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[LLD][ELF] Cortex-M Security Extensions (CMSE) Support

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This commit provides linker support for Cortex-M Security Extensions (CMSE).
The specification for this feature can be found in ARM v8-M Security Extensions:
Requirements on Development Tools.

The linker synthesizes a security gateway veneer in a special section;
`.gnu.sgstubs`, when it finds non-local symbols `__acle_se_<entry>` and `<entry>`,
defined relative to the same text section and having the same address. The
address of `<entry>` is retargeted to the starting address of the
linker-synthesized security gateway veneer in section `.gnu.sgstubs`.

In summary, the linker translates input:

```
    .text
  entry:
  __acle_se_entry:
    [entry_code]

```
into:

```
    .section .gnu.sgstubs
  entry:
    SG
    B.W __acle_se_entry

    .text
  __acle_se_entry:
    [entry_code]
```

If addresses of `__acle_se_<entry>` and `<entry>` are not equal, the linker
considers that `<entry>` already defines a secure gateway veneer so does not
synthesize one.

If `--out-implib=<out.lib>` is specified, the linker writes the list of secure
gateway veneers into a CMSE import library `<out.lib>`. The CMSE import library
will have 3 sections: `.symtab`, `.strtab`, `.shstrtab`. For every secure gateway
veneer <entry> at address `<addr>`, `.symtab` contains a `SHN_ABS` symbol `<entry>` with
value `<addr>`.

If `--in-implib=<in.lib>` is specified, the linker reads the existing CMSE import
library `<in.lib>` and preserves the entry function addresses in the resulting
executable and new import library.

Reviewed By: MaskRay, peter.smith

Differential Revision: https://reviews.llvm.org/D139092
This commit is contained in:
Amilendra Kodithuwakku
2023-06-21 12:48:33 +01:00
parent afc5cca0d4
commit c4fea39056
22 changed files with 1215 additions and 2 deletions
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9
lld/ELF/LinkerScript.cpp
View File

@@ -896,6 +896,15 @@ void LinkerScript::diagnoseOrphanHandling() const {
}
}
void LinkerScript::diagnoseMissingSGSectionAddress() const {
if (!config->cmseImplib || !in.armCmseSGSection->isNeeded())
return;
OutputSection *sec = findByName(sectionCommands, ".gnu.sgstubs");
if (sec && !sec->addrExpr && !config->sectionStartMap.count(".gnu.sgstubs"))
error("no address assigned to the veneers output section " + sec->name);
}
// This function searches for a memory region to place the given output
// section in. If found, a pointer to the appropriate memory region is
// returned in the first member of the pair. Otherwise, a nullptr is returned.