Re: [PATCH v5 13/13] alpha: Use the common syscall table

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Critical] Incorrect `__NR_syscalls` calculation in `syscallhdr.sh` truncates the syscall table bounds check on Alpha, breaking all syscalls >= 472.
- [Low] The modified syscall build scripts use Bash-specific process substitution, which causes syntax errors and build failures on systems where /bin/sh is dash.
--

--- Patch [13]: [PATCH v5 13/13] alpha: Use the common syscall table ---
commit 8a4799a8727ec390bf08ab1390ac21a27d092616
Author: André Almeida <andrealmeid@igalia.com>

    alpha: Use the common syscall table
    
    Remove some of the duplicated code by using the common syscall number
    table.

> diff --git a/arch/alpha/kernel/syscalls/Makefile b/arch/alpha/kernel/syscalls/Makefile
> index b265e4bc16c2e..18682418327bc 100644
> --- a/arch/alpha/kernel/syscalls/Makefile
> +++ b/arch/alpha/kernel/syscalls/Makefile
> @@ -7,12 +7,18 @@ $(shell mkdir -p $(uapi) $(kapi))
>  syscall := $(src)/syscall.tbl
>  syshdr := $(srctree)/scripts/syscallhdr.sh
>  systbl := $(srctree)/scripts/syscalltbl.sh
> +systbl_common := $(srctree)/scripts/syscall_common.tbl
> +abis := common,__clone3
>  
>  quiet_cmd_syshdr = SYSHDR  $@
> -      cmd_syshdr = $(CONFIG_SHELL) $(syshdr) --emit-nr $< $@
> +      cmd_syshdr = $(CONFIG_SHELL) $(syshdr) --emit-nr \
> +		   --common-tbl $(systbl_common) --common-offset 110 \
> +		   --abis $(abis) $< $@

[Severity: Critical]
Does this offset argument truncate the syscall table bounds check on Alpha?

When the common table is processed via scripts/syscallhdr.sh, the maximum
syscall number is stored before applying the offset:

scripts/syscallhdr.sh:gen_hdr() {
    ...
    while read nr abi name native compat; do
        max=$nr

        if [ -n "$offset_nr" ]; then
            nr=$((nr + offset_nr))
        fi
    ...
}

Because max is assigned the un-offset number, it resets to 471 when parsing
the common table, instead of reflecting Alpha's actual maximum (581). This
causes __NR_syscalls to be emitted as 472.

Consequently, does this cause the bounds check in arch/alpha/kernel/entry.S
(entSys) to reject all valid syscalls >= 472 with -ENOSYS? This would break
several valid syscalls when using the offset.

>  
>  quiet_cmd_systbl = SYSTBL  $@
> -      cmd_systbl = $(CONFIG_SHELL) $(systbl) $< $@
> +      cmd_systbl = $(CONFIG_SHELL) $(systbl) \
> +		   --common-tbl $(systbl_common) --common-offset 110 \
> +		   --abis $(abis) $< $@

[Severity: Low]
Do these modified build commands fail on systems where /bin/sh is dash?

Both scripts/syscallhdr.sh and scripts/syscalltbl.sh use a bash-specific
process substitution pattern:

scripts/syscallhdr.sh:gen_hdr() {
    ...
    done < <(grep -E "^[0-9A-Fa-fXx]+[[:space:]]+$abis" "$input")
}

scripts/syscalltbl.sh:gen_tbl() {
    ...
    done < <(grep -E "^[0-9]+[[:space:]]+$abis" "$input")
}

This syntax is a bash extension and results in syntax errors on strictly
POSIX-compliant shells like dash, causing the build to fail.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260812-tonyk-syscall_table-v5-0-3d383927c609@igalia.com?part=13