# \[RFC PATCH v2 15/24\] unwind\_user/eh\_frame: Duplicate registered .eh\_frame\[\_hdr\] section data on clone/fork - From: Jens Remus \ - Date: 2026-08-21 19:53:33 - List: linux-trace-kernel - Page: https://ratatoskr.run/linux-trace-kernel/2026/08/17446883 - Thread: https://ratatoskr.run/linux-trace-kernel/2026/08/17446896/t.md ```text When duplicating a process' virtual memory mappings also duplicate all of its registered .eh_frame_hdr sections stored in the per-mm maple tree to enable stacktracing using eh_frame of the child process. Signed-off-by: Jens Remus --- include/linux/eh_frame.h | 7 +++++ kernel/unwind/eh_frame.c | 48 ++++++++++++++++++++++++++++++++++ kernel/unwind/eh_frame_debug.h | 7 +++++ mm/mmap.c | 5 ++++ 4 files changed, 67 insertions(+) diff --git a/include/linux/eh_frame.h b/include/linux/eh_frame.h index 70b4f9d12828..3c88ab2f7858 100644 --- a/include/linux/eh_frame.h +++ b/include/linux/eh_frame.h @@ -32,6 +32,7 @@ struct eh_frame_section { #define EH_FRAME_MT_FLAGS (MT_FLAGS_USE_RCU) #define INIT_MM_EH_FRAME .eh_frame_mt = MTREE_INIT(eh_frame_mt, EH_FRAME_MT_FLAGS), +extern int eh_frame_dup_mm(struct mm_struct *mm, struct mm_struct *oldmm); extern void eh_frame_free_mm(struct mm_struct *mm); extern int eh_frame_add_section(unsigned long eh_frame_hdr_start, @@ -51,6 +52,12 @@ static inline bool current_has_eh_frame(void) #else /* !CONFIG_HAVE_UNWIND_USER_EH_FRAME */ #define INIT_MM_EH_FRAME + +static inline int eh_frame_dup_mm(struct mm_struct *mm, struct mm_struct *oldmm) +{ + return 0; +} + static inline void eh_frame_free_mm(struct mm_struct *mm) {} static inline int eh_frame_add_section(unsigned long eh_frame_hdr_start, diff --git a/kernel/unwind/eh_frame.c b/kernel/unwind/eh_frame.c index b0be56e31508..1ac7308814a1 100644 --- a/kernel/unwind/eh_frame.c +++ b/kernel/unwind/eh_frame.c @@ -1501,6 +1501,54 @@ int eh_frame_remove_section(unsigned long eh_frame_hdr_start) return 0; } +static void __eh_frame_dup_section(struct eh_frame_section *sec, + struct eh_frame_section *oldsec) +{ + sec->eh_frame_hdr_start = oldsec->eh_frame_hdr_start; + sec->eh_frame_hdr_end = oldsec->eh_frame_hdr_end; + sec->text_start = oldsec->text_start; + sec->text_end = oldsec->text_end; + + sec->eh_frame_start = oldsec->eh_frame_start; + sec->eh_frame_vma_end = oldsec->eh_frame_vma_end; + sec->binary_search_table_start = oldsec->binary_search_table_start; + sec->binary_search_table_end = oldsec->binary_search_table_end; + sec->fde_count = oldsec->fde_count; + sec->binary_search_table_enc = oldsec->binary_search_table_enc; + + dbg_dup(sec, oldsec); +} + +int eh_frame_dup_mm(struct mm_struct *mm, struct mm_struct *oldmm) +{ + struct eh_frame_section *sec, *oldsec; + unsigned long index = 0; + int ret; + + guard(srcu)(&eh_frame_srcu); + + mt_for_each(&oldmm->eh_frame_mt, oldsec, index, ULONG_MAX) { + sec = kzalloc(sizeof(*sec), GFP_KERNEL_ACCOUNT); + if (!sec) + return -ENOMEM; + + __eh_frame_dup_section(sec, oldsec); + + ret = mtree_insert_range(&mm->eh_frame_mt, + sec->text_start, + sec->text_end - 1, + sec, GFP_KERNEL_ACCOUNT); + if (ret) + goto err_free; + } + + return 0; + +err_free: + free_section(sec); + return ret; +} + void eh_frame_free_mm(struct mm_struct *mm) { struct eh_frame_section *sec; diff --git a/kernel/unwind/eh_frame_debug.h b/kernel/unwind/eh_frame_debug.h index bcb2d03ab9ab..e72e011ba539 100644 --- a/kernel/unwind/eh_frame_debug.h +++ b/kernel/unwind/eh_frame_debug.h @@ -41,6 +41,12 @@ static inline void dbg_init(struct eh_frame_section *sec) sec->filename = kstrdup("(vma unknown???)", GFP_KERNEL_ACCOUNT); } +static inline void dbg_dup(struct eh_frame_section *sec, struct eh_frame_section *oldsec) +{ + if (oldsec->filename) + sec->filename = kstrdup(oldsec->filename, GFP_KERNEL_ACCOUNT); +} + static inline void dbg_free(struct eh_frame_section *sec) { kfree(sec->filename); @@ -53,6 +59,7 @@ static inline void dbg_free(struct eh_frame_section *sec) #define dbg_sec_ehfh(args...) no_printk(args) static inline void dbg_init(struct eh_frame_section *sec) {} +static inline void dbg_dup(struct eh_frame_section *sec, struct eh_frame_section *oldsec) {} static inline void dbg_free(struct eh_frame_section *sec) {} #endif /* !CONFIG_DYNAMIC_DEBUG */ diff --git a/mm/mmap.c b/mm/mmap.c index 2311ae7c2ff4..7715a799810e 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -48,6 +48,7 @@ #include #include #include +#include #include #include @@ -1844,6 +1845,9 @@ __latent_entropy int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) goto loop_out; } } + retval = eh_frame_dup_mm(mm, oldmm); + if (retval) + goto loop_out; /* a new mm has just been created */ retval = arch_dup_mmap(oldmm, mm); loop_out: @@ -1893,6 +1897,7 @@ __latent_entropy int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) vm_unacct_memory(charge); } __mt_destroy(&mm->mm_mt); + eh_frame_free_mm(mm); /* * The mm_struct is going to exit, but the locks will be dropped * first. Set the mm_struct as unstable is advisable as it is -- 2.53.0 ```