MIPS: Initial implementation of a VDSO

Add an initial implementation of a proper (i.e. an ELF shared library) VDSO. With this commit it does not export any symbols, it only replaces the current signal return trampoline page. A later commit will add user implementations of gettimeofday()/clock_gettime(). To support both new toolchains and old ones which don't generate ABI flags section, we define its content manually and then use a tool (genvdso) to patch up the section to have the correct name and type. genvdso also extracts symbol offsets ({,rt_}sigreturn) needed by the kernel, and generates a C file containing a "struct mips_vdso_image" containing both the VDSO data and these offsets. This C file is compiled into the kernel. On 64-bit kernels we require a different VDSO for each supported ABI, so we may build up to 3 different VDSOs. The VDSO to use is selected by the mips_abi structure. A kernel/user shared data page is created and mapped below the VDSO image. This is currently empty, but will be used by the user time function implementations which are added later. [[email protected]: - Add more comments - Move abi detection in genvdso.h since it's the get_symbol function that needs it. - Add an R6 specific way to calculate the base address of VDSO in order to avoid the branch instruction which affects performance. - Do not patch .gnu.attributes since it's not needed for dynamic linking. - Simplify Makefile a little bit. - checkpatch fixes - Restrict VDSO support for binutils < 2.25 for pre-R6 - Include atomic64.h for O32 variant on MIPS64] Signed-off-by: Alex Smith <[email protected]> Signed-off-by: Markos Chandras <[email protected]> Cc: Matthew Fortune <[email protected]> Cc: [email protected] Patchwork: https://patchwork.linux-mips.org/patch/11337/ Signed-off-by: Ralf Baechle <[email protected]>
gem5 · Nov 11, 2015 · ebb5e78 · ebb5e78
1 parent 22773aa
commit ebb5e78
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Showing 19 changed files with 1,114 additions and 124 deletions.
diff --git a/arch/mips/Kbuild b/arch/mips/Kbuild
@@ -17,6 +17,7 @@ obj- := $(platform-)
 obj-y += kernel/
 obj-y += mm/
 obj-y += net/
+obj-y += vdso/
 
 ifdef CONFIG_KVM
 obj-y += kvm/

diff --git a/arch/mips/include/asm/abi.h b/arch/mips/include/asm/abi.h
@@ -11,19 +11,20 @@
 
 #include <asm/signal.h>
 #include <asm/siginfo.h>
+#include <asm/vdso.h>
 
 struct mips_abi {
 	int (* const setup_frame)(void *sig_return, struct ksignal *ksig,
 				  struct pt_regs *regs, sigset_t *set);
-	const unsigned long	signal_return_offset;
 	int (* const setup_rt_frame)(void *sig_return, struct ksignal *ksig,
 				     struct pt_regs *regs, sigset_t *set);
-	const unsigned long	rt_signal_return_offset;
 	const unsigned long	restart;
 
 	unsigned	off_sc_fpregs;
 	unsigned	off_sc_fpc_csr;
 	unsigned	off_sc_used_math;
+
+	struct mips_vdso_image *vdso;
 };
 
 #endif /* _ASM_ABI_H */
diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
@@ -8,6 +8,7 @@
 #ifndef _ASM_ELF_H
 #define _ASM_ELF_H
 
+#include <linux/auxvec.h>
 #include <linux/fs.h>
 #include <uapi/linux/elf.h>
 
@@ -419,6 +420,12 @@ extern const char *__elf_platform;
 #define ELF_ET_DYN_BASE		(TASK_SIZE / 3 * 2)
 #endif
 
+#define ARCH_DLINFO							\
+do {									\
+	NEW_AUX_ENT(AT_SYSINFO_EHDR,					\
+		    (unsigned long)current->mm->context.vdso);		\
+} while (0)
+
 #define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1
 struct linux_binprm;
 extern int arch_setup_additional_pages(struct linux_binprm *bprm,

diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h
@@ -36,12 +36,6 @@ extern unsigned int vced_count, vcei_count;
  */
 #define HAVE_ARCH_PICK_MMAP_LAYOUT 1
 
