linux-kernel - [PATCH 3/3] Dwarf: unwind the recorded stack frame of different target address sizes

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Date:	Mon, 20 Jan 2014 22:22:02 +0100
From:	Jean Pihet <jean.pihet@...aro.org>
To:	libunwind-devel <libunwind-devel@...gnu.org>
Cc:	Will Deacon <will.deacon@....com>, Jiri Olsa <jolsa@...hat.com>,
	patches@...aro.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Jean Pihet <jean.pihet@...aro.org>
Subject: [PATCH 3/3] Dwarf: unwind the recorded stack frame of different target address sizes

When in compat mode, correctly unwind the recorded stack frame. The
returned pointers are cast to the desired target address size.

Signed-off-by: Jean Pihet <jean.pihet@...aro.org>
---
 src/dwarf/Gparser.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/src/dwarf/Gparser.c b/src/dwarf/Gparser.c
index b251e31..d676861 100644
--- a/src/dwarf/Gparser.c
+++ b/src/dwarf/Gparser.c
@@ -706,6 +706,29 @@ eval_location_expr (struct dwarf_cursor *c, unw_addr_space_t as,
   return 0;
 }
 
+/* Cast pointer content to the type of target address size */
+static inline int cast_value_to_addr_size(unw_word_t *val, int addr_size)
+{
+    switch (addr_size) {
+    /*
+     * Return the value of the type found at binary load time (e.g. from the
+     * ELF format)...
+     */
+    case TARGET_ADDR_SIZE_32:
+	*val = (uint32_t) *val;
+	break;
+    case TARGET_ADDR_SIZE_64:
+	*val = (uint64_t) *val;
+	break;
+    /* ... otherwise leave it as is */
+    case TARGET_ADDR_SIZE_DEFAULT:
+    default:
+	break;
+    }
+
+    return 0;
+}
+
 static int
 apply_reg_state (struct dwarf_cursor *c, struct dwarf_reg_state *rs)
 {
@@ -743,6 +766,8 @@ apply_reg_state (struct dwarf_cursor *c, struct dwarf_reg_state *rs)
 	  regnum = dwarf_to_unw_regnum (rs->reg[DWARF_CFA_REG_COLUMN].val);
 	  if ((ret = unw_get_reg ((unw_cursor_t *) c, regnum, &cfa)) < 0)
 	    return ret;
+	  /* Cast value to the type as found in the ELF binary format */
+	  cast_value_to_addr_size(&cfa, as->target_addr_size);
 	}
       cfa += rs->reg[DWARF_CFA_OFF_COLUMN].val;
     }
@@ -797,6 +822,8 @@ apply_reg_state (struct dwarf_cursor *c, struct dwarf_reg_state *rs)
     ret = dwarf_get (c, c->loc[c->ret_addr_column], &ip);
     if (ret < 0)
       return ret;
+    /* Cast value to the type as found in the ELF binary format */
+    cast_value_to_addr_size(&ip, as->target_addr_size);
     c->ip = ip;
   }
 
-- 
1.7.11.7

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