| Message ID | 20201119161710.1985083-4-f4bug@amsat.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | linux-user: Support o32 ABI with 64-bit MIPS CPUs | expand |
On Thu, 19 Nov 2020, Philippe Mathieu-Daudé wrote: > MIPS o32 ABI on 64-bit CPUs looks like a ILP32-on-64bit data > model, allowing 64-bit arithmetic and data movement instructions. > > This is the default ABI used by the "Sony Linux Toolkit for > Playstation 2". Please don't, not at least with a generic configuration (i.e. make it unambiguous that this is R5900-specific). This only works with R5900 because it does not implement the MIPS ISA correctly (e.g. see what $ra is set to with JAL/JALR/etc. in the kernel mode), and it is not supported by the standard Linux ABI. Use n32 instead, which has the same functionality and is standard (and is also a better ABI in terms of performance). You'd probably need to implement all the R5900 addressing quirks for your proposed hack to match hardware, or otherwise you'll end up with emulation that creates its own reality. Maciej
Hi Maciej, On 11/19/20 5:45 PM, Maciej W. Rozycki wrote: > On Thu, 19 Nov 2020, Philippe Mathieu-Daudé wrote: > >> MIPS o32 ABI on 64-bit CPUs looks like a ILP32-on-64bit data >> model, allowing 64-bit arithmetic and data movement instructions. >> >> This is the default ABI used by the "Sony Linux Toolkit for >> Playstation 2". > > Please don't, not at least with a generic configuration (i.e. make it > unambiguous that this is R5900-specific). This only works with R5900 > because it does not implement the MIPS ISA correctly (e.g. see what $ra is > set to with JAL/JALR/etc. in the kernel mode), and it is not supported by > the standard Linux ABI. Use n32 instead, which has the same functionality > and is standard (and is also a better ABI in terms of performance). I think there are 2 different interests with the R5900. Fredrik sent a series to run recent userland/kernel on a PS2. For QEMU, it would be easier if these uses the n32 ABI indeed. This series allows me to run unmodified binaries from the PS2 (built maybe 20 years ago, apparently for a kernel 2.2). > You'd probably need to implement all the R5900 addressing quirks for your > proposed hack to match hardware, or otherwise you'll end up with emulation > that creates its own reality. QEMU doesn't model well non-MIPS32 ISA, so the R5900 needs work indeed. Laurent, maybe instead of 'mips64o32el-linux-user' we can call this target 'r5900o32-linux-user', 'ps2-linux-user' or even 'r5900-ps2-user' as Maciej said "it is not supported by the standard Linux ABI." Also I'll see to mark it deprecated so it isn't built by default. Thanks Maciej for your interest, Phil.
Hi Philippe, [ My apologies for the late reply, somehow this thread was treated as spam. ] On Thu, Nov 19, 2020 at 06:13:20PM +0100, Philippe Mathieu-Daudé wrote: > Hi Maciej, > > On 11/19/20 5:45 PM, Maciej W. Rozycki wrote: > > On Thu, 19 Nov 2020, Philippe Mathieu-Daudé wrote: > > > >> MIPS o32 ABI on 64-bit CPUs looks like a ILP32-on-64bit data > >> model, allowing 64-bit arithmetic and data movement instructions. > >> > >> This is the default ABI used by the "Sony Linux Toolkit for > >> Playstation 2". > > > > Please don't, not at least with a generic configuration (i.e. make it > > unambiguous that this is R5900-specific). This only works with R5900 > > because it does not implement the MIPS ISA correctly (e.g. see what $ra is > > set to with JAL/JALR/etc. in the kernel mode), and it is not supported by > > the standard Linux ABI. Use n32 instead, which has the same functionality > > and is standard (and is also a better ABI in terms of performance). > > I think there are 2 different interests with the R5900. Fredrik sent a > series to run recent userland/kernel on a PS2. For QEMU, it would be > easier if these uses the n32 ABI indeed. Modern (4.x and 5.x) R5900 Linux kernels only support o32, due to R5900 complications with n32. The plan is to reintroduce n32 once o32 is usable. The R5900 MMI set is another complication for both ABIs (not mentioning its vector coprocessors). > This series allows me to run unmodified binaries from the PS2 (built > maybe 20 years ago, apparently for a kernel 2.2). Programs in the Debian Black Rhino distribution? I have the impression that there are at least some R5900 specific instructions in some of them, no? The 2.x R5900 Linux kernel does (to some degree) support both o32 and n32, but the implementation had to be reworked (almost entirely) to update it through Linux 3.x, 4.x and 5.x, and n32 was provisionally dropped to simplify this. The GNU C library will have