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authorPedro Alves <palves@redhat.com>2018-03-25 18:02:51 +0100
committerPedro Alves <palves@redhat.com>2018-04-10 22:52:50 +0100
commit91950479c0d751fcb7f9720e3a479afcc80f789b (patch)
tree5c7f80250f1f816138d827e90f7773802b540c5c
parent77999dcd7a079479f54d80938eee29f237e38d5b (diff)
Fix resolving GNU ifunc bp locations when inferior runs resolverusers/palves/ifunc
I noticed that if you set a breakpoint on an ifunc before the ifunc is resolved, and then let the program call the ifunc, thus resolving it, GDB end up with a location for that original breakpoint that is pointing to the ifunc target, but it is left pointing to the first address of the function, instead of after its prologue. After prologue is what you get if you create a new breakpoint at that point. 1) With no debug info for the target function: 1.a) Set before resolving, and then program continued passed resolving: Num Type Disp Enb Address What 1 breakpoint keep y 0x0000000000400753 <final> 1.b) Breakpoint set after inferior resolved ifunc: Num Type Disp Enb Address What 2 breakpoint keep y 0x0000000000400757 <final+4> 2) With debug info for the target function: 1.a) Set before resolving, and then program continued passed resolving: Num Type Disp Enb Address What 1 breakpoint keep y 0x0000000000400753 in final at gdb/testsuite/gdb.base/gnu-ifunc-final.c:20 1.b) Breakpoint set after inferior resolved ifunc: Num Type Disp Enb Address What 2 breakpoint keep y 0x000000000040075a in final at gdb/testsuite/gdb.base/gnu-ifunc-final.c:21 The problem is that elf_gnu_ifunc_resolver_return_stop (called by the internal breakpoint that traps the resolver returning) does not agree with linespec.c:minsym_found. It does not skip to the function's start line (i.e., past the prologue). We can now use the find_function_start_sal overload added by the previous commmit to fix this. New tests included, which fail before the patch, and pass afterwards. gdb/ChangeLog: yyyy-mm-dd Pedro Alves <palves@redhat.com> * elfread.c (elf_gnu_ifunc_resolver_return_stop): Use find_function_start_sal instead of find_pc_line. gdb/testsuite/ChangeLog: yyyy-mm-dd Pedro Alves <palves@redhat.com> * gdb.base/gnu-ifunc.exp (set-break): Test that GDB resolves ifunc breakpoint locations correctly of ifunc breakpoints set while the program resolves the ifunc.
-rw-r--r--gdb/elfread.c3
-rw-r--r--gdb/testsuite/gdb.base/gnu-ifunc.exp18
2 files changed, 16 insertions, 5 deletions
diff --git a/gdb/elfread.c b/gdb/elfread.c
index e724f347b96..e7925a3bc44 100644
--- a/gdb/elfread.c
+++ b/gdb/elfread.c
@@ -1026,7 +1026,8 @@ elf_gnu_ifunc_resolver_return_stop (struct breakpoint *b)
b->type = bp_breakpoint;
update_breakpoint_locations (b, current_program_space,
- find_pc_line (resolved_pc, 0), {});
+ find_function_start_sal (resolved_pc, NULL, true),
+ {});
}
/* A helper function for elf_symfile_read that reads the minimal
diff --git a/gdb/testsuite/gdb.base/gnu-ifunc.exp b/gdb/testsuite/gdb.base/gnu-ifunc.exp
index 827ac1202d2..d6ec6988a7d 100644
--- a/gdb/testsuite/gdb.base/gnu-ifunc.exp
+++ b/gdb/testsuite/gdb.base/gnu-ifunc.exp
@@ -106,6 +106,9 @@ proc_with_prefix set-break {resolver_attr resolver_debug final_debug} {
return 1
}
+ gdb_breakpoint [gdb_get_line_number "break-at-call"]
+ gdb_continue_to_breakpoint "break-at-call" ".*break-at-call.*"
+
set ws "\[ \t\]+"
set dot "\\.?"
@@ -131,19 +134,21 @@ proc_with_prefix set-break {resolver_attr resolver_debug final_debug} {
"Breakpoint $decimal at gnu-indirect-function resolver at $hex"
gdb_test "info breakpoints" \
"$decimal${ws}STT_GNU_IFUNC resolver${ws}keep${ws}y${ws}$hex <${gnu_ifunc_resolver}>"
+
+ # Make the breakpoint conditional on a condition that always
+ # fails. This is so that when the ifunc-resolver breakpoint
+ # triggers, GDB resumes the program immediately.
+ gdb_test_no_output "condition \$bpnum 0"
}
global final_src
with_test_prefix "resolve" {
- delete_breakpoints
gdb_breakpoint [gdb_get_line_number "break-at-exit"]
gdb_continue_to_breakpoint "break-at-exit" ".*break-at-exit.*"
}
with_test_prefix "after resolving" {
- delete_breakpoints
-
if {!$final_debug} {
# Set a breakpoint both at the ifunc, and at the ifunc's
# target. GDB should resolve both to the same address.
@@ -176,7 +181,12 @@ proc_with_prefix set-break {resolver_attr resolver_debug final_debug} {
gdb_test "break gnu_ifunc" "Breakpoint .* at $hex: file .*$final_src, line $lineno\\."
set location "$decimal${ws}breakpoint${ws}keep${ws}y${ws}$hex in final at .*$final_src:$lineno"
}
- gdb_test "info breakpoints" "$location\r\n$location"
+
+ # The first location here is for the breakpoint that was set
+ # before the ifunc was resolved. It should be resolved by
+ # now, and it should have the exact same address/line as the
+ # other two locations.
+ gdb_test "info breakpoints" "$location\r\n.*$location\r\n$location"
}
}