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arm64: remove sigreturn wrappers 

The arm64 sigreturn* syscall handlers are non-standard. Rather than
taking a number of user parameters in registers as per the AAPCS,
they expect the pt_regs as their sole argument.

To make this work, we override the syscall definitions to invoke
wrappers written in assembly, which mov the SP into x0, and branch to
their respective C functions.

On other architectures (such as x86), the sigreturn* functions take no
argument and instead use current_pt_regs() to acquire the user
registers. This requires less boilerplate code, and allows for other
features such as interposing C code in this path.

This patch takes the same approach for arm64.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tentatively-reviewed-by: Dave Martin <dave.martin@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Mark Rutland 2018-07-11 14:56:41 +01:00 committed by Will Deacon
parent f9209e2629
commit 3085e1645e
7 changed files with 11 additions and 27 deletions
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4
arch/arm64/include/asm/unistd32.h
View File

@ -260,7 +260,7 @@ __SYSCALL(117, sys_ni_syscall)
#define __NR_fsync 118
__SYSCALL(__NR_fsync, sys_fsync)
#define __NR_sigreturn 119
__SYSCALL(__NR_sigreturn, compat_sys_sigreturn_wrapper)
__SYSCALL(__NR_sigreturn, compat_sys_sigreturn)
#define __NR_clone 120
__SYSCALL(__NR_clone, sys_clone)
#define __NR_setdomainname 121
@ -368,7 +368,7 @@ __SYSCALL(__NR_getresgid, sys_getresgid16)
#define __NR_prctl 172
__SYSCALL(__NR_prctl, sys_prctl)
#define __NR_rt_sigreturn 173
__SYSCALL(__NR_rt_sigreturn, compat_sys_rt_sigreturn_wrapper)
__SYSCALL(__NR_rt_sigreturn, compat_sys_rt_sigreturn)
#define __NR_rt_sigaction 174
__SYSCALL(__NR_rt_sigaction, compat_sys_rt_sigaction)
#define __NR_rt_sigprocmask 175

8
arch/arm64/kernel/entry.S
View File

@ -1139,14 +1139,6 @@ __entry_tramp_data_start:
#endif /* CONFIG_RANDOMIZE_BASE */
#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
/*
* Special system call wrappers.
*/
ENTRY(sys_rt_sigreturn_wrapper)
mov x0, sp
b sys_rt_sigreturn
ENDPROC(sys_rt_sigreturn_wrapper)
/*
* Register switch for AArch64. The callee-saved registers need to be saved
* and restored. On entry:

10
arch/arm64/kernel/entry32.S
View File

@ -30,16 +30,6 @@
* System call wrappers for the AArch32 compatibility layer.
*/
ENTRY(compat_sys_sigreturn_wrapper)
mov x0, sp
b compat_sys_sigreturn
ENDPROC(compat_sys_sigreturn_wrapper)
ENTRY(compat_sys_rt_sigreturn_wrapper)
mov x0, sp
b compat_sys_rt_sigreturn
ENDPROC(compat_sys_rt_sigreturn_wrapper)
ENTRY(compat_sys_statfs64_wrapper)
mov w3, #84
cmp w1, #88

3
arch/arm64/kernel/signal.c
View File

@ -539,8 +539,9 @@ static int restore_sigframe(struct pt_regs *regs,
return err;
}
asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
asmlinkage long sys_rt_sigreturn(void)
{
struct pt_regs *regs = current_pt_regs();
struct rt_sigframe __user *frame;
/* Always make any pending restarted system calls return -EINTR */

6
arch/arm64/kernel/signal32.c
View File

@ -285,8 +285,9 @@ static int compat_restore_sigframe(struct pt_regs *regs,
return err;
}
asmlinkage int compat_sys_sigreturn(struct pt_regs *regs)
asmlinkage int compat_sys_sigreturn(void)
{
struct pt_regs *regs = current_pt_regs();
struct compat_sigframe __user *frame;
/* Always make any pending restarted system calls return -EINTR */
@ -315,8 +316,9 @@ asmlinkage int compat_sys_sigreturn(struct pt_regs *regs)
return 0;
}
asmlinkage int compat_sys_rt_sigreturn(struct pt_regs *regs)
asmlinkage int compat_sys_rt_sigreturn(void)
{
struct pt_regs *regs = current_pt_regs();
struct compat_rt_sigframe __user *frame;
/* Always make any pending restarted system calls return -EINTR */

3
arch/arm64/kernel/sys.c
View File

@ -48,8 +48,7 @@ SYSCALL_DEFINE1(arm64_personality, unsigned int, personality)
/*
* Wrappers to pass the pt_regs argument.
*/
asmlinkage long sys_rt_sigreturn_wrapper(void);
#define sys_rt_sigreturn sys_rt_sigreturn_wrapper
asmlinkage long sys_rt_sigreturn(void);
#define sys_personality sys_arm64_personality
#undef __SYSCALL

4
arch/arm64/kernel/sys32.c
View File

@ -25,8 +25,8 @@
#include <linux/compiler.h>
#include <linux/syscalls.h>
asmlinkage long compat_sys_sigreturn_wrapper(void);
asmlinkage long compat_sys_rt_sigreturn_wrapper(void);
asmlinkage long compat_sys_sigreturn(void);
asmlinkage long compat_sys_rt_sigreturn(void);
asmlinkage long compat_sys_statfs64_wrapper(void);
asmlinkage long compat_sys_fstatfs64_wrapper(void);
asmlinkage long compat_sys_pread64_wrapper(void);