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| author | Andrew Waterman <andrew@sifive.com> | 2024-07-23 16:00:45 -0700 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2024-07-23 16:00:45 -0700 |
| commit | 3544bba038bcea040b6afd73787dfd7d939beb1e (patch) | |
| tree | 07aa507354255cb50298febe749047802269e73b /src | |
| parent | 6024788dc24a3414af3363489f4302e9df29d61b (diff) | |
| download | riscv-isa-manual-3544bba038bcea040b6afd73787dfd7d939beb1e.zip riscv-isa-manual-3544bba038bcea040b6afd73787dfd7d939beb1e.tar.gz riscv-isa-manual-3544bba038bcea040b6afd73787dfd7d939beb1e.tar.bz2 | |
Add notes about semihosting NOPs; clarify there is only one semihosting exit NOP (#1539)riscv-isa-release-3544bba-2024-07-23
* There is only one semihosting call, not several
The comment suggested otherwise.
* Add NOTE to HINT section about semihosting NOPs
Diffstat (limited to 'src')
| -rw-r--r-- | src/rv32.adoc | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/src/rv32.adoc b/src/rv32.adoc index fac9909..1deda32 100644 --- a/src/rv32.adoc +++ b/src/rv32.adoc @@ -865,6 +865,7 @@ ignore the _predecessor_ and _successor_ fields and always execute a conservative fence on all operations. ==== +[[ecall-ebreak]] === Environment Call and Breakpoints `SYSTEM` instructions are used to access system functionality that might require privileged access and are encoded using the I-type instruction @@ -924,7 +925,7 @@ to distinguish a semihosting EBREAK from a debugger inserted EBREAK. .... slli x0, x0, 0x1f # Entry NOP ebreak # Break to debugger - srai x0, x0, 7 # NOP encoding the semihosting call number 7 + srai x0, x0, 7 # Exit NOP .... Note that these three instructions must be 32-bit-wide instructions, @@ -1063,3 +1064,5 @@ hints, security tags, and instrumentation flags for simulation/emulation. |SLTU |_rd_=`x0` |latexmath:[$2^{10}$] |=== +TIP: When allocating `slli x0, x0, 0x1f` or `srai x0, x0, 7` as custom HINTs, +take note of their use in semihosting calls, as described in <<ecall-ebreak>>. |