Re: [PATCH] xen: unexport __init-annotated xen_xlate_map_ballooned_pages()
On 06.06.22 06:59, Masahiro Yamada wrote: EXPORT_SYMBOL and __init is a bad combination because the .init.text section is freed up after the initialization. Hence, modules cannot use symbols annotated __init. The access to a freed symbol may end up with kernel panic. modpost used to detect it, but it has been broken for a decade. Recently, I fixed modpost so it started to warn it again, then this showed up in linux-next builds. There are two ways to fix it: - Remove __init - Remove EXPORT_SYMBOL I chose the latter for this case because none of the in-tree call-sites (arch/arm/xen/enlighten.c, arch/x86/xen/grant-table.c) is compiled as modular. Fixes: 243848fc018c ("xen/grant-table: Move xlated_setup_gnttab_pages to common place") Reported-by: Stephen Rothwell Signed-off-by: Masahiro Yamada Pushed to xen/tip.git for-linus-5.19a Juergen OpenPGP_0xB0DE9DD628BF132F.asc Description: OpenPGP public key OpenPGP_signature Description: OpenPGP digital signature
Re: [PATCH] xen: unexport __init-annotated xen_xlate_map_ballooned_pages()
On Mon, 6 Jun 2022, Oleksandr wrote: > On 06.06.22 07:59, Masahiro Yamada wrote: > > Hello > > > EXPORT_SYMBOL and __init is a bad combination because the .init.text > > section is freed up after the initialization. Hence, modules cannot > > use symbols annotated __init. The access to a freed symbol may end up > > with kernel panic. > > > > modpost used to detect it, but it has been broken for a decade. > > > > Recently, I fixed modpost so it started to warn it again, then this > > showed up in linux-next builds. > > > > There are two ways to fix it: > > > >- Remove __init > >- Remove EXPORT_SYMBOL > > > > I chose the latter for this case because none of the in-tree call-sites > > (arch/arm/xen/enlighten.c, arch/x86/xen/grant-table.c) is compiled as > > modular. > > Good description. > > > > > > Fixes: 243848fc018c ("xen/grant-table: Move xlated_setup_gnttab_pages to > > common place") > > Reported-by: Stephen Rothwell > > Signed-off-by: Masahiro Yamada > > I think the patch is correct. > > Reviewed-by: Oleksandr Tyshchenko Acked-by: Stefano Stabellini > > --- > > > > drivers/xen/xlate_mmu.c | 1 - > > 1 file changed, 1 deletion(-) > > > > diff --git a/drivers/xen/xlate_mmu.c b/drivers/xen/xlate_mmu.c > > index 34742c6e189e..f17c4c03db30 100644 > > --- a/drivers/xen/xlate_mmu.c > > +++ b/drivers/xen/xlate_mmu.c > > @@ -261,7 +261,6 @@ int __init xen_xlate_map_ballooned_pages(xen_pfn_t > > **gfns, void **virt, > > return 0; > > } > > -EXPORT_SYMBOL_GPL(xen_xlate_map_ballooned_pages); > > struct remap_pfn { > > struct mm_struct *mm; > > -- > Regards, > > Oleksandr Tyshchenko >
Re: [PATCH] xen: unexport __init-annotated xen_xlate_map_ballooned_pages()
On 06.06.22 07:59, Masahiro Yamada wrote: Hello EXPORT_SYMBOL and __init is a bad combination because the .init.text section is freed up after the initialization. Hence, modules cannot use symbols annotated __init. The access to a freed symbol may end up with kernel panic. modpost used to detect it, but it has been broken for a decade. Recently, I fixed modpost so it started to warn it again, then this showed up in linux-next builds. There are two ways to fix it: - Remove __init - Remove EXPORT_SYMBOL I chose the latter for this case because none of the in-tree call-sites (arch/arm/xen/enlighten.c, arch/x86/xen/grant-table.c) is compiled as modular. Good description. Fixes: 243848fc018c ("xen/grant-table: Move xlated_setup_gnttab_pages to common place") Reported-by: Stephen Rothwell Signed-off-by: Masahiro Yamada I think the patch is correct. Reviewed-by: Oleksandr Tyshchenko --- drivers/xen/xlate_mmu.c | 1 - 1 file changed, 1 deletion(-) diff --git a/drivers/xen/xlate_mmu.c b/drivers/xen/xlate_mmu.c index 34742c6e189e..f17c4c03db30 100644 --- a/drivers/xen/xlate_mmu.c +++ b/drivers/xen/xlate_mmu.c @@ -261,7 +261,6 @@ int __init xen_xlate_map_ballooned_pages(xen_pfn_t **gfns, void **virt, return 0; } -EXPORT_SYMBOL_GPL(xen_xlate_map_ballooned_pages); struct remap_pfn { struct mm_struct *mm; -- Regards, Oleksandr Tyshchenko
[PATCH] xen: unexport __init-annotated xen_xlate_map_ballooned_pages()
EXPORT_SYMBOL and __init is a bad combination because the .init.text section is freed up after the initialization. Hence, modules cannot use symbols annotated __init. The access to a freed symbol may end up with kernel panic. modpost used to detect it, but it has been broken for a decade. Recently, I fixed modpost so it started to warn it again, then this showed up in linux-next builds. There are two ways to fix it: - Remove __init - Remove EXPORT_SYMBOL I chose the latter for this case because none of the in-tree call-sites (arch/arm/xen/enlighten.c, arch/x86/xen/grant-table.c) is compiled as modular. Fixes: 243848fc018c ("xen/grant-table: Move xlated_setup_gnttab_pages to common place") Reported-by: Stephen Rothwell Signed-off-by: Masahiro Yamada --- drivers/xen/xlate_mmu.c | 1 - 1 file changed, 1 deletion(-) diff --git a/drivers/xen/xlate_mmu.c b/drivers/xen/xlate_mmu.c index 34742c6e189e..f17c4c03db30 100644 --- a/drivers/xen/xlate_mmu.c +++ b/drivers/xen/xlate_mmu.c @@ -261,7 +261,6 @@ int __init xen_xlate_map_ballooned_pages(xen_pfn_t **gfns, void **virt, return 0; } -EXPORT_SYMBOL_GPL(xen_xlate_map_ballooned_pages); struct remap_pfn { struct mm_struct *mm; -- 2.32.0