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>

5 files changed, 47 insertions, 4 deletions

diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
index 1184f6eea98b..ea77a42c5f8c 100644
--- 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 4063edd79623..c436138945a8 100644
--- 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 145bb81ccaa5..d9592733a7ba 100644
--- 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 087a8884ef06..ab387910009a 100644
--- 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
index 000000000000..cca56aa40ff4
--- /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 */