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| author | Sebastian Huber <sebastian.huber@embedded-brains.de> | 2017-07-17 07:30:46 +0200 |
|---|---|---|
| committer | Sebastian Huber <sebastian.huber@embedded-brains.de> | 2017-07-25 11:41:12 +0200 |
| commit | 146adb1edfaa0271ee0df5180a1f64d54e6e860d (patch) | |
| tree | 4957ce3cfe1c5818ab121bf11465e131042f4952 /c/src/lib/libbsp/sparc/shared/start/start.S | |
| parent | INTERNAL_ERROR_ILLEGAL_USE_OF_FLOATING_POINT_UNIT (diff) | |
| download | rtems-146adb1edfaa0271ee0df5180a1f64d54e6e860d.tar.bz2 | |
sparc: Add lazy floating point switch
The SPARC ABI is a bit special with respect to the floating point context.
The complete floating point context is volatile. Thus, from an ABI point
of view nothing needs to be saved and restored during a context switch.
Instead the floating point context must be saved and restored during
interrupt processing. Historically, the deferred floating point switch was
used for SPARC and the complete floating point context is saved and
restored during a context switch to the new floating point unit owner.
This is a bit dangerous since post-switch actions (e.g. signal handlers)
and context switch extensions may silently corrupt the floating point
context.
The floating point unit is disabled for interrupt handlers. Thus, in case
an interrupt handler uses the floating point unit then this will result in a
trap (INTERNAL_ERROR_ILLEGAL_USE_OF_FLOATING_POINT_UNIT).
In uniprocessor configurations, a lazy floating point context switch is
used. In case an active floating point thread is interrupted (PSR[EF] == 1)
and a thread dispatch is carried out, then this thread is registered as the
floating point owner. When a floating point owner is present during a
context switch, the floating point unit is disabled for the heir thread
(PSR[EF] == 0). The floating point disabled trap checks that the use of the
floating point unit is allowed and saves/restores the floating point context
on demand.
Update #3077.
Diffstat (limited to 'c/src/lib/libbsp/sparc/shared/start/start.S')
| -rw-r--r-- | c/src/lib/libbsp/sparc/shared/start/start.S | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/c/src/lib/libbsp/sparc/shared/start/start.S b/c/src/lib/libbsp/sparc/shared/start/start.S index 3b9f841223..64498c6110 100644 --- a/c/src/lib/libbsp/sparc/shared/start/start.S +++ b/c/src/lib/libbsp/sparc/shared/start/start.S @@ -35,6 +35,15 @@ /* * System call optimized trap table entry */ +#define FPDIS_TRAP(_handler) \ + mov %psr, %l0 ; \ + sethi %hi(_handler), %l4 ; \ + jmp %l4+%lo(_handler); \ + sethi %hi(SPARC_PSR_EF_MASK), %l3 + +/* + * System call optimized trap table entry + */ #define IRQDIS_TRAP(_handler) \ mov %psr, %l0 ; \ sethi %hi(_handler), %l4 ; \ @@ -100,7 +109,11 @@ SYM(trap_table): ! exception BAD_TRAP; ! 02 illegal instruction BAD_TRAP; ! 03 privileged instruction +#if defined(SPARC_USE_LAZY_FP_SWITCH) + FPDIS_TRAP(SYM(syscall_lazy_fp_switch)); ! 04 fp disabled +#else BAD_TRAP; ! 04 fp disabled +#endif WOTRAP(5, SYM(window_overflow_trap_handler)); ! 05 window overflow WUTRAP(6, SYM(window_underflow_trap_handler));! 06 window underflow BAD_TRAP; ! 07 memory address not aligned @@ -209,7 +222,7 @@ SYM(CLOCK_SPEED): */ IRQDIS_TRAP(SYM(syscall_irqdis)); ! 89 IRQ Disable syscall trap IRQEN_TRAP(SYM(syscall_irqen)); ! 8A IRQ Enable syscall trap -#if SPARC_HAS_FPU == 1 +#if defined(SPARC_USE_SYNCHRONOUS_FP_SWITCH) IRQDIS_TRAP(SYM(syscall_irqdis_fp)); ! 8B IRQ disable ! and set PSR[EF] syscall trap #else |