On Mon, Jul 08, 2024 at 03:12:55PM +0000, LEROY Christophe wrote: > > > Le 08/07/2024 à 14:36, Greg KH a écrit : > > On Sun, Jul 07, 2024 at 03:34:15PM +0800, WangYuli wrote: > >> > >> On 2024/7/6 17:30, Greg KH wrote: > >>> This makes it sound like you are reverting this because of a build > >>> error, which is not the case here, right? Isn't this because of the > >>> powerpc issue reported here: > >>> https://lore.kernel.org/r/20240705203413.wbv2nw3747vjeibk@xxxxxxxxxxxx > >>> ? > >> > >> No, it only occurs on ARM64 architecture. The reason is that before being > >> modified, the function > >> > >> bpf_jit_binary_lock_ro() in arch/arm64/net/bpf_jit_comp.c +1651 > >> > >> was introduced with __must_check, which is defined as > >> __attribute__((__warn_unused_result__)). > >> > >> > >> However, at this point, calling bpf_jit_binary_lock_ro(header) > >> coincidentally results in an unused-result > >> > >> warning. > > > > Ok, thanks, but why is no one else seeing this in their testing? > > Probably the configs used by robots do not activate BPF JIT ? > > > > >>> If not, why not just backport the single missing arm64 commit, > >> > >> Upstream commit 1dad391daef1 ("bpf, arm64: use bpf_prog_pack for memory > >> management") is part of > >> > >> a larger change that involves multiple commits. It's not an isolated commit. > >> > >> > >> We could certainly backport all of them to solve this problem, buthas it's not > >> the simplest solution. > > > > reverting the change feels wrong in that you will still have the bug > > present that it was trying to solve, right? If so, can you then provide > > a working version? > > Indeed, by reverting the change you "punish" all architectures because > arm64 hasn't properly been backported, is it fair ? > > In fact, when I implemented commit e60adf513275 ("bpf: Take return from > set_memory_rox() into account with bpf_jit_binary_lock_ro()"), we had > the following users for function bpf_jit_binary_lock_ro() : > > $ git grep bpf_jit_binary_lock_ro e60adf513275~ > e60adf513275~:arch/arm/net/bpf_jit_32.c: > bpf_jit_binary_lock_ro(header); > e60adf513275~:arch/loongarch/net/bpf_jit.c: > bpf_jit_binary_lock_ro(header); > e60adf513275~:arch/mips/net/bpf_jit_comp.c: > bpf_jit_binary_lock_ro(header); > e60adf513275~:arch/parisc/net/bpf_jit_core.c: > bpf_jit_binary_lock_ro(jit_data->header); > e60adf513275~:arch/s390/net/bpf_jit_comp.c: > bpf_jit_binary_lock_ro(header); > e60adf513275~:arch/sparc/net/bpf_jit_comp_64.c: > bpf_jit_binary_lock_ro(header); > e60adf513275~:arch/x86/net/bpf_jit_comp32.c: > bpf_jit_binary_lock_ro(header); > e60adf513275~:include/linux/filter.h:static inline void > bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr) > > But when commit 08f6c05feb1d ("bpf: Take return from set_memory_rox() > into account with bpf_jit_binary_lock_ro()") was applied, we had one > more user which is arm64: > > $ git grep bpf_jit_binary_lock_ro 08f6c05feb1d~ > 08f6c05feb1d~:arch/arm/net/bpf_jit_32.c: > bpf_jit_binary_lock_ro(header); > 08f6c05feb1d~:arch/arm64/net/bpf_jit_comp.c: > bpf_jit_binary_lock_ro(header); > 08f6c05feb1d~:arch/loongarch/net/bpf_jit.c: > bpf_jit_binary_lock_ro(header); > 08f6c05feb1d~:arch/mips/net/bpf_jit_comp.c: > bpf_jit_binary_lock_ro(header); > 08f6c05feb1d~:arch/parisc/net/bpf_jit_core.c: > bpf_jit_binary_lock_ro(jit_data->header); > 08f6c05feb1d~:arch/s390/net/bpf_jit_comp.c: > bpf_jit_binary_lock_ro(header); > 08f6c05feb1d~:arch/sparc/net/bpf_jit_comp_64.c: > bpf_jit_binary_lock_ro(header); > 08f6c05feb1d~:arch/x86/net/bpf_jit_comp32.c: > bpf_jit_binary_lock_ro(header); > 08f6c05feb1d~:include/linux/filter.h:static inline void > bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr) > > Therefore, commit 08f6c05feb1d should have included a backport for arm64. > > So yes, I agree with Greg, the correct fix should be to backport to > ARM64 the changes done on other architectures in order to properly > handle return of set_memory_rox() in bpf_jit_binary_lock_ro(). Ok, but it looks like due to this series, the powerpc tree is crashing at the first bpf load, so something went wrong. Let me go revert these 4 patches for now, and then I will be glad to queue them up if you can provide a working series for all arches. thanks, greg k-h
