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authorBrian Gerst <brgerst@gmail.com>2020-03-13 15:51:42 -0400
committerThomas Gleixner <tglx@linutronix.de>2020-03-21 16:03:24 +0100
commit25c619e59b395a8c970d339f9c714302738e350e (patch)
tree74567402d083b53756dfafac858c9ff6f70168ca /arch/x86/include
parent121b32a58a3af89a780cf194ce3769fc4120e574 (diff)
x86/entry/32: Enable pt_regs based syscalls
Enable pt_regs based syscalls for 32-bit. This makes the 32-bit native kernel consistent with the 64-bit kernel, and improves the syscall interface by not needing to push all 6 potential arguments onto the stack. Signed-off-by: Brian Gerst <brgerst@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Link: https://lkml.kernel.org/r/20200313195144.164260-17-brgerst@gmail.com
Diffstat (limited to 'arch/x86/include')
-rw-r--r--arch/x86/include/asm/syscall.h6
-rw-r--r--arch/x86/include/asm/syscall_wrapper.h111
-rw-r--r--arch/x86/include/asm/syscalls.h29
3 files changed, 61 insertions, 85 deletions
diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index 1ef8d7bffa15..e413c836a826 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -16,13 +16,7 @@
#include <asm/thread_info.h> /* for TS_COMPAT */
#include <asm/unistd.h>
-#ifdef CONFIG_X86_64
typedef asmlinkage long (*sys_call_ptr_t)(const struct pt_regs *);
-#else
-typedef asmlinkage long (*sys_call_ptr_t)(unsigned long, unsigned long,
- unsigned long, unsigned long,
- unsigned long, unsigned long);
-#endif /* CONFIG_X86_64 */
extern const sys_call_ptr_t sys_call_table[];
#if defined(CONFIG_X86_32)
diff --git a/arch/x86/include/asm/syscall_wrapper.h b/arch/x86/include/asm/syscall_wrapper.h
index 0f126e40a464..5e13e2caf2e4 100644
--- a/arch/x86/include/asm/syscall_wrapper.h
+++ b/arch/x86/include/asm/syscall_wrapper.h
@@ -11,6 +11,47 @@ struct pt_regs;
extern asmlinkage long __x64_sys_ni_syscall(const struct pt_regs *regs);
extern asmlinkage long __ia32_sys_ni_syscall(const struct pt_regs *regs);
+/*
+ * Instead of the generic __SYSCALL_DEFINEx() definition, the x86 version takes
+ * struct pt_regs *regs as the only argument of the syscall stub(s) named as:
+ * __x64_sys_*() - 64-bit native syscall
+ * __ia32_sys_*() - 32-bit native syscall or common compat syscall
+ * __ia32_compat_sys_*() - 32-bit compat syscall
+ * __x32_compat_sys_*() - 64-bit X32 compat syscall
+ *
+ * The registers are decoded according to the ABI:
+ * 64-bit: RDI, RSI, RDX, R10, R8, R9
+ * 32-bit: EBX, ECX, EDX, ESI, EDI, EBP
+ *
+ * The stub then passes the decoded arguments to the __se_sys_*() wrapper to
+ * perform sign-extension (omitted for zero-argument syscalls). Finally the
+ * arguments are passed to the __do_sys_*() function which is the actual
+ * syscall. These wrappers are marked as inline so the compiler can optimize
+ * the functions where appropriate.
+ *
+ * Example assembly (slightly re-ordered for better readability):
+ *
+ * <__x64_sys_recv>: <-- syscall with 4 parameters
+ * callq <__fentry__>
+ *
+ * mov 0x70(%rdi),%rdi <-- decode regs->di
+ * mov 0x68(%rdi),%rsi <-- decode regs->si
+ * mov 0x60(%rdi),%rdx <-- decode regs->dx
+ * mov 0x38(%rdi),%rcx <-- decode regs->r10
+ *
+ * xor %r9d,%r9d <-- clear %r9
+ * xor %r8d,%r8d <-- clear %r8
+ *
+ * callq __sys_recvfrom <-- do the actual work in __sys_recvfrom()
+ * which takes 6 arguments
+ *
+ * cltq <-- extend return value to 64-bit
+ * retq <-- return
+ *
+ * This approach avoids leaking random user-provided register content down
+ * the call chain.
+ */
+
/* Mapping of registers to parameters for syscalls on x86-64 and x32 */
#define SC_X86_64_REGS_TO_ARGS(x, ...) \
__MAP(x,__SC_ARGS \
@@ -68,6 +109,26 @@ extern asmlinkage long __ia32_sys_ni_syscall(const struct pt_regs *regs);
#define __X64_SYS_NI(name)
#endif /* CONFIG_X86_64 */
+#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
+#define __IA32_SYS_STUB0(name) \
+ __SYS_STUB0(ia32, sys_##name)
+
+#define __IA32_SYS_STUBx(x, name, ...) \
+ __SYS_STUBx(ia32, sys##name, \
+ SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))
+
+#define __IA32_COND_SYSCALL(name) \
+ __COND_SYSCALL(ia32, sys_##name)
+
+#define __IA32_SYS_NI(name) \
+ __SYS_NI(ia32, sys_##name)
+#else /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
+#define __IA32_SYS_STUB0(name)
+#define __IA32_SYS_STUBx(x, name, ...)
