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firmware: Initialize stack guard via Zkr

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Try to initialize stack protection guard via the zkr extension.

Signed-off-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260104051812.128496-1-wxjstz@126.com
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Xiang W
2026-01-04 13:18:10 +08:00
committed by Anup Patel
parent b27ecec76b
commit ecdb6c90c8
2 changed files with 34 additions and 0 deletions
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24
firmware/fw_base.S
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@@ -107,6 +107,30 @@ _bss_zero:
add s4, s4, __SIZEOF_POINTER__ add s4, s4, __SIZEOF_POINTER__
blt s4, s5, _bss_zero blt s4, s5, _bss_zero
/* Trying to initialize the stack guard via the Zkr extension */
lla t0, __stack_chk_guard_done
csrw CSR_MTVEC, t0
li t0, 0
li t3, SEED_OPTS_ES16
li t4, SEED_ENTROPY_MASK
li t5, __SIZEOF_POINTER__
__stack_chk_guard_loop:
csrrw t1, CSR_SEED, x0
li t2, SEED_OPTS_MASK
and t2, t2, t1
bgtu t2, t3, __stack_chk_guard_done
bltu t2, t3, __stack_chk_guard_loop
and t1, t1, t4
slli t0, t0, 16
or t0, t0, t1
addi t5, t5, -2
bgtz t5, __stack_chk_guard_loop
lla t1, __stack_chk_guard
REG_S t0, 0(t1)
j __stack_chk_guard_done
.align 3
__stack_chk_guard_done:
/* Setup temporary trap handler */ /* Setup temporary trap handler */
lla s4, _start_hang lla s4, _start_hang
csrw CSR_MTVEC, s4 csrw CSR_MTVEC, s4

10
include/sbi/riscv_encoding.h
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@@ -261,6 +261,16 @@
#define CSR_FRM 0x002 #define CSR_FRM 0x002
#define CSR_FCSR 0x003 #define CSR_FCSR 0x003
/* User entropy source */
#define CSR_SEED 0x015
#define SEED_OPTS_SHIFT 30
#define SEED_OPTS_MASK (_UL(3) << SEED_OPTS_SHIFT)
#define SEED_OPTS_BIST (_UL(0) << SEED_OPTS_SHIFT)
#define SEED_OPTS_WAIT (_UL(1) << SEED_OPTS_SHIFT)
#define SEED_OPTS_ES16 (_UL(2) << SEED_OPTS_SHIFT)
#define SEED_OPTS_DEAD (_UL(3) << SEED_OPTS_SHIFT)
#define SEED_ENTROPY_MASK 0xffff
/* User Counters/Timers */ /* User Counters/Timers */
#define CSR_CYCLE 0xc00 #define CSR_CYCLE 0xc00
#define CSR_TIME 0xc01 #define CSR_TIME 0xc01