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riscv: prevent pt_regs corruption for secondary idle threads

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Top of the kernel thread stack should be reserved for pt_regs. However
this is not the case for the idle threads of the secondary boot harts.
Their stacks overlap with their pt_regs, so both may get corrupted.

Similar issue has been fixed for the primary hart, see c7cdd96eca
("riscv: prevent stack corruption by reserving task_pt_regs(p) early").
However that fix was not propagated to the secondary harts. The problem
has been noticed in some CPU hotplug tests with V enabled. The function
smp_callin stored several registers on stack, corrupting top of pt_regs
structure including status field. As a result, kernel attempted to save
or restore inexistent V context.

Fixes: 9a2451f186 ("RISC-V: Avoid using per cpu array for ordered booting")
Fixes: 2875fe0561 ("RISC-V: Add cpu_ops and modify default booting method")
Signed-off-by: Sergey Matyukevich <sergey.matyukevich@syntacore.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20240523084327.2013211-1-geomatsi@gmail.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Sergey Matyukevich 2024-05-23 11:43:23 +03:00 committed by Palmer Dabbelt
parent 1613e604df
commit a638b0461b
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GPG key ID: 2E1319F35FBB1889
2 changed files with 2 additions and 3 deletions
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2
arch/riscv/kernel/cpu_ops_sbi.c
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@ -72,7 +72,7 @@ static int sbi_cpu_start(unsigned int cpuid, struct task_struct *tidle)
/* Make sure tidle is updated */
smp_mb();
bdata->task_ptr = tidle;
bdata->stack_ptr = task_stack_page(tidle) + THREAD_SIZE;
bdata->stack_ptr = task_pt_regs(tidle);
/* Make sure boot data is updated */
smp_mb();
hsm_data = __pa(bdata);

3
arch/riscv/kernel/cpu_ops_spinwait.c
View file

@ -34,8 +34,7 @@ static void cpu_update_secondary_bootdata(unsigned int cpuid,
/* Make sure tidle is updated */
smp_mb();
WRITE_ONCE(__cpu_spinwait_stack_pointer[hartid],
task_stack_page(tidle) + THREAD_SIZE);
WRITE_ONCE(__cpu_spinwait_stack_pointer[hartid], task_pt_regs(tidle));
WRITE_ONCE(__cpu_spinwait_task_pointer[hartid], tidle);
}