Le 27/09/2021 à 15:11, Michael Ellerman a écrit :
Christophe Leroy <christophe.leroy@xxxxxxxxxx> writes:Commit 7a5da02de8d6 ("locking/lockdep: check for freed initmem in static_obj()") added arch_is_kernel_initmem_freed() which is supposed to report whether an object is part of already freed init memory. For the time being, the generic version of arch_is_kernel_initmem_freed() always reports 'false', allthough free_initmem() is generically called on all architectures. Therefore, change the generic version of arch_is_kernel_initmem_freed() to check whether free_initmem() has been called. If so, then check if a given address falls into init memory. In order to use function init_section_contains(), the fonction is moved at the end of asm-generic/section.h Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx> --- include/asm-generic/sections.h | 31 +++++++++++++++++-------------- 1 file changed, 17 insertions(+), 14 deletions(-) diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index d16302d3eb59..d1e5bb2c6b72 100644 --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -172,4 +158,21 @@ static inline bool is_kernel_rodata(unsigned long addr) addr < (unsigned long)__end_rodata; }+/*+ * Check if an address is part of freed initmem. This is needed on architectures + * with virt == phys kernel mapping, for code that wants to check if an address + * is part of a static object within [_stext, _end]. After initmem is freed, + * memory can be allocated from it, and such allocations would then have + * addresses within the range [_stext, _end]. + */ +#ifndef arch_is_kernel_initmem_freed +static inline int arch_is_kernel_initmem_freed(unsigned long addr) +{ + if (system_state < SYSTEM_RUNNING) + return 0; + + return init_section_contains((void *)addr, 1); +} +#endifThis will return an incorrect result for a short period during boot won't it? See init/main.c: static int __ref kernel_init(void *unused) { ... free_initmem(); <- memory is freed here mark_readonly(); /* * Kernel mappings are now finalized - update the userspace page-table * to finalize PTI. */ pti_finalize(); system_state = SYSTEM_RUNNING; After free_initmem() we have address ranges that are now freed initmem, but arch_is_kernel_initmem_freed() continues to return 0 (false) for all addresses, until we update system_state. Possibly that doesn't matter for any of the current callers, but it seems pretty dicey to me.
Yes I saw it but as function core_kernel_text() uses that criteria for deciding whether a given init text address is valid or not, I thought it was just ok.
Should we add an intermediate state called for exemple SYSTEM_FREEING_INIT just before SYSTEM_RUNNING ?
Christophe
