
 
-typedef unsigned long mm_context_t[NR_CPUS];
+typedef struct {
+       unsigned long asid[NR_CPUS];
+       void *vdso;
+} mm_context_t;
 
 #endif /* __ASM_MMU_H */

diff --git a/arch/mips/include/asm/mmu_context.h b/arch/mips/include/asm/mmu_context.h
index 145bb81ccaa5094efec3806568f7fbb1087031f1..d9592733a7ba4759dbebc01f82efaef4a783e1e5 100644 (file)
--- a/arch/mips/include/asm/mmu_context.h
+++ b/arch/mips/include/asm/mmu_context.h
@@ -104,7 +104,7 @@ extern unsigned long smtc_asid_mask;
 
 #endif
 
-#define cpu_context(cpu, mm)   ((mm)->context[cpu])
+#define cpu_context(cpu, mm)   ((mm)->context.asid[cpu])
 #define cpu_asid(cpu, mm)      (cpu_context((cpu), (mm)) & ASID_MASK)
 #define asid_cache(cpu)                (cpu_data[cpu].asid_cache)
 

diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h
index 087a8884ef06e261e46f3480040cd9667066bdd8..ab387910009a3d1fd100f79aa94560552680750a 100644 (file)
--- a/arch/mips/include/asm/processor.h
+++ b/arch/mips/include/asm/processor.h
@@ -33,13 +33,19 @@ extern void (*cpu_wait)(void);
 
 extern unsigned int vced_count, vcei_count;
 
+/*
+ * A special page (the vdso) is mapped into all processes at the very
+ * top of the virtual memory space.
+ */
+#define SPECIAL_PAGES_SIZE PAGE_SIZE
+
 #ifdef CONFIG_32BIT
 /*
  * User space process size: 2GB. This is hardcoded into a few places,
  * so don't change it unless you know what you are doing.
  */
 #define TASK_SIZE      0x7fff8000UL
-#define STACK_TOP      TASK_SIZE
+#define STACK_TOP      ((TASK_SIZE & PAGE_MASK) - SPECIAL_PAGES_SIZE)
 
 /*
  * This decides where the kernel will search for a free chunk of vm
@@ -59,7 +65,8 @@ extern unsigned int vced_count, vcei_count;
 #define TASK_SIZE32    0x7fff8000UL
 #define TASK_SIZE      0x10000000000UL
 #define STACK_TOP      \
-      (test_thread_flag(TIF_32BIT_ADDR) ? TASK_SIZE32 : TASK_SIZE)
+       (((test_thread_flag(TIF_32BIT_ADDR) ?                           \
+          TASK_SIZE32 : TASK_SIZE) & PAGE_MASK) - SPECIAL_PAGES_SIZE)
 
 /*
  * This decides where the kernel will search for a free chunk of vm

diff --git a/arch/mips/include/asm/vdso.h b/arch/mips/include/asm/vdso.h
new file mode 100644 (file)
index 0000000..cca56aa
--- /dev/null
+++ b/arch/mips/include/asm/vdso.h
@@ -0,0 +1,29 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2009 Cavium Networks
+ */
+
+#ifndef __ASM_VDSO_H
+#define __ASM_VDSO_H
+
+#include <linux/types.h>
+
+
+#ifdef CONFIG_32BIT
+struct mips_vdso {
+       u32 signal_trampoline[2];
+       u32 rt_signal_trampoline[2];
+};
+#else  /* !CONFIG_32BIT */
+struct mips_vdso {
+       u32 o32_signal_trampoline[2];
+       u32 o32_rt_signal_trampoline[2];
+       u32 rt_signal_trampoline[2];
+       u32 n32_rt_signal_trampoline[2];
+};
+#endif /* CONFIG_32BIT */
+
+#endif /* __ASM_VDSO_H */

diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index ef20957ca14b7af284f604fe321317e5ecc09157..7a6ac501cbb5abc07cb4f78f43c2e806200ce023 100644 (file)
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -6,7 +6,7 @@ extra-y         := head.o init_task.o vmlinux.lds
 
 obj-y          += cpu-probe.o branch.o entry.o genex.o irq.o process.o \
                   ptrace.o reset.o setup.o signal.o syscall.o \
-                  time.o topology.o traps.o unaligned.o watch.o
+                  time.o topology.o traps.o unaligned.o watch.o vdso.o
 
 ifdef CONFIG_FUNCTION_TRACER
 CFLAGS_REMOVE_ftrace.o = -pg

diff --git a/arch/mips/kernel/syscall.c b/arch/mips/kernel/syscall.c
index 9587abc67f35cfec1851c609f40e08e460436356..dd81b0f875183d887e97996ee14f961f79055118 100644 (file)
--- a/arch/mips/kernel/syscall.c
+++ b/arch/mips/kernel/syscall.c
@@ -79,7 +79,11 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
        int do_color_align;
        unsigned long task_size;
 
