Since we plan to replace stacktrace with stackprof (& the associated
test case) in a subsequent patchset, this is a minimal patch to
illustrate where the existing code using libdwfl_stacktrace needs to
generalize.
* src/stacktrace.c: Enable for ARM architectures.
(expected_frame_nregs): New function.
(sp_reg_index): New function.
(sysprof_find_dwfl): Replace hardcoded SP index with new functions.
(sysprof_unwind_frame_cb): Likewise.
(main): Open default_ebl backend appropriate to the current arch.
---
src/stacktrace.c | 51 +++++++++++++++++++++++++++++++++++-------------
1 file changed, 37 insertions(+), 14 deletions(-)
diff --git a/src/stacktrace.c b/src/stacktrace.c
index 0740a2bc..c1888b67 100644
--- a/src/stacktrace.c
+++ b/src/stacktrace.c
@@ -80,13 +80,14 @@
#include <locale.h>
#include <system.h>
+#include <sys/utsname.h>
#include <linux/perf_event.h>
-/* TODO: Need to generalize the code beyond x86 architectures. */
+/* TODO: Need to generalize the code beyond x86/ARM architectures. */
#include <asm/perf_regs.h>
-#ifndef _ASM_X86_PERF_REGS_H
-#error "eu-stacktrace is currently limited to x86 architectures"
+#if !defined(_ASM_X86_PERF_REGS_H) && !defined(_ASM_ARM_PERF_REGS_H) &&
!defined(_ASM_ARM64_PERF_REGS_H)
+#error "eu-stacktrace is currently limited to x86/ARM architectures"
#endif
/*************************************
@@ -853,6 +854,26 @@ sysprof_init_dwfl_cb (Dwflst_Process_Tracker *cb_tracker,
return dwfl;
}
+uint32_t expected_frame_nregs (Ebl *ebl)
+{
+ int m = ebl_get_elfmachine(ebl);
+ /* For aarch64, we use fewer and ebl->frame_nregs to unwind. */
+ if (m == EM_ARM)
+ return 14;
+ if (m == EM_X86_64 || m == EM_386)
+ return ebl_frame_nregs(ebl);
+ /* In general, it's better to be on the permissive side. */
+ return 1;
+}
+
+int sp_reg_index (Ebl *ebl, bool is_abi32)
+{
+ int m = ebl_get_elfmachine(ebl);
+ if (m == EM_X86_64 || m == EM_386) return is_abi32 ? 4 : 7;
+ else if (m == EM_ARM) return is_abi32 ? 13 : 31;
+ else return 0; /* XXX unwinding will likely not continue */
+}
+
Dwfl *
sysprof_find_dwfl (struct sysprof_unwind_info *sui,
SysprofCaptureStackUser *ev,
@@ -860,10 +881,7 @@ sysprof_find_dwfl (struct sysprof_unwind_info *sui,
Elf **out_elf)
{
pid_t pid = ev->frame.pid;
- /* XXX: Note that sysprof requesting the x86_64 register file from
- perf_events will result in an array of 17 regs even for 32-bit
- applications. */
- if (regs->n_regs < ebl_frame_nregs(default_ebl)) /* XXX expecting everything
except FLAGS */
+ if (regs->n_regs < expected_frame_nregs(default_ebl))
{
if (show_failures)
fprintf(stderr, N_("sysprof_find_dwfl: n_regs=%d, expected %ld\n"),
@@ -891,12 +909,11 @@ sysprof_find_dwfl (struct sysprof_unwind_info *sui,
}
reuse:
- /* TODO: Generalize to other architectures than x86_64. */
- sui->last_sp = regs->regs[7];
+ bool is_abi32 = (regs->abi == PERF_SAMPLE_REGS_ABI_32);
+ sui->last_sp = regs->regs[sp_reg_index(default_ebl, is_abi32)];
sui->last_base = sui->last_sp;
if (show_frames) {
- bool is_abi32 = (regs->abi == PERF_SAMPLE_REGS_ABI_32);
fprintf(stderr, "sysprof_find_dwfl pid %lld%s: size=%ld%s pc=%lx
sp=%lx+(%lx)\n",
(long long) pid, cached ? " (cached)" : "",
ev->size, is_abi32 ? " (32-bit)" : "",
@@ -924,11 +941,9 @@ sysprof_unwind_frame_cb (Dwfl_Frame *state, void *arg)
Dwarf_Addr pc_adjusted = pc - (isactivation ? 0 : 1);
Dwarf_Addr sp;
- /* TODO: Need to generalize this code beyond x86 architectures. */
struct sysprof_unwind_info *sui = (struct sysprof_unwind_info *)arg;
int is_abi32 = (sui->last_abi == PERF_SAMPLE_REGS_ABI_32);
- /* DWARF register order cf. elfutils backends/{x86_64,i386}_initreg.c: */
- int user_regs_sp = is_abi32 ? 4 : 7;
+ int user_regs_sp = sp_reg_index(default_ebl, is_abi32);
int rc = dwfl_frame_reg (state, user_regs_sp, &sp);
if (rc < 0)
{
@@ -1376,7 +1391,15 @@
https://sourceware.org/cgit/elfutils/tree/README.eu-stacktrace?h=users/serhei/eu
error (EXIT_BAD, errno, N_("Could not initialize Dwfl table"));
/* TODO: Generalize to other architectures. */
- default_ebl = ebl_openbackend_machine(EM_X86_64);
+ struct utsname u;
+ uname(&u);
+ int em = EM_NONE;
+ if (strcmp(u.machine, "x86_64") == 0) em = EM_X86_64;
+ else if (strcmp(u.machine, "i686") == 0 || strcmp(u.machine, "i386") ==
0) em = EM_386;
+ else if (strcmp(u.machine, "aarch64") == 0 || strcmp(u.machine,
"armv7l")) em = EM_ARM;
+ else
+ error (EXIT_BAD, errno, N_("Unsupported architecture: %s"), u.machine);
+ default_ebl = ebl_openbackend_machine(em);
struct sysprof_unwind_info sui;
sui.output_fd = output_fd;
--
2.53.0
