From: hlsong89 <[email protected]> The syscall trace path reloads syscall arguments from pt_regs before calling the syscall handler. On C-SKY ABIv2, the 5th and 6th syscall arguments are prepared as stack arguments before invoking syscallid.
The current code adjusts sp before loading LSAVE_A4 and LSAVE_A5. Since those offsets are relative to the original pt_regs base, loading them after changing sp fetches the wrong slots. As a result, traced syscalls that use the 5th or 6th argument may receive corrupted arguments. This is visible with mmap2(), which takes six arguments. A small PTRACE_SYSCALL reproducer opens a file and maps one page with: mmap(NULL, 4096, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0) Before the fix, the traced child fails the mmap and exits with 12. After the fix, the mapping succeeds and the child exits with 0. Fix the trace path by using the correct pt_regs offsets after adjusting sp. Tested on: ck860f, linux-4.19.15, C-SKY abiv2 Signed-off-by: hlsong89 <[email protected]> --- arch/csky/kernel/entry.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/csky/kernel/entry.S b/arch/csky/kernel/entry.S index c68cdcc76..98692fc78 100644 --- a/arch/csky/kernel/entry.S +++ b/arch/csky/kernel/entry.S @@ -94,9 +94,9 @@ csky_syscall_trace: ldw a3, (sp, LSAVE_A3) #if defined(__CSKYABIV2__) subi sp, 8 - ldw r9, (sp, LSAVE_A4) + ldw r9, (sp, LSAVE_A4 + 8) stw r9, (sp, 0x0) - ldw r9, (sp, LSAVE_A5) + ldw r9, (sp, LSAVE_A5 + 8) stw r9, (sp, 0x4) jsr syscallid /* Do system call */ addi sp, 8 -- 2.25.1
