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arch: riscv: reset global pointer on exception 

Reset the gp on exception entry from u-mode to protect the kernel
against a possible rogue user thread.

Signed-off-by: Yong Cong Sin <yongcong.sin@gmail.com>
Signed-off-by: Yong Cong Sin <ycsin@meta.com>
This commit is contained in:
Yong Cong Sin 2024-11-09 02:15:21 +08:00 committed by Dan Kalowsky
parent de3a845612
commit e30db2d53f
1 changed files with 8 additions and 0 deletions
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8
arch/riscv/core/isr.S
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@ -163,6 +163,14 @@ SECTION_FUNC(exception.entry, _isr_wrapper)
lr t0, ___cpu_t_current_OFFSET(s0) lr t0, ___cpu_t_current_OFFSET(s0)
lr tp, _thread_offset_to_tls(t0) lr tp, _thread_offset_to_tls(t0)
/* Make sure global pointer is sane */
#ifdef CONFIG_RISCV_GP
.option push
.option norelax
la gp, __global_pointer$
.option pop
#endif /* CONFIG_RISCV_GP */
/* Clear our per-thread usermode flag */ /* Clear our per-thread usermode flag */
lui t0, %tprel_hi(is_user_mode) lui t0, %tprel_hi(is_user_mode)
add t0, t0, tp, %tprel_add(is_user_mode) add t0, t0, tp, %tprel_add(is_user_mode)