On Mon, Oct 13, 2025 at 4:13 AM Yong-Xuan Wang <[email protected]> wrote: > > The vector regset uses the maximum possible vlenb 8192 to allocate a > 2^18 bytes buffer to copy the vector register. But most platforms > don’t support the largest vlenb. > > The regset has 2 users, ptrace syscall and coredump. When handling the > PTRACE_GETREGSET requests from ptrace syscall, Linux will prepare a > kernel buffer which size is min(user buffer size, limit). A malicious > user process might overwhelm a memory-constrainted system when the > buffer limit is very large. The coredump uses regset_get_alloc() to > get the context of vector register. But this API allocates buffer > before checking whether the target process uses vector extension, this > wastes time to prepare a large memory buffer. > > The buffer limit can be determined after getting platform vlenb in the > early boot stage, this can let the regset buffer match real hardware > limits. Also add .active callbacks to let the coredump skip vector part > when target process doesn't use it. > > After this patchset, userspace process needs 2 ptrace syscalls to > retrieve the vector regset with PTRACE_GETREGSET. The first ptrace call > only reads the header to get the vlenb information. Then prepare a > suitable buffer to get the register context. The new vector ptrace > kselftest demonstrates it.
For the entire series: Tested-by: Andy Chiu <[email protected]> [on rv64 v enabled qemu] Thanks! > > --- > v2: > - fix issues in vector ptrace kselftest (Andy) > > Yong-Xuan Wang (2): > riscv: ptrace: Optimize the allocation of vector regset > selftests: riscv: Add test for the Vector ptrace interface > > arch/riscv/include/asm/vector.h | 1 + > arch/riscv/kernel/ptrace.c | 24 +++- > arch/riscv/kernel/vector.c | 2 + > tools/testing/selftests/riscv/vector/Makefile | 5 +- > .../selftests/riscv/vector/vstate_ptrace.c | 134 ++++++++++++++++++ > 5 files changed, 162 insertions(+), 4 deletions(-) > create mode 100644 tools/testing/selftests/riscv/vector/vstate_ptrace.c > > -- > 2.43.0 >
