diff options
Diffstat (limited to 'arch/x86/include/asm/syscall_wrapper.h')
| -rw-r--r-- | arch/x86/include/asm/syscall_wrapper.h | 111 |
1 files changed, 61 insertions, 50 deletions
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__));\ |