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| author | fanzha02 <fannie.zhang@arm.com> | 2019-12-19 08:15:06 +0000 |
|---|---|---|
| committer | Keith Randall <khr@golang.org> | 2020-03-31 02:37:05 +0000 |
| commit | 71d477469c5529b56779cdb3bc235d0a87fe9877 (patch) | |
| tree | 00461b1597290e4e2e0e2f1fb0cdf45aea2ed83c /src/cmd/internal/obj/textflag.go | |
| parent | fde6868ac3f3f049247084f2c76efec3555a2395 (diff) | |
| download | go-71d477469c5529b56779cdb3bc235d0a87fe9877.tar.gz go-71d477469c5529b56779cdb3bc235d0a87fe9877.zip | |
cmd/asm: align an instruction or a function's address
Recently, the gVisor project needs an instruction's address
with 128 bytes alignment and a function's start address with
2K bytes alignment to fit the architecture requirement for
interrupt table.
This patch allows aligning the address of an instruction to be
aligned to a specific value (2^n and not higher than 2048) and
the address of a function to be 2048 bytes.
The main changes include:
1. Adds ALIGN2048 flag to align a function's address with
2048 bytes.
e.g. "TEXT ·Add(SB),NOSPLIT|ALIGN2048" indicates that the
address of Add function should be aligned to 2048 bytes.
2. Adds a new element in the FuncInfo structure defined in
cmd/internal/obj/link.go file to record the alignment
information.
3. Adds a new element in the Func structure defined in
cmd/internal/goobj/read.go file to read the alignment
information.
4. Because go introduces a new object file format, also add
a new element in the FuncInfo structure defined in
cmd/internal/goobj2/funcinfo.go to record the alignment
information.
5. Adds the assembler support to align an intruction's offset
with a specific value (2^n and not higher than 2048).
e.g. "PCALIGN $256" indicates that the next instruction should
be aligned to 256 bytes.
This CL also adds a test.
Change-Id: I31cfa6fb5bc35dee2c44bf65913e90cddfcb492a
Reviewed-on: https://go-review.googlesource.com/c/go/+/212767
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Diffstat (limited to 'src/cmd/internal/obj/textflag.go')
| -rw-r--r-- | src/cmd/internal/obj/textflag.go | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/src/cmd/internal/obj/textflag.go b/src/cmd/internal/obj/textflag.go index d2cec734b1..3681a3b67b 100644 --- a/src/cmd/internal/obj/textflag.go +++ b/src/cmd/internal/obj/textflag.go @@ -51,4 +51,9 @@ const ( // Function is the top of the call stack. Call stack unwinders should stop // at this function. TOPFRAME = 2048 + + // ALIGN2048 means that the address of the function must be aligned to a + // 2048 bytes boundary. + // Only works on arm64 at present. + ALIGN2048 = 4096 ) |