diff options
| author | Dave Martin <Dave.Martin@arm.com> | 2017-08-01 15:35:54 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2017-08-07 09:58:33 +0100 |
| commit | 17c28958600928109049a3bcc814b0d5bfb1ff3a (patch) | |
| tree | 901508d772cc2fe2b33013b01b59ca990bd8f6c5 /arch/arm64/include | |
| parent | 35d0e6fb4d219d64ab3b7cffef7a11a0662140f5 (diff) | |
arm64: Abstract syscallno manipulation
The -1 "no syscall" value is written in various ways, shared with
the user ABI in some places, and generally obscure.
This patch attempts to make things a little more consistent and
readable by replacing all these uses with a single #define. A
couple of symbolic helpers are provided to clarify the intent
further.
Because the in-syscall check in do_signal() is changed from >= 0 to
!= NO_SYSCALL by this patch, different behaviour may be observable
if syscallno is set to values less than -1 by a tracer. However,
this is not different from the behaviour that is already observable
if a tracer sets syscallno to a value >= __NR_(compat_)syscalls.
It appears that this can cause spurious syscall restarting, but
that is not a new behaviour either, and does not appear harmful.
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/include')
| -rw-r--r-- | arch/arm64/include/asm/processor.h | 2 | ||||
| -rw-r--r-- | arch/arm64/include/asm/ptrace.h | 21 |
2 files changed, 22 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 379def1d6b67..b7334f11c4cf 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -112,7 +112,7 @@ void tls_preserve_current_state(void); static inline void start_thread_common(struct pt_regs *regs, unsigned long pc) { memset(regs, 0, sizeof(*regs)); - regs->syscallno = ~0; + forget_syscall(regs); regs->pc = pc; } diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index 21c87dc240e1..4f64373b84fd 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -72,8 +72,19 @@ #define COMPAT_PT_TEXT_ADDR 0x10000 #define COMPAT_PT_DATA_ADDR 0x10004 #define COMPAT_PT_TEXT_END_ADDR 0x10008 + +/* + * If pt_regs.syscallno == NO_SYSCALL, then the thread is not executing + * a syscall -- i.e., its most recent entry into the kernel from + * userspace was not via SVC, or otherwise a tracer cancelled the syscall. + * + * This must have the value -1, for ABI compatibility with ptrace etc. + */ +#define NO_SYSCALL (-1) + #ifndef __ASSEMBLY__ #include <linux/bug.h> +#include <linux/types.h> /* sizeof(struct user) for AArch32 */ #define COMPAT_USER_SZ 296 @@ -128,6 +139,16 @@ struct pt_regs { u64 unused; // maintain 16 byte alignment }; +static inline bool in_syscall(struct pt_regs const *regs) +{ + return regs->syscallno != NO_SYSCALL; +} + +static inline void forget_syscall(struct pt_regs *regs) +{ + regs->syscallno = NO_SYSCALL; +} + #define MAX_REG_OFFSET offsetof(struct pt_regs, pstate) #define arch_has_single_step() (1) |