-/*
- * 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
 #ifdef CONFIG_KVM_GUEST
 /* User space process size is limited to 1GB in KVM Guest Mode */
@@ -80,7 +74,7 @@ extern unsigned int vced_count, vcei_count;
 
 #endif
 
-#define STACK_TOP	((TASK_SIZE & PAGE_MASK) - SPECIAL_PAGES_SIZE)
+#define STACK_TOP	(TASK_SIZE & PAGE_MASK)
 
 /*
  * 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
@@ -1,29 +1,70 @@
 /*
- * 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) 2015 Imagination Technologies
+ * Author: Alex Smith <[email protected]>
  *
- * Copyright (C) 2009 Cavium Networks
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
  */
 
 #ifndef __ASM_VDSO_H
 #define __ASM_VDSO_H
 
-#include <linux/types.h>
+#include <linux/mm_types.h>
 
+/**
+ * struct mips_vdso_image - Details of a VDSO image.
+ * @data: Pointer to VDSO image data (page-aligned).
+ * @size: Size of the VDSO image data (page-aligned).
+ * @off_sigreturn: Offset of the sigreturn() trampoline.
+ * @off_rt_sigreturn: Offset of the rt_sigreturn() trampoline.
+ * @mapping: Special mapping structure.
+ *
+ * This structure contains details of a VDSO image, including the image data
+ * and offsets of certain symbols required by the kernel. It is generated as
+ * part of the VDSO build process, aside from the mapping page array, which is
+ * populated at runtime.
+ */
+struct mips_vdso_image {
+	void *data;
+	unsigned long size;
 
-#ifdef CONFIG_32BIT
-struct mips_vdso {
-	u32 signal_trampoline[2];
-	u32 rt_signal_trampoline[2];
+	unsigned long off_sigreturn;
+	unsigned long off_rt_sigreturn;
+
+	struct vm_special_mapping mapping;
 };
-#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];
+
+/*
+ * The following structures are auto-generated as part of the build for each
+ * ABI by genvdso, see arch/mips/vdso/Makefile.
+ */
+
+extern struct mips_vdso_image vdso_image;
+
+#ifdef CONFIG_MIPS32_O32
+extern struct mips_vdso_image vdso_image_o32;
+#endif
+
+#ifdef CONFIG_MIPS32_N32
+extern struct mips_vdso_image vdso_image_n32;
+#endif
+
+/**
+ * union mips_vdso_data - Data provided by the kernel for the VDSO.
+ *
+ * This structure contains data needed by functions within the VDSO. It is
+ * populated by the kernel and mapped read-only into user memory.
+ *
+ * Note: Care should be taken when modifying as the layout must remain the same
+ * for both 64- and 32-bit (for 32-bit userland on 64-bit kernel).
+ */
+union mips_vdso_data {
+	struct {
+	};
+
+	u8 page[PAGE_SIZE];
 };
-#endif /* CONFIG_32BIT */
 
 #endif /* __ASM_VDSO_H */
diff --git a/arch/mips/include/uapi/asm/Kbuild b/arch/mips/include/uapi/asm/Kbuild
@@ -1,9 +1,9 @@
 # UAPI Header export list
 include include/uapi/asm-generic/Kbuild.asm
 
-generic-y += auxvec.h
 generic-y += ipcbuf.h
 
+header-y += auxvec.h
 header-y += bitfield.h
 header-y += bitsperlong.h
 header-y += break.h

