Hi Palmer,
Could you help move the patch into your next-tree with Kees' review added?
On Sat, Nov 14, 2020 at 6:57 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>
> On Sun, Oct 18, 2020 at 12:38:17PM +0000, guoren@xxxxxxxxxx wrote:
> > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> >
> > This enables the use of per-task stack canary values if GCC has
> > support for emitting the stack canary reference relative to the
> > value of tp, which holds the task struct pointer in the riscv
> > kernel.
> >
> > After compare arm64 and x86 implementations, seems arm64's is more
> > flexible and readable. The key point is how gcc get the offset of
> > stack_canary from gs/el0_sp.
> >
> > x86: Use a fix offset from gs, not flexible.
> >
> > struct fixed_percpu_data {
> > /*
> > * GCC hardcodes the stack canary as %gs:40. Since the
> > * irq_stack is the object at %gs:0, we reserve the bottom
> > * 48 bytes of the irq stack for the canary.
> > */
> > char gs_base[40]; // :(
> > unsigned long stack_canary;
> > };
> >
> > arm64: Use -mstack-protector-guard-offset & guard-reg
> > gcc options:
> > -mstack-protector-guard=sysreg
> > -mstack-protector-guard-reg=sp_el0
> > -mstack-protector-guard-offset=xxx
> >
> > riscv: Use -mstack-protector-guard-offset & guard-reg
> > gcc options:
> > -mstack-protector-guard=tls
> > -mstack-protector-guard-reg=tp
> > -mstack-protector-guard-offset=xxx
> >
> > GCC's implementation has been merged:
> > commit c931e8d5a96463427040b0d11f9c4352ac22b2b0
> > Author: Cooper Qu <cooper.qu@xxxxxxxxxxxxxxxxx>
> > Date: Mon Jul 13 16:15:08 2020 +0800
> >
> > RISC-V: Add support for TLS stack protector canary access
> >
> > In the end, these codes are inserted by gcc before return:
> >
> > * 0xffffffe00020b396 <+120>: ld a5,1008(tp) # 0x3f0
> > * 0xffffffe00020b39a <+124>: xor a5,a5,a4
> > * 0xffffffe00020b39c <+126>: mv a0,s5
> > * 0xffffffe00020b39e <+128>: bnez a5,0xffffffe00020b61c <_do_fork+766>
> > 0xffffffe00020b3a2 <+132>: ld ra,136(sp)
> > 0xffffffe00020b3a4 <+134>: ld s0,128(sp)
> > 0xffffffe00020b3a6 <+136>: ld s1,120(sp)
> > 0xffffffe00020b3a8 <+138>: ld s2,112(sp)
> > 0xffffffe00020b3aa <+140>: ld s3,104(sp)
> > 0xffffffe00020b3ac <+142>: ld s4,96(sp)
> > 0xffffffe00020b3ae <+144>: ld s5,88(sp)
> > 0xffffffe00020b3b0 <+146>: ld s6,80(sp)
> > 0xffffffe00020b3b2 <+148>: ld s7,72(sp)
> > 0xffffffe00020b3b4 <+150>: addi sp,sp,144
> > 0xffffffe00020b3b6 <+152>: ret
> > ...
> > * 0xffffffe00020b61c <+766>: auipc ra,0x7f8
> > * 0xffffffe00020b620 <+770>: jalr -1764(ra) # 0xffffffe000a02f38 <__stack_chk_fail>
> >
> > Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
>
> Thanks for getting this working! It looks good to me. :)
>
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
>
> --
> Kees Cook
--
Best Regards
Guo Ren
ML: https://lore.kernel.org/linux-csky/
