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@citrix.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/arch/x86/kernel/cpu/amd_64.c b/arch/x86/kernel/cpu/amd_64.c
index 7c36fb8a28d46455c2a51b8adabc8511e1f9386c..d1692b2a41ffac4bf6b9423d38af42741a847b36 100644 (file)
--- 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(struct cpuinfo_x86 *c)
        /* 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)

diff --git a/arch/x86/kernel/cpu/common_64.c b/arch/x86/kernel/cpu/common_64.c
index 15419cd3c5a474ad320f3016505db1a32e24d744..736f50fa433d4b54c29c56d3649bac8db8227539 100644 (file)
--- a/arch/x86/kernel/cpu/common_64.c
+++ b/arch/x86/kernel/cpu/common_64.c
@@ -317,9 +317,6 @@ static void __cpuinit early_identify_cpu(struct cpuinfo_x86 *c)
                c->x86_phys_bits = eax & 0xff;
        }
 
-       /* 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);

diff --git a/arch/x86/vdso/Makefile b/arch/x86/vdso/Makefile
index b7ad9f89d21f8898dbf792de05b0dddd21f3a803..4d6ef0a336d6d3499580b32958d59c93639bc647 100644 (file)
--- a/arch/x86/vdso/Makefile
+++ b/arch/x86/vdso/Makefile
@@ -62,7 +62,7 @@ $(obj)/%-syms.lds: $(obj)/%.so.dbg FORCE
 # Build multiple 32-bit vDSO images to choose from at boot time.
 #
 obj-$(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
 

diff --git a/arch/x86/vdso/vdso32-setup.c b/arch/x86/vdso/vdso32-setup.c
index 0bce5429a51546de1fab7f0acd29e921d38a9870..513f330c58326b2126e6cfe4c78214eaa77226e8 100644 (file)
--- a/arch/x86/vdso/vdso32-setup.c
+++ b/arch/x86/vdso/vdso32-setup.c
@@ -193,17 +193,12 @@ static __init void relocate_vdso(Elf32_Ehdr *ehdr)
        }
 }
 
-/*
- * 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 map)
 #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);

diff --git a/arch/x86/vdso/vdso32.S b/arch/x86/vdso/vdso32.S
index 1e36f72cab865e450cc3f17a9fdf53a7da485a14..2ce5f82c333b15c255b621e63d7bc57b7278b361 100644 (file)
--- 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:

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 3e11779755c3babc2509f5784367dc7f0026b62d..e3648e64a6376787293185fd23070f62038b3fea 100644 (file)
--- 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
 }

diff --git a/include/asm-x86/vdso.h b/include/asm-x86/vdso.h
index 86e085e003d2b6b4ea46c7591d7db8ae0e9c244b..8e18fb80f5e641ac3683b8c84c68cb511c4ab30f 100644 (file)
--- a/include/asm-x86/vdso.h
+++ b/include/asm-x86/vdso.h
@@ -36,4 +36,12 @@ extern const char VDSO32_PRELINK[];
 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 */