| Message ID | 20200625234516.31406-2-atish.patra@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add UEFI support for RISC-V | expand |
On Thu, Jun 25, 2020 at 7:43 PM Heinrich Schuchardt <xypron.glpk@gmx.de> wrote: > > On 6/26/20 1:45 AM, Atish Patra wrote: > > 32bit gcc doesn't support modulo operation on 64 bit data. It results in > > a __umoddi3 error while building EFI for 32 bit. > > > > Use bitwise operations instead of modulo operations to fix the issue. > > > > Signed-off-by: Atish Patra <atish.patra@wdc.com> > > --- > > drivers/firmware/efi/libstub/alignedmem.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/firmware/efi/libstub/alignedmem.c b/drivers/firmware/efi/libstub/alignedmem.c > > index cc89c4d6196f..1de9878ddd3a 100644 > > --- a/drivers/firmware/efi/libstub/alignedmem.c > > +++ b/drivers/firmware/efi/libstub/alignedmem.c > > @@ -44,7 +44,7 @@ efi_status_t efi_allocate_pages_aligned(unsigned long size, unsigned long *addr, > > *addr = ALIGN((unsigned long)alloc_addr, align); > > > > if (slack > 0) { > > - int l = (alloc_addr % align) / EFI_PAGE_SIZE; > > + int l = (alloc_addr & (align - 1)) / EFI_PAGE_SIZE; > > Here you rely on the compiler to silently convert the division by > EFI_PAGE_SIZE into a right shift. Wouldn't it be cleaner to use > EFI_PAGE_SHIFT to explicitly avoid a dependency on __udivdi3()? > > slack = (align >> EFI_PAGE_SHIFT) - 1; > ... > int l = (alloc_addr & (align - 1)) >> EFI_PAGE_SHIFT; > Sure. I will update it in the next version. Thanks for the suggestion. > Best regards > > Heinrich > > > > > if (l) { > > efi_bs_call(free_pages, alloc_addr, slack - l + 1); > > >
On Fri, 26 Jun 2020 at 23:56, Atish Patra <atishp@atishpatra.org> wrote: > > On Thu, Jun 25, 2020 at 7:43 PM Heinrich Schuchardt <xypron.glpk@gmx.de> wrote: > > > > On 6/26/20 1:45 AM, Atish Patra wrote: > > > 32bit gcc doesn't support modulo operation on 64 bit data. It results in > > > a __umoddi3 error while building EFI for 32 bit. > > > > > > Use bitwise operations instead of modulo operations to fix the issue. > > > > > > Signed-off-by: Atish Patra <atish.patra@wdc.com> > > > --- > > > drivers/firmware/efi/libstub/alignedmem.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/firmware/efi/libstub/alignedmem.c b/drivers/firmware/efi/libstub/alignedmem.c > > > index cc89c4d6196f..1de9878ddd3a 100644 > > > --- a/drivers/firmware/efi/libstub/alignedmem.c > > > +++ b/drivers/firmware/efi/libstub/alignedmem.c > > > @@ -44,7 +44,7 @@ efi_status_t efi_allocate_pages_aligned(unsigned long size, unsigned long *addr, > > > *addr = ALIGN((unsigned long)alloc_addr, align); > > > > > > if (slack > 0) { > > > - int l = (alloc_addr % align) / EFI_PAGE_SIZE; > > > + int l = (alloc_addr & (align - 1)) / EFI_PAGE_SIZE; > > > > Here you rely on the compiler to silently convert the division by > > EFI_PAGE_SIZE into a right shift. Wouldn't it be cleaner to use > > EFI_PAGE_SHIFT to explicitly avoid a dependency on __udivdi3()? > > > > slack = (align >> EFI_PAGE_SHIFT) - 1; > > ... > > int l = (alloc_addr & (align - 1)) >> EFI_PAGE_SHIFT; > > > > Sure. I will update it in the next version. Thanks for the suggestion. Please don't. Dividing by EFI_PAGE_SIZE is perfectly fine, and is more readable.
On Sat, 27 Jun 2020 at 00:03, Ard Biesheuvel <ardb@kernel.org> wrote: > > On Fri, 26 Jun 2020 at 23:56, Atish Patra <atishp@atishpatra.org> wrote: > > > > On Thu, Jun 25, 2020 at 7:43 PM Heinrich Schuchardt <xypron.glpk@gmx.de> wrote: > > > > > > On 6/26/20 1:45 AM, Atish Patra wrote: > > > > 32bit gcc doesn't support modulo operation on 64 bit data. It results in > > > > a __umoddi3 error while building EFI for 32 bit. > > > > > > > > Use bitwise operations instead of modulo operations to fix the issue. > > > > > > > > Signed-off-by: Atish Patra <atish.patra@wdc.com> > > > > --- > > > > drivers/firmware/efi/libstub/alignedmem.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/firmware/efi/libstub/alignedmem.c b/drivers/firmware/efi/libstub/alignedmem.c > > > > index cc89c4d6196f..1de9878ddd3a 100644 > > > > --- a/drivers/firmware/efi/libstub/alignedmem.c > > > > +++ b/drivers/firmware/efi/libstub/alignedmem.c > > > > @@ -44,7 +44,7 @@ efi_status_t efi_allocate_pages_aligned(unsigned long size, unsigned long *addr, > > > > *addr = ALIGN((unsigned long)alloc_addr, align); > > > > > > > > if (slack > 0) { > > > > - int l = (alloc_addr % align) / EFI_PAGE_SIZE; > > > > + int l = (alloc_addr & (align - 1)) / EFI_PAGE_SIZE; > > > > > > Here you rely on the compiler to silently convert the division by > > > EFI_PAGE_SIZE into a right shift. Wouldn't it be cleaner to use > > > EFI_PAGE_SHIFT to explicitly avoid a dependency on __udivdi3()? > > > > > > slack = (align >> EFI_PAGE_SHIFT) - 1; > > > ... > > > int l = (alloc_addr & (align - 