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sh: Handle the DWARF op, DW_CFA_undefined

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Allow a DWARF register to have an undefined value. When applied to the
DWARF return address register this lets lets us label a function as
having no direct caller, e.g. kernel_thread_helper().

Signed-off-by: Matt Fleming <matt@console-pimps.org>
This commit is contained in:
Matt Fleming 2009-08-20 19:53:49 +01:00
parent 5480675dc6
commit 5580e9044d
2 changed files with 14 additions and 2 deletions
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3
arch/sh/include/asm/dwarf.h
View file

@ -297,6 +297,7 @@ struct dwarf_reg {
unsigned long flags;
#define DWARF_REG_OFFSET (1 << 0)
#define DWARF_VAL_OFFSET (1 << 1)
#define DWARF_UNDEFINED (1 << 2)
};
/*
@ -370,6 +371,7 @@ extern struct dwarf_frame *dwarf_unwind_stack(unsigned long,
#define CFI_DEF_CFA .cfi_def_cfa
#define CFI_REGISTER .cfi_register
#define CFI_REL_OFFSET .cfi_rel_offset
#define CFI_UNDEFINED .cfi_undefined
#else
@ -383,6 +385,7 @@ extern struct dwarf_frame *dwarf_unwind_stack(unsigned long,
#define CFI_DEF_CFA CFI_IGNORE
#define CFI_REGISTER CFI_IGNORE
#define CFI_REL_OFFSET CFI_IGNORE
#define CFI_UNDEFINED CFI_IGNORE
#ifndef __ASSEMBLY__
static inline void dwarf_unwinder_init(void)

13
arch/sh/kernel/dwarf.c
View file

@ -452,6 +452,8 @@ static int dwarf_cfa_execute_insns(unsigned char *insn_start,
case DW_CFA_undefined:
count = dwarf_read_uleb128(current_insn, &reg);
current_insn += count;
regp = dwarf_frame_alloc_reg(frame, reg);
regp->flags |= DWARF_UNDEFINED;
break;
case DW_CFA_def_cfa:
count = dwarf_read_uleb128(current_insn,
@ -629,9 +631,16 @@ struct dwarf_frame * dwarf_unwind_stack(unsigned long pc,
UNWINDER_BUG();
}
/* If we haven't seen the return address reg, we're screwed. */
reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG);
UNWINDER_BUG_ON(!reg);
/*
* If we haven't seen the return address register or the return
* address column is undefined then we must assume that this is
* the end of the callstack.
*/
if (!reg || reg->flags == DWARF_UNDEFINED)
goto bail;
UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
addr = frame->cfa + reg->addr;