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Date: Sat, 12 Jul 2008 02:22:00 -0700
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: Ingo Molnar <mingo@...e.hu>
CC: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
the arch/x86 maintainers <x86@...nel.org>
Subject: [PATCH 1/3] x86_64: further cleanup of 32-bit compat syscall mechanisms
AMD only supports "syscall" from 32-bit compat usermode.
Intel and Centaur(?) only support "sysenter" from 32-bit compat usermode.
Set the X86 feature bits accordingly, and set up the vdso in
accordance with those bits. On the offchance we run on in a 64-bit
environment which supports neither syscall nor sysenter from 32-bit
mode, then fall back to the int $0x80 vdso.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
arch/x86/kernel/cpu/amd_64.c | 2 ++
arch/x86/kernel/cpu/common_64.c | 3 ---
arch/x86/vdso/Makefile | 2 +-
arch/x86/vdso/vdso32-setup.c | 19 +++++++++----------
arch/x86/vdso/vdso32.S | 13 ++++++++-----
arch/x86/xen/setup.c | 10 +++++++---
include/asm-x86/vdso.h | 8 ++++++++
7 files changed, 35 insertions(+), 22 deletions(-)
===================================================================
--- a/arch/x86/kernel/cpu/amd_64.c
+++ b/arch/x86/kernel/cpu/amd_64.c
@@ -115,6 +115,8 @@ static void __cpuinit early_init_amd(str
/* c->x86_power is 8000_0007 edx. Bit 8 is constant TSC */
if (c->x86_power & (1<<8))
set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
+
+ set_cpu_cap(c, X86_FEATURE_SYSCALL32);
}
static void __cpuinit init_amd(struct cpuinfo_x86 *c)
===================================================================
--- a/arch/x86/kernel/cpu/common_64.c
+++ b/arch/x86/kernel/cpu/common_64.c
@@ -315,9 +315,6 @@ static void __cpuinit early_identify_cpu
if (c->extended_cpuid_level >= 0x80000007)
c->x86_power = cpuid_edx(0x80000007);
- /* Assume all 64-bit CPUs support 32-bit syscall */
- set_cpu_cap(c, X86_FEATURE_SYSCALL32);
-
if (c->x86_vendor != X86_VENDOR_UNKNOWN &&
cpu_devs[c->x86_vendor]->c_early_init)
cpu_devs[c->x86_vendor]->c_early_init(c);
===================================================================
--- a/arch/x86/vdso/Makefile
+++ b/arch/x86/vdso/Makefile
@@ -62,7 +62,7 @@ endef
# Build multiple 32-bit vDSO images to choose from at boot time.
#
obj-$(VDSO32-y) += vdso32-syms.lds
-vdso32.so-$(CONFIG_X86_32) += int80
+vdso32.so-$(VDSO32-y) += int80
vdso32.so-$(CONFIG_COMPAT) += syscall
vdso32.so-$(VDSO32-y) += sysenter
===================================================================
--- a/arch/x86/vdso/vdso32-setup.c
+++ b/arch/x86/vdso/vdso32-setup.c
@@ -193,17 +193,12 @@ static __init void relocate_vdso(Elf32_E
}
}
-/*
- * These symbols are defined by vdso32.S to mark the bounds
- * of the ELF DSO images included therein.
- */
-extern const char vdso32_default_start, vdso32_default_end;
-extern const char vdso32_sysenter_start, vdso32_sysenter_end;
static struct page *vdso32_pages[1];
#ifdef CONFIG_X86_64
#define vdso32_sysenter() (boot_cpu_has(X86_FEATURE_SYSENTER32))
+#define vdso32_syscall() (boot_cpu_has(X86_FEATURE_SYSCALL32))
/* May not be __init: called during resume */
void syscall32_cpu_init(void)
@@ -226,6 +221,7 @@ static inline void map_compat_vdso(int m
#else /* CONFIG_X86_32 */
#define vdso32_sysenter() (boot_cpu_has(X86_FEATURE_SEP))
+#define vdso32_syscall() (0)
void enable_sep_cpu(void)
{
@@ -296,12 +292,15 @@ int __init sysenter_setup(void)
gate_vma_init();
#endif
- if (!vdso32_sysenter()) {
- vsyscall = &vdso32_default_start;
- vsyscall_len = &vdso32_default_end - &vdso32_default_start;
- } else {
+ if (vdso32_syscall()) {
+ vsyscall = &vdso32_syscall_start;
+ vsyscall_len = &vdso32_syscall_end - &vdso32_syscall_start;
+ } else if (vdso32_sysenter()){
vsyscall = &vdso32_sysenter_start;
vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
+ } else {
+ vsyscall = &vdso32_int80_start;
+ vsyscall_len = &vdso32_int80_end - &vdso32_int80_start;
}
memcpy(syscall_page, vsyscall, vsyscall_len);
===================================================================
--- a/arch/x86/vdso/vdso32.S
+++ b/arch/x86/vdso/vdso32.S
@@ -2,14 +2,17 @@
__INITDATA
- .globl vdso32_default_start, vdso32_default_end
-vdso32_default_start:
-#ifdef CONFIG_X86_32
+ .globl vdso32_int80_start, vdso32_int80_end
+vdso32_int80_start:
.incbin "arch/x86/vdso/vdso32-int80.so"
-#else
+vdso32_int80_end:
+
+ .globl vdso32_syscall_start, vdso32_syscall_end
+vdso32_syscall_start:
+#ifdef CONFIG_COMPAT
.incbin "arch/x86/vdso/vdso32-syscall.so"
#endif
-vdso32_default_end:
+vdso32_syscall_end:
.globl vdso32_sysenter_start, vdso32_sysenter_end
vdso32_sysenter_start:
===================================================================
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -83,12 +83,16 @@ static void xen_idle(void)
/*
* Set the bit indicating "nosegneg" library variants should be used.
+ * We only need to bother in pure 32-bit mode; compat 32-bit processes
+ * can have un-truncated segments, so wrapping around is allowed.
*/
static void __init fiddle_vdso(void)
{
-#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
- extern const char vdso32_default_start;
- u32 *mask = VDSO32_SYMBOL(&vdso32_default_start, NOTE_MASK);
+#ifdef CONFIG_X86_32
+ u32 *mask;
+ mask = VDSO32_SYMBOL(&vdso32_int80_start, NOTE_MASK);
+ *mask |= 1 << VDSO_NOTE_NONEGSEG_BIT;
+ mask = VDSO32_SYMBOL(&vdso32_sysenter_start, NOTE_MASK);
*mask |= 1 << VDSO_NOTE_NONEGSEG_BIT;
#endif
}
===================================================================
--- a/include/asm-x86/vdso.h
+++ b/include/asm-x86/vdso.h
@@ -36,4 +36,12 @@ extern void __user __kernel_sigreturn;
extern void __user __kernel_sigreturn;
extern void __user __kernel_rt_sigreturn;
+/*
+ * These symbols are defined by vdso32.S to mark the bounds
+ * of the ELF DSO images included therein.
+ */
+extern const char vdso32_int80_start, vdso32_int80_end;
+extern const char vdso32_syscall_start, vdso32_syscall_end;
+extern const char vdso32_sysenter_start, vdso32_sysenter_end;
+
#endif /* asm-x86/vdso.h */
--
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