[PATCH 0/5] linux-user: support writing floating-point registers to a core dump

[Matt Turner <mattst88@gmail.com>]

Write an NT_FPREGSET note for targets that opt in: a target_elf.h that
defines HAVE_ELF_CORE_FPREGS and target_elf_fpregset_t, and supplies an
elf_core_copy_fpregs() beside the existing elf_core_copy_regs().

Signed-off-by: Matt Turner <mattst88@gmail.com>
---
Apologies -- this prerequisite patch was accidentally omitted from the
series I sent earlier today (Message-ID:
<20260805171507.3119442-1-mattst88@gmail.com>).  It should be applied
before patches 1-5 of that series.
 linux-user/elfload.c | 19 +++++++++++++++++++
 linux-user/loader.h  |  3 +++
 2 files changed, 22 insertions(+)

diff --git ./linux-user/elfload.c ./linux-user/elfload.c
index e7c56af8ed..88508deac5 100644
--- ./linux-user/elfload.c
+++ ./linux-user/elfload.c
@@ -1887,6 +1887,17 @@ static void fill_elf_note_phdr(struct elf_phdr *phdr, size_t sz, off_t offset)
     bswap_phdr(phdr, 1);
 }
 
+#ifdef HAVE_ELF_CORE_FPREGS
+static void fill_fpregset_note(void *data, CPUState *cpu)
+{
+    /* Fill locally and copy: note memory is only aligned to 4. */
+    target_elf_fpregset_t fpregs = {};
+
+    elf_core_copy_fpregs(&fpregs, cpu_env(cpu));
+    memcpy(data, &fpregs, sizeof(fpregs));
+}
+#endif
+
 static void fill_prstatus_note(void *data, CPUState *cpu, int signr)
 {
     /*
@@ -2166,6 +2177,9 @@ static int elf_core_dump(int signr, const CPUArchState *env)
     offset += size_note("CORE", ts->info->auxv_len);
     offset += size_note("CORE", sizeof(struct target_elf_prpsinfo));
     offset += size_note("CORE", sizeof(struct target_elf_prstatus)) * cpus;
+#ifdef HAVE_ELF_CORE_FPREGS
+    offset += size_note("CORE", sizeof(target_elf_fpregset_t)) * cpus;
+#endif
     note_size = offset - note_offset;
     data_offset = TARGET_PAGE_ALIGN(offset);
 
@@ -2222,6 +2236,11 @@ static int elf_core_dump(int signr, const CPUArchState *env)
             dptr = fill_note(&hptr, NT_PRSTATUS, "CORE",
                              sizeof(struct target_elf_prstatus));
             fill_prstatus_note(dptr, cpu_iter, cpu_iter == cpu ? signr : 0);
+#ifdef HAVE_ELF_CORE_FPREGS
+            dptr = fill_note(&hptr, NT_FPREGSET, "CORE",
+                             sizeof(target_elf_fpregset_t));
+            fill_fpregset_note(dptr, cpu_iter);
+#endif
         }
 
         if (dump_write(fd, header, data_offset) < 0) {
diff --git ./linux-user/loader.h ./linux-user/loader.h
index da9ad28db5..5ddd140276 100644
--- ./linux-user/loader.h
+++ ./linux-user/loader.h
@@ -109,6 +109,9 @@ bool init_guest_commpage(void);
 
 struct target_elf_gregset_t;
 void elf_core_copy_regs(struct target_elf_gregset_t *, const CPUArchState *);
+/* Only defined by a target whose target_elf.h sets HAVE_ELF_CORE_FPREGS. */
+struct target_elf_fpregset_t;
+void elf_core_copy_fpregs(struct target_elf_fpregset_t *, const CPUArchState *);
 
 typedef struct {
     const uint8_t *image;
-- 
2.54.0