1)) >> EFI_PAGE_SHIFT; > > > > > > > Sure. I will update it in the next version. Thanks for the suggestion. > > Please don't. Dividing by EFI_PAGE_SIZE is perfectly fine, and is more readable. Actually, I will take this patch as a fix right away - 32-bit ARM has the same issue (although it does not actually incorporate this object file) In the meantime, please check how the stub gets pulled into your kernel: the idea of a static library is that only the objects that are used are included in the final build, but this turned out to be broken for arm64 [0]. IOW, simply applying a similar change might fix your build issue as well (assuming RISC-V does not actually call efi_allocate_pages_aligned() anywhere) [0] https://lore.kernel.org/linux-arm-kernel/20200604022031.164207-1-masahiroy@kernel.org/
On Sat, Jun 27, 2020 at 2:22 AM Ard Biesheuvel <ardb@kernel.org> wrote: > > On Sat, 27 Jun 2020 at 00:03, Ard Biesheuvel <ardb@kernel.org> wrote: > > > > On Fri, 26 Jun 2020 at 23:56, Atish Patra <atishp@atishpatra.org> wrote: > > > > > > On Thu, Jun 25, 2020 at 7:43 PM Heinrich Schuchardt <xypron.glpk@gmx.de> wrote: > > > > > > > > On 6/26/20 1:45 AM, Atish Patra wrote: > > > > > 32bit gcc doesn't support modulo operation on 64 bit data. It results in > > > > > a __umoddi3 error while building EFI for 32 bit. > > > > > > > > > > Use bitwise operations instead of modulo operations to fix the issue. > > > > > > > > > > Signed-off-by: Atish Patra <atish.patra@wdc.com> > > > > > --- > > > > > drivers/firmware/efi/libstub/alignedmem.c | 2 +- > > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > > > diff --git a/drivers/firmware/efi/libstub/alignedmem.c b/drivers/firmware/efi/libstub/alignedmem.c > > > > > index cc89c4d6196f..1de9878ddd3a 100644 > > > > > --- a/drivers/firmware/efi/libstub/alignedmem.c > > > > > +++ b/drivers/firmware/efi/libstub/alignedmem.c > > > > > @@ -44,7 +44,7 @@ efi_status_t efi_allocate_pages_aligned(unsigned long size, unsigned long *addr, > > > > > *addr = ALIGN((unsigned long)alloc_addr, align); > > > > > > > > > > if (slack > 0) { > > > > > - int l = (alloc_addr % align) / EFI_PAGE_SIZE; > > > > > + int l = (alloc_addr & (align - 1)) / EFI_PAGE_SIZE; > > > > > > > > Here you rely on the compiler to silently convert the division by > > > > EFI_PAGE_SIZE into a right shift. Wouldn't it be cleaner to use > > > > EFI_PAGE_SHIFT to explicitly avoid a dependency on __udivdi3()? > > > > > > > > slack = (align >> EFI_PAGE_SHIFT) - 1; > > > > ... > > > > int l = (alloc_addr & (align - 1)) >> EFI_PAGE_SHIFT; > > > > > > > > > > Sure. I will update it in the next version. Thanks for the suggestion. > > > > Please don't. Dividing by EFI_PAGE_SIZE is perfectly fine, and is more readable. > > Actually, I will take this patch as a fix right away - 32-bit ARM has > the same issue (although it does not actually incorporate this object > file) > Thanks. I will drop it from my next version in that case. > In the meantime, please check how the stub gets pulled into your > kernel: the idea of a static library is that only the objects that are > used are included in the final build, but this turned out to be broken > for arm64 [0]. IOW, simply applying a similar change might fix your > build issue as well (assuming RISC-V does not actually call > efi_allocate_pages_aligned() anywhere) > Sorry. I missed this thread earlier. Yes. Applying a similar change fixes the static library linking for RISC-V. I don't see efi_allocate_pages_aligned or efi_random_alloc in vmlinux anymore. I will update my patch. Thanks. I did not see any new version of the next patch in that series [1]. Thus, I am leaving libstub/Makefile changes as it is. Please let me know if I missed something. [1] https://lore.kernel.org/linux-efi/CAMj1kXGg-w6N7jyG0pBJmeRctAhG2wWGoU=ryWj+Qi2UH-_m9Q@mail.gmail.com/ > [0] https://lore.kernel.org/linux-arm-kernel/20200604022031.164207-1-masahiroy@kernel.org/
diff --git a/drivers/firmware/efi/libstub/alignedmem.c b/drivers/firmware/efi/libstub/alignedmem.c index cc89c4d6196f..1de9878ddd3a 100644 --- a/drivers/firmware/efi/libstub/alignedmem.c +++ b/drivers/firmware/efi/libstub/alignedmem.c @@ -44,7 +44,7 @@ efi_status_t efi_allocate_pages_aligned(unsigned long size, unsigned long *addr, *addr = ALIGN((unsigned long)alloc_addr, align); if (slack > 0) { - int l = (alloc_addr % align) / EFI_PAGE_SIZE; + int l = (alloc_addr & (align - 1)) / EFI_PAGE_SIZE; if (l) { efi_bs_call(free_pages, alloc_addr, slack - l + 1);
32bit gcc doesn't support modulo operation on 64 bit data. It results in a __umoddi3 error while building EFI for 32 bit. Use bitwise operations instead of modulo operations to fix the issue. Signed-off-by: Atish Patra <atish.patra@wdc.com> --- drivers/firmware/efi/libstub/alignedmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)