From 5665bc35c1ed917ac8fd06cb651317bb47a65b10 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Thu, 20 May 2021 21:19:30 +1000 Subject: powerpc/64s/syscall: Use pt_regs.trap to distinguish syscall ABI difference between sc and scv syscalls The sc and scv 0 system calls have different ABI conventions, and ptracers need to know which system call type is being used if they want to look at the syscall registers. Document that pt_regs.trap can be used for this, and fix one in-tree user to work with scv 0 syscalls. Fixes: 7fa95f9adaee ("powerpc/64s: system call support for scv/rfscv instructions") Cc: stable@vger.kernel.org # v5.9+ Reported-by: "Dmitry V. Levin" Suggested-by: "Dmitry V. Levin" Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210520111931.2597127-1-npiggin@gmail.com --- Documentation/powerpc/syscall64-abi.rst | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'Documentation') diff --git a/Documentation/powerpc/syscall64-abi.rst b/Documentation/powerpc/syscall64-abi.rst index dabee3729e5a..56490c4c0c07 100644 --- a/Documentation/powerpc/syscall64-abi.rst +++ b/Documentation/powerpc/syscall64-abi.rst @@ -109,6 +109,16 @@ auxiliary vector. scv 0 syscalls will always behave as PPC_FEATURE2_HTM_NOSC. +ptrace +------ +When ptracing system calls (PTRACE_SYSCALL), the pt_regs.trap value contains +the system call type that can be used to distinguish between sc and scv 0 +system calls, and the different register conventions can be accounted for. + +If the value of (pt_regs.trap & 0xfff0) is 0xc00 then the system call was +performed with the sc instruction, if it is 0x3000 then the system call was +performed with the scv 0 instruction. + vsyscall ======== -- cgit v1.2.3-58-ga151