On 2020/7/15 上午5:37, Palmer Dabbelt wrote:
On Fri, 10 Jul 2020 09:19:58 PDT (-0700), [email protected] wrote:
From: Guo Ren <[email protected]>
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
Here is riscv gcc's work [1].
[1] https://gcc.gnu.org/pipermail/gcc-patches/2020-July/549583.html
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 <[email protected]>
Signed-off-by: cooper <[email protected]>
IIRC we're required to use full names here. I'm assuming that's meant
to be
"Signed-off-by: Cooper Qu ...", and I know it's a bit procedural but I
can't
make that change.
Otherwise these two look good, the first one is on for-next. I can
boot with a
defconfig ammended with CONFIG_STACKPROTECTOR=y,
Thanks!
Hi Palmer,
That's ok to change it to full names as follows.
Signed-off-by: Cooper Qu <[email protected]>
Best Regards,
Cooper
