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libdrgn: kdump: pass architecture and vmcoreinfo to libkdumpfile

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It's not immediately obvious from the API, but libkdumpfile allows
setting the vmcoreinfo attribute. However, setting the vmcoreinfo is not
enough, we must also set the platform information given by the user.
Further, we need to specify these elements in the correct order with
respect to the file descriptor.

If done correctly, then libkdumpfile can successfully handle a core
whose vmcoreinfo is not present in the diskdump or ELF metadata. Of
course, the user must find the vmcoreinfo note and manually give this to
Drgn, along with the platform architecture.

Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
This commit is contained in:
Stephen Brennan 2023-09-13 14:26:38 -07:00 committed by Omar Sandoval
parent 79c2e27969
commit 6c7b271a53
1 changed files with 89 additions and 1 deletions
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90
libdrgn/kdump.c
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@ -63,6 +63,40 @@ static struct drgn_error *drgn_platform_from_kdump(kdump_ctx_t *ctx,
return NULL;
}
static struct drgn_error *drgn_platform_to_kdump(kdump_ctx_t *ctx,
const struct drgn_platform *platform)
{
kdump_status ks;
char *arch_str = NULL;
if (platform->arch == &arch_info_x86_64)
arch_str = KDUMP_ARCH_X86_64;
else if (platform->arch == &arch_info_i386)
arch_str = KDUMP_ARCH_IA32;
else if (platform->arch == &arch_info_aarch64)
arch_str = KDUMP_ARCH_AARCH64;
else if (platform->arch == &arch_info_arm)
arch_str = KDUMP_ARCH_ARM;
else if (platform->arch == &arch_info_ppc64)
arch_str = KDUMP_ARCH_PPC64;
/* libkdumpfile doesn't support RISC-V */
else if (platform->arch == &arch_info_s390x)
arch_str = KDUMP_ARCH_S390X;
else if (platform->arch == &arch_info_s390)
arch_str = KDUMP_ARCH_S390;
if (arch_str) {
ks = kdump_set_string_attr(ctx, KDUMP_ATTR_ARCH_NAME, arch_str);
if (ks != KDUMP_OK) {
return drgn_error_format(DRGN_ERROR_OTHER,
"kdump_set_string_attr(\"%s\"): %s",
arch_str, kdump_get_err(ctx));
}
}
return NULL;
}
static struct drgn_error *drgn_read_kdump(void *buf, uint64_t address,
size_t count, uint64_t offset,
void *arg, bool physical)
@ -94,6 +128,38 @@ struct drgn_error *drgn_program_set_kdump(struct drgn_program *prog)
"kdump_new() failed");
}
/*
* We need to be careful to set libkdumpfile attributes in the correct
* order, in order to achive the desired result in the rare cases when
* the program has the architecture and/or vmcoreinfo already set. In
* these cases, frequently, the information is not available to
* libkdumpfile, and so the user is providing it instead. We should set:
*
* - Architecture before file descriptor. This is because when
* libkdumpfile reads the vmcore, it immediately parses the notes in
* the header. If it doesn't know the current architecture, it will
* skip the architecture-specific notes, such as the PRSTATUS. This
* manifests to users as a missing "cpu.number" attribute, and thus a
* failure to get accurate stack traces for on-CPU tasks.
* - Vmcoreinfo after architecture. This is because when libkdumpfile
* gets a new vmcoreinfo note set, it marks the address translation
* metadata as dirty and resets its address translation info using the
* new data. If no architecture is set, it skips this setup since it
* won't know how to do so. This manifests for users as FaultError
* when they access almost any memory address.
*
* For the common case, where we are just setting the FD and OS type,
* and then letting libkdumpfile give us the vmcoreinfo and platform
* info, the only ordering constraint is the obvious one: we need to set
* the FD before getting data from libkdumpfile.
*/
if (prog->has_platform) {
err = drgn_platform_to_kdump(ctx, drgn_program_platform(prog));
if (err)
goto err;
}
ks = kdump_set_number_attr(ctx, KDUMP_ATTR_FILE_FD, prog->core_fd);
if (ks == KDUMP_ERR_NOTIMPL) {
err = drgn_error_format(DRGN_ERROR_INVALID_ARGUMENT,
@ -114,7 +180,29 @@ struct drgn_error *drgn_program_set_kdump(struct drgn_program *prog)
goto err;
}
if (!prog->vmcoreinfo.raw) {
if (prog->vmcoreinfo.raw) {
char *vmcoreinfo = memdup(prog->vmcoreinfo.raw, prog->vmcoreinfo.raw_size);
if (!vmcoreinfo) {
err = &drgn_enomem;
goto err;
}
kdump_blob_t *blob = kdump_blob_new(vmcoreinfo, prog->vmcoreinfo.raw_size);
if (!blob) {
free(vmcoreinfo);
err = &drgn_enomem;
goto err;
}
kdump_attr_t attr;
attr.type = KDUMP_BLOB;
attr.val.blob = blob;
ks = kdump_set_attr(ctx, "linux.vmcoreinfo.raw", &attr);
if (ks != KDUMP_OK) {
err = drgn_error_format(DRGN_ERROR_OTHER,
"kdump_set_attr(linux.vmcoreinfo.raw): %s",
kdump_get_err(ctx));
goto err;
}
} else {
#if KDUMPFILE_VERSION >= KDUMPFILE_MKVER(0, 4, 1)
char *vmcoreinfo;
#else