| Message ID | 20171129234442.655-6-samitolvanen@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Nov 29, 2017 at 3:44 PM, Sami Tolvanen <samitolvanen@google.com> wrote: > Make sure the linker doesn't remove .altinstructions or > .altinstr_replacement when CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is > enabled. This sounds like a bug in the original implementation of CONFIG_LD_DEAD_CODE_DATA_ELIMINATION? If so, this can likely get merged regardless of the rest of the patchset, ie. gold support.
On Wed, 29 Nov 2017 15:57:53 -0800 Nick Desaulniers <ndesaulniers@google.com> wrote: > On Wed, Nov 29, 2017 at 3:44 PM, Sami Tolvanen <samitolvanen@google.com> wrote: > > Make sure the linker doesn't remove .altinstructions or > > .altinstr_replacement when CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is > > enabled. > > This sounds like a bug in the original implementation of > CONFIG_LD_DEAD_CODE_DATA_ELIMINATION? If so, this can likely get > merged regardless of the rest of the patchset, ie. gold support. Yes, also patch 3/7 probably (thanks for doing these, btw). The LD_DCDE option is actually been broken upstream thanks to lack of time (which is a known issue, this is why no arch enables it). Basically it just needs a bit more effort to go through and ensure nothing is discarded incorrectly, and all new sections are placed into output sections, before each arch is enabled. (Comparing `readelf -S` before/after is a way to spot bugs.) So yes please if it's not too much trouble, could you remove the "gold" name from the generic patch and put it at the front of the series with this arm64 patch. Possibly then you could also do a 3rd patch to allow arm64 to select it if it's working with gcc? Thanks, Nick
On Wed, Nov 29, 2017 at 5:58 PM, Nicholas Piggin <npiggin@gmail.com> wrote:
> (Comparing `readelf -S` before/after is a way to spot bugs.)
Do you have a script that can be used to diff 2 `readelf -S`, look for
missing references, and report an error? Might be easier to rerun that
every so often and see what's missing.
On Thu, Nov 30, 2017 at 11:58:27AM +1000, Nicholas Piggin wrote: > So yes please if it's not too much trouble, could you remove > the "gold" name from the generic patch and put it at the front > of the series with this arm64 patch. Sure, I'll do this in v2. > Possibly then you could also do a 3rd patch to allow arm64 to > select it if it's working with gcc? These patches only fix the issues I ran into with clang and gold when testing on a single device. I feel like more testing would be needed before enabling this by default for arm64. Sami
On Thu, 30 Nov 2017 09:00:35 -0800 Nick Desaulniers <ndesaulniers@google.com> wrote: > On Wed, Nov 29, 2017 at 5:58 PM, Nicholas Piggin <npiggin@gmail.com> wrote: > > (Comparing `readelf -S` before/after is a way to spot bugs.) > > Do you have a script that can be used to diff 2 `readelf -S`, look for > missing references, and report an error? Might be easier to rerun that > every so often and see what's missing. I don't, I was just doing it by hand. Thanks, Nick
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 7da3e5c366a0..15479995869c 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -138,11 +138,11 @@ SECTIONS . = ALIGN(4); .altinstructions : { __alt_instructions = .; - *(.altinstructions) + KEEP(*(.altinstructions)) __alt_instructions_end = .; } .altinstr_replacement : { - *(.altinstr_replacement) + KEEP(*(.altinstr_replacement)) } . = ALIGN(PAGE_SIZE);
Make sure the linker doesn't remove .altinstructions or .altinstr_replacement when CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is enabled. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> --- arch/arm64/kernel/vmlinux.lds.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)