[libcamera-devel] libcamera: ipa_module: Fix valgrind assertion failure
diff mbox series

Message ID 20200608005442.1771-1-laurent.pinchart@ideasonboard.com
State Accepted
Commit 96fab38e02792a109c0d35ca2154e95a7b4c8fcb
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Series
  • [libcamera-devel] libcamera: ipa_module: Fix valgrind assertion failure
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Commit Message

Laurent Pinchart June 8, 2020, 12:54 a.m. UTC 
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>
---
 src/libcamera/ipa_module.cpp | 42 ++++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 19 deletions(-)

Comments

Niklas Söderlund June 10, 2020, 12:17 a.m. UTC | #1 
Hi Laurent,

Thanks for your work.

On 2020-06-08 03:54:42 +0300, Laurent Pinchart wrote:
> 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>

> ---
>  src/libcamera/ipa_module.cpp | 42 ++++++++++++++++++++----------------
>  1 file changed, 23 insertions(+), 19 deletions(-)
> 
> diff --git a/src/libcamera/ipa_module.cpp b/src/libcamera/ipa_module.cpp
> index 72e357ec97ca..de512a7f3a0d 100644
> --- a/src/libcamera/ipa_module.cpp
> +++ b/src/libcamera/ipa_module.cpp
> @@ -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;
> -- 
> Regards,
> 
> Laurent Pinchart
> 
> _______________________________________________
> libcamera-devel mailing list
> libcamera-devel@lists.libcamera.org
> https://lists.libcamera.org/listinfo/libcamera-devel
Paul Elder June 10, 2020, 2:04 p.m. UTC | #2 
Hi Laurent,

Thank you for the patch.

On Mon, Jun 08, 2020 at 03:54:42AM +0300, Laurent Pinchart wrote:
> 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>

Looks good to me.

Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>

> ---
>  src/libcamera/ipa_module.cpp | 42 ++++++++++++++++++++----------------
>  1 file changed, 23 insertions(+), 19 deletions(-)
> 
> diff --git a/src/libcamera/ipa_module.cpp b/src/libcamera/ipa_module.cpp
> index 72e357ec97ca..de512a7f3a0d 100644
> --- a/src/libcamera/ipa_module.cpp
> +++ b/src/libcamera/ipa_module.cpp
> @@ -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;
> -- 
> Regards,
> 
> Laurent Pinchart
> 
> _______________________________________________
> libcamera-devel mailing list
> libcamera-devel@lists.libcamera.org
> https://lists.libcamera.org/listinfo/libcamera-devel

Patch
diff mbox series 

diff --git a/src/libcamera/ipa_module.cpp b/src/libcamera/ipa_module.cpp
index 72e357ec97ca..de512a7f3a0d 100644
--- a/src/libcamera/ipa_module.cpp
+++ b/src/libcamera/ipa_module.cpp
@@ -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;