Re: [PATCH v3 3/6] syscall.h: introduce syscall_set_nr()

Christophe Leroy
2025-01-28T15:20:18Z

Le 28/01/2025 à 10:16, Dmitry V. Levin a écrit :
> Similar to syscall_set_arguments() that complements
> syscall_get_arguments(), introduce syscall_set_nr()
> that complements syscall_get_nr().
>
> syscall_set_nr() is going to be needed along with
> syscall_set_arguments() on all HAVE_ARCH_TRACEHOOK
> architectures to implement PTRACE_SET_SYSCALL_INFO API.
>
> Signed-off-by: Dmitry V. Levin <ldv@strace.io>
> Tested-by: Charlie Jenkins <charlie@rivosinc.com>
> Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
> ---
> arch/arc/include/asm/syscall.h | 11 +++++++++++
> arch/arm/include/asm/syscall.h | 24 ++++++++++++++++++++++++
> arch/arm64/include/asm/syscall.h | 16 ++++++++++++++++
> arch/hexagon/include/asm/syscall.h | 7 +++++++
> arch/loongarch/include/asm/syscall.h | 7 +++++++
> arch/m68k/include/asm/syscall.h | 7 +++++++
> arch/microblaze/include/asm/syscall.h | 7 +++++++
> arch/mips/include/asm/syscall.h | 14 ++++++++++++++
> arch/nios2/include/asm/syscall.h | 5 +++++
> arch/openrisc/include/asm/syscall.h | 6 ++++++
> arch/parisc/include/asm/syscall.h | 7 +++++++
> arch/powerpc/include/asm/syscall.h | 10 ++++++++++
> arch/riscv/include/asm/syscall.h | 7 +++++++
> arch/s390/include/asm/syscall.h | 12 ++++++++++++
> arch/sh/include/asm/syscall_32.h | 12 ++++++++++++
> arch/sparc/include/asm/syscall.h | 12 ++++++++++++
> arch/um/include/asm/syscall-generic.h | 5 +++++
> arch/x86/include/asm/syscall.h | 7 +++++++
> arch/xtensa/include/asm/syscall.h | 7 +++++++
> include/asm-generic/syscall.h | 14 ++++++++++++++
> 20 files changed, 197 insertions(+)
>

> diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
> index 76020b66286b..712daa90e643 100644
> --- a/arch/arm64/include/asm/syscall.h
> +++ b/arch/arm64/include/asm/syscall.h
> @@ -61,6 +61,22 @@ static inline void syscall_set_return_value(struct task_struct *task,
> regs->regs[0] = val;
> }
>
> +static inline void syscall_set_nr(struct task_struct *task,
> + struct pt_regs *regs,
> + int nr)
> +{
> + regs->syscallno = nr;
> + if (nr == -1) {
> + /*
> + * When the syscall number is set to -1, the syscall will be
> + * skipped. In this case the syscall return value has to be
> + * set explicitly, otherwise the first syscall argument is
> + * returned as the syscall return value.
> + */
> + syscall_set_return_value(task, regs, -ENOSYS, 0);
> + }
> +}
> +
> #define SYSCALL_MAX_ARGS 6
>
> static inline void syscall_get_arguments(struct task_struct *task,

> diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
> index 521f279e6b33..7505dcfed247 100644
> --- a/arch/powerpc/include/asm/syscall.h
> +++ b/arch/powerpc/include/asm/syscall.h
> @@ -39,6 +39,16 @@ static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
> return -1;
> }
>
> +static inline void syscall_set_nr(struct task_struct *task, struct pt_regs *regs, int nr)
> +{
> + /*
> + * Unlike syscall_get_nr(), syscall_set_nr() can be called only when
> + * the target task is stopped for tracing on entering syscall, so
> + * there is no need to have the same check syscall_get_nr() has.
> + */
> + regs->gpr[0] = nr;

Doesn't the same as for ARM64 apply here as well ?

> +}
> +
> static inline void syscall_rollback(struct task_struct *task,
> struct pt_regs *regs)
> {