Messages in this thread | | | Date | Thu, 7 Sep 2023 00:17:39 +0200 | From | Ingo Molnar <> | Subject | Re: [patch 2/2] x86/boot/32: Disable stackprotector and tracing for mk_early_pgtbl_32() |
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* Thomas Gleixner <tglx@linutronix.de> wrote:
> Stackprotector cannot work before paging is enabled. The read from the per > CPU variable __stack_chk_guard is always accessing the virtual address > either directly on UP or via FS on SMP. In physical address mode this > results in an access to memory above 3GB. > > So this works by chance as the hardware returns the same value when there > is no RAM at this physical address. When there is RAM populated above 3G > then the read is by chance the same as nothing changes that memory during > the very early boot stage. > > Stop relying on pure luck and disable the stack protector for the only C > function which is called during early boot before paging is enabled. > > Remove function tracing from the whole source file as there is no way to > trace this at all, but in case of CONFIG_DYNAMIC_FTRACE=n > mk_early_pgtbl_32() would access global function tracer variables in > physcial address mode which again might work by chance. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > --- > arch/x86/kernel/Makefile | 1 + > arch/x86/kernel/head32.c | 3 ++- > 2 files changed, 3 insertions(+), 1 deletion(-)
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Thanks,
Ingo
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