diff --git a/arch/mips/include/uapi/asm/auxvec.h b/arch/mips/include/uapi/asm/auxvec.h
@@ -0,0 +1,17 @@
+/*
+ * Copyright (C) 2015 Imagination Technologies
+ * Author: Alex Smith <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
+ */
+
+#ifndef __ASM_AUXVEC_H
+#define __ASM_AUXVEC_H
+
+/* Location of VDSO image. */
+#define AT_SYSINFO_EHDR		33
+
+#endif /* __ASM_AUXVEC_H */
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
@@ -36,7 +36,6 @@
 #include <asm/ucontext.h>
 #include <asm/cpu-features.h>
 #include <asm/war.h>
-#include <asm/vdso.h>
 #include <asm/dsp.h>
 #include <asm/inst.h>
 #include <asm/msa.h>
@@ -752,16 +751,15 @@ static int setup_rt_frame(void *sig_return, struct ksignal *ksig,
 struct mips_abi mips_abi = {
 #ifdef CONFIG_TRAD_SIGNALS
 	.setup_frame	= setup_frame,
-	.signal_return_offset = offsetof(struct mips_vdso, signal_trampoline),
 #endif
 	.setup_rt_frame = setup_rt_frame,
-	.rt_signal_return_offset =
-		offsetof(struct mips_vdso, rt_signal_trampoline),
 	.restart	= __NR_restart_syscall,
 
 	.off_sc_fpregs = offsetof(struct sigcontext, sc_fpregs),
 	.off_sc_fpc_csr = offsetof(struct sigcontext, sc_fpc_csr),
 	.off_sc_used_math = offsetof(struct sigcontext, sc_used_math),
+
+	.vdso		= &vdso_image,
 };
 
 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
@@ -801,11 +799,11 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 	}
 
 	if (sig_uses_siginfo(&ksig->ka))
-		ret = abi->setup_rt_frame(vdso + abi->rt_signal_return_offset,
+		ret = abi->setup_rt_frame(vdso + abi->vdso->off_rt_sigreturn,
 					  ksig, regs, oldset);
 	else
-		ret = abi->setup_frame(vdso + abi->signal_return_offset, ksig,
-				       regs, oldset);
+		ret = abi->setup_frame(vdso + abi->vdso->off_sigreturn,
+				       ksig, regs, oldset);
 
 	signal_setup_done(ret, ksig, 0);
 }

diff --git a/arch/mips/kernel/signal32.c b/arch/mips/kernel/signal32.c
@@ -31,7 +31,6 @@
 #include <asm/ucontext.h>
 #include <asm/fpu.h>
 #include <asm/war.h>
-#include <asm/vdso.h>
 #include <asm/dsp.h>
 
 #include "signal-common.h"
@@ -406,14 +405,12 @@ static int setup_rt_frame_32(void *sig_return, struct ksignal *ksig,
  */
 struct mips_abi mips_abi_32 = {
 	.setup_frame	= setup_frame_32,
-	.signal_return_offset =
-		offsetof(struct mips_vdso, o32_signal_trampoline),
 	.setup_rt_frame = setup_rt_frame_32,
-	.rt_signal_return_offset =
-		offsetof(struct mips_vdso, o32_rt_signal_trampoline),
 	.restart	= __NR_O32_restart_syscall,
 
 	.off_sc_fpregs = offsetof(struct sigcontext32, sc_fpregs),
 	.off_sc_fpc_csr = offsetof(struct sigcontext32, sc_fpc_csr),
 	.off_sc_used_math = offsetof(struct sigcontext32, sc_used_math),
+
+	.vdso		= &vdso_image_o32,
 };
diff --git a/arch/mips/kernel/signal_n32.c b/arch/mips/kernel/signal_n32.c
@@ -38,7 +38,6 @@
 #include <asm/fpu.h>
 #include <asm/cpu-features.h>
 #include <asm/war.h>
-#include <asm/vdso.h>
 
 #include "signal-common.h"
 
@@ -151,11 +150,11 @@ static int setup_rt_frame_n32(void *sig_return, struct ksignal *ksig,
 
 struct mips_abi mips_abi_n32 = {
 	.setup_rt_frame = setup_rt_frame_n32,
-	.rt_signal_return_offset =
-		offsetof(struct mips_vdso, n32_rt_signal_trampoline),
 	.restart	= __NR_N32_restart_syscall,
 
 	.off_sc_fpregs = offsetof(struct sigcontext, sc_fpregs),
 	.off_sc_fpc_csr = offsetof(struct sigcontext, sc_fpc_csr),
 	.off_sc_used_math = offsetof(struct sigcontext, sc_used_math),
+
+	.vdso		= &vdso_image_n32,
 };