On Wed, 2023-09-13 at 12:18 -0700, Sohil Mehta wrote: > On 9/11/2023 2:10 PM, Edgecombe, Rick P wrote: > > On Mon, 2023-09-11 at 18:02 +0000, Sohil Mehta wrote: > > > diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl > > > b/arch/powerpc/kernel/syscalls/syscall.tbl > > > index 20e50586e8a2..2767b8a42636 100644 > > > --- a/arch/powerpc/kernel/syscalls/syscall.tbl > > > +++ b/arch/powerpc/kernel/syscalls/syscall.tbl > > > @@ -539,3 +539,4 @@ > > > 450 nospu set_mempolicy_home_node sys_set_mempolicy > > > _hom > > > e_node > > > 451 common cachestat sys_cachestat > > > 452 common fchmodat2 sys_fchmodat2 > > > +453 common map_shadow_stack sys_map_shadow_st > > > ack > > > > I noticed in powerpc, the not implemented syscalls are manually > > mapped > > to sys_ni_syscall. It also has some special extra sys_ni_syscall() > > implementation bits to handle both ARCH_HAS_SYSCALL_WRAPPER and > > !ARCH_HAS_SYSCALL_WRAPPER. So wondering if it might need special > > treatment. Did you see those parts? > > > > Thanks for pointing this out. Powerpc seems to be unique in their > handling of not implemented syscalls. Maybe it's because of their > special casing of the ARCH_HAS_SYSCALL_WRAPPER. > > The code below in arch/powerpc/include/asm/syscalls.h suggests to me > that it should be safe to map map_shadow_stack() to sys_ni_syscall() > and > the special handling will be taken care of. > > #ifndef CONFIG_ARCH_HAS_SYSCALL_WRAPPER > long sys_ni_syscall(void); > #else > long sys_ni_syscall(const struct pt_regs *regs); > #endif > > I don't quite understand the underlying reasoning for it though. Do > you > have any additional insight into how we should handle this? > > I am thinking of doing the following in the next iteration unless > someone chimes in and says otherwise. > > --- a/arch/powerpc/kernel/syscalls/syscall.tbl > +++ b/arch/powerpc/kernel/syscalls/syscall.tbl > @@ -539,4 +539,4 @@ > 450 nospu set_mempolicy_home_node > sys_set_mempolicy_home_node > 451 common cachestat sys_cachestat > 452 common fchmodat2 sys_fchmodat2 > -453 common map_shadow_stack sys_map_shadow_stack > +453 common map_shadow_stack sys_ni_syscall It might have something to do with that powerpc's COND_SYSCALL() implementation only defines the struct pt_regs variety, but TBH I get a bit lost when I get to the inline assembly symbol definitions parts and how it all ties together. Doing powerpc's version as sys_ni_syscall seems to be consistent at least, and makes sense with respect to the code you quoted.
