Re: [PATCH 12/13] riscv: define syscall_get_arch()

From: Palmer Dabbelt
Date: Fri Nov 09 2018 - 13:45:59 EST


On Thu, 08 Nov 2018 19:17:13 PST (-0800), ldv@xxxxxxxxxxxx wrote:
syscall_get_arch() is required to be implemented on all architectures
that use tracehook_report_syscall_entry() in order to extend
the generic ptrace API with PTRACE_GET_SYSCALL_INFO request.

Signed-off-by: Dmitry V. Levin <ldv@xxxxxxxxxxxx>
---
arch/riscv/include/asm/syscall.h | 6 ++++++
include/uapi/linux/audit.h | 1 +
2 files changed, 7 insertions(+)

diff --git a/arch/riscv/include/asm/syscall.h b/arch/riscv/include/asm/syscall.h
index 8d25f8904c00..7e1e26ca7317 100644
--- a/arch/riscv/include/asm/syscall.h
+++ b/arch/riscv/include/asm/syscall.h
@@ -18,6 +18,7 @@
#ifndef _ASM_RISCV_SYSCALL_H
#define _ASM_RISCV_SYSCALL_H

+#include <uapi/linux/audit.h>
#include <linux/sched.h>
#include <linux/err.h>

@@ -99,4 +100,9 @@ static inline void syscall_set_arguments(struct task_struct *task,
memcpy(&regs->a1 + i * sizeof(regs->a1), args, n * sizeof(regs->a0));
}

+static inline int syscall_get_arch(void)
+{
+ return AUDIT_ARCH_RISCV;
+}
+
#endif /* _ASM_RISCV_SYSCALL_H */
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index c4c8b131af48..ad4105c602a1 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -405,6 +405,7 @@ enum {
/* do not define AUDIT_ARCH_PPCLE since it is not supported by audit */
#define AUDIT_ARCH_PPC64 (EM_PPC64|__AUDIT_ARCH_64BIT)
#define AUDIT_ARCH_PPC64LE (EM_PPC64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
+#define AUDIT_ARCH_RISCV (EM_RISCV|__AUDIT_ARCH_64BIT)
#define AUDIT_ARCH_S390 (EM_S390)
#define AUDIT_ARCH_S390X (EM_S390|__AUDIT_ARCH_64BIT)
#define AUDIT_ARCH_SH (EM_SH)

I think this is incorrect: EM_RISCV has 32-bit and 64-bit variants, and if I understand what's going on here this is marking all RISC-V targets as 64-bit. Since this is a userspace header, I think the right thing to switch on is __riscv_xlen, which will be defined to either 32 or 64 depending on the base ISA.

We're also little endian.