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Rui Qi bd4c6578e7 riscv: stacktrace: Remove bogus -0x4 offset in non-FP walk_stackframe 
[ Upstream commit 8ac35bac70 ]

In the non-frame-pointer version of walk_stackframe, each value read
from the stack is treated as a potential return address and has 0x4
subtracted before being used as the program counter. This was intended
to convert the return address (the instruction after a call) back to
the call site, but it is incorrect:

1. RISC-V has variable-length instructions due to the RVC (compressed
   instruction) extension. A call instruction can be either 4 bytes
   (regular) or 2 bytes (compressed, e.g. c.jal). Subtracting a fixed
   0x4 assumes all call instructions are 4 bytes, which is wrong for
   compressed instructions.

2. Stack traces conventionally report return addresses, not call sites.
   Other architectures (ARM64, x86, ARM) do not subtract instruction
   size from return addresses in their stack unwinding code.

3. The frame-pointer version of walk_stackframe already dropped the
   -0x4 offset. Commit b785ec129b ("riscv/ftrace: Add
   HAVE_FUNCTION_GRAPH_RET_ADDR_PTR support") replaced "pc =
   frame->ra - 0x4" with ftrace_graph_ret_addr(), and the commit
   message explicitly noted that "the original calculation, pc =
   frame->ra - 4, is buggy when the instruction at the return address
   happened to be a compressed inst." The non-FP version was simply
   overlooked.

Remove the bogus -0x4 offset to match the FP version and the
conventions used by other architectures.

Fixes: 5d8544e2d0 ("RISC-V: Generic library routines and assembly")
Signed-off-by: Rui Qi <qirui.001@bytedance.com>
Link: https://patch.msgid.link/20260603115329.791603-2-qirui.001@bytedance.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-07-24 15:51:33 +02:00
arch riscv: stacktrace: Remove bogus -0x4 offset in non-FP walk_stackframe 2026-07-24 15:51:33 +02:00
block partitions: aix: bound the pp_count scan to the ppe array 2026-07-24 15:51:24 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: asymmetric_keys - fix OOB read in pefile_digest_pe_contents 2026-07-24 15:51:28 +02:00
Documentation cpufreq: Documentation: fix sampling_down_factor range 2026-07-24 15:51:29 +02:00
drivers wifi: wcn36xx: fix OOB read from firmware count in PRINT_REG_INFO indication 2026-07-24 15:51:33 +02:00
fs ocfs2: fix race between ocfs2_control_install_private() and ocfs2_control_release() 2026-07-24 15:51:32 +02:00
include ipv6: guard against possible NULL deref in __in6_dev_stats_get() 2026-07-24 15:51:30 +02:00
init randomize_kstack: Maintain kstack_offset per task 2026-06-19 13:33:41 +02:00
io_uring io_uring/io-wq: re-check IO_WQ_BIT_EXIT for each linked work item 2026-07-24 15:51:21 +02:00
ipc ipc/shm: serialize orphan cleanup with shm_nattch updates 2026-06-19 13:33:38 +02:00
kernel bpf: fix UAF by restoring RCU-delayed inode freeing in bpffs 2026-07-24 15:51:32 +02:00
lib lib/test_meminit: use && for bools 2026-07-24 15:51:32 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/huge_memory: update file PMD counter before folio_put() 2026-06-19 13:33:49 +02:00
net bpf: Update transport_header when encapsulating UDP tunnel in lwt 2026-07-24 15:51:33 +02:00
samples samples: mei: Fix building on musl libc 2025-08-28 16:24:07 +02:00
scripts kconfig: fix potential NULL pointer dereference in conf_askvalue 2026-07-24 15:51:28 +02:00
security evm: terminate and bound the evm_xattrs read buffer 2026-07-24 15:51:28 +02:00
sound ALSA: usb-audio: Update US-16x08 EQ/comp shadow state after successful writes 2026-07-24 15:51:19 +02:00
tools bpftool: Use libbpf error code for flow dissector query 2026-07-24 15:51:32 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-06-27 11:05:22 +01:00
virt KVM: Replace guest-triggerable BUG_ON() in ioeventfd datamatch with get_unaligned() 2026-07-24 15:51:16 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-17 15:11:10 +02:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS staging: rtl8712: Remove driver using deprecated API wext 2025-12-07 06:09:36 +09:00
Makefile Linux 5.15.211 2026-07-04 13:39:41 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.