+#define __IA32_COND_SYSCALL(name)
+#define __IA32_SYS_NI(name)
+#endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
+
#ifdef CONFIG_IA32_EMULATION
/*
* For IA32 emulation, we need to handle "compat" syscalls *and* create
@@ -90,27 +151,11 @@ extern asmlinkage long __ia32_sys_ni_syscall(const struct pt_regs *regs);
#define __IA32_COMPAT_SYS_NI(name) \
__SYS_NI(ia32, compat_sys_##name)
-#define __IA32_SYS_STUB0(name) \
- __SYS_STUB0(ia32, sys_##name)
-
-#define __IA32_SYS_STUBx(x, name, ...) \
- __SYS_STUBx(ia32, sys##name, \
- SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))
-
-#define __IA32_COND_SYSCALL(name) \
- __COND_SYSCALL(ia32, sys_##name)
-
-#define __IA32_SYS_NI(name) \
- __SYS_NI(ia32, sys_##name)
#else /* CONFIG_IA32_EMULATION */
#define __IA32_COMPAT_SYS_STUB0(name)
#define __IA32_COMPAT_SYS_STUBx(x, name, ...)
#define __IA32_COMPAT_COND_SYSCALL(name)
#define __IA32_COMPAT_SYS_NI(name)
-#define __IA32_SYS_STUB0(name)
-#define __IA32_SYS_STUBx(x, name, ...)
-#define __IA32_COND_SYSCALL(name)
-#define __IA32_SYS_NI(name)
#endif /* CONFIG_IA32_EMULATION */
@@ -180,40 +225,6 @@ extern asmlinkage long __ia32_sys_ni_syscall(const struct pt_regs *regs);
#endif /* CONFIG_COMPAT */
-
-/*
- * Instead of the generic __SYSCALL_DEFINEx() definition, this macro takes
- * struct pt_regs *regs as the only argument of the syscall stub named
- * __x64_sys_*(). It decodes just the registers it needs and passes them on to
- * the __se_sys_*() wrapper performing sign extension and then to the
- * __do_sys_*() function doing the actual job. These wrappers and functions
- * are inlined (at least in very most cases), meaning that the assembly looks
- * as follows (slightly re-ordered for better readability):
- *
- * <__x64_sys_recv>: <-- syscall with 4 parameters
- * callq <__fentry__>
- *
- * mov 0x70(%rdi),%rdi <-- decode regs->di
- * mov 0x68(%rdi),%rsi <-- decode regs->si
- * mov 0x60(%rdi),%rdx <-- decode regs->dx
- * mov 0x38(%rdi),%rcx <-- decode regs->r10
- *
- * xor %r9d,%r9d <-- clear %r9
- * xor %r8d,%r8d <-- clear %r8
- *
- * callq __sys_recvfrom <-- do the actual work in __sys_recvfrom()
- * which takes 6 arguments
- *
- * cltq <-- extend return value to 64-bit
- * retq <-- return
- *
- * This approach avoids leaking random user-provided register content down
- * the call chain.
- *
- * If IA32_EMULATION is enabled, this macro generates an additional wrapper
- * named __ia32_sys_*() which decodes the struct pt_regs *regs according
- * to the i386 calling convention (bx, cx, dx, si, di, bp).
- */
#define __SYSCALL_DEFINEx(x, name, ...) \
static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
diff --git a/arch/x86/include/asm/syscalls.h b/arch/x86/include/asm/syscalls.h
index 91b7b6e1a115..06cbdca634d6 100644
--- a/arch/x86/include/asm/syscalls.h
+++ b/arch/x86/include/asm/syscalls.h
@@ -17,33 +17,4 @@
/* kernel/ioport.c */
long ksys_ioperm(unsigned long from, unsigned long num, int turn_on);
-#ifdef CONFIG_X86_32
-/*
- * These definitions are only valid on pure 32-bit systems; x86-64 uses a
- * different syscall calling convention
- */
-asmlinkage long sys_ioperm(unsigned long, unsigned long, int);
-asmlinkage long sys_iopl(unsigned int);
-
-/* kernel/ldt.c */
-asmlinkage long sys_modify_ldt(int, void __user *, unsigned long);
-
-/* kernel/signal.c */
-asmlinkage long sys_rt_sigreturn(void);
-
-/* kernel/tls.c */
-asmlinkage long sys_set_thread_area(struct user_desc __user *);
-asmlinkage long sys_get_thread_area(struct user_desc __user *);
-
-/* X86_32 only */
-
-/* kernel/signal.c */
-asmlinkage long sys_sigreturn(void);
-
-/* kernel/vm86_32.c */
-struct vm86_struct;
-asmlinkage long sys_vm86old(struct vm86_struct __user *);
-asmlinkage long sys_vm86(unsigned long, unsigned long);
-
-#endif /* CONFIG_X86_32 */
#endif /* _ASM_X86_SYSCALLS_H */

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