[ELF] --no-rosegment: don't mark read-only PT_LOAD segments executable (#81223)
Once we move `.lrodata` after .bss (#78521), or if we use `SECTIONS`
commands, certain read-only sections may be in their own PT_LOAD, not in
the traditional "text segment". Current --no-rosegment code may
unnecessarily mark read-only PT_LOAD executable. Fix it.
GitOrigin-RevId: 0329c1b6d838ec983f215244549b3c5ff2d5fb51
diff --git a/ELF/Writer.cpp b/ELF/Writer.cpp
index 6df43a3..53ca70b 100644
--- a/ELF/Writer.cpp
+++ b/ELF/Writer.cpp
@@ -2353,17 +2353,12 @@
return true;
}
-// Linker scripts are responsible for aligning addresses. Unfortunately, most
-// linker scripts are designed for creating two PT_LOADs only, one RX and one
-// RW. This means that there is no alignment in the RO to RX transition and we
-// cannot create a PT_LOAD there.
+// Adjust phdr flags according to certain options.
static uint64_t computeFlags(uint64_t flags) {
if (config->omagic)
return PF_R | PF_W | PF_X;
if (config->executeOnly && (flags & PF_X))
return flags & ~PF_R;
- if (config->singleRoRx && !(flags & PF_W))
- return flags | PF_X;
return flags;
}
@@ -2451,7 +2446,7 @@
// Segments are contiguous memory regions that has the same attributes
// (e.g. executable or writable). There is one phdr for each segment.
// Therefore, we need to create a new phdr when the next section has
- // different flags or is loaded at a discontiguous address or memory region
+ // compatible flags or is loaded at a discontiguous address or memory region
// using AT or AT> linker script command, respectively.
//
// As an exception, we don't create a separate load segment for the ELF
@@ -2465,13 +2460,22 @@
// so when hasSectionsCommand, since we cannot introduce the extra alignment
// needed to create a new LOAD)
uint64_t newFlags = computeFlags(sec->getPhdrFlags());
+ // When --no-rosegment is specified, RO and RX sections are compatible.
+ uint32_t diff = flags ^ newFlags;
+ if (config->singleRoRx && !(newFlags & PF_W))
+ diff &= ~PF_X;
+ if (diff)
+ load = nullptr;
+
bool sameLMARegion =
load && !sec->lmaExpr && sec->lmaRegion == load->firstSec->lmaRegion;
- if (!(load && newFlags == flags && sec != relroEnd &&
- sec->memRegion == load->firstSec->memRegion &&
- (sameLMARegion || load->lastSec == Out::programHeaders) &&
- (script->hasSectionsCommand || sec->type == SHT_NOBITS ||
- load->lastSec->type != SHT_NOBITS))) {
+ if (load && sec != relroEnd &&
+ sec->memRegion == load->firstSec->memRegion &&
+ (sameLMARegion || load->lastSec == Out::programHeaders) &&
+ (script->hasSectionsCommand || sec->type == SHT_NOBITS ||
+ load->lastSec->type != SHT_NOBITS)) {
+ load->p_flags |= newFlags;
+ } else {
load = addHdr(PT_LOAD, newFlags);
flags = newFlags;
}
diff --git a/test/ELF/segments.s b/test/ELF/segments.s
index ee17117..1fe248a 100644
--- a/test/ELF/segments.s
+++ b/test/ELF/segments.s
@@ -44,7 +44,7 @@
# NOROSEGMENT1-NEXT: LOAD 0x001006 0x0000000000000006 0x0000000000000006 0x000001 0x000001 RW 0x1000
# NOROSEGMENT1-NEXT: LOAD 0x001007 0x0000000000000007 0x0000000000000007 0x000002 0x000002 R E 0x1000
# NOROSEGMENT1-NEXT: LOAD 0x001009 0x0000000000000009 0x0000000000000009 0x000001 0x000001 RW 0x1000
-# NOROSEGMENT1-NEXT: LOAD 0x00100a 0x000000000000000a 0x000000000000000a 0x000001 0x000001 R E 0x1000
+# NOROSEGMENT1-NEXT: LOAD 0x00100a 0x000000000000000a 0x000000000000000a 0x000001 0x000001 R 0x1000
# NOROSEGMENT1-NEXT: GNU_STACK 0x000000 0x0000000000000000 0x0000000000000000 0x000000 0x000000 RW 0
# RUN: ld.lld -N a.o -o omagic
