[PATCH v10 14/14] unwind_user/x86: Enable compat mode frame pointer unwinding on x86
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2025-06-11 01:03:08
Also in:
bpf, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit), x86 stack unwinding · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Josh Poimboeuf, Peter Zijlstra
From: Josh Poimboeuf <jpoimboe@kernel.org> Use ARCH_INIT_USER_COMPAT_FP_FRAME to describe how frame pointers are unwound on x86, and implement the hooks needed to add the segment base addresses. Enable HAVE_UNWIND_USER_COMPAT_FP if the system has compat mode compiled in. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> --- Changes since v9: https://lore.kernel.org/linux-trace-kernel/20250513223551.966925463@goodmis.org/ (local) - Remove unneeded include of perf_event.h arch/x86/Kconfig | 1 + arch/x86/include/asm/unwind_user.h | 49 ++++++++++++++++++++++++ arch/x86/include/asm/unwind_user_types.h | 17 ++++++++ 3 files changed, 67 insertions(+) create mode 100644 arch/x86/include/asm/unwind_user_types.h
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2cdb5cf91541..3f7bdc9e3cec 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig@@ -302,6 +302,7 @@ config X86 select HAVE_SYSCALL_TRACEPOINTS select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL select HAVE_UNSTABLE_SCHED_CLOCK + select HAVE_UNWIND_USER_COMPAT_FP if IA32_EMULATION select HAVE_UNWIND_USER_FP if X86_64 select HAVE_USER_RETURN_NOTIFIER select HAVE_GENERIC_VDSO
diff --git a/arch/x86/include/asm/unwind_user.h b/arch/x86/include/asm/unwind_user.h
index 8597857bf896..43f8554c1d70 100644
--- a/arch/x86/include/asm/unwind_user.h
+++ b/arch/x86/include/asm/unwind_user.h@@ -2,10 +2,59 @@ #ifndef _ASM_X86_UNWIND_USER_H #define _ASM_X86_UNWIND_USER_H +#include <linux/unwind_user_types.h> +#include <asm/ptrace.h> + #define ARCH_INIT_USER_FP_FRAME \ .cfa_off = (s32)sizeof(long) * 2, \ .ra_off = (s32)sizeof(long) * -1, \ .fp_off = (s32)sizeof(long) * -2, \ .use_fp = true, +#ifdef CONFIG_IA32_EMULATION + +#define ARCH_INIT_USER_COMPAT_FP_FRAME \ + .cfa_off = (s32)sizeof(u32) * 2, \ + .ra_off = (s32)sizeof(u32) * -1, \ + .fp_off = (s32)sizeof(u32) * -2, \ + .use_fp = true, + +#define in_compat_mode(regs) !user_64bit_mode(regs) + +static inline void arch_unwind_user_init(struct unwind_user_state *state, + struct pt_regs *regs) +{ + unsigned long cs_base, ss_base; + + if (state->type != UNWIND_USER_TYPE_COMPAT_FP) + return; + + scoped_guard(irqsave) { + cs_base = segment_base_address(regs->cs); + ss_base = segment_base_address(regs->ss); + } + + state->arch.cs_base = cs_base; + state->arch.ss_base = ss_base; + + state->ip += cs_base; + state->sp += ss_base; + state->fp += ss_base; +} +#define arch_unwind_user_init arch_unwind_user_init + +static inline void arch_unwind_user_next(struct unwind_user_state *state) +{ + if (state->type != UNWIND_USER_TYPE_COMPAT_FP) + return; + + state->ip += state->arch.cs_base; + state->fp += state->arch.ss_base; +} +#define arch_unwind_user_next arch_unwind_user_next + +#endif /* CONFIG_IA32_EMULATION */ + +#include <asm-generic/unwind_user.h> + #endif /* _ASM_X86_UNWIND_USER_H */
diff --git a/arch/x86/include/asm/unwind_user_types.h b/arch/x86/include/asm/unwind_user_types.h
new file mode 100644
index 000000000000..d7074dc5f0ce
--- /dev/null
+++ b/arch/x86/include/asm/unwind_user_types.h@@ -0,0 +1,17 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_UNWIND_USER_TYPES_H +#define _ASM_UNWIND_USER_TYPES_H + +#ifdef CONFIG_IA32_EMULATION + +struct arch_unwind_user_state { + unsigned long ss_base; + unsigned long cs_base; +}; +#define arch_unwind_user_state arch_unwind_user_state + +#endif /* CONFIG_IA32_EMULATION */ + +#include <asm-generic/unwind_user_types.h> + +#endif /* _ASM_UNWIND_USER_TYPES_H */
--
2.47.2