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I am trying to use a core file now. I am running `nios2-linux-gnu-gdb mynios2program`, with set solib-absolute-prefix /data/nios/nios2-linux/uClinux-dist/romfs/ in .gdbinit. Then core-file mycorefile, but all I can get is:
warning: Couldn't find general-purpose registers in core file.
# 0 0x00000000 in ?? ()
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I hit the same problem here too and traced it down to the kernel writing a faulty corefile, missing the .reg and .reg/<N> section. The cause for this was ELF_NGREG in arch/nios2/include/asm/elf.h being too small ((sizeof (struct pt_regs) / sizeof(elf_greg_t)), while ELF_CORE_COPY_REGS also writes all registers from struct switch_stack to the buffer.
If ELF_NGREG is defined as in the following patch, the corefile is generated properly and can be used with nios2-linux-gnu-gdb:
-#define ELF_NGREG (sizeof (struct pt_regs) / sizeof(elf_greg_t))
+#define ELF_NGREG ((sizeof(struct pt_regs) + sizeof(struct switch_stack)) / sizeof(elf_greg_t))
I'll also apply this fix to the nios2 branch of the nios2-linux kernel git repository.
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