to be updated for n32 too. I'm presently implementing device drivers, that involve the companion MIPS 3000A I/O processor. > > You'd probably need to implement all the R5900 addressing quirks for your > > proposed hack to match hardware, or otherwise you'll end up with emulation > > that creates its own reality. > > QEMU doesn't model well non-MIPS32 ISA, so the R5900 needs work indeed. > > Laurent, maybe instead of 'mips64o32el-linux-user' we can call this > target 'r5900o32-linux-user', 'ps2-linux-user' or even 'r5900-ps2-user' > as Maciej said "it is not supported by the standard Linux ABI." Would "ps2" in the name imply emulating all PlayStation 2 hardware, as opposed to "r5900" that is only its main processor? There are also two interesting vector coprocessors (VPU0 and VPU1) to go with it. :) > Also I'll see to mark it deprecated so it isn't built by default. Presently o32 is the main use case for modern 5.x R5900 Linux, and so regardless of deprecation I have a copy of QEMU supporting it here: https://github.com/frno7/qemu We are building modern Gentoo Linux for the R5900, as described in https://github.com/frno7/linux/issues/33 where R5900 QEMU having o32 is a requirement. Fredrik
On Thu, Nov 19, 2020 at 04:45:29PM +0000, Maciej W. Rozycki wrote: > On Thu, 19 Nov 2020, Philippe Mathieu-Daudé wrote: > > > MIPS o32 ABI on 64-bit CPUs looks like a ILP32-on-64bit data > > model, allowing 64-bit arithmetic and data movement instructions. > > > > This is the default ABI used by the "Sony Linux Toolkit for > > Playstation 2". > > Please don't, not at least with a generic configuration (i.e. make it > unambiguous that this is R5900-specific). This only works with R5900 > because it does not implement the MIPS ISA correctly (e.g. see what $ra is > set to with JAL/JALR/etc. in the kernel mode), and it is not supported by > the standard Linux ABI. Use n32 instead, which has the same functionality > and is standard (and is also a better ABI in terms of performance). > > You'd probably need to implement all the R5900 addressing quirks for your > proposed hack to match hardware, or otherwise you'll end up with emulation > that creates its own reality. I agree. Modern Linux kernel and GCC are important too. It seems both o32 and n32, with quirks, are generally accepted, but R5900 MMIs and other special features are less clear: For example, given the fact that the 128-bit MMIs are unconditionally executable on R5900 hardware, a user may be forgiven to believe that they always work. But unless the Linux kernel restores 128-bit registers in its operating mode switches, which could be o32, there will be silent data corruption (and ensuing frustration). (For this reason I favour full register restores in all operating modes.) Fredrik
diff --git a/docs/user/main.rst b/docs/user/main.rst index 8dfe232a3af..2cef1320ff3 100644 --- a/docs/user/main.rst +++ b/docs/user/main.rst @@ -211,6 +211,9 @@ Other binaries * ``qemu-mipsel`` executes 32-bit little endian MIPS binaries (MIPS O32 ABI). + * ``qemu-mips64o32el`` executes 64-bit little endian MIPS binaries (MIPS O32 + ABI). + * ``qemu-mips64`` executes 64-bit big endian MIPS binaries (MIPS N64 ABI). * ``qemu-mips64el`` executes 64-bit little endian MIPS binaries (MIPS N64 diff --git a/default-configs/targets/mips64o32el-linux-user.mak b/default-configs/targets/mips64o32el-linux-user.mak new file mode 100644 index 00000000000..ecd57ff949f --- /dev/null +++ b/default-configs/targets/mips64o32el-linux-user.mak @@ -0,0 +1,7 @@ +TARGET_ARCH=mips64 +TARGET_BASE_ARCH=mips +TARGET_ABI_MIPSO32=y +TARGET_ABI32=y +TARGET_SYSTBL_ABI=o32 +TARGET_SYSTBL=../mips/syscall_o32.tbl +TARGET_ALIGNED_ONLY=y
MIPS o32 ABI on 64-bit CPUs looks like a ILP32-on-64bit data model, allowing 64-bit arithmetic and data movement instructions. This is the default ABI used by the "Sony Linux Toolkit for Playstation 2". As we don't know big-endian uses, we only introduce the little-endian variant. Inspired-by: Richard Henderson <rth@twiddle.net> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org> --- Cc: Fredrik Noring <noring@nocrew.org> Cc: Maciej W. Rozycki <macro@linux-mips.org> Cc: Jürgen Urban <JuergenUrban@gmx.de> Cc from https://lists.debian.org/debian-mips/2015/05/msg00014.html: Cc: Mathieu Malaterre <malat@debian.org> Cc: James Cowgill <james410@cowgill.org.uk> Cc: YunQiang Su <wzssyqa@gmail.com> Cc: David Daney <ddaney.cavm@gmail.com> --- docs/user/main.rst | 3 +++ default-configs/targets/mips64o32el-linux-user.mak | 7 +++++++ 2 files changed, 10 insertions(+) create mode 100644 default-configs/targets/mips64o32el-linux-user.mak