[PATCH v2] selftests: sud_test: return correct emulated syscall value on RISC-V
Clément Léger
cleger at rivosinc.com
Wed Dec 6 05:44:37 PST 2023
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 at rivosinc.com>
Reviewed-by: Palmer Dabbelt <palmer at rivosinc.com>
Acked-by: Palmer Dabbelt <palmer at 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)
--
2.43.0
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