Re: [PATCH v9 15/15] arm: Use common syscall table

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential
issues to consider:
- [High] arm: syscalls: missing oabic entry for sys_syscall() breaks
  OABI syscall(113)
- [Low] arm: syscalls: gen-y overwrite in arch/arm/tools/Makefile breaks
  !CONFIG_AEABI
--

commit d6fa13c999788d3882cc5cb046177290257ed17e
Author: André Almeida <andrealmeid@igalia.com>

arm: Use common syscall table

This commit switches arch/arm to use the shared scripts/syscall_common.tbl
for common syscall numbers 403 and above, updating arch/arm/tools/Makefile
and removing the duplicated entries from arch/arm/tools/syscall.tbl.

> diff --git a/arch/arm/tools/Makefile b/arch/arm/tools/Makefile
> index cde235b382bdc..6fed368c3df77 100644
> --- a/arch/arm/tools/Makefile
> +++ b/arch/arm/tools/Makefile
> @@ -12,6 +12,8 @@ syshdr := $(srctree)/scripts/syscallhdr.sh
>  sysnr := $(src)/syscallnr.sh
>  systbl := $(srctree)/scripts/syscalltbl.sh
>  syscall := $(src)/syscall.tbl
> +syscalltbl_common := $(srctree)/scripts/syscall_common.tbl
> +abis := common,clone3,32
>  
>  gen-y := $(gen)/calls-oabi.S
>  gen-y := $(gen)/calls-oabic.S

[Severity: Low]
Does assigning gen-y := $(gen)/calls-oabic.S with := instead of += here in
arch/arm/tools/Makefile break builds when CONFIG_AEABI is disabled?

Because := overwrites gen-y, $(gen)/calls-oabi.S is dropped from both
targets and the kapi prerequisites in arch/arm/tools/Makefile:

    gen-y := $(gen)/calls-oabi.S
    gen-y := $(gen)/calls-oabic.S
    gen-y += $(gen)/calls-eabi.S
    ...
    targets := $(patsubst $(src)/%,%,$(kapi-hdrs-y) $(uapi-hdrs-y) $(gen-y))

    PHONY += kapi uapi
    kapi:   $(kapi-hdrs-y) $(gen-y)

When building a non-AEABI kernel (such as rpc_defconfig or assabet_defconfig),
sys_call_table in arch/arm/kernel/entry-common.S includes <calls-oabi.S>:

    #ifdef CONFIG_AEABI
    #include <calls-eabi.S>
    #else
    #include <calls-oabi.S>
    #endif

Since arch/arm/include/generated/calls-oabi.S is no longer generated, the
build fails with a missing header error. Should the second assignment use
+= instead?

[ ... ]

> diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
> index 944f11030ab4a..36c1e5cc3e022 100644
> --- a/arch/arm/tools/syscall.tbl
> +++ b/arch/arm/tools/syscall.tbl
> @@ -463,72 +463,3 @@
>  400	common	migrate_pages		sys_migrate_pages
>  401	common	kexec_file_load		sys_kexec_file_load
>  # 402 is unused

[Severity: High]
With the switch to calls-oabic.S for CONFIG_OABI_COMPAT earlier in this
series (commit f142c55483ad), is syscall 113 (sys_syscall) missing an oabic
entry in arch/arm/tools/syscall.tbl?

Currently arch/arm/tools/syscall.tbl only defines syscall 113 for oabi:

    # syscall to call a syscall!
    113	oabi	syscall			sys_syscall

In arch/arm/kernel/entry-common.S, sys_oabi_call_table (built under
CONFIG_OABI_COMPAT) now includes <calls-oabic.S>, which is generated with
--abis $(abis),oabic:

    	syscall_table_start sys_oabi_call_table
    #undef __SYSCALL_WITH_COMPAT
    #define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, native)
    #include <calls-oabic.S>
    	syscall_table_end sys_oabi_call_table

And sys_syscall in arch/arm/kernel/entry-common.S explicitly handles OABI
indirect syscalls by clearing __NR_OABI_SYSCALL_BASE and indexing into tbl:

    sys_syscall:
    		bic	scno, r0, #__NR_OABI_SYSCALL_BASE
    		cmp	scno, #__NR_syscall - __NR_SYSCALL_BASE
    		cmpne	scno, #NR_syscalls	@ check range

Without a matching oabic entry for syscall 113 in arch/arm/tools/syscall.tbl,
calls-oabic.S emits __SYSCALL(113, sys_ni_syscall), causing indirect
syscall(2) invocations from OABI user-space binaries under CONFIG_OABI_COMPAT
to fail with -ENOSYS.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261105-tonyk-syscall_table-v9-0-8d1275885d9c@igalia.com?part=15