https://bugs.kde.org/show_bug.cgi?id=479699
Bug ID: 479699
Summary: Add support for stack-clash-protection on 32bit Arm
Classification: Developer tools
Product: valgrind
Version: 3.20.0
Platform: Debian unstable
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: memcheck
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Hi,
The ARM Architecture Procedure Call Standard relaxed the limitations on memory
accesses below the stack pointer in 2018Q4:
| 6.2.1.3 Stack probing
| In order to ensure stack integrity a process may emit stack probes
immediately
| prior to allocating additional stack space (moving SP from SP_old to SP_new).
| Stack probes must be in the region of [SP_new, SP_old - 1] and may be either
| read or write operations. The minimum interval for stack probing is defined
by
| the target platform but must be a minimum of 4KBytes. No recoverable data can
| be saved below the currently allocated stack region.
See
https://github.com/ARM-software/abi-aa/blob/2a70c42d62e9c3eb5887fa50b71257f20daca6f9/aapcs32/aapcs32.rst#6213stack-probing
Currently, valgrind considers all memory accesses below SP as errors, see for
example: https://lists.debian.org/debian-arm/2023/12/msg00002.html
GCC implements the AAPCS rules when using stack-clash protection, so please
consider updating valgrind accordingly.
Additionally, valgrind may segfault when debugging programs built
with stack-clash-protection turned on. For example:
valgrind --track-origins=yes --leak-check=full apt-get update
[...]
==3102620== Process terminating with default action of signal 11 (SIGSEGV)
==3102620== Access not within mapped region at address 0xFEDCBDAC
==3102620== at 0x49476E8: ReadMessages(int,
std::vector<std::__cxx11::basic_string<char, std::char_traits<char>,
std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> > > >&) (strutl.cc:888)
See https://people.debian.org/~ema/valgrind-segfault-apt-get-update.log for
full output.
Disassembled code at https://people.debian.org/~ema/apt-scp-armhf.log. The
memory location pointed at by r12 is out of the stack.
Another example of valgrind segfaulting when checking programs built with
stack-clash-protection on 32bit arm is at
https://bugzilla.redhat.com/show_bug.cgi?id=1522678
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