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| author | Joel Sing <joel@sing.id.au> | 2023-08-17 01:13:32 +1000 |
|---|---|---|
| committer | Joel Sing <joel@sing.id.au> | 2023-09-19 18:10:13 +0000 |
| commit | bda5e6c3d07c23d477f68f09e3414e495b12a87e (patch) | |
| tree | 0dc955380cf1ba0bf7c9819e4a6ff5f9eb7192c6 /src/cmd/asm | |
| parent | 3c4f12a7d6bc6839b3dd2f4b04aeca962745afb3 (diff) | |
| download | go-bda5e6c3d07c23d477f68f09e3414e495b12a87e.tar.xz | |
cmd/internal/obj/riscv,cmd/link: rework riscv64 call relocations
The riscv64 assembler and linker generate three types of calls.
Most calls are made via a single JAL instruction, however this is
limited to +/-1MB of text. In the case where a call target is
unreachable (or unknown), the JAL targets an AUIPC+JALR trampoline.
All other cases use AUIPC+JALR pairs, including the case where a
single function exceeds 1MB in text size, potentially making it
impossible to reach trampolines.
Currently, the single instruction JAL call is marked with R_RISCV_CALL
and the two instruction AUIPC+JALR call is marked with
R_RISCV_PCREL_ITYPE, which is also used for memory load instructions.
This means that we have no way to identify that the latter is a call.
Switch to using R_RISCV_CALL to mark the AUIPC+JALR pair (aligning
somewhat with the elf.R_RISCV_CALL, which is deprecated in favour of
elf.R_RISCV_CALL_PLT). Add R_RISCV_JAL and use this to mark the single
instruction JAL direct calls. This is clearer and allows us to map
elf.R_RISCV_CALL_PLT to Go's R_RISCV_CALL.
Add all three types to IsDirectCall, so that direct calls are correctly
identified when a function exceeds 1MB of text.
Fixes #62465
Change-Id: Id3eea09688a2b7d6e481eae9ed0aa0d1f9a3a48f
Reviewed-on: https://go-review.googlesource.com/c/go/+/520095
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: Than McIntosh <thanm@google.com>
Diffstat (limited to 'src/cmd/asm')
| -rw-r--r-- | src/cmd/asm/internal/asm/testdata/riscv64.s | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/src/cmd/asm/internal/asm/testdata/riscv64.s b/src/cmd/asm/internal/asm/testdata/riscv64.s index 9899ec9e7b..2afa457105 100644 --- a/src/cmd/asm/internal/asm/testdata/riscv64.s +++ b/src/cmd/asm/internal/asm/testdata/riscv64.s @@ -381,7 +381,7 @@ start: JMP 4(X5) // 67804200 // CALL and JMP to symbol are encoded as JAL (using LR or ZERO - // respectively), with a R_RISCV_CALL relocation. The linker resolves + // respectively), with a R_RISCV_JAL relocation. The linker resolves // the real address and updates the immediate, using a trampoline in // the case where the address is not directly reachable. CALL asmtest(SB) // ef000000 |