Messages in this thread | | | From | Khem Raj <> | Date | Tue, 29 Nov 2022 18:56:48 -0800 | Subject | Re: [PATCH 1/2] RISC-V: Align the shadow stack |
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On Tue, Nov 29, 2022 at 6:50 PM Palmer Dabbelt <palmer@rivosinc.com> wrote: > > On Tue, 29 Nov 2022 18:47:55 PST (-0800), Khem Raj wrote: > > Hi Palmer > > > > On Tue, Nov 29, 2022 at 6:36 PM Palmer Dabbelt <palmer@rivosinc.com> wrote: > >> > >> The standard RISC-V ABIs all require 16-byte stack alignment. We're > >> only calling that one function on the shadow stack so I doubt it'd > >> result in a real issue, but might as well keep this lined up. > > > > Is 16-byte alignment required on rv32 as well ? > > For the standard ABIs that's the case, it's so the Q extension can spill > without aligning the stack. There's also at least a proposed embedded > ABI that has just XLEN (32-bit on rv32) alignment, as the bigger stack > alignment has an impact on some use cases.
Thanks, so in this case 16byte will be valid for both rv64/rv32 here.
> > >> Fixes: 31da94c25aea ("riscv: add VMAP_STACK overflow detection") > >> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> > >> --- > >> arch/riscv/kernel/traps.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c > >> index be54ccea8c47..acdfcacd7e57 100644 > >> --- a/arch/riscv/kernel/traps.c > >> +++ b/arch/riscv/kernel/traps.c > >> @@ -206,7 +206,7 @@ static DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], > >> * shadow stack, handled_ kernel_ stack_ overflow(in kernel/entry.S) is used > >> * to get per-cpu overflow stack(get_overflow_stack). > >> */ > >> -long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)]; > >> +long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)] __aligned(16); > >> asmlinkage unsigned long get_overflow_stack(void) > >> { > >> return (unsigned long)this_cpu_ptr(overflow_stack) + > >> -- > >> 2.38.1 > >> > >> > >> _______________________________________________ > >> linux-riscv mailing list > >> linux-riscv@lists.infradead.org > >> http://lists.infradead.org/mailman/listinfo/linux-riscv
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