-       task_size = STACK_TOP;
+#ifdef CONFIG_32BIT
+       task_size = TASK_SIZE;
+#else /* Must be CONFIG_64BIT*/
+       task_size = test_thread_flag(TIF_32BIT_ADDR) ? TASK_SIZE32 : TASK_SIZE;
+#endif
 
        if (len > task_size)
                return -ENOMEM;

diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c
new file mode 100644 (file)
index 0000000..b773c11
--- /dev/null
+++ b/arch/mips/kernel/vdso.c
@@ -0,0 +1,112 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2009, 2010 Cavium Networks, Inc.
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/init.h>
+#include <linux/binfmts.h>
+#include <linux/elf.h>
+#include <linux/vmalloc.h>
+#include <linux/unistd.h>
+
+#include <asm/vdso.h>
+#include <asm/uasm.h>
+
+/*
+ * Including <asm/unistd.h> would give use the 64-bit syscall numbers ...
+ */
+#define __NR_O32_sigreturn             4119
+#define __NR_O32_rt_sigreturn          4193
+#define __NR_N32_rt_sigreturn          6211
+
+static struct page *vdso_page;
+
+static void __init install_trampoline(u32 *tramp, unsigned int sigreturn)
+{
+       uasm_i_addiu(&tramp, 2, 0, sigreturn);  /* li v0, sigreturn */
+       uasm_i_syscall(&tramp, 0);
+}
+
+static int __init init_vdso(void)
+{
+       struct mips_vdso *vdso;
+
+       vdso_page = alloc_page(GFP_KERNEL);
+       if (!vdso_page)
+               panic("Cannot allocate vdso");
+
+       vdso = vmap(&vdso_page, 1, 0, PAGE_KERNEL);
+       if (!vdso)
+               panic("Cannot map vdso");
+       clear_page(vdso);
+
+       install_trampoline(vdso->rt_signal_trampoline, __NR_rt_sigreturn);
+#ifdef CONFIG_32BIT
+       install_trampoline(vdso->signal_trampoline, __NR_sigreturn);
+#else
+       install_trampoline(vdso->n32_rt_signal_trampoline,
+                          __NR_N32_rt_sigreturn);
+       install_trampoline(vdso->o32_signal_trampoline, __NR_O32_sigreturn);
+       install_trampoline(vdso->o32_rt_signal_trampoline,
+                          __NR_O32_rt_sigreturn);
+#endif
+
+       vunmap(vdso);
+
+       pr_notice("init_vdso successfull\n");
+
+       return 0;
+}
+device_initcall(init_vdso);
+
+static unsigned long vdso_addr(unsigned long start)
+{
+       return STACK_TOP;
+}
+
+int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+{
+       int ret;
+       unsigned long addr;
+       struct mm_struct *mm = current->mm;
+
+       down_write(&mm->mmap_sem);
+
+       addr = vdso_addr(mm->start_stack);
+
+       addr = get_unmapped_area(NULL, addr, PAGE_SIZE, 0, 0);
+       if (IS_ERR_VALUE(addr)) {
+               ret = addr;
+               goto up_fail;
+       }
+
+       ret = install_special_mapping(mm, addr, PAGE_SIZE,
+                                     VM_READ|VM_EXEC|
+                                     VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
+                                     VM_ALWAYSDUMP,
+                                     &vdso_page);
+
+       if (ret)
+               goto up_fail;
+
+       mm->context.vdso = (void *)addr;
+
+up_fail:
+       up_write(&mm->mmap_sem);
+       return ret;
+}
+
+const char *arch_vma_name(struct vm_area_struct *vma)
+{
+       if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
+               return "[vdso]";
+       return NULL;
+}