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libcamera: ipa_module: Fix valgrind assertion failure

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As the ELF parsing code uses non-const pointers to the ELF mapping, we
have to map the module in private read-write mode. This causes issues
with valgrind, due to the IPA manager mapping the module in shared
read-only mode and valgrind having trouble loading debugging symbols
later at dlopen time due to conflicting mappings.

This is likely a bug in valgrind (reported as [1]), but we can easily
work around it by using shared read-only mappings only. As such a
mapping shouldn't be less efficient than private read-write mappings,
switch the mapping type. This requires modifying the ELF parsing
functions to operate on const memory, which is a good idea anyway as
they're not supposed to modify the ELF file.

[1] https://bugs.kde.org/show_bug.cgi?id=422601

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
This commit is contained in:
Laurent Pinchart
2020-06-08 03:08:30 +03:00
parent 33d71af84e
commit 96fab38e02
1 changed files with 23 additions and 19 deletions
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42
src/libcamera/ipa_module.cpp
View File

@@ -45,26 +45,27 @@ LOG_DEFINE_CATEGORY(IPAModule)
namespace {
template<typename T>
typename std::remove_extent_t<T> *elfPointer(Span<uint8_t> elf, off_t offset,
size_t objSize)
typename std::remove_extent_t<T> *elfPointer(Span<const uint8_t> elf,
off_t offset, size_t objSize)
{
size_t size = offset + objSize;
if (size > elf.size() || size < objSize)
return nullptr;
return reinterpret_cast<typename std::remove_extent_t<T> *>
(reinterpret_cast<char *>(elf.data()) + offset);
(reinterpret_cast<const char *>(elf.data()) + offset);
}
template<typename T>
typename std::remove_extent_t<T> *elfPointer(Span<uint8_t> elf, off_t offset)
typename std::remove_extent_t<T> *elfPointer(Span<const uint8_t> elf,
off_t offset)
{
return elfPointer<T>(elf, offset, sizeof(T));
}
int elfVerifyIdent(Span<uint8_t> elf)
int elfVerifyIdent(Span<const uint8_t> elf)
{
char *e_ident = elfPointer<char[EI_NIDENT]>(elf, 0);
const char *e_ident = elfPointer<const char[EI_NIDENT]>(elf, 0);
if (!e_ident)
return -ENOEXEC;
@@ -88,14 +89,15 @@ int elfVerifyIdent(Span<uint8_t> elf)
return 0;
}
ElfW(Shdr) *elfSection(Span<uint8_t> elf, ElfW(Ehdr) *eHdr, ElfW(Half) idx)
const ElfW(Shdr) *elfSection(Span<const uint8_t> elf, const ElfW(Ehdr) *eHdr,
ElfW(Half) idx)
{
if (idx >= eHdr->e_shnum)
return nullptr;
off_t offset = eHdr->e_shoff + idx *
static_cast<uint32_t>(eHdr->e_shentsize);
return elfPointer<ElfW(Shdr)>(elf, offset);
return elfPointer<const ElfW(Shdr)>(elf, offset);
}
/**
@@ -106,26 +108,26 @@ ElfW(Shdr) *elfSection(Span<uint8_t> elf, ElfW(Ehdr) *eHdr, ElfW(Half) idx)
* \return The memory region storing the symbol on success, or an empty span
* otherwise
*/
Span<uint8_t> elfLoadSymbol(Span<uint8_t> elf, const char *symbol)
Span<const uint8_t> elfLoadSymbol(Span<const uint8_t> elf, const char *symbol)
{
ElfW(Ehdr) *eHdr = elfPointer<ElfW(Ehdr)>(elf, 0);
const ElfW(Ehdr) *eHdr = elfPointer<const ElfW(Ehdr)>(elf, 0);
if (!eHdr)
return {};
ElfW(Shdr) *sHdr = elfSection(elf, eHdr, eHdr->e_shstrndx);
const ElfW(Shdr) *sHdr = elfSection(elf, eHdr, eHdr->e_shstrndx);
if (!sHdr)
return {};
off_t shnameoff = sHdr->sh_offset;
/* Locate .dynsym section header. */
ElfW(Shdr) *dynsym = nullptr;
const ElfW(Shdr) *dynsym = nullptr;
for (unsigned int i = 0; i < eHdr->e_shnum; i++) {
sHdr = elfSection(elf, eHdr, i);
if (!sHdr)
return {};
off_t offset = shnameoff + sHdr->sh_name;
char *name = elfPointer<char[8]>(elf, offset);
const char *name = elfPointer<const char[8]>(elf, offset);
if (!name)
return {};
@@ -146,16 +148,17 @@ Span<uint8_t> elfLoadSymbol(Span<uint8_t> elf, const char *symbol)
off_t dynsym_nameoff = sHdr->sh_offset;
/* Locate symbol in the .dynsym section. */
ElfW(Sym) *targetSymbol = nullptr;
const ElfW(Sym) *targetSymbol = nullptr;
unsigned int dynsym_num = dynsym->sh_size / dynsym->sh_entsize;
for (unsigned int i = 0; i < dynsym_num; i++) {
off_t offset = dynsym->sh_offset + dynsym->sh_entsize * i;
ElfW(Sym) *sym = elfPointer<ElfW(Sym)>(elf, offset);
const ElfW(Sym) *sym = elfPointer<const ElfW(Sym)>(elf, offset);
if (!sym)
return {};
offset = dynsym_nameoff + sym->st_name;
char *name = elfPointer<char>(elf, offset, strlen(symbol) + 1);
const char *name = elfPointer<const char>(elf, offset,
strlen(symbol) + 1);
if (!name)
return {};
@@ -176,7 +179,8 @@ Span<uint8_t> elfLoadSymbol(Span<uint8_t> elf, const char *symbol)
if (!sHdr)
return {};
off_t offset = sHdr->sh_offset + (targetSymbol->st_value - sHdr->sh_addr);
uint8_t *data = elfPointer<uint8_t>(elf, offset, targetSymbol->st_size);
const uint8_t *data = elfPointer<const uint8_t>(elf, offset,
targetSymbol->st_size);
if (!data)
return {};
@@ -277,14 +281,14 @@ int IPAModule::loadIPAModuleInfo()
return file.error();
}
Span<uint8_t> data = file.map(0, -1, File::MapPrivate);
Span<const uint8_t> data = file.map();
int ret = elfVerifyIdent(data);
if (ret) {
LOG(IPAModule, Error) << "IPA module is not an ELF file";
return ret;
}
Span<uint8_t> info = elfLoadSymbol(data, "ipaModuleInfo");
Span<const uint8_t> info = elfLoadSymbol(data, "ipaModuleInfo");
if (info.size() != sizeof(info_)) {
LOG(IPAModule, Error) << "IPA module has no valid info";
return -EINVAL;