On Wed, 06 Dec 2023 05:44:37 PST (-0800), cleger@rivosinc.com wrote:

Currently, the sud_test expects the emulated syscall to return the emulated syscall number. This assumption only works on architectures were the syscall calling convention use the same register for syscall number/syscall return value. This is not the case for RISC-V and thus the return value must be also emulated using the provided ucontext.

Signed-off-by: Clément Léger cleger@rivosinc.com Reviewed-by: Palmer Dabbelt palmer@rivosinc.com Acked-by: Palmer Dabbelt palmer@rivosinc.com

---

Changes in V2:

• Changes comment to be more explicit
• Use A7 syscall arg rather than hardcoding MAGIC_SYSCALL_1

---

.../selftests/syscall_user_dispatch/sud_test.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)

diff --git a/tools/testing/selftests/syscall_user_dispatch/sud_test.c b/tools/testing/selftests/syscall_user_dispatch/sud_test.c index b5d592d4099e..d975a6767329 100644 --- a/tools/testing/selftests/syscall_user_dispatch/sud_test.c +++ b/tools/testing/selftests/syscall_user_dispatch/sud_test.c @@ -158,6 +158,20 @@ static void handle_sigsys(int sig, siginfo_t *info, void *ucontext)

/* In preparation for sigreturn. */ SYSCALL_DISPATCH_OFF(glob_sel);

• /*

• * The tests for argument handling assume that `syscall(x) == x`. This
  

• * is a NOP on x86 because the syscall number is passed in %rax, which
  

• * happens to also be the function ABI return register.  Other
  

• * architectures may need to swizzle the arguments around.
  

• */
  

+#if defined(__riscv) +/* REG_A7 is not defined in libc headers */ +# define REG_A7 (REG_A0 + 7)

• ((ucontext_t *)ucontext)->uc_mcontext.__gregs[REG_A0] =

• 	((ucontext_t *)ucontext)->uc_mcontext.__gregs[REG_A7];
  

+#endif }

TEST(dispatch_and_return)

Thanks.

Thomas: looks like you picked up all the commits that touched this? No rush on my end, just LMK if you want me to pick it up -- I'm going to leave it alone for now.