On Mon, 13 Jan 2025, Dmitry V. Levin wrote: > Fix the following get_syscall_info test assertion on mips O32: > # get_syscall_info.c:218:get_syscall_info:Expected exp_args[5] (3134521044) == info.entry.args[4] (4911432) > # get_syscall_info.c:219:get_syscall_info:wait #1: entry stop mismatch > > Fix the following get_syscall_info test assertion on mips64 O32 and mips64 N32: > # get_syscall_info.c:209:get_syscall_info:Expected exp_args[2] (3134324433) == info.entry.args[1] (18446744072548908753) > # get_syscall_info.c:210:get_syscall_info:wait #1: entry stop mismatch How did you produce these results? > This makes ptrace/get_syscall_info selftest pass on mips O32, > mips64 O32, and mips64 N32. > > Signed-off-by: Dmitry V. Levin <ldv@xxxxxxxxx> > --- > > Note that I'm not a MIPS expert, so I cannot tell why the get_user() > approach doesn't work for O32. Also, during experiments I discovered that > regs->pad0 approach works for O32, but why it works remains a mystery. The patch is definitely broken, the calling convention is the same between n32 and n64: 64-bit arguments in $4 through $11 registers as required, and your change makes n32 truncate arguments to 32 bits. The regs->pad0 approach works due to this piece: /* * Ok, copy the args from the luser stack to the kernel stack. */ .set push .set noreorder .set nomacro load_a4: user_lw(t5, 16(t0)) # argument #5 from usp load_a5: user_lw(t6, 20(t0)) # argument #6 from usp load_a6: user_lw(t7, 24(t0)) # argument #7 from usp load_a7: user_lw(t8, 28(t0)) # argument #8 from usp loads_done: sw t5, 16(sp) # argument #5 to ksp sw t6, 20(sp) # argument #6 to ksp sw t7, 24(sp) # argument #7 to ksp sw t8, 28(sp) # argument #8 to ksp .set pop .section __ex_table,"a" PTR_WD load_a4, bad_stack_a4 PTR_WD load_a5, bad_stack_a5 PTR_WD load_a6, bad_stack_a6 PTR_WD load_a7, bad_stack_a7 .previous in arch/mips/kernel/scall32-o32.S (and arch/mips/kernel/scall64-o32.S has analogous code to adapt to the native n64 calling convention instead), but this doesn't seem to me to be the correct approach here. At first glance `mips_get_syscall_arg' does appear fine as it is, so I'd like to know how you obtained your results. Maciej
