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cmd/internal/obj/riscv: prevent panics on bad branches

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Syntactically incorrect branches, such as

BEQ	X5, X6, $1
BEQ	X5, X6, 31(X10)

cause the assembler to panic, which they shouldn't really do.  It's
better for the user to see a normal error, as reported for other
syntax errors in riscv64 assembly.  The panics also prevent us
from writing negative tests for these sorts of errors.

Here we fix the issue by ensuring we generate a normal error instead
of panicking when the user provides an invalid branch target.  We
also add a couple of negative tests.

Change-Id: I1da568999a75097484b61a01d418f5d4be3e04fa
Reviewed-on: https://go-review.googlesource.com/c/go/+/637316
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Joel Sing <joel@sing.id.au>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Meng Zhuo <mengzhuo1203@gmail.com>
This commit is contained in:
Mark Ryan 2024-12-11 14:03:17 +01:00 • committed by Joel Sing
parent 24b395119b
commit 1aee4f3464
2 changed files with 8 additions and 2 deletions
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2
src/cmd/asm/internal/asm/testdata/riscv64error.s vendored
View file

@ -30,6 +30,8 @@ TEXT errors(SB),$0
SLLI $64, X5, X6 // ERROR "immediate out of range 0 to 63"
SRLI $64, X5, X6 // ERROR "immediate out of range 0 to 63"
SRAI $64, X5, X6 // ERROR "immediate out of range 0 to 63"
BEQ X5, X6, $1 // ERROR "instruction with branch-like opcode lacks destination"
BEQ X5, X6, 31(X10) // ERROR "instruction with branch-like opcode lacks destination"
RORI $-1, X5, X6 // ERROR "immediate out of range 0 to 63"
SLLI $-1, X5, X6 // ERROR "immediate out of range 0 to 63"
SRLI $-1, X5, X6 // ERROR "immediate out of range 0 to 63"

8
src/cmd/internal/obj/riscv/obj.go
View file

@ -769,7 +769,8 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
switch p.As {
case ABEQ, ABEQZ, ABGE, ABGEU, ABGEZ, ABGT, ABGTU, ABGTZ, ABLE, ABLEU, ABLEZ, ABLT, ABLTU, ABLTZ, ABNE, ABNEZ:
if p.To.Type != obj.TYPE_BRANCH {
panic("assemble: instruction with branch-like opcode lacks destination")
ctxt.Diag("%v: instruction with branch-like opcode lacks destination", p)
break
}
offset := p.To.Target().Pc - p.Pc
if offset < -4096 || 4096 <= offset {
@ -853,7 +854,10 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
case obj.TYPE_BRANCH:
p.To.Type, p.To.Offset = obj.TYPE_CONST, p.To.Target().Pc-p.Pc
case obj.TYPE_MEM:
panic("unhandled type")
if ctxt.Errors == 0 {
// An error should have already been reported for this instruction
panic("unhandled type")
}
}
case AJAL: