[PATCH 2/3] ARM: convert to generated system call tables
From: arnd@arndb.de (Arnd Bergmann)
Date: 2016-10-19 15:30:49
On Tuesday, October 18, 2016 8:31:38 PM CEST Russell King wrote:
Convert ARM to use a similar mechanism to x86 to generate the unistd.h system call numbers and the various kernel system call tables. This means that rather than having to edit three places (asm/unistd.h for the total number of system calls, uapi/asm/unistd.h for the system call numbers, and arch/arm/kernel/calls.S for the call table) we have only one place to edit, making the process much more simple. The scripts have knowledge of the table padding requirements, so there's no need to worry about __NR_syscalls not fitting within the immediate constant field of ALU instructions anymore. Signed-off-by: Russell King <redacted>
Ah, very nice! I have some vague plans to do something like this for all architectures, so having it done for one of the more complex examples (there are very few architectures with more than one table) simplifies it a lot. The next step is probably to do it for asm-generic/unistd.h, which covers a lot of architectures, and then we can introduce a shared table for all future additions so we only have to add the new calls in one place, and change the scripts so they can merge two input files into one.
quoted hunk ↗ jump to hunk
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl new file mode 100644 index 000000000000..62285cbd09c0 --- /dev/null +++ b/arch/arm/tools/syscall.tbl@@ -0,0 +1,428 @@ +# +# Linux system call numbers and entry vectors +# +# The format is: +# <num> <abi> <name> <entry point> <oabi compat entry point> +# +# Where abi is: +# common - for system calls shared between oabi and eabi +# oabi - for oabi-only system calls (may have compat) +# eabi - for eabi-only system calls
Why do we need all three? I would have guessed that these two are sufficient to cover all cases: arm - one entry for eabi, optional second entry for oabi if different oabi - only one entry for oabi, syscall is not used on eabi
+180 oabi pread64 sys_pread64 sys_oabi_pread64 +180 eabi pread64 sys_pread64 +181 oabi pwrite64 sys_pwrite64 sys_oabi_pwrite64 +181 eabi pwrite64 sys_pwrite64
That would avoid having to list those numbers twice, which looks a bit odd here, and is inconsistent with how x86 handles their compat table for x32
quoted hunk ↗ jump to hunk
diff --git a/arch/arm/tools/syscallhdr.sh b/arch/arm/tools/syscallhdr.sh new file mode 100644 index 000000000000..72d4b2e3bdec --- /dev/null +++ b/arch/arm/tools/syscallhdr.sh
The scripts are still very similar to the x86 version. Any chance we can move them to a top-level scripts/syscall/ directory and make them work for both architectures? It would be good to avoid duplicating them for all the other architectures too, so starting out with a common version could make that easier. If necessary, I can do that once I get to the following stage of doing the asm-generic/unistd.h replacement. Arnd