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| author |   Rich Felker <dalias@libc.org> | 2015-12-17 01:04:25 +0000 |
|---|---|---|
| committer | Rich Felker <dalias@libc.org> | 2016-03-17 19:46:06 +0000 |
| commit | 3623d138213aedf0e2c89720f6a3cd0e164cb310 (patch) | |
| tree | 09dfa5d4a2610f5b1b9b20e964a0ae82e2f64b61 /arch/sh/kernel/cpu/sh2/entry.S | |
| parent | sh: New gcc support (diff) | |
| download | linux-dev-3623d138213aedf0e2c89720f6a3cd0e164cb310.tar.xz linux-dev-3623d138213aedf0e2c89720f6a3cd0e164cb310.zip | |
sh: provide unified syscall trap compatible with all SH models
Historically SH-2 Linux (and originally uClinux) used a syscall
calling convention incompatible with the established SH-3/4 Linux ABI.
This choice was made because the trap range used by the existing ABI,
0x10-0x17, overlaps with the hardware exception/interrupt trap range
reserved by SH-2, and in particular, with the SH-2A divide-by-zero and
division-overflow exceptions.
Despite the documented syscall convention using the low bits of the
trap number to signal the number of arguments the kernel should
expect, no version of the kernel has ever used this information, nor
is it useful; all of the registers need to be saved anyway. Therefore,
it is possible to pick a new trap number, 0x1f, that is both supported
by all existing SH-3/4 kernels and unassigned as a hardware trap in
the SH-2 range. This makes it possible to produce SH-2 application
binaries that are forwards-compatible with running on SH-3/4 kernels
and to treat SH as a unified platform with varying ISA support levels
rather than multiple gratuitously-incompatible platforms.
This patch adjusts the range checking SH-2 and SH-2A kernels make for
the syscall trap to accept the range 0x1f-0x2f rather than just
0x20-0x2f. As a result, trap 0x1f now acts as a syscall for all SH
models.
Signed-off-by: Rich Felker <dalias@libc.org>
Diffstat (limited to 'arch/sh/kernel/cpu/sh2/entry.S')
| -rw-r--r-- | arch/sh/kernel/cpu/sh2/entry.S | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/sh/kernel/cpu/sh2/entry.S b/arch/sh/kernel/cpu/sh2/entry.S index c8a4331d9b8d..a1505956ef28 100644 --- a/arch/sh/kernel/cpu/sh2/entry.S +++ b/arch/sh/kernel/cpu/sh2/entry.S @@ -144,9 +144,9 @@ ENTRY(exception_handler) mov #64,r8 cmp/hs r8,r9 bt interrupt_entry ! vec >= 64 is interrupt - mov #32,r8 + mov #31,r8 cmp/hs r8,r9 - bt trap_entry ! 64 > vec >= 32 is trap + bt trap_entry ! 64 > vec >= 31 is trap mov.l 4f,r8 mov r9,r4 @@ -178,9 +178,9 @@ interrupt_entry: trap_entry: mov #0x30,r8 - cmp/ge r8,r9 ! vector 0x20-0x2f is systemcall + cmp/ge r8,r9 ! vector 0x1f-0x2f is systemcall bt 1f - add #-0x10,r9 ! convert SH2 to SH3/4 ABI + mov #0x1f,r9 ! convert to unified SH2/3/4 trap number 1: shll2 r9 ! TRA bra system_call ! jump common systemcall entry |