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x86/entry/32: Enable pt_regs based syscalls

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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
This commit is contained in:
Brian Gerst
2020-03-13 15:51:42 -04:00
committed by Thomas Gleixner
parent 121b32a58a
commit 25c619e59b
6 changed files with 64 additions and 114 deletions
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111
arch/x86/include/asm/syscall_wrapper.h
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@@ -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__));\